The World of Footbridges - From the Utilitarian to the Spectacular by Klaus Idelberger and Linda Wilharm

Klaus Idelberger

The World of Footbridges From the Utilitarian to the Spectacular

Klaus Idelberger

The World of Footbridges From the Utilitarian to the Spectacular

Dipl.-Ing. Klaus Idelberger Untere Marktstraße 8 D - 97688 Bad Kissingen / Rhön

Translated by Linda Wilharm, Hannover, Germany

Cover photo: Double arch bridge over the Rhine-Herne Canal near Gelsenkirchen, Germany.

Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.d-nb.de. © 2011 Wilhelm Ernst & Sohn, Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Rotherstr. 21, 10245 Berlin, Germany All rights reserved, particularly those of translation into other languages. No part of this book may be reproduced in any form – by photocopy, microfilm or any other means – nor transmitted or translated into a machine language without permission in writing from the publisher. The reproduction of product descriptions, trade names and other designations in this book does not imply that these may be freely used by any person. These may be registered trade names or other designations protected by law even when they have not been specifically identified as such. All books published by Ernst & Sohn are carefully produced. Nevertheless, authors, editors and publisher accept no liability whatsoever for the accuracy of information contained in this or any book or for printing errors. Production: HillerMedien, Berlin Design: Sophie Bleifuß, Berlin Typesetting: Uta-Beate Mutz, Leipzig Cover: Design pur, Berlin Printing: Medialis, Berlin Binding: Buchbinderei Büge, Celle Printed in the Federal Republic of Germany. Printed on acid-free paper. First Edition ISBN 978-3-433-02943-5 Electronic version available, o-book ISBN 978-3-433-60084-9

Preface Although footbridges may seem very modest in comparison with railway or

The book contains a multitude of photographs and construction drawings,

road bridges, they are often important landmarks in the urban or rural land-

often as isometric perspectives, and is intended as a stimulus not only for

scape.

structural engineers and architects in their daily practice, but also for clients,

This book contains 85 studies of selected pedestrian and cycle bridges as

teachers and students. May they all be encouraged to turn their attention to the

open footbridges or enclosed skywalks to protect bridge users from wind and

fascinating world of footbridges.

weather and frequently with an additional function as a utility bridge

During the course of his research, the author set himself the task of dis-

carrying conduits and pipelines. All the bridges described were built in Europe

covering the identities of the people involved in the construction of each bridge

(for example, in Switzerland, Germany, France, Great Britain, Italy, Norway

and contacted them in order to obtain the technical data and drawings needed

and Cyprus) and in Asia (for example Singapore, Hong Kong, Malaysia and

for a systematic analysis – this was difficult even in Germany because of new

Japan) or Australia in the past 30 years. The bridges are presented in chapters

regulations for data privacy. He viewed and photographed almost every bridge

according to their load bearing systems and span lengths, which seemed the

in the book and verified the structural descriptions with the builders of the

most sensible way to deal with the large number of structures contained in

bridges. The construction drawings were all supplied in the usual sizes of AO

the collection. It begins with wide-span suspension and cable-stayed bridges

to A2 which could not be reduced to A5 or 1/32 to 1/64 and had to be redrawn.

and continues with girder bridges and arch bridges. Chapter 5 is devoted to

Thanks go to Mr Fritz Rinschede, Düsseldorf, for the drawings he produced on

enclosed footbridges connecting buildings. These skywalks represent a type of

the basis of the original plans.

bridge that frequently has no need for stairways, ramps and support columns.

Every effort has been made to name the clients, designers, architects, struc-

Each chapter begins with a spectacular and iconic footbridge of international

tural planners, photographers and authors involved with each structure and,

significance followed by a series of “collector’s items” in the form of unique

when applicable, to provide sources and literature likely to facilitate the

and remarkable footbridges likely to inform and inspire future bridge builders.

reader’s own research.

Each bridge is separately described with subsections dealing with location,

May the tenacity of the author and the labours of the editors be rewarded!

local conditions and span length as the key data for design, the load bearing system, whether the bridge is of steel or composite steel construction and,

Klaus Idelberger,

when relevant, details are given of pylons, corrosion protection and construc-

Bad Kissingen, February 2011

tion methods. The chapter on skywalks also describes the tubular or boxshaped structure enclosing the walkway.

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

7

Contents Introduction .......... 11 1

Suspension bridges .......... 12

1.1

Duisburg, Germany: suspension-lift bridge over former branch of Rhine, worldwide innovation ! .......... 14

1.2

Bochum, Gahlensche Straße, Germany: suspension bridge, S-shaped on plan .......... 16

1.3

Sierre, Switzerland: arched, asymmetric suspension bridge over the Rhône .......... 18

1.4

Kempten-Rosenau, Germany: asymmetric suspension bridge over the Iller .......... 20

1.5

Essen, Germany: stiffened suspension bridge over main road B 224 .......... 22

1.6

Overview: seven suspension bridges in Switzerland with span lengths up to 120 m .......... 24

1.6.1

Locarno /Ascona: suspension bridge over the Melezza .......... 26

1.6.2

Aurigeno / Ronchini: impressive suspension bridge over the Maggia .......... 28

1.6.3

Giumaglio: unstiffened suspension bridge over the Maggia .......... 30

1.6.4

Lavertezzo: unstiffened suspension bridge over the River Verzasca .......... 32

2

Cable-stayed and bar-stayed girder bridges .......... 34

2.1

Turin, Italy: “Passerella” – cable fans support bridge from an inclined pylon .......... 36

2.2

Overview: London Docklands: two long-span footbridges .......... 39

2.2.1

London-Docklands: cable-stayed footbridge with pedestrian transporter .......... 40

2.2.2

London Canary Wharf: harp cable-stayed swing bridge, S-shaped .......... 42

2.3

Near Kyoto, Japan: footbridge, cable-stayed from above, below and longitudinally .......... 44

2.4

Weiden, Germany: spiral cable-stayed bridge with three-chord truss over road B 22 .......... 47

2.5

Berlin-Schöneweide, Germany: cable-stayed footbridge “Kaiser Bridge” over the Spree .......... 50

2.6

Cham, Germany: bar-stayed bridge with arch pylon over River Regen and raft harbour .......... 52

2.7

Overview: Walldorf and Wiesloch, Germany: “family” of four cable-stayed girder bridges .......... 54

A

Walldorf, SAP: beam bridge over main entrance .......... 55

B + C Walldorf, SAP: two similar girder bridges with Y-pylons .......... 56 D

Walldorf, SAP: simple girder bridge; Cross sections of bridges A to D .......... 57

2.8

Lemesos, Cyprus: the first fan cable-stayed footbridge in Cyprus .......... 58

2.9

Redwitz, Germany: bar-stayed bridge with “crow’s nest” over the River Rodach .......... 60

2.10

Weil der Stadt, Germany: cable-stayed footbridge over road B 295 .......... 62

2.11

Metzingen, Germany: bar fans on an inclined pylon over B 312 .......... 64

2.12

Montabaur, Germany: bar-stayed, galvanised girder bridge .......... 66

2.13

Osnabrück, Germany: cable-stayed bridge and arch bridge over the River Hase .......... 68

2.14

Bamberg, Germany: under-deck cable-stayed (hyperboloid) cycle and pedestrian brigde over a branch of the River Regnitz .......... 69

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

8

3

Girder bridges .......... 70

3.1

Berlin Central Station, Germany: long-span footbridge as a rigid frame bridge over the River Spree .......... 72

3.2

Baden, Switzerland: truss footbridge over River Limmat with elevator tower .......... 74

3.3

Immenstadt, Germany: truss bridge over B 19 N, River Iller and flood channel .......... 76

3.4

Leverkusen, Germany: footbridge in wave form over avenue and landfill .......... 78

3.5

Reutlingen, Germany: steel footbridge with glass planks over the River Echaz and the B 312 .......... 80

3.6

Nikosia, Cyprus: curved girder bridge with tubular spine over Lemesos Avenue .......... 82

3.7

Recklinghausen, Germany: a “dragon” footbridge over a road .......... 84

3.8

Hammelburg, Germany: two truss footbridges over the River Saale .......... 86

3.9

Gelsenkirchen / Essen, Germany: steel fans support footbridge over road and stream .......... 88

3.10

Overview: Bad Kissingen, Germany: two cycle and footbridges, curved on plan .......... 91

3.10.1 Bad Kissingen: Luitpold footbridge as a girder bridge with a tubular spine over river Saale .......... 92 3.10.2 Bad Kissingen, Schweizerhaus footbridge: a trapezoidal box girder bridge .......... 94 3.11

Bad Kissingen, Germany: galvanised, bolted footbridge over ring road B 278 .......... 96

3.12

Rietberg, Germany: a flame red, rigid frame footbridge over a new lake .......... 98

3.13

Bochum, Germany: girder bridge with tubular spine over industrial railway .......... 100

3.14

Zurich, Switzerland: 500 m footbridge with spiral box girder arms over junction .......... 102

3.15

Gelsenkirchen-Horst, Germany: bridge on tubular “serpentine” support over hollow .......... 104

4

Arch bridges .......... 106

4.1

Basle Border Triangle: arch bridge over the Rhine – a world record footbridge .......... 108

4.2

Overview: Gelsenkirchen, German Federal Garden Show: three arch bridges .......... 111

4.2.1

Gelsenkirchen, Germany: double arch bridge over the Rhine-Herne Canal .......... 112

4.2.2

Gelsenkirchen, Germany: arch bridge over Färsenbruch Road .......... 114

4.2.3

Gelsenkirchen, Germany: arch bridge over River Emscher .......... 115

4.3

Dessau, Germany: arch bridge with curved deck over the River Mulde .......... 116

4.4

Oberhausen, Germany: arch bridge over main road B 223 .......... 118

4.5

Castrop-Rauxel, Germany: serpentine arch footbridge over main road B 226 .......... 120

4.6

Munich, Germany: tubular arch bridge “zur Wies’n” over Bayer Straße .......... 122

4.7

Bensheim, Germany: middle deck arch bridge of composite structure over road .......... 124

4.8

Osnabrück, Germany: arch footbridge over River Hase .......... 126

4.9

Sindelfingen, Germany: an arch footbridge leaps into a multi-storey car park .......... 128

4.10

Overview: three arch footbridges in Southeast Asia .......... 129

4.10.1 Singapore: concave-convex rigid frame bridge (Alkaff Bridge) .......... 130 4.10.2 Singapore: an asymmetric, divided arch supports a straight bridge (Robertson Bridge) .......... 132 4.10.3 Singapore: a curved bridge panel supported by a symmetric arch (Jiak Kim Bridge) .......... 134

9

4.11

Melbourne, Australia: arch bridge, horizontally and vertically angled (Flinders Bridge) .......... 136

4.12

Hong Kong: arch bridge, horizontally and vertically curved over airport approach road .......... 138

5

Enclosed skywalks .......... 140

5.1

Kuala Lumpur, Malaysia: “Skybridge” at the 41st floor .......... 142

5.2

Enclosed suspension bridges .......... 143

5.2.1

Berlin, Germany: suspended rigid frame bridge with suspension cables over Seller Straße .......... 143

5.2.2

Bietigheim, Germany: a box-shaped footbridge connects two furniture stores .......... 144

5.2.3

Fulda, Germany: glass walls and roof for a box bridge with chain suspension .......... 146

5.3

Cable and bar-stayed girder bridges .......... 148

5.3.1

Munich, Germany: box bridge over underground station and sidings .......... 148

5.3.2

Overview: Walldorf, SAP, Germany: a “family” of five skywalks .......... 150

A

Walldorf, SAP: a cable-stayed box bridge over main road .......... 151

B

Walldorf, SAP: two-storey girder box bridge .......... 152

C

Walldorf, SAP: girder box bridge .......... 153

D

Walldorf, SAP: girder box bridge .......... 154

E

Walldorf, SAP: truss bridge, angled on plan .......... 155

5.3.3

Poplar, London: cable-stayed tubular bridge over road, rail and motorway .......... 156

5.3.4

Ålesund, Norway: a box skywalk becomes a logo for a shopping centre .......... 158

5.4

Cable and bar-stayed bridges .......... 160

5.4.1

Tuttlingen, Germany: bar-stayed, steel-glass box bridge over main road .......... 160

5.4.2

Bielefeld, Germany: bar-stayed skywalk from hotel to Civic Hall .......... 162

5.4.3

Manchester: spatial truss tube connecting retail store and shopping centre .......... 164

5.4.4

Berlin-Tempelhof, Germany: skywalk as a cylindrical spatial truss .......... 166

5.4.5

Berlin-Tempelhof, Germany: three-storey, cable-stayed enclosed footbridge .......... 168

5.5

Girder bridges .......... 169

5.5.1

Kassel, Germany: girder bridge with triangular cross section connecting factory halls .......... 169

5.5.2

Oslo, Norway: truss bridge with a glass tube on steel frames .......... 170

5.5.3

Hannover, Germany: long double-tube skywalk to exhibition centre and Expo .......... 171

5.5.4

Dresden, Germany: skywalk for passengers at airport .......... 172

5.5.5

Hildesheim, Germany: truss bridge over Speicher Straße .......... 174

5.5.6

Metzingen, Germany: girder bridge with perforated web girders .......... 176

5.5.7

Sulz am Neckar, Germany: girder bridge with perforated web girders connecting school buildings .......... 178

5.5.8

Leukerbad, Switzerland: a glazed truss bridge for a school centre .......... 180

Sources and further literature .......... 182

11

Introduction HISTORY

The basic function of every bridge is to connect two points, one each

OSCILLATION

caused by pedestrians or wind (gusts) is often more significant

side of an obstacle, using the shortest route. The bridge must be structurally

for structural analysis than dead, live or seismic loads because footbridges

sound and long-lasting, while limited financial resources normally require it

are lighter and more slender than road and rail bridges and therefore more

to be built as cheaply as possible. The footbridge is the original bridge type,

susceptible to oscillation. Pedestrians are disturbed by oscillation far more

dating back to prehistory before the invention of the wheel, the wheeled

than by any feeling of inadequate stability. Some animals, such as cattle, may

vehicle and of course the road bridge for vehicle traffic. The oldest remaining

react much more violently than human beings.

footbridge in Germany is the chain bridge over the River Pegnitz in Nuremberg,

THE LOAD BEARING SYSTEMS

for footbridges include all the structures known

which was built in 1825.

in road and rail bridge construction: suspension bridges, continuous single-

The automobile boom in the mid 20th century resulted in the widening of many

or multi-span girders, cable- or bar-stayed structures, arch, truss and spatial

roads in the USA. This process continued throughout Europe from around 1960

trusses. The balustrades are often part of the load bearing system in girder

onwards. Pedestrians were frequently forced into gloomy underpasses or onto

bridges, supporting the pedestrian deck at their bottom flanges: these belong

pedestrian bridges. The term “footbridge” is generally used today, although

to the particularly lively sub-group of stress ribbon bridges. Most European building regulations require a minimum

“pedestrian and cycle bridge” would in many cases be more accurate.

EFFECTIVE WIDTH

The first German survey of footbridges was published as a 52-page brochure

width of 2 m for open public footbridges, although bridges with effective

“Fußwegbrücken” by the Steel Council in Düsseldorf in 1980. The systematic

widths of 2.5 to 2.65 m are common when they are expected to be used by

collection of illustrations, drawings, data and descriptions of this bridge type

cyclists, groups of joggers or in some cases, herds of cattle.

was continued and is the basis of this book. Numerous special issues on foot-

BALUSTRADES

bridges have been published since the millennium, some of which appear in

quently used by cyclists. The balustrades must be designed for a shear force of

the bibliography at the end of this book.

1 kN per metre at the height of the handrail. Illumination is commonly installed

PLANNING

Footbridges are not required to be straight on plan. They can curve

must be at least 1 m high, or 1.2 m when the bridge is fre-

in the balustrades or, in the floor of the bridge, whereby the risk of vandalism

and form angles in the horizontal plane, while the vertical plane can include

must always be considered.

arches, humps, stairs and slopes (although these should be limited to a 6 %

PEDESTRIAN DECKS

gradient to accommodate wheelchair users). Road and rail bridges, in contrast,

corundum grit for slip resistance), embossed steel, steel grids (a problem for

are forced by the race for ever-increasing speeds (v > 400 km/h) to be as

ladies with high-heel shoes), reinforced concrete (also in connection with steel

straight (R > 2 km) and as flat as possible. STRUCTURAL ANALYSIS

is generally based on an assumed constant load of

consist of steel plate (covered with epoxy resin containing

load bearing structures), asphalt, glass, polycarbonate glass, hardwood and fibreglass reinforced plastic. The load bearing structure is generally made of

5 kN/m2 = 500 kg/m2 = 0.5 t/m2. When the footbridge is designed for occa-

S 235, (formerly St 37), S 355 (formerly St 52) or in certain cases S 690 high

sional use by certain vehicles (such as emergency services or road sweepers),

tensile fine-grained structural steel.

the parameters are increased to include point loads of 40 to 80 kN = 4 to 8 t,

CORROSION PROTECTION

while accepting higher permissible stresses in load bearing components.

were given several coatings of paint in almost every imaginable shade.

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

Steel components were hot-dip galvanised and/or

Suspension bridges

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

1

Suspension bridges

14

1.1

Duisburg, Germany: suspension-lift bridge over former branch of Rhine, worldwide innovation!

Client: City of Duisburg Design: Schlaich Bergermann & Partner, Consultant Structural

Engineers, Stuttgart Construction: Stahlbau Raulf, Duisburg Source: Fußgängerbrücke im Innenhafen Duisburg. 1999, [20] Photos: H. G. ESCH, Hennef-Blankenberg, Germany

LOCALITY

Duisburg is famous for its steel industry and used to be the largest

inland port in Europe. After the closure of many steel works and coal mines in the Rhine-Ruhr district, Duisburg was obliged to find new uses for its docklands including the “Duisburg Basin”, a former branch of the Rhine extending into what is today the city centre. The industrial dock with its grain silos and flour mills was transformed into a marina. An open footbridge with a 73.73 m span and an effective width of 3.5 m now crosses the new marina. As a world innovation, the pedestrian deck can be raised in the middle by approx. 10 m to allow yachts to manoeuvre even when water levels in the Rhine are high. THE INNOVATIVE LOAD BEARING SYSTEM

is that of a rear-anchored (true) sus-

pension bridge with two pairs of pylons that can be hydraulically inclined and a 14-part pedestrian deck that can be arched at 15 hinges (like the links of a bracelet). This is why the bridge has been nicknamed “the hump back”. STEEL SUPERSTRUCTURE

Two cables T (VVS 63 mm ø) are suspended over

the basin between two reinforced concrete anchor blocks and two singlecolumn pylons P (ø 419 / 40 mm) at each side of the marina; 13 × 2 virtually perpendicular hangers H of high grade steel (20 mm ø) are suspended from

Pylon with lifting mechanism

the cables and attached to the hinged axes between the 14 sections of the pedestrian deck. The tubular hinged axes are at the same time the transverse girders Q and, together with the longitudinal girders L, form a rectangular frame for the reinforced concrete slabs of the pedestrian deck, which in turn serves as the stiffening girder. Pedestrians and cyclists are protected by a 1.10 m high balustrade G of galvanised flat steel. LIFT

To arch the bridge, the pylons are pulled landwards by hydraulic cylinders

(Fig. 1.1b) and tilted; the tension on the cables T raises the pedestrian deck and gates at each end of the bridge are drawn up to a vertical position to close the bridge to pedestrians and cyclists. The lifting motion can be observed and controlled from a control room at the nearby lift road bridge at “Schwanentor”. The mass lifted is 150 t. Building costs were around € 7.5 million.

Fig. 1.1a A “hump back” bridge that can be arched and raised over

Duisburg Marina, formerly an industrial dock. Fig. 1.1b Four hydraulic cylinders, each 3.5 m long, apply tension to

the cables to incline the pylons and arch the bridge. Fig. 1.1c The 14 deck sections can be arched like the links of a bracelet.

1.1

Duisburg, Germany: suspension-lift bridge over former branch of Rhine

15

Longitudinal section

Plan

Hinge (side view)

Fig. 1.1d Longitudinal section: normal horizontal position; middle position,

bridge is raised 4.5 m and is open to pedestrians and cyclists; fully raised position, bridge is raised approx. 9 m and is closed to pedestrians and cyclists. Fig. 1.1e Plan, side view, cross section.

Cross section

1

Suspension bridges

16

1.2

Bochum, Gahlensche Straße, Germany: suspension bridge, S-shaped on plan

Client: Local government association of the Ruhr district (KVR) and “Ruhr Grün” e. V., Essen Design: Architects: von Gerkan, Marg & Partner, Hamburg Structural engineering: Schlaich, Bergermann & Partner, Consultant Structural Engineers, Stuttgart Building Construction: MSD Maschinen- und Stahlbau, Dresden; Pfeifer Seil- und Hebetechnik, Memmingen Sources: Anette Bögler et al.: leicht weit – light structures: Jörg Schlaich – Rudolf Bergermann. 2005, [21] Knut Göppert et al.: Entwurf und Konstruktion einer S-förmigen Fußgängerbrücke in Bochum. 2005, [22]

LOCATION

The local government association of the Ruhr district; “Green

Ruhr”; transformed the railway line that formerly transported iron ore from the Rhein-Herne Canal Basin in Gelsenkirchen to the Bochum steel works (Bochumer Verein BV / Krupp) into a theme cycle path “Industry / Culture / Nature”. The “ore” line (Erzbahn), which is built on embankments up to 15 m in height, crosses other industrial railway lines, German Rail lines (DB) and roads such as Gahlensche Straße in Bochum. At this point a wide span bridge now connects several cycle routes. The bridge is slightly inclined and is S-shaped on plan with a span length of (25 + 50 + 25) m = 100 m between the pylons and a total length of (33 + 66 + 33) m = 132 m. Its effective width is 3 m and the balustrades are 1.2 m high. THE LOAD BEARING SYSTEM

of this deck bridge in Bochum is that of a true

suspension bridge with two pylons and an axial main stiffening girder beneath the pedestrian deck. The pylons P and the main stiffening girder H are built of high calibre hollow round steel profiles (ø 460 × 15 mm). The pylons are mounted on spherical bearings and, contrary to the original plans, are inclined. This made rear anchorage unnecessary. Deep pile foundations were needed for the anchor blocks A to secure them in the former railway embankment, built in 1900. THE PEDESTRIAN DECK

is made of 12 mm thick steel plate and is transver-

sely stiffened with cross girders Q of heavy plate, 36 mm thick, and longitudinally with girders of built-up double-T section. Pedestrians and cyclists are protected by minimalistic wire mesh fencing mounted between two cables, 16 mm ø. The cables and wire mesh are of high grade V2A steel with 18 % chromium + 8 % nickel. THE FULLY ENCLOSED GALVANISED MAIN CABLES T

are 85 mm in diameter

with 32 wires. The hangers are 10 mm ø and are made of high grade “stainless” V4A steel with 18 % chromium + 10 % nickel.

Fig. 1.2a The suspension bridge is known locally as the “winged bridge”.

The S-shaped structure is the third traffic level over Galensche Str. in Bochum and several railway lines. Fig. 1.2b The angle of the pylon was calculated to make rear anchorage unnecessary. Photo: Schwarze-Rodrian.

1.2

Bochum, Gahlensche Straße, Germany: suspension bridge, S-shaped on plan

17

View (elongated)

Plan

2

Fig. 1.2c View (elongated), plan and cross sections. The bridge connects cycle paths built on abandoned railway embankments.



Cross section II



Cross section I

1

Suspension bridges

18

1.3

Sierre, Switzerland: arched, asymmetric suspension bridge over the Rhône

Client: Etat du Valais (Canton Wallis) Service des Routes et des Cours d’Eau, Switzerland Structural engineering: Dr. Hans-G. Dauner, Sion, Valais, Bureau d’Ingénieurs Dauner, Joliat & Associés SA, Switzerland Source: Laurent Moix: Passerelle sur le Rhône – Ouvrage d’art. 1998, [23]

LOCATION

The A 9 motorway Geneva – Lausanne – Sierre – Brig through the

Cross section (pylon)

Swiss canton Wallis enters a tunnel ~5 km north-east of Sierra and continues as a viaduct over the River Rhône. At this point an elegantly arched steel pe-



destrian bridge was built to replace the former wooden footbridge providing access to the area of natural beauty Ile Falcon /Val d’Anniviers. This light construction with a span of 68 m “leaps” in a 60 + 8 m arch over the Rhône. Its effective width is 2.5 m. THE LOAD BEARING SYSTEM

is that of a true suspension bridge, even though 

only one half – in an arched form – has been realised. The bridge is asymmetric: the single pylon is on the south bank of the river. There is also a certain bridge arch is held by tension through the main cables and anchored under



similarity with the systems of cable-stayed and arch bridges. Dynamically, the 

tension and compression at the abutments. THE STEEL STRUCTURE

of the bridge over the Rhône, ~5 km upstream from

Sierre, consists of a pair of unnoticeably convexly aligned main girders, welded

girders made of medium width IPE 200 sectional steel at 2 m intervals and





of heavy plate, steel grade Fe E 355, in a form similar to that of an HEA 500 broad flange girder. These main girders are connected by a grid of transverse stiffened by a diagonal cross wind brace of RND 35 round steel under the wooden pedestrian deck. The main girders are suspended from 11 pairs of hangers of 16.5 mm inox steel wire cable from a pair of upper main cables. These, like the lower main cables, are double enclosed and galvanised wire cables of 55 mm diameter. All main cables extend from the 8 m cantilever of



the concrete anchor block A north in the river bed to the anchor block A south in the mountain side on the south bank of the river, ending in rear anchoring in the rock face F.

Fig. 1.3a An aging wooden footbridge was replaced by a dynamic

asymmetric suspension bridge: structural sophistication and first-class integration into the landscape – the new footbridge in Sierre, Switzerland. Fig. 1.3b Cross section through bridge and pylon.

1.3

Sierre, Switzerland: arched, asymmetric suspension bridge over the Rhône

19

View

P

F Rhône A south

A north 15,00

Total length



THE PYLON

is 26 m high and in the shape of an H opening towards the top to a

width of 21 m. It consists of two box columns of 20, 25 or 40 mm thick heavy plate that taper at both ends (Fig. 1.3b). The two columns are connected at approx. one third of their height by a crossbeam T of similar construction. The crossbeam narrows slightly in the middle for a lighter appearance. THE PEDESTRIAN DECK

of 20 mm × 60 mm wooden planks rests on four C- or

Z-shaped galvanised cold-drawn steel profiles and is enclosed by inwardly inclined balustrades with a tubular stainless steel top rail and eight horizontal wire cables. CONSTRUCTION

At first the pylon was erected and provisionally secured with

cables.The superstructure was lifted in three prefabricated sections and placed on trestles standing on the river bed, which was virtually dry in the summer. The sections were then welded together. Finally the main cables and hangers were placed in position and connected. Construction work was not disrupted to any great extent by a main gas line located under anchor block A north.

Fig. 1.3c View and plan. Fig. 1.3d The unconventional H-shape of the pylon is a striking feature

of the asymmetric bridge.













Plan

1

Suspension bridges

20

1.4

Kempten-Rosenau, Germany: asymmetric suspension bridge over the Iller

Client: EPTAGON Immobilienholding GmbH & Co. KG, Frankfurt; Fünfte Eptagon Immobilien GmbH & Co KG, VS Villingen Planning: Dr. Schütz Ingenieure im Bauwesen GmbH, Kempten, Dipl.-Ing. Gerhard Pahl Steel construction: STS Stahltechnik GmbH, Regensburg Cable construction: Pfeifer Seil- und Hebetechnik GmbH, Memmingen Sources: Gerhard Pahl: Die neue Rosenaubrücke über die Iller in Kempten. 2007, [24]; companies’ press releases

In 2009, an investor redeveloped the “Rosenau” district, a part of

girder grid during construction and later served to strengthen the pedestrian

Kempten with good access to the town centre, by converting an abandoned

deck of the finished bridge at the hanger connections. The deck itself consists

LOCATION

spinning mill on the east bank of the River Iller and the weaving mill on the

of a row of 100 mm thick precast concrete sections covered with a 150 mm

other side into a residential area. Prior to this the “Iron Bridge”, a decrepit

concrete layer. The steel superstructure was calculated as a spatial frame.

truss bridge built in 1886 to connect the two factories and listed as a historical

THE PYLONS

structure, had been partly dismantled because its two iron piers had caused

(away from the river). They are of seamless hot-rolled tubular steel, 457 mm ø,

a dangerous back-up of water extending into the old town of Kempten during

each bearing an 85 mm main cable. The hangers are 21 mm in diameter and,

are 25.4 m high and inclined 7.2° to the side and 10° backwards

the floods of 1999 and 2005. The client, the investor, the local authorities and

like the pylons, are inclined at 10°. They are positioned at intervals of 5.7 m,

the department for the preservation of historical monuments considered three

corresponding to the spacing of the transverse girders.

types of superstructure:

THE ASSUMED LOAD

1. a suspension bridge without piers,

load.

was 5 kN/m2 plus cleaning vehicle as a concentrated The cambered box girders were manufactured

2. a single-span truss bridge,

PRODUCTION AND ERECTION

3. a two-span truss bridge with a centre pier.

in two sections. The girder grid was assembled on the river bank near the

The first option of a single pylon suspension bridge was chosen and became

eastern abutment and then pushed onto the two piers of the old iron bridge,

the first suspension bridge in the Allgäu region. It has a span of 54 m and an

which had been left for this purpose. The precast reinforced concrete slabs of

unusually generous effective width of 3.5 m. The transparency of the modern

the deck, each up to 2.2 t in weight, were then lifted into position. A concrete

steel suspension construction (Fig. 1.4a) encroaches less on the surrounding

top layer could then be applied without the need for complicated formwork.

historic buildings than the original iron truss bridge. Although the bridge spans

The inclination of the pylons was slightly increased from their position during

the river from bank to bank without a pier, it was not necessary to compensate

erection (shown as a dashed line), lifting the bridge off the piers, which

this with a thick deck structure, which would have detracted from the appear-

were then dismantled. The use of the old piers as temporary supports during

ance of the ensemble. The banks were raised by nearly 1 m to further reduce

erection was therefore efficient and cost effective.

the flood risk.

DYNAMIC ANALYSIS

was regarded as essential because a soft and light load

is a self-anchored suspension bridge as a deck

bearing structure is susceptible to oscillation. The original plan had been to

bridge of composite construction with a low-maintenance reinforced concrete

install tuned mass dampers in the final construction. Instead, a dynamic ana-

THE LOAD BEARING SYSTEM

pedestrian deck flanked by steel box girders and back-anchored at two slightly

lysis was made, which led to adjustment of the load bearing structure. The

inclined tubular steel pylons.

calculated values for the resonant frequencies of oscillation were found to be

consists of two parallel seamlessly welded box girders,

within the limits given in professional literature, suggesting that dampers were

3.9 m apart, with a trapezoidal cross section and a height of only 450 mm. The

not necessary. Oscillation measurements were later carried out on the finished

transverse girders, which are placed at intervals of 5.7 m, provided a sturdy

bridge which confirmed these findings.

THE STEEL STRUCTURE

Fig. 1.4a The new Rosenau bridge over the Iller in Kempten.

1.4

Kempten-Rosenau, Germany: asymmetric suspension bridge over the Iller

View

Plan

Cross section

Fig. 1.4b View (dashed line = position of pylons during erection), plan and cross section through deck.

21

1

Suspension bridges

22

1.5

Essen, Germany: stiffened suspension bridge over main road B 224

Client: City of Essen Property developer: steag Walsum Immobilien AG, Duisburg-Walsum Structural engineering: Ingenieurberatung VBI Pühl & Becker GbR,

Essen Inspection engineer: Dipl.-Ing. Martin Neff, Oberhausen Steel construction: Johannes Dörnen, Stahlbauwerk GmbH & Co. KG,

Dortmund

LOCATION

Two main arterial roads pass through the city centre of Essen: the

THE LOAD BEARING SYSTEM

was analysed using the 4-H-FRAP program by

E 34 /A 40 “Ruhr motorway” on the east-west axis and the B 224 Friedrich-

PCAE GmbH, Hannover, assuming a spatial frame structure. The calculated

straße – Bismarckstraße running north-south and converging with Hohen-

value of the first resonant frequency was 3.10 Hz. This was confirmed by

zollernstraße at Bismarck Platz in Essen-Rüttenscheidt.

a comparative analysis performed by the independent inspection engineer

At this point, in May 2002, an open pedestrian bridge was built over the B 224

Dipl.-Ing. Neff, who calculated the first resonant frequency to be 3.2 Hz.

in the form of a suspension bridge, which is highly unusual for inner-city

Oscillation measurements on the finished bridge in 2001 arrived at a value of

locations. Traffic there is extremely heavy and the bridge crosses the four to

3.25 Hz, well on the safe side.

six lanes of Bismarckstraße plus sidewalks with a total span of 66 m (80 m

THE STEEL SUPERSTRUCTURE

including ramp), middle span of 27 m and 58.8 m span between the anchor

girder V, i.e. two transversely connected main girders (ROR 406.4 mm ø ×

blocks. The effective width is 2.7 m between the balustrades (Figs. 1.5a –

12.5 mm). Twelve connecting bow-shaped transverse girders Q are welded on

1.5c).

to the longitudinal girders at stub connection points. The main and transverse

of the bridge in Essen consists of a stiffening

is that of the currently very popular suspension

girders are of hollow round steel (ROR 244.5 mm ø × 6.3 mm and 12.5 mm;

bridge with stiffening girders V. The main cable T (48 mm ø) extends over the

S 355). The pedestrian deck D is freely suspended between the pylons; it is

road between A-shaped pylons at each side of the road. The deck D rests on a

made of 15 mm thick heavy plate with a layer of mastic asphalt containing

pair of stiffening girders V and is suspended from the main cable on 12 splayed

corundum grit for slip resistance.

hangers (25 mm ø). The two pylons are each back-anchored by a main cable

THE TWO PYLONS

attached to a gusset plate from which the two splayed anchor cables R (also

(ROR 457 mm × 10 mm ø) spread in an A-shape and tapering at the ends.

48 mm ø) extend. A guy rope U (40 mm ø) beneath the bridge secures the

The upper main cable T is attached to each side of a plate fitted between the

pedestrian deck against lifting caused by load reversal, for example strong

columns at the head of each pylon. Each column is decorated and optically

wind or an asymmetric load on the bridge. The superstructure is thereby stif-

lightened by an eye-catching “wing” of 15 mm heavy plate with circular cut-

fened to the extent that the lowest eigenfrequency of its bending and torsional

outs of increasing and decreasing diameter. They are painted light grey – an

oscillations is greater than the limit value 3.0 Hz, as specified by the client. All

important design feature of the bridge. The feet of the pylon columns rest on

cables are of fully enclosed spiral steel wire.

permanently elastic neoprene pads and are protected from traffic impact by

THE LOAD BEARING SYSTEM

are trestles with columns of hollow round steel

concrete pedestals.

Fig. 1.5a A footbridge over a main road in Essen with unusually elegant and eye-catching pylons.

1.5

Essen, Germany: stiffened suspension bridge over main road B 224

23

Longitudinal section

Pylon

A RAMP

with a 5 % gradient and 26.25 m in length continues from the east

end of the bridge, curving and leading down to a small park. A STAIRWAY

with two intermediate landings is located at the west end of the

bridge. The stainless steel steps are extremely slip resistant thanks to a special spherical cap embossment. A GLAZED LIFT TOWER

adjacent to the stairway greatly enhanced public ac-

ceptance of the bridge. There is a retirement home close to the west end of the bridge whose sponsor, steag, has headquarters near the ramp at the other end. THE BALUSTRADES

consist of hollow round steel (ROR 70 mm ø × 5 mm) and

panels of ornamental glass.

Isometry

Fig. 1.5b Longitudinal section: The bridge in Essen-Rüttenscheidt has a middle span of 27 m, is 58.8 m long between the anchor blocks and has total length of almost 80 m including ramp. Fig. 1.5c Details: lower bracing, longitudinal girders, bow-shaped transverse girders fitted convexly to the deck. Fig. 1.5d The load bearing system as an isometric drawing.

1

Suspension bridges

24

1.6

Overview: seven suspension bridges in Switzerland with span lengths up to 120 m

The picturesque wild-water rivers Verzasca, Melezza and Maggia

the need to connect isolated houses and villages along the courses of the

pour into the north end of Lake Maggiore (close to the river Ticino) in the Swiss

rivers to mains water supplies and, particularly, to the collection systems of

canton of Tessin; the Maggia separates the villages of Locarno and Ascona.

communal waste water treatment plants such as in Locarno. The same ap-

It is a challenging region for bridge builders: the lower course of the Maggia

plies to the River Verzasca, which pours into Lake Maggiore 5 km north of the

is a nature conservation area and the river bed is rocky. The water volume of

Maggia between Locano and Bellinzona. A bridge of this construction type is

the Maggia can increase more than one thousand-fold in a matter of hours. In

also located in Sierre on the Rhône.

LOCATION

1975 it swelled from ~2

m3/s

to 5000

m3/s

(the normal volume of the Rhine!)

THE SUPERSTRUCTURES

of all utility pipe, cycle and footbridges in this area

after cloudbursts in the surrounding mountains. Bridges, footbridges and even

are bolted together from small, mostly serial steel components, and are there-

houses were swept away. When these bridges were rebuilt or new bridges

fore predestined for hot-dip galvanisation. This was used as a very long lasting

planned, the piers were generally placed outside the river bed, resulting in

corrosion protection for the bridges listed and described in the following.

extra-long spans of up to 120 m in the form of suspension bridges with or

INCIDENTALLY:

without stiffening girders or, in exceptional cases, as arch bridges. Another

is said to be the Altenburg Bridge over the River Aare in the centre of Berne

reason to build new bridges, especially utility pipe bridges, was and remains

(see [2], p. 39).

the oldest remaining chain suspension bridge in Switzerland

Fig. 1.6a The delta of the Maggia between Locarno and Ascona,

Lake Maggiore, Switzerland. Source: Little Joe.

1.6

Overview: seven suspension bridges in Switzerland with span lengths up to 120 m

25

N

Examples of long-span suspension footbridges in Tessin, southern Switzerland Span length

Total length

Over river

Location

Distance from

Year of

at / between

Lake Maggiore

Construction

120 m

120 m

Melezza

Locarno (Ascona)

96 m

120 m

Maggia

Aurigeno (Ronchini)

100 m

135 m

Maggia

Avegno

82 m × 3

246 m

Maggia

52 m

60 m

60 m 68 m

Engineer /Architect

5 km

1997

Meister

12 km

1986

Meister

8 km

1978

Dazio

Giumaglio

25 km

1997

Municipality

Bavona

Sabbione (Dreone)

35 km

1991

Mattai

75 m

Verzasca

Lavertezzo

15 km

1997

Passera SA

106 m

Rhône

Sierre (Valais)

near Brieg

1999

Dauner

Fig. 1.6b Locations of suspension footbridges in the Italian-speaking

Swiss canton of Tessin.

1

Suspension bridges

26

1.6.1 Locarno / Ascona: suspension bridge over the Melezza

Client: ATVC Municipalities Joint Venture Design, photos: Ufficio d’Ingegneria Maggia SA, Locarno, Switzerland Steel construction, erection: Schaetti AG, Wallisellen/Zurich,

Switzerland

In the Swiss canton of Tessin, ~5 km above the point where the

of the larger outer pipes are the attachment points for the longitudinal girders

Maggia flows into Lake Maggiore, the wild waters of the Maggia converge

of IPE 200 sectional steel. The pedestrian deck lies on the longitudinal girders

LOCATION

with its tributary, the Melezza, close to the Ponte Brolla conservation area. Two

and consists of precast white reinforced concrete slabs 2.6 m wide, 1.5 m

villages, Tegna above Locarno and Losone above Ascona, are connected by a

long and 100 mm thick.

120 m long, 120 m span and 2.70 m wide combination bridge for pedestrians,

THE TWO PYLONS

ground level with a total length of 21 m including fixings in a valve chamber for

cyclists and utility pipelines. THE LOAD BEARING SYSTEM

are of 570 / 500 mm ø tubular steel and rise 18 m above

of this bridge upstream from Locarno is that of

the mains and waste water pipes. The valve chamber is built deep in the stony

a suspension bridge with a stiffening girder. The stiffening girder consists of a

bank of the river on two approx. 14 m long foundation piles.

mains water pipe and two waste water pipes, which were the main reason to

THE BALUSTRADE SECTIONS

build the bridge, together with a conduit for electricity cables. The main cables

BEARINGS

T are suspended between a pair of massive anchor blocks A and a mast pylon

it is guided in its longitudinal axis over rollers in the valve chambers at each

(2 × 1 m) are fitted onto stub connections.

Two short pin-ended columns serve as bearings for the bridge and

P on each bank. The bridge deck D, which lies on the stiffening girder V, is sus-

side of the river. The bridge can therefore expand in each direction from its

pended from a pair of main cables, each with 18 hangers H. Each main cable T

fixed point at mid span. The expansion joints in the pedestrian deck above the

with its 18 splayed hangers forms a plane with an almost constant inclination,

valve chambers are concealed and protected by rubber covers.

just off the perpendicular.

CORROSION PROTECTION

for almost all structural components is by hot-dip

of this multi-purpose bridge con-

galvanisation and an additional double coating of Duplex rust protection in

tains four pipes coupled together to form a stiffening girder V. The two larger

flame red. The railings were only galvanised because this protection was re-

pipes, with diameters of 520 and 508 mm, are located under the outer edges

garded as adequate and because the light silver appearance is an attractive

THE GALVANISED STEEL SUPERSTRUCTURE

of the pedestrian deck and the two narrower inner pipes, with diameters of

contrast to the red of the other structural components. The pylons were only

420 and 406.4 mm, run adjacent to the longitudinal axis. Each pipeline is

coated (four coats with a top coat in flame red) because they were too long

divided into 19 sections, each 6 m long, and two end sections, each 3 m long,

for the galvanising baths in Tessin. The hangers H and the threaded cable

all with flange connections. Each flange joint contains a third flange of greater

end connections are of stainless steel 18/8 with 18 % chromium and 8 %

diameter. I 160 / 120 steel sections are welded on to the top and bottom of

nickel. The wires of the main cables are protected from corrosion by the Galfan

these flanges to form transverse girders coupling the pipes, with eyes for the

process, in which plate, strip or wire is continuously drawn through molten

hangers welded on to the outer flanges. Cross bracing of 60 × 35 mm steel

zinc with a high proportion of aluminium additive to create an Fe-Zn-Al alloy

bars is located between the two larger outer pipes and above and below the

coating with excellent corrosion resistance. The HT bolts in the stiffening

smaller inner pipes. The six gusset plate joints of the cross bracing facilitated

girder were Cobao galvanised. All these measures were taken to ensure that

connection on site and are easily removed if it later becomes necessary to

the service life of the main cables and the connections would be the same as

replace pipes. T-stubs welded onto the transverse sections at the inner sides

that of the structural components less liable to corrode.

Fig. 1.6.1a Cloudbursts are typical for the region and can fill the dry,

120 m wide valley of the river in a matter of hours.

1.6.1

Locarno / Ascona: suspension bridge over the Melezza

27

Partial view

spl aye d

high water level

THE UNUSUAL METHOD OF ERECTION

was the work of a specialised sub-

contractor. Using mobile cranes, they erected the two pylons complete with their cable saddles and then suspended the main cables with their 18 hangers between them. An auxiliary cable between the pylon heads served to lift the prefabricated stiffening girder sections with their four pipes into place, beginning at mid span and working outwards symmetrically. The cross bracing and the longitudinal girders, on which the future deck would lie, were then fitted, followed by the balustrades. Another specialised subcontractor inserted exchangeable endless polyethylene inner pipes, previously butt welded on the river bank, into the steel pipes of the stiffening girder. Spacing lamellae ensured concentricity of the outer and inner pipes.

Cross section

Plan

M

Fig. 1.6.1b Bridge over the Melezza between Locarno-Tegna and Ascona-Losone; partial view. Fig. 1.6.1c Erection. Fig. 1.6.1d Plan and cross section.

1

Suspension bridges

28

1.6.2 Aurigeno / Ronchini: impressive suspension bridge over the Maggia

Project: IM Engineering Maggia AG, Ing. Hansrüedi Meister, Locarno,

Switzerland

LOCATION

A combination bridge for pedestrians, cyclists and pipelines, also

120 m long, but with a span of only 96 m and width 1.2 m was built as a connection between Aurigeno and Ronchini, 12 km north of where the Maggia flows into Lake Maggiore, to replace a bridge destroyed by floods following a cloudburst. THE LOAD BEARING SYSTEM

is that of a trough bridge in the contemporary

form of a suspension bridge with stiffening girder. Two main upper cables OT are slung between one single massive anchor block A and H-shaped pylon on each bank, from which the trough-shaped bridge girder is suspended. The two main upper cables OT with the 46 V-shaped hangers H and a lower bracing cable UT form a virtually perpendicular plane. THE GALVANISED STEEL SUPERSTRUCTURE

comprises two parallel longitudi-

nal stiffening girders V of IPE 160 steel section, 1.10 m apart, connected by 41 trough-shaped transverse frames Q (also welded IPE 160).The top edges of the transverse frames are fixed to the lower cables UT. These lower cables (32 mm ø) are connected to the upper cables OT (45 mm ø) by V-shaped hangers. The upper main cables end in “eyes” at the heads of the pylons, which meant that complicated cable saddles were unnecessary. Cross bracing made of stainless steel wire (8 mm ø) with turnbuckles is located under the transverse frames and serves as horizontal stiffening. A close-meshed open grid was selected for the bridge deck because cattle are driven over the bridge. THE TWO PYLONS P

are H-shaped with spread “arms” and “legs”. The co-

lumns are made of welded heavy plate box girders, 500 × 300 mm at the “waist” and tapering to 300 × 300 mm at the upper and lower ends. They are

CORROSION PROTECTION

All steel parts were galvanised, which was no

connected at the top by a cross bar of tubular steel, 101 mm in diameter, and

problem because of the bolted construction method and the relatively small

in the middle by a box section, which was designed in two parts for easier

size of all the parts. The zinc coating was examined in 2009 after two decades

handling and joined on site with 24 M16 HV bolts. The high grade steel foot-

of exposure to the elements and showed no signs of corrosion. All parts are

plate of the pylon can slide on an intermediate layer of neoprene.

of stainless steel with 18 % chromium and 8 % nickel (V2A).

THE BALUSTRADES

are bolted between the transverse frames and consist of

60 × 40 mm angle steel sections with vertical strands of 8 mm corrugated wire.

Fig. 1.6.2a The combination bridge over the Maggia connects the villages

of Aurigeno and Ronchini (see also p. 13). Fig. 1.6.2b The impressive H-pylons with spread “arms” and “legs”.

1.6.2

Aurigeno / Ronchini: impressive suspension bridge over the Maggia

29

View

P

OT H UT

V

A

Total length

Plan

Cross section

Pylon

T

H

H UT

UT

OT

OT

H

V

H

V UT

Pier

Fig. 1.6.2c View, plan and cross section with pylon.

1

Suspension bridges

30

1.6.3 Giumaglio: unstiffened suspension bridge over the Maggia

Client: Patriziato Giumaglio, Casa Communale, Giumaglio, Switzerland Design: Studio d’Ingegneria Andreotti + Parnter, Locarno, Switzerland Steel construction: Olivero Patocchi, Metalcostruzioni, Cevio,

Switzerland Erection: Schätti AG, Cableways, cable haulage, Tuggen, Switzerland Steel cables: Provided by OFIMA

LOCATION

The village of Giumaglio (25 km upstream from Locarno, Switzer-

land) virtually rebuilt an old and rusted footbridge over the Maggia in 1997. The new bridge has three spans, each 82 m long and, with its total length of approx. 245 m, is the longest footbridge in the Maggia valley, although it does not have the longest span. There is an anchor block A on the north-east side towards the road but to the south-west, towards the present river bed, it is anchored in the rock of the mountain side F, which made a fourth pylon unnecessary. THE LOAD BEARING SYSTEM

is that of the archaic suspension bridge without

a stiffening girder. THE GALVANISED SUPERSTRUCTURE

consists of a pair of upper main cables

OT and lower main / bracing cables UT, each of 30 mm ø. Transverse frames Q of bar steel, U 50 mm × 40 mm, are suspended from hangers H (11 mm ø), at intervals of 4.8 m. Pedestrians are protected by two cables K1 and K2 and a handrail cable Ha (11 mm ø) of stainless steel wire. A stiffening girder was not considered necessary because only hikers cross the bridge; cattle would not be using it, nor was it needed to carry utility pipelines. A pedestrian deck of steel grid G and only 0.6 m effective width was deemed sufficient. Building costs were very low, but because there is no stiffening girder, the deck structure is very light and relatively unstable. The bridge therefore bears a notice “Dondolare prohibito” – “Do not rock the bridge”. Similar bridges without stiffening girders can be found in Sabbione and Lavertezzo (Section 1.6.4), and are described separately. THE SIMPLE STEEL PYLONS

are in the shape of portals of varying height and

consist of welded HEB 180 sectional steel. The grid of the pedestrian deck rests on the HEB 140 girder which forms the cross beam at mid height of the

Fig. 1.6.3a Grid of the simple deck, “Do not rock the bridge!” Fig. 1.6.3b Footbridge for hikers over the Maggia near Giumaglio.

1.6.3

Giumaglio: unstiffened suspension bridge over the Maggia

31

View

L Island

Pile

Total length

portal. Two of the three portal supports are located on an island at approximately mid-span. These portals are stiffened by cross bracing in the half beneath the bridge deck. CORROSION PROTECTION

All steel components were hot-dip galvanised,

which should always be standard procedure for steel structures subjected to the elements. THE COST

of a bridge of this construction and span would normally be in the

region of 1.5 million Swiss francs. This bridge cost only 200,000 Swiss francs. The low price was possible because the designer and draftsman worked for only a minimum fee and the cables were “used” cables provided by OFIMA, a company with its own cable haulage facilities.

Cross section

Fig. 1.6.3c View, standard cross section and pylon portal.

Pylons

1

Suspension bridges

32

1.6.4 Lavertezzo: unstiffened suspension bridge over the River Verzasca

Client: Luigi Togni, Gordola, Switzerland Design: Passera Pedretti & Partners Ltd, Consulting Engineers,

Grancia-Lugano, Switzerland Steel construction: C. S. T. Impresa Costruzioni SA, Biasca, Switzerland

LOCATION

In 1997, a private individual built a 75 m long and 1 m wide bridge

with a span of 60 m over the Verzasca above the majestic reservoir “Lago di Vogorno”, upstream from Locarno-Gordola near the village of Lavertezzo. He wanted private access to his holiday residence located on a bluff on the other side of the mountain stream, presumably followed by his wife and faithful hound. THE LOAD BEARING SYSTEM

is that of the archaic bridge type: suspension

bridge without stiffening girder. STEEL SUPERSTRUCTURE

A pair of upper main cables OT (28 mm ø) extends

from the anchor plate A and an H-shaped pylon P, both on the east bank of the Verzasca, to the other pylon P', on the west bank. Because there was no room for an anchor block next to the house, the pylon P' was rear anchored in the rock by two braces of U 200 steel section. THE TWO PYLONS

are 2.5 m high frames of IPB 200 sectional steel. The upper

columns are bolted to the portal to reduce size and weight for helicopter transport. The load bearing structure of the bridge was kept to a minimum to reduce costs and weight, and all structural components were galvanised to achieve the longest possible maintenance-free service life. THE PEDESTRIAN DECK

is of grating (with 35 × 35 mm apertures because of

the dog) and rests on longitudinal girders L 60 × 60 × 5 mm; these are coupled with transverse girders L 40 × 40 × 4 mm and zigzag bracing of the same bar steel. The handrail is 0.9 m high with two lower protective rails of height 0.6 and 0.3 m, all of stainless steel wire cable, 10 mm ø. The perpendicular hangers are of 8 mm stainless steel wire cable and are 1.5 m apart.

Fig. 1.6.4a Minimalised bridge over the Verzasca near Gordola. Fig. 1.6.4b Suspended in mid air: the perpendicular hangers are 1.5 m apart.

1.6.4

Lavertezzo: unstiffened suspension bridge over the River Verzasca

View

Pylon

Plan

Fig. 1.6.4c View, plan and cross section. Fig. 1.6.4d The bridge has a span of 60 m high over the waters

of the Verzasca.

33

Cable-stayed and bar-stayed girder bridges

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

2

Cable-stayed and bar-stayed girder bridges

36

2.1

Turin, Italy: “Passerella” – cable fans support bridge from an inclined pylon

Client: Agenzia Torino 2006 (RUP Ing. Marco Operto), Italy Description, design of bridge/pylon: HDA Hugh Dutton Associés,

Paris Steel construction: Falcone F. lli s. r. l., Villafaletto CN, Italy Damper calculation: ARUP Partnership, London Damper construction: Maurer Söhne GmbH & Co. KG, Munich Sources: Ouvrages Metalliques. Bulletin N°5/2008, [10]

With a total length of 369 m, a free span of ~150 m, a pylon arch

of the forces involved (typical talk for architects!). This can be compared with

69 m high and an effective width of 4 m, the “Passerella” foot and cycle bridge

the beauty perceived in the body of an athlete in the moment when tensed

LOCATION

over main railway tracks at Turin station is the highest structure in this collec-

muscles release their maximum strength. It also means that good design fo-

tion. It was built between 2003 and 2005 as part of an extensive construction

cuses on the essential.

programme for the 2006 Winter Olympics and became a landmark for Turin

THE INCLINED PYLON

has an “upright” height of ~85 m and an “inclined”

and a symbol of the regeneration of the city after the demise of the car in-

height of ~61 m; it is 55 m wide at the base. The angle of its inclination over

dustry.

the railway tracks is ~65° to optimise the geometry of the cables. The height

The former FIAT works at Lingotto to the east of the railway became the Olym-

of the pylon was defined by the critical angle of the longest (130 m) cable.

pic village, which has since been turned into a residential area with apartments

There is also a slight transverse inclination of the arch to optimise the crossing

for young families. The Olympic centre for communication and logistics was

angles of the cables in relation to the gentle curve of the pedestrian deck.

built on the grounds of an abandoned wholesale market, Mercato Ortofrutti-

The pylon is in the shape of a horseshoe and is built from 370 t of welded

colo all’Ingrosso (MOI) to the west of the railway lines. The “Passerella” MOI

heavy plate Fe 355K in the form of pre-cut, conically shaped sections. Its cross

footbridge connects the two districts.

section is an equilateral triangle with a side length of 3 m, which was selected

The design and erection of the bridge was

to enable internal access for maintenance and in response to the predicted

greatly influenced by safety considerations because the bridge was to cross

behaviour of the structure in terms of bulging and tilting between the cable

PROGRAMME, CONSTRUCTION

main line traffic of the Italian state railway Ferrovie dello Stato (FS). Safety and

insertion points (lateral torsional buckling). The triangular cross section con-

dimensional regulations stipulated by FS had to be observed, but also the rele-

tains stiffeners and load-distributing diaphragms at the cable insertion points,

vant Euro Codes. Railway traffic was not to be impeded or jeopardised during

consisting of tubes to accommodate standard cable fittings. The cable an-

construction. The electrification system of the railway uses direct current; steel

chorages are concealed within the pylon and do not therefore detract from its

components and, in particular, the foundations had to be protected from the

purist appearance.

corrosive effects of residual current in the damp ground.

The inclined pylon was a particular challenge to the structural analysts and

AN ARCHITECTURAL COMPETITION

for the 2006 Winter Olympics included

engineers because it had to withstand the oscillation likely to occur in a cable-

the design of a footbridge. The winning design, “Passerella” by Hugh Dutton

stayed bridge structure, a phenomenon well known after the publicity received

Associés HDA, Paris, provided a focal point for the entire Olympic Village and

by the problems of the Millennium Bridge across the Thames in London. Spe-

was, as such, a symbol of the Olympic Games, but also of the dynamic rege-

cialists in oscillation damping from London and Munich provided an innovative

neration process in Turin as a city. At the same time this cable-stayed bridge

solution to the problem.

is an expression of the dynamism and potential of present-day Italian steel

The arch pylon is painted a bright red-orange (RAL 2032) reminiscent of the

construction.

traditional orange of the red lead coatings formerly used as corrosion protec-

DESIGN

The design philosophy of the winning architects, Hugh Dutton

tion. The preliminary zinc spray treatment was followed by coatings of ep-

Associés HDA, was that the architectural composition and conception should

oxy resin and polyurethane before the decorative colour coating was applied.

find their logical expression in the load bearing structure. HDA believes that

The luminous red-orange underlines the formal dynamism of the arch. During

observers experience aesthetic pleasure and sensual satisfaction in the

the day it is visible for miles and at night it almost has the effect of a light-

dynamics of the structure when they perceive and understand the interaction

house.

Fig. 2.1a All at an angle – the horseshoe pylon and fan-shaped cable

configuration of a footbridge in the centre of Turin.

2.1

Turin, Italy: “Passerella” – cable fans support bridge from an inclined pylon

37

The pylon arch is founded on the only piece of land available, a narrow strip

tions of the railway authorities. In addition to its curve on plan, the bridge deck

between the railway tracks at the former wholesale market, MOI, and a main

has a slight “hump” to allow adequate clearance of the overhead electricity

road.

lines of the railway and at the same time achieve the lowest possible deck

The inclined pylon is anchored to the pedestrian deck by eight pairs of galva-

height at the two points of access.

nised cables, each 7560 / 55 mm ø, attached in pairs at each side of deck at

THE BRIDGE DECK

18 m intervals. Further anchorage cables in a diamond configuration at the

tom flange is bolted to transverse girders of HEB 20 steel section at intervals

consists of two built-up I-girders, 1 m in height. The bot-

base of the pylon tie the pylon arch and the bridge deck together. In case of

of approx. 4 m and HEA 160 diagonals (Fig. 2.1c shows a cross section of the

failure of any support, the dead weight of the pylon arch can be supported by

welded construction). The pylon bearings are the fixed points of the bridge.

only two of the 8 × 2 cables.

Sliding bearings are located at each of the two bridgeheads.

The complex geometry of the cables between the arch and the bridge deck

THE PARAPET

creates the virtual volume of a sculpture imparting dynamism and grace to the

section, which give the “Passerella” an aerodynamic profile. The underside of

architectural composition.

the bridge is also clad in flat panels. The bridge was calculated for wind pres-

PIEDRITTI

“Little legs, supports” made of tubular steel welded in the form of

is encased in panels of sheet aluminium, arrow-shaped in cross

sures of up to 250 kg/m², more than specified by the Euro Code. have to withstand the dead load of the arch of 460 t and the

a V or N provide rear anchorage points for the cables. Their sliding bearings

THE BEARINGS

allow longitudinal movement of the bridge deck when temperatures fluctuate.

660 t of the bridge plus tension from the stay cables; they additionally have

is in two sections strictly separated from each

to absorb 3 % torsional stress. A Munich manufacturer specialising in bridge

other. The larger of the two, “Strallata” (the cable-stayed structure), is 235 m

bearings supplied the spherical bearings with ~25 000 kN permitted overload.

THE STEEL SUPERSTRUCTURE

Assuming a flat, curved deck, there is a danger of

long and spans the railway tracks. It is suspended from the pylon and can-

COUNTERBRACING CABLES

tilevered at each end towards MOI and Lingotto. The smaller 120 m section

torsional buckling because a moving load could alter the configuration of the

known as “Lingotto” connects the Strallata middle section with an already

cables. Counterbracing cables solved this problem.

existing bridge to the Lingotto shopping centre; this section of the bridge rests

THE FOUNDATIONS OF THE ARCH PYLON

on its own V and N-shaped supports.

to 18 m in the alluvial sedimentary ground with high groundwater levels, but

were designed to reach a depth of up

The ~18 m spacing of the cable attachment points corresponds to the greatest

hit an impenetrable substratum, causing last-minute changes to be made in

possible span of a rolled I-girder, 1.2 m in height, and fulfilled the specifica-

the foundation procedure originally proposed by a local consultant.

Fig. 2.1b Aerial view of the “Passerella” connecting two districts over railway lines in Turin.

38

Deck section

Plan

Railway lines

Isometry

Parking

Pylon section

View from west

Turin, Italy: “Passerella” – cable fans support bridge from an inclined pylon

View

2.1

Fig. 2.1c The structure consists of two separate load bearing systems;

section of the pedestrian deck.

2.2

Overview: London Docklands: two long-span footbridges

2.2

Overview: London Docklands: two long-span footbridges

LOCATION

Many river wharves in Europe have been unable to accommoda-

te the large, deep-draught vessels in use today. This was the reason for the demise of the shipbuilding industry in London’s East End from about 1970 onwards. The gigantic industrial wasteland that remained has been an area of redevelopment and regeneration for decades now. Businesses, office buildings and housing have emerged with the help of huge public funding. PUBLIC ROADS AND TRANSPORT

The London Docklands Development Corpo-

ration LDDC has built several footbridges with spans of up to 130 m and has opened the Docklands Light Railway to connect the area to a new line of the London Underground.

Fig. 2.2 Satellite photo of the London Docklands. From the left: Canary Wharf, O2 Arena (former Millennium Dome), ExCel Exhibition and Convention Centre. Source: Courtesy of the TopSat consortium, copyright QinetiQ.

39

2

Cable-stayed and bar-stayed girder bridges

40

2.2.1 London-Docklands: cable-stayed footbridge with pedestrian transporter

Client: London Docklands Development Corporation LDDC, London Structural engineering: Techniker Ltd, London Architects: Lifschutz Davidson, Thames Wharf Studios, London Steel construction: Kent Structures Marine Ltd, Queensborough

LOCATION

The harbour in the East London Docklands was formerly surroun-

ded by the facilities of the Royal Victoria Docks. Today an exclusive residential

THE PRESENT

Architects and structural engineers rediscovered and revived

the principles of the old transporter bridges or suspended ferries to create a

area with apartments and town houses looks onto a harbour primarily used for

light and elegant footbridge that has already become a landmark in the once

water sports. A footbridge with an impressive span (130 m) and width (5.2 m)

depressingly bleak East End.

was built over the huge basin, providing access to public transport in a section

A COMPETITION

of the Thames served with very few bridges. The bridge deck is at a height

cross section to reduce wind turbulence and with adequate clearance for

had initially specified an enclosed footbridge with a slender

of 15 m to allow high-masted sailing vessels to pass. A transporter for up

yachts. Taken literally, this suggested a somewhat tedious long tube that

to 40 passengers travels under the deck from one side of the dock to the

would have cut pedestrians off from the outside world. Then the architects

other.

entered their proposal for an open bridge with an enclosed transporter beneath The transporter bridge with a suspended “ferry” is not an entirely

the deck. An adjustable travelling cable mechanism lifts the cabin from the

new concept, but goes back to the robust and ingenious engineering of the

starting point on one side of the dock up to the travelling height under the

HISTORY

Victorian era. The English engineer Charles Smith had the idea of ferrying

bridge and lowers it again to the landing point on the other side. Alternatively,

people and vehicles over a stretch of water on a mobile open platform or in

the cabin can also travel just above the water level when there is no shipping

an enclosed cabin, whereby the platform or cabin was suspended from ro-

in the vicinity. The 5.2 m wide promenade on the deck of the footbridge provi-

pes between portals or trestles on each bank. The French engineer Ferdinand

des a spectacular view over the Docklands. It cannot be used in bad weather,

Arnodin developed the concept in the early 20 th century and these trans-

because it is not enclosed; pedestrians then use the transporter.

porter bridges were used to cross deep water at places where heavy ship

THE LOAD BEARING SYSTEM

is a deck bridge as a cable-stayed girder on two

traffic prevented the use of normal lift or swing bridges. Transporter bridges

support trestles, the stairway and elevator towers on each bank. The stiffening

became familiar sights in industrial docks from Middlesbrough to Bilbao.

main girder is multiple self-braced with overlapping triangular bracing and is

A similar suspended ferry can be found under the railway bridge over the

also rear anchored on each bank with a kind of bowsprit (Fig. 2.2.1a). This

famous Kaiser Wilhelm Canal, known today as the Kiel Canal.

load bearing system is known as an “upturned” Fink truss as patented by

Fig. 2.2.1a The Royal Victoria Dock Pedestrian Bridge in Newham, Greater London (London Docklands) – an open footbridge over the former Royal Victoria Dock. Enclosed stairway, elevator tower, transporter cabin.

2.2.1

London-Docklands: cable-stayed footbridge with pedestrian transporter

41

View

Cross section

Albert Fink, born in 1827 in Darmstadt, Germany, who migrated to America, later becoming president of the Baltimore Ohio Railroad, and who died in New York in 1897.

lights up the bridge at night. The slender

masts. Indirect lighting in the balustrades spreads a glow through the wooden

THE STEEL STRUCTURE

of the bridge over the Royal Victoria Dock Basin in

London consists of an aerodynamic three-cell box as the stiffening main girder. The underside of the box is slit to contain the cables and rails of the drive gear, which carries the glass cabin and also serves as a platform for maintenance of the underside of the bridge. A multiple-cell box girder was chosen because it combines a low weight with a high degree of stiffness and is suitable for wide spans. THE SIX PYLONS

ALMOST MAGICAL ILLUMINATION

“skyline” of the bridge is emphasised with downlighters picking out the cable

are at three different heights, conically pointed and extremely

slender. They are arranged over the longitudinal axis of the deck with cables fixed to anchoring points along the bridge. A cable bundle at each end of the bridge transfers the tensile force to anchors in the ground. These anchors are reminiscent of ships’ bowsprits and are important features contributing to the dynamic appearance of the composition as a whole. They were inspired by the maritime environment with its ships’ masts and the remaining warehouses and cranes. All materials reflect a functional, maritime severity – the steel structure has a hardwood deck and balustrade. The stairway and elevator towers are clad in perforated stainless steel plate.

Fig. 2.2.1b View and cross section, showing the load bearing system.

planking to reveal the “whale-spine” of the main box girder. This structure is a credit to its builders.

2

Cable-stayed and bar-stayed girder bridges

42

2.2.2 London Canary Wharf: harp cable-stayed swing bridge, S-shaped

Client: London Docklands Development Corporation LDDC, London Architects: Wilkinson Eyre Architects, London Structural engineering: Jan Bobrowski & Partners Steel construction: Kent Structures Marine Ltd, Queensborough

LOCATION

In 1994 the London Docklands Development Corporation LDDC

held a design competition for an open footbridge with the specification that it should first be movable but later permanently anchored, first fixed but later to be relocated. The winning design was built and opened in May 1997 to great public and professional acclaim, receiving six awards for architecture and steel construction. It is a swing bridge with a 90 + 90 m span over West India Dock South between the north and south quays (Heron Quays) in the vicinity of a monumental crane in Docklands’ Canary Wharf. Building costs were around £ 2.5 million. THE SPECIFICATIONS

were unusual and obviously contradictory because they

called for a bridge with both permanent and temporary sections but also one that could be opened to allow passage for ships. Part of it had to be swung (to Canary Wharf basin 100 m to the east) but the design also had to provide for subsequent shortening of the bridge because a station for the extension of the London Underground “Jubilee” line was to be built in part of the basin, which has only one main girder for each bridge half, positi-

would therefore become much narrower. The winning entry fulfilled all these

THE STEEL STRUCTURE

requirements without reconstruction, demolition or scrapping of any parts of

oned eccentrically on the inside of each curve of the bridge. Cantilever girders

the bridge. The design is S-shaped on plan and consists of two identical halves,

to support the deck extend horizontally from this spine girder and the posts of

one of which is rigid while the other can be swung on a turning mechanism

the balustrades extend vertically or with a slight inward inclination. The main

located on an artificial island. At present the “S” crosses the basin diagonally;

girder is a heavy calibre round hollow section of BS S 355 J2H steel with an

the southern half swings to allow ships to pass – as specified, the northern

outer diameter of 914 mm and 40 mm wall thickness. A section at the end of

half is rigid. In the future the southern half will simply be swung into its final

the girder is filled with concrete as a counterweight to the two slightly asym-

position in the middle of the transverse axis of the basin and the northern

metric sections of the swing half of the bridge.

half will be removed to a new location in the neighbourhood (the entire steel

THE STEEL PYLONS

structure will be “recycled”).

away from the inside of each curve of the bridge. These masts are made of the

THE LOAD BEARING SYSTEM

of this dividable footbridge is that of a deck

are inclined at an angle of 20° off perpendicular pointing

same tubular section as the main girder. Their tips extend beyond the highest

bridge in the form of two cable stayed girders, each supported at the end and

cable attachment point and are tapered for a more elegant appearance.

in the middle. The bridge joints at the abutment and between the two girders

THE CABLE HARP

are connected with bolts that can be released by remote control.

total of 28 cables. The cable anchorages are distributed almost equidistantly

consists of seven cables on each side of each pylon, i.e. a

Fig. 2.2.2a The South Quay Footbridge in the London Docklands, a former

industrial wasteland that has now become a modern business centre (Photo: Wilkinson Architects / Alan Williams). Fig. 2.2.2b Heavy calibre tubular steel for the main girders and masts dominates the design of a footbridge reminiscent of a ship (see also p. 35).

2.2.2

London Canary Wharf: harp cable-stayed swing bridge, S-shaped

Plan

Cross section

along the pylon and the length of the main girder. The curve of the bridge creates an interplay of cable planes and constantly changing perspectives when viewed from different points along the bridge. THE BALUSTRADES

are in the traditional form of a ship’s railing – as to be

expected. The balustrade inside the curve of the bridges is vertical and is protected from wind by perforated stainless steel sheet. The outer balustrade is inclined approx. 25° inwards. Light fittings in the handrails accentuate the highly attractive shape of the bridge during night illumination.

Fig. 2.2.2c The southern half (left) was originally swung up to 52° to allow

ships to pass and later fixed in the transverse axis of the basin. The northern half was later reused in another location. Fig. 2.2.2d Cross section through mast and bridge showing the balustrade, which is inclined by 25°.

43

2

Cable-stayed and bar-stayed girder bridges

44

2.3

Near Kyoto, Japan: footbridge, cable-stayed from above, below and longitudinally

Client: Shinji Shumeikai Location: Momodani, Shigaraki Mountains, Prefecture Shigaraki,

Honshu Architects: Pei Partnership Architects LLP (Tim Colbert), New York Engineers: Leslie E. Robertson Associates (LERA), R.L.L.P., New York Photos: LERA, New York Source: Klaus Idelberger: Offener Steg als Museumszugang

bei Kyoto. 2001, [25] Saw-Teen See, Daniel A. Sesil: The Museum Bridge. 1998, [28]

A Japanese religious community donated an art collection to the

the third of the bridge farthest from the tunnel) and of the upper run (with turn-

general public on 04.11.1997. The collection had been acquired from all over

buckles at the sides of the deck) created a combination of forces and halved

the world and included works of art up to 4000 years old from Egypt, Persia,

the bending moment. This enabled the designers to reduce the truss height to

China and, primarily, Japan. The patrons also provided a 216 million US $,

only 2 m and the diameter of all truss members to max. 267 mm. In this way

LOCATION

175 000

m2

museum, designed by the New York Pei Partnership Architects

the structural engineers were able to comply with the architect’s aim for mini-

and LERA structural engineers, to house the still-growing collection. The

mum dimensions using bars with a minimum of variations in diameter.

museum is located in the centre of the main Japanese island of Honshu, 30 km

THE LOAD BEARING STRUCTURE

from the hubbub of Kyoto with its 4 million inhabitants, and is surrounded by

components:

a nature conservation area of mountains and primeval forest. The only access

1. A pylon inclined at 60° and the stay cables in the mouth of the tunnel.

to the museum is from the side of a neighbouring hill top, through a cunningly

2. Longitudinal and transverse stiffening in the form of a four-chord truss under

curved 200 m long tunnel leading to the bridge which is suspended over a

the entire length of the bridge.

deep ravine. The bridge is 120 m long, 7.5 m wide and designed for pedestri-

3. Cross-stabilising flat trusses each side at deck level in the half of the bridge

ans and light vehicle traffic.

nearer to the tunnel.

THREE LOAD BEARING SYSTEMS

are united in this bridge:

of this pedestrian/car bridge has four main

4. A spreading cable harp.

1. The system of a free cantilever girder, rigidly fixed at one end, which leads

Thanks to the excellent bearing capacity of the rock, it was possible to use the

to longitudinal compressional stress in the main girder (the bridge deck is

mouth of the tunnel as a “root” and foundation for a free cantilever over the

continuously connected to the mouth of the tunnel).

deep ravine. The bridge crosses a steep ravine,

2. and 3. The system of a girder stayed from above and a girder stayed from

HURRICANE AND SEISMIC RESISTANCE

below, which leads to tensile stress in the cables thus reducing the stress in

and hurricanes are not uncommon, with a risk of fluttering vibration. For this

the main girder, a point emphasised by the structural engineers responsible.

reason the dynamic behaviour of the bridge and the ravine were tested in a

This ingenious combination of three static systems, together with the sub-

wind channel with 1:100 and 1:60 models and wind speeds of up to 90 m/s.

sequent tensioning of the lower run of cables (by extension of the king post in

The result: fluttering vibrations occur but do not reach disturbing amplitudes

Fig. 2.3a Visitors arrive at the MIHO Museum after an hour’s drive through the wilderness ending in a tunnel followed by this bridge for pedestrians and electric vehicles. The journey is in preparation for what awaits them: a world-class museum.

2.3

Near Kyoto, Japan: footbridge, cable-stayed from above, below and longitudinally

45

Longitudinal section

Plan

Forces

Section at bridge end

Section at mid-span

Querschnitt (Stegende)

Querschnitt (Stegmitte)

2,00 m

7,50 m

1

4

2 Lower run

Fig. 2.3b The horizontal section and plan show the effective coupling of three load bearing systems: it is stayed from above and below and longitudinally. The bridge is flanked by two horizontal trusses with turnbuckles for cable adjustment. Cross sections at mid-span (four-chord truss) and at the end of the bridge (two- and four-chord trusses, turnbuckles).

3 Upper run

2.3

Near Kyoto, Japan: footbridge, cable-stayed from above, below and longitudinally

46

at critical wind speeds. The maximum transverse forces on the bridge are not

section of heavy plate with a constant cross section of 300 × 400 mm and

from wind but from seismic activity, which is possible in the area. The bridge

20 mm wall thickness.

is furthermore designed for pedestrians and groups of pedestrians, for electric

THE CABLE FAN

shuttle buses with a maximum of eight passengers and a double row of

sions increase in six steps up to the vertex of the parabola; the shortest cable

armoured limousines (for important guests; maximum axle load 12 kN). CONSTRUCTION

consists of 96 galvanised spiral wire cables. Cable dimen-

is 24 m long and 22.4 mm in diameter; the longest cable has 127 wires, is

The bridge was cambered by 400 mm = 1/30 of the span

48 m long and 60 mm in diameter. These cables are fixed at one end with turn-

length. The bending moments thereby introduced into the main truss virtually

buckles to the horizontal trusses already mentioned, pass through the pylon

disappear when the bridge is in use.

at equidistant intervals and are then anchored in a concrete ring at the other

All four- and two-chord trusses were prefabricated using hollow round com-

end. This ring is largely concealed by its position 8 m back from the portal of

ponents of sectional steel, all with 267 mm outer diameter but with different

the tunnel.

wall thicknesses.

THE DECK

is covered in a material originally developed for tennis court sur-

Incidentally, because it is located in a nature reserve, only the skylights of the

facing. It is porous to allow rain and melting snow to trickle through to the

museum were allowed to project from the vegetation. A special roof structure

vegetation below.

was designed for this purpose: a spatial truss of 150 different spherical nodes

SURFACE PROTECTION

with welded butt straps, coupled with uniformly dimensioned hollow round

tilayer coating.

rods.

STEEL WAS CHOSEN

A KING POST

protrudes 2 m in the perpendicular beneath the deck as the

All steel components are protected by a silvery mul-

by the architects and structural engineers because of

its high load bearing capacity, which enhances the aesthetic appeal by kee-

deflection point for the lower bracing cables. It can be extended for fine adjust-

ping the “amount” of material to a minimum and because of its relatively light

ment of the tension in the cables.

weight – the bridge was built in a remote hillside 800 m above sea level.

THE STEEL PORTAL OF THE PYLON

is a parabolic box girder at the mouth of

the tunnel. It is mounted on ball bearings and its vertex is 19 m high and inclined at 30° towards the bridge. The box girder is a rectangular welded hollow

Fig. 2.3c The open bridge is a ceremonial gateway to the MIHO Museum

near Kyoto. It is stayed by 92 steel cables at the pylon portal and in the mouth of the tunnel.

2.4

Weiden, Germany: spiral cable-stayed bridge with three-chord truss over road B 22

47

2.4

Weiden, Germany: spiral cable-stayed bridge with three-chord truss over road B 22

Client: Town of Weiden, Oberpfalz, Germany Design and Structural Planning: Dipl.-Ing. Architect

Richard J. Dietrich, Engineering Architecture, Traunstein and Munich Structural analysis: Ing.-Büro Dr. Schroeter & Dr. Kneidel, Weiden Fabrication, erection: Maurer Söhne GmbH & Co. KG, Munich Source: Richard J. Dietrich: Faszination Brücken – Baukunst, Technik, Geschichte. 2001, [8] Photos and drawings: were kindly made available by Dipl.-Ing. Richard J. Dietrich

LOCATION

This cable-stayed bridge, spiral on plan, was completed in 1998

and spans a main road, the B 22 in Weiden, Germany, providing a safe connec-

THE TRUSS IS SUSPENDED

on nine sets of round steel bars of 48 mm ø. The

suspension bars are connected with fork fittings to eye plates, hinged on one

tion for school children from a residential area to a school centre on the other

side. At deck level, however, the hangers are cardanically connected with ball

side of the road. Part of the bridge had to cross a protected biotope with ponds

and socket joints; this means that their height and inclination can be adjusted,

and the specification was for a filigree structure with as much transparency

which proved very useful during erection. Constraints which might have had

as possible. The chosen structure is suspended from steel bars and begins

an unfavourable effect on the threaded suspension bars could be avoided.

with a spiral access section. The truss of the deck is spatially curved, and the

THE PYLON

pedestrian follows an upward spiral to the main section of the bridge across

wards the top. It is rigidly fixed in its foundation and inclines away from the

the B 22, which is at a tangent to the access section. The bridge is 81 m long

main load, which is an advantage both structurally and in appearance. Addi-

at its middle axis and ~3.5 m wide with an effective width of 2.6 m between

tional rear bracing is provided by three of the nine hanger bars which extend

the handrails.

to the ground and are anchored to pedestals on auger piles. A non-rigid pylon

THE STEEL SUPERSTRUCTURE

that satisfied all the specifications was a

three-chord truss without gusset plates or spherical nodes. The spatial truss

is built of conical sheet steel sections and therefore tapers to-

might have impaired the oscillation behaviour of the bridge. DESIGN

The structural engineer and architect first defined the exact geometric

consists of round hollow sections (tubular steel) and could also be seen as a

data using a three-dimensional model and transferred these by dxf file to a 3D

sequence of tetrahedrons and semi-octahedrons.

AutoCAD application. There the hollow round bars (tubes) were entered so that

The curved truss is horizontally stable – like the brim of a hat. It is suspended

structural design work could commence immediately. The planning model be-

at one side from a slightly conical pylon inside the spiral. The pedestrian deck

came a 3D structural model from which component drawings and component

is covered in 10 mm standard ribbed metal sheet.

quantities were generated.

Fig. 2.4a An ingenious footbridge in Weiden crosses a main road

and a biotope.

2

Cable-stayed and bar-stayed girder bridges

48

Pylon head

CORROSION PROTECTION

The entire steel structure is triple coated against

Pylon base

corrosion. The pedestrian deck is surfaced with epoxy polyurethane quartz sand, 6 mm in thickness. THE BALUSTRADES

of 18/10 stainless steel echo the design features of the

bridge: the posts and handrails are of round hollow section (tubular steel) and, together with their struts, provide a stiff frame for wire cables. The cables only extend from post to post; the tension in a continuous strand along the entire length of the bridge might have deformed the balustrade or even have affected the entire load bearing structure of the bridge. The height of the balustrade is the standard 1.2 m to protect cyclists. This is unfortunate because it detracts from the fine proportions of the bridge. Two labyrinth barriers at the end of the spiral force speeding cyclists and moped riders to slow down. ILLUMINATION

Spotlights installed at the head of the pylon at the connection

points of the bar hangers direct light down the length of the hanger. The deck is efficiently lit, glare is avoided and the bridge is effectively and attractively illuminated. THE FOOTBRIDGE

is very popular among local inhabitants, joggers and parti-

cularly school children, probably because its light appearance is reminiscent of a chain carousel. Japanese visitors have admired and taken photos of the bridge, even suggesting that it would look good in their highly artistic stone gardens.

Fig. 2.4b The gradient of this slender footbridge begins at the bottom like the thread of a screw, spirals out and then arches over the road. Fig. 2.4c A partially spiral bar stay bridge in Weiden: unique in plan, elevation and details.

2.4

Weiden, Germany: spiral cable-stayed bridge with three-chord truss over road B 22

49

Plan

View

View railing

Cross section

Plan

2

Cable-stayed and bar-stayed girder bridges

50

2.5

Berlin-Schöneweide, Germany: cable-stayed footbridge “Kaiser Bridge” over the Spree

Client: Senate Administration for City Development, Berlin Erection planning, photo: Martin Krone Engineering, Berlin General contractor: Hochtief Construction AG, Engineering

and Environment, Berlin Steel construction: SIBAU GmbH, Genthin Bearings, dampers: Maurer Söhne GmbH & Co. KG, Munich Cables: Pfeifer Seil- und Hebetechnik GmbH, Memmingen Source: Martin Krone and Klaus-Dieter Reinke: Neubau des Kaiserstegs über die Spree in Berlin. 2008, [29]

LOCATION

The “Kaiser Bridge” in East Berlin near Schöneweide railway sta-

tion crosses the River Spree between Oberschöneweide (Laufener Straße) and Niederschöneweide (Hasselmann Straße). It was completed in September 2007. Its total length of 140 m consists of a main span of 92 m over the shipping lane (width = 75 m, height = 5.25 m) and a further span of 48 m, with a generous effective width of 5 m. It replaced a bridge built in 1898 by Allgemeine Electricitäts-Gesellschaft (AEG) to provide access to their cable factory. This was a filigree combination of arch and suspension (erected by August Klönne, Dortmund, and Philipp Holzmann, Frankfurt am Main), but was blown up by German troops on 22.04.1945. The gap that remained in Berlin’s street system has now been filled, 60 years later, by a simple cable-stayed pedestrian and cycle bridge. THE LOAD BEARING SYSTEM

is that of an elastically supported trough bridge

as a two-span system with two pairs of cables in the main span and two in the auxiliary span. Approx. 385 t of S 355 steel were used. THE STEEL SUPERSTRUCTURE

is straight on plan and forms a slight arch with

a rise of only 1.4 m (radius 700 m). It consists of two main girders 5.4 m apart and a pedestrian deck 5 m in width. Both main girders are parallel flange I-plate girders with flange widths of 400 mm. The upper flange is 50 mm thick and the lower flange 35 mm; the webs are 1765 and 1680 mm high and 15 mm thick (20 mm at the cable anchoring points). The orthotropic bridge plate is 15 mm thick with longitudinal ribs 25 mm thick and with an average height of 525 mm at intervals of 600 mm. There is a groove for rainwater along the axis of the bridge. The transverse girders, box girders in part, are spaced 2.3 m apart. The pedestrian deck has reaction resin bound surfacing only 8 mm thick.

Fig. 2.5a The “Kaiser Bridge”, rebuilt in 2007, connects the Berlin districts of Oberschöneweide and Niederschöneweide. Fig. 2.5b View from Niederschöneweide.

2.5

Berlin-Schöneweide, Germany: cable-stayed footbridge “Kaiser Bridge” over the Spree

51

View
 

 
 




  
 


 


THE STEEL PYLON

 
 


 


is 30 m high and rests on a reinforced concrete pier

approx. 6.5 m high, measured from the river bed. The original plan was for

 


 
 


avoiding adjustment to the configuration of the superstructure and additional damping. Spotlights are installed near the top of the inside walls of the

an H-shaped pylon with two cross beams; this shape would, however, have

ILLUMINATION

allowed critical lateral oscillation and therefore needed additional damping.

I-plate girders at intervals of 4.5 m. The pylon is additionally accentuated by

This was avoided by selecting a pylon in the stiffer A-shape, although it

spotlights on the piers. of the pylon piers and the north abutment were built

lengthened construction time, and 3D planning was more complex. It consists

THE FOUNDATIONS

of two columns of box girders, 800 × 1200 × 20 mm / 15 mm, a crossbeam

using sheet pile walls directly in the river. The south abutment was built on

of 500 × 500 × 20 mm under the deck of the bridge and a pylon footplate

land.

of 1750 × 850 × 100 mm. The A-pylon also provides intermediate support for

ERECTION

The two bridge sections were transported by barge to the building

site. A floating crane was used to raise, anchor and concrete the pylon. The

the superstructure. THE MAIN GIRDER AND THE LONGITUDINAL RIBS

are rigidly fixed at the

northern abutment.

92 m main span and the 48 m auxiliary span were then lifted into position. STRUCTURAL ANALYSIS

was based on the German Code DIN 1055 and per-

consists of 2 + 2 cable pairs of fully enclosed VVS 3

tinent reports. Analysis of oscillation behaviour was of particular importance

spiral wire; beginning from the left the cable diameter at plane 1 is 75 mm,

because of the slenderness of the structure. The aeroelastic response of the

60 mm at plans 2 and 3 and 95 mm at plan 4. A cable diameter of 75 mm

bridge had to be investigated both in respect of wind action and resonances

THE CABLE BRACING

would have been adequate for the calculated load, but there was still a risk of

caused by pedestrians. After intensive analysis and consultation it was deci-

torsional “galloping” through wind action. A cable diameter of 95 mm with an

ded that resonance damping or prevention was unnecessary. According to the

accordingly higher torsional resonant frequency was selected for level 4, thus

source, dampers could be retrofitted if required, see [29].

Isometry

   

Fig. 2.5c View and isometry of the pedestrian and cycle bridge.

2

Cable-stayed and bar-stayed girder bridges

52

2.6

Cham, Germany: bar-stayed bridge with arch pylon over River Regen and raft harbour

Client: Town of Cham Design and structural planning: Dipl.-Ing. Univ. Gerd Schierer,

Structural Engineering, Cham Structural analysis: Dipl.-Ing. (FH) Klaus Baier, Schönthal Source: Gerd Schierer and Klaus Schwaab: Markanter Übergang: Die Fuß- und Radwegbrücke in Cham. 2002, [30]

Cham is a small town with 17 300 inhabitants 50 km north-east of

a pair of box girders 500 × 500 × 20 mm of S 235 steel, like the pylons them-

Regensburg, Germany. The River Regen flows along the southern perimeter

selves. The segment arches are stiffened at the “top” with three box transverse

LOCATION

of the town and widens at one point, forming what used to be a raft harbour.

girders 450 × 400 × 20/15 mm. Two of these are inserted into the elonga-

A pedestrian and cycle bridge was needed that would harmonise with both

ted axis of the segment supports (the “legs”), the third at mid-point between

the townscape and the countryside. Various designs were considered: girder

them.

bridges, cable or bar-stayed girder bridges with pylon(s), arch bridges and also

The bridge trough is suspended from the segment arches by 2 + 2 tension

a bridge with arch segments. This was the bridge opened in September 2000,

bars (manufactured by Besista) at its quarter points. This, together with the

an unusually long-span segment arch bridge with 16.8 m + 50.4 m = 67.2 m

inclusion of the balustrade in the load effects of the trough, enabled the bridge

total length and 3 m effective width between the handrails.

designers to keep the trough dimensions to a minimum. Its lateral trusses of

of this trough bridge is that of a cable or bar-

S 355 JG2 steel have chords and posts of HEB 160 sectional steel, diagonals

stayed girder bridge. A continuous girder rests on two abutments and a pier

of steel bar (30 or 36 mm in diameter) or they are hollow round profiles RR

THE LOAD BEARING SYSTEM

and is at the same time suspended at the quarter points from two distinctive

48.3 × 8.0 or 5.0 mm. The handrails are of stainless steel with 18 % chromium

pylons.

+ 10 % nickel (V4A).

THE STEEL SUPERSTRUCTURE

consists of two “pylons” in the shape of quarter

MANUFACTURE

The entire structure was prefabricated in its component parts

circles, ~13 m high at the crown, with a box section of 1200 × 500 × 20 mm

and assembled on site using bolt connections only. Component parts were given a multi-layer blue

in the crown tapering to 500 × 500 × 20 mm at the base and suspension

CORROSION PROTECTION

point. The segment arches logically have their largest cross sections in the

coating during manufacture. Minor damage to the surface was repaired after

area with the greatest bending moments. Each segment arch is supported by

assembly on site.

Fig. 2.6a A footbridge over the River Regen in Cham is suspended

from a pair of cantilevered arch pylons.

2.6

Cham, Germany: bar-stayed bridge with arch pylon over River Regen and raft harbour

53

View

Plan

Cross section

Fig. 2.6b View, plan and cross section of the bridge trough; suspension detail of the segment arch.

Detail

2

Cable-stayed and bar-stayed girder bridges

54

2.7

Overview: Walldorf and Wiesloch, Germany: “family” of four cable-stayed girder bridges

Walldorf

Client: Town of Walldorf Concept: Jöllenbeck & Wolf, Architects BDA and town planners,

Wiesloch

C

Design and erection planning: BUNG AG, Ingenieure AG,

B3

9

J. Hymon, Heidelberg

A

D

B

L723

Steel construction: Stahlbau Main GmbH, Erlensee Source: Michael Jöllenbeck and Armin Wolf:

Di

et m ar -H op pAl le e

Vier Bauwerke im Kontext: Die „Brückenfamilie“ in Walldorf. 2007, [31]

SAP

LOCATION

One of the world’s leading concerns in business management

THE BRIDGES

have span lengths of up to 47 m and effective widths of ge-

software, SAP AG, has its headquarters in Walldorf (~15 km south of Heidel-

nerally 3.5 m. They were designed as a “family” (see Source). All have the

berg) where over 16 000 employees work in an organically developed com-

same composite cycle and pedestrian decks on steel I-girders and tubular

plex of offices and laboratories connected by enclosed skywalks (see Section

steel supports, but three are cable-stayed, whereby a different configuration

5.3.2).

was selected for each bridge: one with a truss mast and two with Y-shaped

In 2003, a new four- to six-lane bypass, the B 39 N, cut the “workplace” Wall-

pylons, according to the location and span length required. The fourth bridge

dorf off from the neighbouring residential areas, such as Wiesloch. Three years

is a simple girder.

later Walldorf and Wiesloch were reconnected by four class 5 kN/m² cycle and

BUILDING COSTS

pedestrian bridges at intervals of only ~1 km. The middle bridge was built with

limits.

a centre bus lane and walkways at each side.

AWARD

came to an average of 2000 €/m2, well within the normal

The “family” of bridges received the “Good Structure Award 2006”

from the Association of German Architects BDA. This is awarded to architects, town planners and clients working together on specific projects. Four similary footbridges near Heidelberg No.

Bridge

Span lengths

Length

Special feature

Costs

A

pedestrian and cycle bridge,

47 m + 22 m

69 m

truss pylon

€ 1.3 mill.

9.60 m + 24 m + 9.60 m + 14 m + 14 m + 11 m

82.20 m

four Y-pylons

€ 1.9 mill.

9.60 m + 24 m + 9.60 m

43.20 m

four Y-pylons

46 m

none

main entrance SAP, crossing Neurott Straße B

pedestrian and single track bus traffic, crossing B 39 Hochholzer Weg

C

pedestrian and cycle bridge, crossing B 39

D

pedestrian and cycle bridge,

~ 23 m

crossing Hasso-Plathner-Ring, SAP Campus

Fig. 2.7 Locations of the award-winning footbridges south of Heidelberg. (Drawing: Peter Palm, Berlin)

2.7

Walldorf and Wiesloch, Germany: “family” of four cable-stayed girder bridges

A

Walldorf, SAP: beam bridge over main entrance

55

FEATURES

The special features of this footbridge are the truss pylon, which

can be seen from miles around, and the almost symmetric cable fans. It is a two-span bridge (47 m + 22 m) at the junction of two roads at the south entrance to SAP AG. PYLON

The pylon is a tower of four stacked cubes with pronounced stiff-

ening at the nodes. It is built of welded seamless hot-rolled S 355 tubular steel, 193.7 mm in diameter, with a maximum wall thickness of 25 mm. The 2 × (3 + 3) fully enclosed steel spiral wire cables of 40 and 55 mm ø extend from two sides of the pylon truss, which is also designed for the additional load of advertising panels on all four sides. THE MAIN GIRDERS

are of welded steel plate and are similar to European

IPE 450 sections, but with the upper flange reduced to provide more effective width for the bridge deck. The main girders are on floating bearings with neoprene pads at one abutment and at the pylon at approximately mid-bridge. The fixed bearing is at the other abutment, where the bracing cables for the pylon are also anchored. This bridge cost € 1.3 million for a surface area of 242 m2.

ca. 20,00 m

View | Longitudinal section

0,00 m

47,00 m

22,00 m 69,00 m

Plan

N Fig. 2.7Aa The 20 m truss pylon is the distinguishing feature

of this footbridge. Some of the cubes can be used for advertising and announcements. Fig. 2.7Ab View and plan. Bridge A with span lengths of 47 m and 22 m. The new bridge crosses the B 39 N Walldorf bypass. (See p. 57 for cross section.)

2

Cable-stayed and bar-stayed girder bridges

B and C

FEATURES

56

Walldorf, SAP: two similar girder bridges with Y-pylons

These two footbridges to SAP are characterised by their four

Y-shaped pylons; the distances to be spanned here were only 9.6 m + 24 m + 9.6 m + 14 m + 14 m + 11 m and 9.6 m + 24 m + 9.6 m. THE Y-SHAPED PYLONS

are of welded tubular S 355 steel, 273 to 355.6 mm in

diameter with 25 mm wall thickness. The composite bridge girder is supported by tubular steel transverse girders, 298.5 mm in diameter, at the forks of

Fig. 2.7Ba Four Y-shaped pylons, 10.5 m high are characteristic of the

the Y-pylons and at other points (see drawing). The points of cable entry into

two bridges. They are a variation in the structural design of the pylon truss of bridge A, a “family” resemblance. Fig. 2.7Bb Meticulously designed cable connections of the bridge family in Walldorf. Pylon bracing and bearing. Fig. 2.7Bc View, longitudinal section and plan of bridge B. (See p. 57 for cross section.)

the transverse girders are remarkable in their design. Towards the ramps, the bridge rests on tubular pin-ended supports in the form of portals. The costs were approx. € 1.9 million for bridge B, ground area 673 m².

View | Longitudinal section 4,80 m

4,80 m

4,80 m

4,80 m

4,80 m

7,80 m

0,00 m 9,60 m

24,00 m

9,60 m

43,20 m

Plan

N

2.7

Walldorf and Wiesloch, Germany: “family” of four cable-stayed girder bridges

D

Walldorf, SAP: simple girder bridge Cross sections of bridges A to D

Cross section bridges C and D

57

FEATURE BRIDGE D

Two rigid V-supports, also of tubular steel (round hollow

section) were adequate for the fourth bridge to SAP over Hasso-Plattner-Allee 1,20 m

because of its moderate ~25 m span and overall length of only 46 m. 3,50 m

THE BALUSTRADES

are all 1.2 m high with built-in illumination and, like the

rain gutter, are meticulously but sustainably manufactured of stainless chrome

0,60

nickel steel 18/10 (V4A).

0,50

2,50 m 3,50 m

0,50

Cross section bridge B 8,25 m 5,25 m

1,50 m

0,60

1,20 m

1,50 m

1,13

4,80 m 7,06 m

1,13

Cross section bridge A

0,67

1,20 m

3,50 m

1,00 m

2,50 m

1,00 m

4,50 m

Fig. 2.7D Cross section of bridge C and D without load bearing members. Fig. 2.7Bd Cross section of bridge B. Fig. 2.7Ac Cross section of bridge A.

2

Cable-stayed and bar-stayed girder bridges

2.8

Lemesos, Cyprus: the first fan cable-stayed footbridge in Cyprus

LOCATION

Nikosia, the capital city in the centre of the Mediterranean island

58

THE CABLE FANS

each consist of 4 + 4 spiral wire cables with forked end fit-

of Cyprus, is linked by the A 1 motorway to the holiday resort Lemesos on the

tings, which are bolted to the top of the pylons at anchor plates. At the bottom

south coast. In 2008 a largely elevated bypass was built between the A 1 and

they are attached to the ends of the transverse girders by adjustable sleeves.

A 6 to relieve the traffic situation in the centre of Lemesos. A 46 m span foot-

Each pylon is braced in the longitudinal axis of the bridge with four cables

bridge runs at a tangent to Junction 26, a roundabout with three traffic levels,

anchored in triangular concrete blocks off the bridge. The cables are protected

and is said to be the first fan cable-stayed footbridge in Cyprus. The deck width

against corrosion and damage by plastic sheathing.

of 4.5 m (including two central pylons, Figs. 2.8a and b) was selected because

THE PYLONS

the bridge would also be used by the occasional cyclist.

round hollow section, 640 mm in diameter.

THE LOAD BEARING SYSTEM

of a cable-stayed girder was chosen as suitable

for the considerable but not enormous span of 46 m. THE STEEL SUPERSTRUCTURE

of the footbridge consists of a girder grid sus-

pended from inclined pylons on 16 inclined cables. The orthogonal grid con-

SPOTLIGHTS

incline outwards ~15° off the perpendicular. They are built of at the points of cable entry accentuate the cables and illuminate

the bridge. ARCHITECTS AND ENGINEERS

remained unknown in spite of my research in

Lemesos and written inquiries.

sists of one axial and two flanking main girders (tubular steel ~250 mm ø), connected by 16 welded I girders with a web height of ~350 mm and rounded at the ends. The pedestrian deck is stiffened by cross bracing beneath the deck panel. The surface of the deck is made slip resistant by a top layer of concrete strewn with corundum. The balustrades are 1.2 m high and in 3 m sections with wired glass panels.

Fig. 2.8a The A 1 and A 3 motorways meet near Lemesos at the traffic island

of the N26 junction, where a bridge was built to shorten the route for pedestrians and cyclists. The pylons divide the deck for two-way cycle traffic.

2.8

Lemesos, Cyprus: the first fan cable-stayed footbridge in Cyprus

59

View

q 12,00 m

~ 75°

q

6,00 m

10,00 m q 5,00 m

~ 640 mm Ø

0,00 m q

10,00 m

12,00 m

2m 46,00 m

Cross section

~ 640 mm Ø 4,50 m

5,30 m 7,00 m

Fig. 2.8b Footbridge over the motorway near Lemesos,

view and cross section.

12,00 m

10,00 m

2

Cable-stayed and bar-stayed girder bridges

60

2.9

Redwitz, Germany: bar-stayed bridge with “crow’s nest” over the River Rodach

Design: Ingenieurgesellschaft Neuner + Graf mbH, Garmisch-Partenkirchen Steel superstructure: Stahlbau Wegscheid GmbH, Wegscheid Tension bars: BESISTA Betschart GmbH, Bad Boll Source: Florian Neuner and Hans Hemmerlein: Fußgängerbrücke mit Aussichtsplattform an der Rodach. 2004, [32]

LOCATION

The River Rodach flows through a natural lake near Redwitz

(~36 km north-north-east of Bamberg) and continues as a tributary to the River Main. In 2001, a bridge for pedestrians and cyclists was built following the course of a historic timber rafting route. The bridge is 57 m long with a span length of 43 m and an effective width of 1.85 m on one side, where a low ramp leads onto the bridge, widening to 4 m at the bridge head, which is higher and ends in three staircases. THE LOAD BEARING SYSTEM

is that of a bar-stayed girder suspended at the

fourth points by a fan of three pairs of tension bars, and back-anchored by a pair of bars. All the bars come together at the head of the pylon. THE STAY AND ANCHORING BARS

are S 355 tension bars and, like their anchor

connections, are of nodular graphite cast iron GGG 40.3 EN GJT 400.18-LT with guaranteed notch toughness to –20°C (Besista system). THE STEEL SUPERSTRUCTURE

consists of a pair of extra light wide flanged

European IPB = HE-AA 450 main girders in S 355, at first 2.20 m apart, increasing gradually to 4.20 m at the bridgehead at the other end to accommodate

round section with a 329 mm outer cross section extends from deck level

two stairways down to the bank and a stairway up to the viewing platform.

and deflects the back-anchor bars from the head of the pylon into the perpen-

The grooved oak planks of the pedestrian deck are bolted to two longitudinal

dicular. The viewing platform is at the head of the boom.

IPE 100 girders within the main girders. The main girders are coupled with

THE BALUSTRADE

IPE = HEA 200 transverse girders and transverse end plates, 500 mm × 30 mm,

with six rows of horizontal bars of tubular steel, 18 mm in diameter. This is

is a 1 m high railing of flat steel posts at intervals of 2.15 m

also by tubular cross members for attachment of the stay bars. The main

potentially dangerous because bridge users might climb the railings. The hand-

girders are additionally stiffened by V-shaped bracing of round hollow steel,

rail is made of hollow round “smoke tube”, 48.3 mm in diameter.

70 mm in diameter

THE THREE STAIRWAYS

THE TWO-COLUMN PYLON

is A-shaped, 14.6 m high and stands vertically on

at the pylon are 1 m wide grids between stringers of

U 200. A daring colour was chosen for the four-layer coating: a red

pile foundations. It is constructed of heavy calibre hollow round S 355 sec-

COLOUR SCHEME

tion, 406.4 mm in diameter and with 8.8 mm wall thickness. A boom of hollow

tending towards violet in contrast to the green of the water meadow.

Fig. 2.9a The cycle and pedestrian bridge over the Rodach in a biotope

near Redwitz. Fig. 2.9b The “crow’s nest” provides a view over the water meadows

of the rivers Rodach and Main.

2.9

Redwitz, Germany: bar-stayed bridge with “crow’s nest” over the River Rodach

View

Plan

Cross section

Isometry

Fig. 2.9c Pedestrian bridge near Redwitz, view, plan, cross section and isometry.

61

2

Cable-stayed and bar-stayed girder bridges

62

2.10 Weil der Stadt, Germany: cable-stayed footbridge over road B 295

Client: Town of Weil der Stadt Design, photos: Leonhardt, Andrä & Partners, Consultant Engineers

VBI, Berlin office, Dipl.-Ing. Uwe Häberle Steel construction: STS Stahltechnik GmbH, Regensburg Builders: Fa. Gottlob Brodbeck, Roadbuilding and Engineering,

Metzingen Source: Hans-Peter Andrä, Katrin Burghagen, Uwe Häberle, Nils

Svensson: Geh- und Radwegbrücke Weil der Stadt. 2007, [33]; Hans-Peter Andrä and Uwe Häberle: Am Übergang von Tal und Ort. 2007, [34]

LOCATION

The town of Weil der Stadt (25 km south-west of Stuttgart) is

bypassed by the B 295, which was widened for three-lane traffic in 2006. A

THE BRIDGE DECK

is a 250 mm thick reinforced concrete slab with 300 mm

thick edge beams. It was concreted on falsework in mid 2006. The cable

footbridge over the bypass and a parallel farm track were needed to provide

attachment points lie 300 mm outside the bridge deck; their steel component

access to an area of natural beauty for the general public and particularly for

parts were built into the reinforced concrete slab.

the residents of a senior citizens’ home on the other side. One specification

THE PYLON

was that the bridge should not impede the view over the town for approaching

The result was a 15 m high pylon, extending only slightly above the cable

motorists.

penetration points, inclined 3.5° towards the town. It is cigar-shaped, 850 mm

All the main bridge types were considered:

thick in the middle, tapering to 400 mm at the top and base, thus reflecting

1. a suspension bridge was not appropriate for the relatively short span

the path of the bending moment. A- or Y-shaped pylons were regarded as too

16 variations in height, inclination and thickness were considered.

needed,

bulky.

2. a cable-stayed bridge (without the earth ramp at the south end) was

The single column of the pylon was inserted through the bridge plate and fric-

too expensive,

tion locked with a collared steel fixture. The point of insertion is covered with

3. a girder bridge was the cheapest but did not fulfil the aesthetic require-

walk-on laminated safety glass which, like the pylon, is illuminated from below.

ments,

The bridge deck is wider at this point to maintain the effective width. The pylon

4. a truss bridge would have impeded the view,

of S 355 J2G3 steel rests on a GS 20 MN 5V cast iron ball bearing.

5. and an arch bridge even more so. LOAD BEARING SYSTEM

In the end, a cable-stayed bridge with 31.5 m span

length, 38 m total length, a constant 2.5 m effective width and a 3.5 % longitudinal gradient was selected. An earth ramp was to be built at the south end of the bridge. Various cable configurations were drawn up and analysed. The result was a fan of four cable pairs of 30 mm diameter on the road side of the bridge and one pair of anchoring cables, 55 mm in diameter, on the town side of the bridge. All cables are of fully enclosed spiral steel wire.

Fig. 2.10a Fitted into the slope and landscape – footbridge in Weil der Stadt. (Photo: LAP)

2.10

Weil der Stadt, Germany: cable-stayed footbridge over road B 295

View

Ansicht

63

15,00 m

3,5 % 5,0 %

Weil der Stadt

B 295 0,00 m

6,50 m

31,50 m 38,00 m

Plan

Grundriss

N

B 295

0,30 m

1,20 m

Cross section Querschnitt

2,50 m 3,00 m 3,60 m

Fig. 2.10b View, plan, cross section of pedestrian deck and pylon head.

2

Cable-stayed and bar-stayed girder bridges

64

2.11 Metzingen, Germany: bar fans on an inclined pylon over B 312

Client: Town of Metzingen Design: ITR-Engineering Team Rieber, Tuttlingen-Möhringen General contractor: Gottlob Brodbeck GmbH & Co. KG, Roadbuilding

and Engineering, Metzingen

Three arterial roads, B 28 / B 312 / B 313, all with predominantly

ribs with a triangular cross section. This girder grid is connected at the trans-

long-distance traffic, converge in Metzingen, 40 km south of Stuttgart. Heavy

verse girders to two pairs of bar stays (DETAN ø 36) and suspended from a

LOCATION

goods vehicles were redirected onto bypasses, such as the North Tangent,

pylon inclined at 75° or 70°, respectively. The pylon is of welded, 22 to 40 mm

opened in 2001 as a connection between the B 312 and B 313. This is now

thick heavy plate, and is also of triangular cross section with edge lengths of

crossed by the “blue and white bridge”, as it came to be known locally, even

3.10 m × 1.05 m at the base and tapering to a point at the top of the pylon

during the erection phase. The distinctive architecture and design of this pe-

11.5 m above the deck. The continuation of the pylon tip for 3.2 m (here with

destrian and cycle bridge originated more in the desire to convey a message:

a plate thickness of only 10 mm) beyond the cable attachment is a design

“this way to Metzingen – link road B 312 / 313”, than in any technical necessity;

feature of the bridge composition. The pedestrian deck was covered with a

the span of only 21.9 m = 3 × 7.30 m could have been built without a pylon

15 mm coating with corundum grit for slip resistance.

and bar stays. The class 3/3 (6 t) footbridge has an effective width of 3 m and

THE PYLON

connects a new housing area with an existing school centre.

at an angle of almost 20° away from the longitudinal axis of the ridge and is

has a vertical height of 11.50 m and is 17.65 m long. It is turned

goes under the general heading of the cable-

braced with 18 single bar anchors to an eccentric concrete anchor block in the

stayed bridge and is, in particular, a bar-stayed girder grid as a beam suppor-

embankment of the road. The other end of the bridge rests on a concrete slab,

THE LOAD BEARING SYSTEM

ted at two points. THE SUPERSTRUCTURE

which also forms the abutment of a ramp and provides a stairway for pedesof S 255 steel couples a steel plate deck, 15 mm thick,

trians. Type 4 elastomeric bearings and compact expansion joints were used.

with five longitudinal girders and two transverse girders Q1, Q2 , whereby these

THE BALUSTRADES

main and transverse girders are constructed of heavy plate and shaped like

tubular steel frames G.

are 1.1 m high and consist of corrugated wire grids in

Fig. 2.11a A bar-stayed bridge over the northern bypass near Metzingen.

2.11

Metzingen, Germany: bar fans on an inclined pylon over B 312

65

View

Plan

Cross section/span

Fig. 2.11b A footbridge near Metzingen: approx. 22 m span,

3 m effective width, 11 m pylon height above the pedestrian deck. Fig. 2.11c The design is based on the shape of a triangle: triangular

cross sections for pylon, longitudinal and transverse girders.

Cross section/bridge end

2

Cable-stayed and bar-stayed girder bridges

66

2.12 Montabaur, Germany: bar-stayed, galvanised girder bridge

Client: The property developer “Baugrund“ for the town of Montabaur Design: Stefan Schmitz, BDA, Architect and Town Planner, Cologne

LOCATION

Montabaur is on the high speed railway line from Cologne Station

to Cologne-Bonn airport and via Limburg to Frankfurt Station and Frankfurt Airport. It runs alongside the old A 3 motorway and was opened in autumn 2002. A new, prize-winning footbridge, completed in 2003, now connects the town centre over the River Aubach with the new bus station below the Intercity and Regional Station, on the top of the new railway embankment on the edge of Montabaur. THE LOAD BEARING SYSTEM

of this deck bridge is that of a straight, bar-stayed

girder, designed as a continuous girder over two main spans, each 16.8 m long and two auxiliary spans of 6.6 and 6.4 m, with a total bridge length of 65.4 m and 2.8 m effective width. The bridge has an almost imperceptible ~2.5 % gradient to the north and lies on three pairs of pylons on hinged supports. The northern section of the bridge rests on a pin-ended support and the concrete outer wall of the new underground car park beneath the bus station, while the southern section is on neoprene pads and a concrete beam with pile foundations in the bank to the south of the stream. THE STEEL SUPERSTRUCTURE

is a girder grid consisting of a pair of main gir-

ders of rectangular hollow section 300 × 200 × 16 mm, 1.68 m apart, and 11 transverse girders of round hollow section ROR 273.6 ø × 60 mm wall thickness. The girder frame is stiffened with cross bracing in the middle of each main span. Secondary HEA 160 transverse girders are arranged in a 6.55 m grid. The grid carries four rows of wooden beams, 140 × 100 mm, to which the 50 × 130 mm transverse deck planks are fixed. These deck components are all of bongossi wood.

Fig. 2.12a The footbridge at the new Intercity Station and

business centre at Montabaur is the winning entry of a design competition. Fig. 2.12b Pylon on hinged bearing.

2.12

Montabaur, Germany: bar-stayed, galvanised girder bridge

67

View

THE THREE PAIRS OF PORTAL PYLONS

with columns of hollow round section,

ROR 406 mm ø (30 mm wall thickness) and a crossbeam of hollow round section, ROR 273.6 mm ø (60 mm wall thickness), support the main girders. The crossbeam is welded to the portal columns using butt straps with eyes to which the cross bracing (DETAN 52 mm ø) is attached. All portal columns are topped with luminaires of the same diameter. THE BAR STAYS

from the first abutment through the three pylons to the op-

posite abutment are solid round bars, 52 mm in diameter, manufactured by DETAN. THE BALUSTRADES

consist of flat steel posts, a handrail of hollow round steel,

ROR (48 mm ø), both of V2A with eight stainless steel 18/8 horizontal wires, approx. 8 mm in diameter. CORROSION PROTECTION

All steel parts were hot-dip galvanised and coated

with mica-iron paint, DB 703 / RAL 7135, except for the bar stays, which are in flame red.

Plan

Fig. 2.12c A bar-stayed girder is an unusual construction for a footbridge.

View, cross section and plan of the footbridge at Montabaur station.

Cross section

2

Cable-stayed and bar-stayed girder bridges

68

2.13 Osnabrück, Germany: cable-stayed bridge and arch bridge over the River Hase

Client: Town of Osnabrück Structural planning: IPP Polónyi + Partner GmbH, Cologne

The Hase meanders through Osnabrück, flowing under two open

2 U 100, which also fix the sectional steel posts of the balustrade. The main

pedestrian bridges, each with 16 m spans and effective widths of 2.2 m and

girders are stiffened with steel-bar cross bracing. The pedestrian deck is fitted

LOCATION

3.1 m. Their load bearing systems are:

with hardwood planks.

1. a cable-stayed bridge at “Öwer de Hase”,

THE PYLONS

2. an arch bridge over a landing stage at the “Herren Pool”

lengths of 250 mm × 220 mm of welded, S 355, 12 mm heavy plate.The pylon

(see Section 4.8).

columns are connected in pairs by crossbeams at their heads (capitals) and

of the bridge are box girders, 5 m high, with constant edge

of the cable-stayed bridge “Öwer

cross braced with round bars. (There is a certain similarity to a footbridge at

de Hase” consists of two sectional steel IPE 600 main girders of S 355, 2.2 m

Brindley Place and the International Congress Centre, with a 25 m span and

apart; six main HEB 100 transverse girders at intervals of 1.5 m at the points

rear-anchored pylons, built in 1994 to plans by Arup Partnership.)

of cable entry, which are approximately at the eighth points of the span.

THE BALUSTRADES

Between the main transverse girders are secondary transverse girders, each

steel (18 % Cr + 8 % Ni) horizontal wires, 10 mm in diameter.

THE GALVANISED STEEL SUPERSTRUCTURE

View

have posts of HEA 100 sectional steel with seven stainless

Cross section

Plan

Fig. 2.13a The pedestrian bridge “Öwer de Hase” in Osnabrück’s town centre. Fig. 2.13b View, plan and cross section of the cable-stayed bridge.

2.14

Bamberg, Germany: under-deck cable-stayed (hyperboloid) cycle and pedestrian bridge over a branch of the River Regnitz

69

2.14 Bamberg, Germany: under-deck cable-stayed (hyperboloid) cycle and pedestrian bridge over a branch of the River Regnitz Client: City of Bamberg Planning: Architect Hans Maurer (deceased), Munich Structural planning, photos: Mayr / Ludescher / Partner,

Consultant Engineers, Munich Steel construction: Stahlbau Wegscheid (previously Techno Metall), Wegscheid Cables: Pfeifer Seilbau und Hebetechnik, Memmingen

In 1994, the Bamberg Congress Hall, which is also a concert hall for

The transverse girder segments, the middle main girder and the six longitud-

the Bamberg Symphony, was linked to the Hotel Residenzschloss by a 31 m

inal ribs at each side (10 mm steel plate) together with their deck panel form

span, and 2.63 m wide pedestrian bridge, the Heinrich-Bosch Bridge over the

an orthogonal-anisotropic plate for the pedestrian deck. This has a thin, non-

LOCATION

“left” branch of the Regnitz. THE LOAD BEARING SYSTEM

slip gritted coating which at the same time serves as corrosion protection. is that of a cable-stayed girder bridge, although

its cable harp is not above, but almost entirely beneath the deck. THE CABLE CONFIGURATION

consists of two clusters, each of 15 straight

CABLE ABUTMENTS

The cables are attached to white concrete abutments,

also in the shape of hyperboloids. The railings are 1.2 m high with vertical rods set very close together to protect small children and other bridge users. as a tension member beneath the arched

stainless steel wire cables, 18 mm in diameter, which cross each other at

THE SPATIAL CABLE STRUCTURE

sharp angles and are anchored in a semicircle at the concrete abutments. The

orthogonal-anisotropic plate enables a highly filigree and economical struc-

result is a hyperboloid with 77 crossing points, all secured with stainless steel

ture, which seems to draw the user onto the bridge. The bridge sways slightly,

screw clamps. The trough of this hyperbolic cable net contains 11 transverse

but no one has complained so far and many find it amusing. The cable hyper-

girders positioned at intervals of 2.05 – 3.63 m. These are in the form of circle

boloid is slightly more slender at mid span, giving the bridge a gently arched

segments of 12 mm steel, decorated and lightened by four holes in the plate.

appearance in keeping with its surroundings.

Plan

Cross section

Isometry

Fig. 2.14a Something different: an under-deck cablestayed footbridge over the Regnitz. Fig. 2.14b Plan from below: the cable net hyperboloid of the footbridge in Bamberg.

Girder bridges

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

3

Girder bridges

72

3.1

Berlin Central Station, Germany: long-span footbridge as a rigid frame bridge over the River Spree

Client: Senate Administration for City Development, Dept. XPIA Design: Max Dudler, Berlin Structural planning: KLW Ingenieure GmbH, Engineering Consultants,

Berlin Steel construction: SIBAU Genthin GmbH & Co. KG Mass dampers: Maurer Söhne GmbH & Co. KG, Munich Sources: Ingbert Mangerig, Cedrik Zapfe: Bewertung des Schwingungs-

verhaltens und der Dämpfungseigenschaften der Fußgängerbrücke Gustav-Heinemann-Steg über die Spree in Berlin. 2006, [35]; Eva-Marie Zimmer, Michael Mündecke: Die Gustav-Heinemann-Brücke über die Spree im neuen Zentrum Berlins. 2006 [36] (naming eight further sources)

LOCATION

A footpath only a few hundred metres long leads from the inter-

THE PEDESTRIAN DECK

consists of the transverse girders, two outer HEB 200

section of high speed traffic Intercity, regional and city trains at Berlin Cen-

sections and three inner HEA 100 sections as longitudinal girders. The deck is

tral Station to the government quarter in the bend of the Spree. Pedestrians

covered and additionally stiffened with cross-laid oak planking.

and cyclists can cross the river over a (9.03 + 65.90 + 12.76) m = 87.69 m

BEARINGS

footbridge with an effective width of 4.00 m between the balustrades. The

rigidly fixed in the transverse direction on the western sides of the two piers,

The structure rests on elastomer bearings on the two piers. It is

bridge was opened on 30 June 2005 and is known as the “Gustav Heinemann

and longitudinally fixed on the southern pier in the direction of the government

Bridge”.

quarter. Because the two side spans are short, tension anchorages were need-

THE LOAD BEARING SYSTEM

was chosen after an international competition in

which city planners and bridge designers were invited to send in their ideas

ed at the abutments. The mid span appears to be fixed into the side spans. AFTER PRE-ASSEMBLY

on land not far from the building site, the 70 t steel

and after various expert assessments. It is a straight girder in the form of an

construction was brought into position by floating cranes.

extremely slender truss with a h:l ratio of ~1:40. From the start it was seen as

OSCILLATION TESTS

were carried out with a group of 25 people – they mar-

torsionally soft and prone to oscillation, both due to wind and to the action of

ched across the bridge with synchronised steps and jumped up and down at

pedestrians walking over the bridge. This was a phenomenon that had already

random intervals. The horizontal and vertical dampers reduced all oscillations

occurred in new footbridges such as the Millennium Bridge over the Thames

to an acceptable level.

in London, the footbridge over the Seine from the National Library of France to Bercy Park in Paris and the footbridge over the B 8 near Würzburg-Höchberg in Germany. For this reason a thorough analysis was made before building work began, and this showed that mass dampers would have to be installed. See [36] for details. THE STEEL SUPERSTRUCTURE

consists of a pair of 2.25 m high Vierendeel

frames of welded steel HEM 400 European girders with a system dimension of 1.82 × 1.82 m. The main trusses are connected at approx. mid-height with HEM 200 transverse girders. The wind bracing consists of crossed angle sections, 70 × 7 mm, inserted above the lower flange of the transverse girders. The superstructure has a camber of ~0.6 m. S 355 J2G3 steel was used throughout the bridge.

Fig. 3.1a The Gustav Heinemann Bridge extends over the Spree

from the government quarter to Berlin Central Station.

3.1

Berlin Central Station, Germany: long-span footbridge as a rigid frame bridge over the River Spree

Längsschnitt Longitudinal section

View from east

Total length

View from above Draufsicht

Isometry (standard cross section)

Fig. 3.1b Side view, view from above and isometry of the Vierendeel truss.

Plan Grundriss

73

3

Girder bridges

74

3.2

Baden, Switzerland: truss footbridge over River Limmat with elevator tower

Design: Leuppi & Schaffroth, Architects, Zurich Structural planning: Henauer Gugler AG, Engineers and Planners,

Zurich Structural analysis: Dipl.-Ing. Roman Juon, Switzerland Steel construction: Zwahlen & Mair SA, Glattbrugg, Switzerland

LOCATION

Baden is ~20 km north-west of Zurich; the Limmat flows through

both towns. The town centre of Baden is on a crest in the hillside of the Limmat valley some 40 m above the river. The town centre and its railway station were only recently (in June 2007) linked to the west bank of the Limmat by a ~16 m long “passerelle” and a ~35 m high elevator tower. At the base of the tower a cycle and footbridge with a span of almost 52 m and an effective width of 2.3 m leads over the river to the east Limmet water meadow path in the neighbouring village of Ennetbaden. A 1:1 model of the bridge was constructed on the bank of the river, limited to a 3.22 span section with a height of 3.8 m, to give the electors of the town an impression of what was being proposed. The project was approved. THE LOAD BEARING SYSTEM

The elevator tower is effectively a column fixed

at the base with rear anchorage in the cliff; whereas the footbridge, with its trough cross section, is a girder supported at two points. THE STEEL STRUCTURES

of the elevator tower and the footbridge are strongly

influenced by aesthetic considerations and create an architectural entirety; they are the same shape and have the same dimensions. Both consist of a pair of main trusses with 65° diagonal members (Warren truss) connected at both chord levels by a pair of frame girders (Vierendeel girders) to absorb the wind loads. This could almost be called a spatial truss, but without diagonals in the third dimension, which would have impeded the elevator or pedestrians and cyclists. The steel structure is markedly over-dimensioned, not only for reasons of design, but also to keep bending and natural frequencies as low as possible. Structural analysis arrived at a first natural frequency of + 2.45 Hz, which meant that oscillation might have frequencies and amplitudes that would be unpleasant for bridge users. If rocking should occur, for example caused by groups of joggers, tuned mass dampers could be installed later after analysis of the completed structure – as in the case of the spectacular footbridges over the Thames in London and over the Seine in Paris or the two footbridges over the B 8 in Höchberg near Würzburg, Germany, where provision for the subsequent installation of dampers was made right from the planning stage. Fig. 3.2a The cycle and footbridge is 52 m long and only 3.8 m high

and therefore one of the most slender bridges of this type: h : s ~ 1 : 14. Fig. 3.2b The elevator tower and footbridge were built with truss systems

of similar appearance to enhance the aesthetic quality of the composition.

3.2

Baden, Switzerland: truss footbridge over River Limmat with elevator tower

Plan

75

Baden side

Railway station

Passerelle

Ennetbaden side

Lift

Truss bridge

consists of grids mounted on two sec-

then installed in the tower; the galvanised grid of the pedestrian deck and the

ondary longitudinal girders at the lower chord level of the truss. The abutments

balustrades with integrated illumination were fitted. The “passerelle” section

are of concrete and were cast on site.

weighed only 12.7 t and was erected using a 120 t mobile crane.

THE CYCLE AND PEDESTRIAN DECK

ERECTION

The footbridge and the elevator tower were each prefabricated in

STEEL LOAD BEARING COMPONENTS

Steel was chosen as the main material

two parts, treated with a red coating, and transported to Ennetbaden, across

for the load bearing components because it enabled a high degree of prefab-

the river from Baden. The two bridge sections were welded together to a 52 t

rication and therefore reduced the amount of work needed on site. This is an

unit and were lifted into position by a 500 t crawler crane on 15 March 2007.

advantage when conditions on site are cramped and it reduces the impact on

Auxiliary trestles were unnecessary. The two 24 t sections of the elevator

the environment.

tower were lifted separately into their final position from the other bank of

THE BRIDGE WAS OPENED

the river on 19 – 20 March 2007 and welded together. The elevator car was

which ~2.5 million was for the steel construction.

View

Cross sections

Passerelle

Fig. 3.2c Plan, view and cross sections. The footbridge over the Limmat and the elevator tower both rest on minimum pile foundations.

in July 2007. Building costs ~4.2 million CHF, of

Elevator tower

Truss bridge

3

Girder bridges

76

3.3

Immenstadt, Germany: truss bridge over B 19 N, River Iller and flood channel

Client: Staatliches Bauamt Kempten Design, drawings and photos: WSP CBP Ingenieurbau GmbH,

Consulting Engineers, Munich, with Schultz-Brauns & Reinhardt, Architects and Town Planners BDA, Munich Steel construction: Max Bögl GmbH & Co. KG, Neumarkt Prime contractor: Josef Rädlinger Bauunternehmen GmbH, Cham and Dipl.-Ing. Bernhard, Vilshofen Source: Hans Pflisterer, Walter Streit, Thomas Hanrieder: Rad- und Gehwegbrücke über die Iller und die B 19 bei Immenstadt. 2006, [18]

LOCATION

A >1 km stretch of the bed of the River Iller north of Immenstadt

Plan of location

in Allgäu, Bavaria had been widened and in part rerouted for flood protection. A wooden footbridge was replaced by a bridge with a longer span. Almost at the same time, the B 19 through road, which runs almost parallel to the river, was rerouted and widened to four traffic lanes over a length of ~25 km. Opened in 2006, the new footbridge now crosses the new B 19, the widened Iller and the flood channel to Weidachswiesen polder. Its total length is 225 m, with a maximum span length of 49.36 m, and 2.5 to 3.5 m effective width. There had been a lot of public pressure because a new bridge was seen as a major invasion of the landscape. For this reason a design competition was held limited to five planning associations. The final decision of the distinguished

Standard cross section

members of the jury resulted in the present bridge. LOAD BEARING SYSTEM

The prize-winning design is a continuous truss with a

trough cross section rigidly connected with – and running continuously over – four supports in the form of concrete piers with spread capitals. THE STEEL SUPERSTRUCTURE

consists of two welded trusses of double T sec-

tion which are connected to the deck slab of reinforced concrete by transverse I-section girders at the lower chord level. The posts and beams are also of welded double T section, whereas the struts are flat steel bars. Bridge users are protected by stainless steel balustrades. The bridge widens continuously from abutment to mid-span where it reaches its maximum width. This is intended to “invite” the user to stay a while on the bridge. THE ESTIMATED BUILDING COSTS

for the winning entry were € 1.1 million;

the entry placed second would have cost € 1.8 m; and the third € 1.3 m. The first prize was a generous € 10 000, the second € 6000, and the third € 4000. All competitors were given a flat rate fee of € 4000 to cover expenses.

Fig. 3.3a The new cycle and footbridge over the River Iller, a main road and a polder was the winning entry in a design competition. Fig. 3.3b Plan of location and cross section of pier and deck.

3.3

Immenstadt, Germany: truss bridge over B 19 N, River Iller and flood channel

77

View Crown

6,8 %

Total length

Grundriss

2,50 m

Plan

Immenstadt

Kempten

Isometry

Isometrie

Abutment (6) Widerlager (6)

Regelquerschnitt

Pier (5) Stützpfeiler (5)

Fig. 3.3c The plan shows how the bridge widens by 1 m from the abutments

to mid-span. The superstructure rests on V-shaped struts rising from monolithic columns.

Abutment

3

Girder bridges

78

3.4

Leverkusen, Germany: footbridge in wave form over avenue and landfill

Client: Landesgartenschau Leverkusen GmbH, Leverkusen Design: Agirbas / Winstroer, Architects and Town Planners, Neuss Structural planning: Arup GmbH, Düsseldorf Detail planning: Stuhlemer Engineering Office, Ettlingen Inspection: Uhlenberg Engineering Office, Leverkusen Steel construction: Maurer Söhne GmbH & Co. KG, Munich Source: Jochen Wehrle: Neulandbrücke in Leverkusen.

Höchste Präzision in der Fertigung. 2005, [57]; Ercan Agirbas, Eckehard Wienstroer, Torsten Wilde-Schröter: Neulandbrücke Leverkusen. 2005, [26]

LOCATION

An unusual, wave-shaped cycle and footbridge was an eye-

catching feature of the 2006 Garden Show of the State of North-Rhine Westphalia, Germany. This “New Land Bridge” over an avenue running parallel to the River Rhine, connects two exhibition areas created on a former landfill site for Bayer chemical works. One important specification was that the bridge should not damage the seal at the bottom of the landfill; for this reason soil pressure was limited to 33 kN/m2. This meant that heavy bridge structures were eliminated from the competition from the start. The winning bridge is supported by four concrete piers on shallow foundations. Its effective width is ~3.5 m. THE LOAD BEARING SYSTEM

selected was a pair of 157 m long continuous

trusses over the three spans with a maximum span length of 44 m over the avenue and 6 m cantilever sections at each end of the bridge. THE STEEL STRUCTURE

consists of two trusses of heavy calibre tubular steel

which form two equal curves with a radius of 220 m on plan and waves in the elevation. The trusses have curved upper and lower chords (round hollow section KHP 355.6 mm ø), connected by posts (KHP 323.9 mm) and relatively slender diagonals (KHP 114.3 mm), all of which are fully welded. KHP transverse girders and wide-flange HEB sections support the pedestrian deck at different elevations between the waves of the trusses, forming a flat pedestrian and cycle path, regardless of the waves.

Fig. 3.4a The load bearing structure of the New Land Bridge

reflects the waves of the nearby Rhine. Leverkusen, grounds of the 2005 Garden Show. Fig. 3.4b View towards Rhine with sliding plate and orthotropic deck plate.

3.4

Leverkusen, Germany: footbridge in wave form over avenue and landfill

THE PEDESTRIAN DECK

consists of steel plate only 10 mm thick (like the

79

THE BALUSTRADES

of stainless steel are also design features of the bridge.

bridges over the River Fränkische Saale in Bad Kissingen) with a thin tribo-

They consist of slender posts of steel plate supporting upper and lower longi-

logical coating, keeping weight, dimensions and therefore building costs to

tudinal steel wire cables with a stainless steel net between the cables. The

a minimum. The plates of the deck measure 6.2 m × 3.5 m; each plate had

cables extend for up to 145 m and are attached to strengthened posts at the

to be individually drawn and cut because of the curves and slight turn of the

bridge ends. The handrail is 76.1 mm in diameter and contains specially de-

bridge. Numerous templates were needed for a three-dimensional simulation

signed luminaires arranged on alternating sides and inclined to cast light onto

of the course of the bridge and dimensions had to be checked constantly to

the deck.

ensure that the plates were a perfect fit.

THE BRIDGE SECTIONS

The six bridge sections were welded together in pairs

The New Land Bridge was prefabricated in six sec-

to form three elements which were then lifted into position. The laborious and

tions up to 35 t in weight, 4 m high and 5.2 m wide. The steel constructor in

time-consuming monitoring of dimensions at the steel works paid off: every

Munich thereby reached the absolute limits of what can today be manufactu-

joint to be connected on site was a perfect fit! Crowds of people came to watch

red, handled and transported. Six abnormal load transports were needed to

the final and largest element being lifted into position over Rheinallee in a

take the bridge sections to Leverkusen.

spectacular manoeuvre using a 500 t mobile crane.

RATIONAL PRODUCTION

CORROSION PROTECTION

had to be effected under a canopy instead of in the

THE NEW PARK LANDSCAPE ON THE RHINE

now has a cycle and pedestrian

usual protected coating facility because of the enormous size of the parts. In

bridge that is extraordinary in its curved shape and daring colour scheme but

accordance with ZTV-KOR regulations, four coats were applied, and the joints

nevertheless fits perfectly into its surroundings. One of the biggest challenges

to be welded later on site were masked. The designers and their client were

in building this bridge was the precise prefabrication of its unusual geometry.

also daring in their choice of colour: instead of the usual “mouse grey”, the

The bridge was completed on schedule in September 2004, allowing plenty of

trusses were painted in a pale blue-green, the bottom of the deck violet and

time for planting work in preparation for the Garden Show. A second footbridge

the top of the deck red-brown. The steel plates of the deck had previously

of tubular steel crosses the road at a point closer to the town centre. Plans of

received transport coatings.

the two structures were not available.

Fig. 3.4c Aerial view of the New Land Bridge in Leverkusen.

3

Girder bridges

80

3.5

Reutlingen, Germany: steel footbridge with glass planks over the River Echaz and the B 312

Client: Town of Reutlingen Detail design: Muffler Architects BDA DWB, Tuttlingen Design and Analysis: Schlaich, Bergermann & Partner, Consultant

Engineers, Stuttgart, with Dipl.-Ing. Marc Quint, Reutlingen Steel construction, bridge: Maurer Söhne GmbH & Co. KG, Munich

LOCATION

An innovative footbridge of heated glass planks on a tubular steel

spine was built to cross the four-lane B 312, the River Echaz and a reopened basin of the same river at the border between Reutlingen and Pfullingen, 55 km south of Stuttgart. The basin “Wässere” had originally been used by tanners and fabric dyers and had been covered over for many years. The housing of the elevator tower and most of the balustrade panels are also glass – despite fears about vandalism. The bridge has a total length of 50.7 m and two spans of 28 m and 18.3 m with an effective width of 3.4 m. The bridge “floats” an average of 5 m above ground level. THE LOAD BEARING SYSTEM

is that of a continuous steel girder over two

spans of different lengths supported on a rigidly fixed portal with an elevator at one end of the bridge, a ramp at the other end and a rigidly fixed intermediate column between the spans. The portal, ramp and column are all of reinforced concrete. THE STEEL SUPERSTRUCTURE

mainly consists of a spine of thick-walled,

heavy calibre hollow round steel H (406.4 mm ø) bearing cantilever arms of flat steel, 25 mm thickness, at intervals of 3 m. The arms angle upwards to become the posts of the balustrades. THE BALUSTRADES

are 1.2 m high with glass panels on the bridge itself and

five parallel stainless steel bars with a diameter of approx. 10 mm at the ramp and staircase. Here there is a potential danger of children climbing up the bars. THE INTERMEDIATE COLUMN

is 5 m high, oval in section with a diameter of

500 and 1000 mm and is built of reinforced concrete, as is generally suitable for structural components subjected only to compression. THE STRUCTURALLY SEPARATE ELEVATOR TOWER

at the river basin consists of

four vertical posts (square hollow section 120 mm × 120 mm) with transverse girders of the same material.

Fig. 3.5a A footbridge with a total length of 50.7 m crosses a road, a river and a river basin once used by tanners and dyers. Fig. 3.5b A calculated risk: balustrade and pedestrian deck of glass on a tubular steel spine with cantilever arms.

3.5

Reutlingen, Germany: steel footbridge with glass planks over the River Echaz and the B 312

View

Plan

Cross section

Longitudinal section

Fig. 3.5c View, plan, cross section, section (longitudinal view).

81

3

Girder bridges

82

3.6

Nikosia, Cyprus: curved girder bridge with tubular spine over Lemesos Avenue

The names of designers and steel constructors were not disclosed,

allegedly for security reasons in this divided country or the threat of terrorism. Further examples of structures with a tubular steel spine:

– Reutlingen, footbridge over river and road (Section 3.5), – Recklinghausen, “dragon” bridge” over road (Section 3.7), and – Bad Kissingen, “Luitpoldsteg” over River Saale (Section 3.10.1).

LOCATION

The A 1 motorway in Cyprus connects the capital in the middle of

the Mediterranean island with the south coast and the tourist centre and holi-

THE LOAD BEARING SYSTEM

selected is a continuous steel girder over four

spans (16.5 + 25.5 + 16.5 + 90) m = 67.5 m total length supported on three

day resort of Lemesos.

columns of reinforced concrete between the concrete abutments.

At the beginning of 2009, a mostly raised bypass was built between the A 1 and

THE STEEL STRUCTURE

A 6 motorways to reduce traffic in the town centre of Lemesos. Junction 26 is

with an outer diameter of 743 mm and a maximum wall thickness of 24 mm

consists of a main girder H of hollow round section

a roundabout with three traffic levels and a 46 m span footbridge, the first

in the main bridge section and 525 mm ø in the two ramps. Trapezoidal bulk-

fan cable-stayed footbridge in Cyprus. Its effective width is 4.5 m, generous

heads M and transverse girders Q in the shape of triangular brackets (T-sec-

enough to accommodate the occasional cyclist (Section 2.8).

tion, 180 mm wide, 80mm high and 20 mm thick) are welded onto the main

Previously, in 2004, a footbridge had been built in Nikosia city over the main

girder at intervals of 1.25 m. The 3.2 m wide deck panel of galvanised beaded

road leading to the motorway to Lemesos to provide students of a nearby col-

steel plate was welded onto this and coated with a ~10 mm layer of concrete

lege safe access to their school. Although a simple and straight bridge would

with a 1 % camber. Spotlights L are embedded in the sides of the deck, thereby

have been an adequate and also a shorter and more economical connection,

protected against vandalism. Welded heavy plate fork heads transfer loads

the opportunity was used to enhance the area with a slender, elegant structure

through neoprene pads N into the columns. are reinforced concrete cylinders of 732 mm ø in

sweeping round in a quarter circle and with an unusual main girder: a round

THE SUPPORT COLUMNS S

hollow section, 743 mm in diameter, painted flame red. The main section has

the bridge section and 525 mm ø in the ramps, all rigidly fixed on piles. are of 18 / 10 stainless steel with 1.5 m wide and 1.2 m

a length and radius of 67.5 m, and 2.8 m effective width between the balus-

THE BALUSTRADES

trades. The two straight ramps are each 24 m long and only 2 m wide because

high frames of tubular steel and panels of close-meshed wire. These, however,

two stairways also serve the bridge in different directions. There is a ramp at

show signs of vandalism and are in places dented or even destroyed.

right angles to the bridge and also a stairway at the west abutment; a similar steel ramp goes off at a tangent to the east, in the curve of the bridge, where there is an additional, two-stringer spiral steel stairway.

Fig. 3.6a A curved bridge enhances the townscape in Nikosia, Cyprus.

3.6

Nikosia, Cyprus: curved girder bridge with tubular spine over Lemesos Avenue

83

View

Path

4 – 6 lane

Path

(elongated) (elongated)

East bridge ramp

Cross section

Earth ramp

West brigde ramp

Plan

Concrete

p hram Eart

Fig. 3.6b View, plan and cross section.

3

Girder bridges

84

3.7

Recklinghausen, Germany: a “dragon” footbridge over a road

Client: RVR Ruhr Regional Association, Essen Design and Planning: Wörzberger Engineering, Rösrath near Cologne Steel construction: Rippe Brückenbau GmbH, Syke near Delmenhorst Source: Ralf Wörzberger: Begehbare Skulptur zur Erbauung.

Die Drachenbrücke in Recklinghausen. 2008, [37]

LOCATION

The regional association of local authorities “RVR Ruhr” connec-

ted a park in Recklinghausen with Hoheward, an abandoned coal mine with

A MASS DAMPER

was invisibly fitted into the tube of the dragon’s neck to

damp oscillations caused by wind action and, in particular, to avoid resonan-

a ~100 m high slag heap, by building a footbridge over Cranger Straße. The

ces. Small cylindrical dampers were also fitted to some of the raised ribs of the

heap was to be renaturalised and made into a leisure area. At first, in 2004, a

balustrades (the others are 1.3 m in height) as protection against vandalism.

simple, straight bridge was planned but it was then decided to turn the bridge

DETAILS

into a sculpture by adding a few elements: a dragon’s neck and head and a

cular attention to detail. The anatomy of the creature portrayed must not be

dragon’s body suggested by a few extended balustrade posts. Completed in

allowed to become ridiculous: the neck of the dragon, with its metal scales, is

A bridge that also aspires to be a symbolic sculpture requires parti-

2008, this abstract mythical creature has become a magnet for visitors to the

turned by nearly 180° but still maintains its anatomic credibility.

newly opened panoramic viewpoint on the former slag heap, the home of the

A DESIGN COMPETITION

dragon. An elevated pathway, 160 m in length, with a 5.5 % gradient, was

engineering offices participated: amongst them were Leonhardt, Andrä &

built between two fixed abutments. At first it leads through a copse, curving

Partner, Stuttgart; Schlaich, Bergermann & Partner, Stuttgart; and Wörzberger

was held in 2004 in which several distinguished

around the trees; the dragon’s head, as a light-hearted and unmistakable

Engineers, Rösrath near Cologne. The last designed the winning entry.

symbol of the area, becomes visible only after the visitor has crossed the

SOME DETAILS:

two-lane Cranger Straße at the end of the bridge (span = 25 m, width = 3.5 m).

Height of dragon’s neck: ~18 m above deck

A steel construction was chosen as best in keeping with the surroundings.

Dragon’s head:

folded steel sheet 5 m × 3 m; 15 mm

Expansion joints:

at the beginning, in the middle and at the end

THE LOAD BEARING SYSTEM

The main bearing element is a heavy calibre

hollow round section with a high degree of bending and torsional stiffness,

sheet thickness

610 mm in diameter with wall thicknesses of 14.2 – 28 mm. Ribs of flat steel, 20 mm thick, are welded on to the tube at intervals of 2 m as transverse gir-

of the bridge Main girder:

ders to carry the 3.5 m wide and 15 mm thick deck panel. The load bearing

S 355 J0; diameter = 610 mm; thickness = 14.2 – 28.0 mm

capability of the structure was greatly enhanced by the shear bond strength

Support columns:

S 355 J0; diameter = 415 mm; thickness = 20 mm

of the connection between the deck panel and the main girder: a plate girder

Support bases:

S 235 JR; thickness = 30 mm; flat steel

effect. The deck panel is stiffened against buckling and therefore contributes

Foundations:

Piles under the angled columns on the slope side

to the overall load bearing effect.

Vertical supports:

S 235 JR HEB 450 and 550 wide flange section

A comparable footbridge over the Rhine Railway in Bochum with four 15 m

Scales and deck plate: S 235 JR; thickness = 15 mm

spans used a similar principle in 2003 without, however, a shear bond (Section

Transverse girders:

S 235 JR; thickness= 20 mm

3.13).

Balustrades:

elliptically curved ribs with a T-cross section

The slenderness of the footbridge in Recklinghausen, with spans of up to 25 m,

Steel:

198 t

could not otherwise have been achieved.

Concrete:

370 m3

Costs:

€ 1.5 million on completion in February 2008

Fig. 3.7a The fiery dragon high above Cranger Straße in Recklinghausen

symbolises the furnaces of the local steel industry.

3.7

Recklinghausen, Germany: a “dragon” footbridge over a road

85

View

ca. 18,00 m

5,5 %

160,00 m

Cross section

Detail

3,50 m

Forces e = 2,00 m

T-beam

F

MT = F • e e

e traß

rS nge Cra

Plan

Fig. 3.7b View, plan and details of the dragon’s spine. Fig. 3.7c A dragon that breathes fire at night – thanks to the local gasworks

Ruhrgas.

3

Girder bridges

86

3.8

Hammelburg, Germany: two truss footbridges over the River Saale

Client: Town of Hammelburg, Rural district of Bad Kissingen Design, structural analysis: Consulting Engineer J. Hockgeiger,

Hammelburg Steel construction: Schuster Stahl- & Apparatebau, Fuchsstadt Galvanisation: FV Würzburg GmbH, Rottendorf

LOCATION

The rivers Sinn and Saale flow into the River Main in Gemün-

den, where the cycle touring paths along the Main and Saale valleys also converge (Neustadt / Bocklet / Kissingen Westheim – Hammelburg – Gemünden). The pedestrian and cycle path through the Saale water meadows is part of this system and crosses the Saale on two footbridges south of Westheim and north of Hammelburg. THE LOAD BEARING SYSTEM

of these bridges is that of a single span gir-

der bridge on two abutments with pile foundations. The slightly arched pedestrian and cycle deck lies at the bottom chord level of the truss, putting the structure in the trough bridge category. An estimated traffic load of 425 kg/m2 = 4.25 kN/m2 was considered adequate. THE GALVANISED SUPERSTRUCTURE

of the two bridges consists of longitu-

dinal trusses, 25 m long, 2.66 m apart and slightly arched (130.5 m radius). Each bridge has two concrete abutments founded on two piles

The chords are of hollow round sectional steel (133 ø × 5.6 mm). The posts

ABUTMENTS

are of rectangular hollow section (120 × 80 × 8 mm) and inclined at an ang-

9 m in length and 0.67 m in diameter driven through the loam of the water

le of 10°; the diagonals are of square hollow section (70 × 70 × 4 mm), all

meadow into the underlying red clay.

of S 355 steel. These main trusses H are connected under the bridge deck,

The ramps to the abutments were filled in and the former farm track was

by means of bolted end plate joints, to 17 transverse girders Q of HEA 140

asphalted. The bridges were now part of the cycle touring trail. The bridges are protected from the damp of the wa-

sectional steel S 235 at intervals of 1.5 m. Four equidistant lines of IPE 100

CORROSION PROTECTION

sectional steel, likewise S 235, lie on the transverse girders and support the

ter meadow by hot-dip galvanisation. This was done in a local galvanisation

cycle deck of 60 × 148 mm larch planking. The structure is stiffened by cross

plant with a limited capacity which meant that the main trusses had to be di-

bracing (Besista M 16) under the transverse girders. The dead load is 8 t for

vided into two end sections 6 m in length and a 13 m middle section. The trusses were then transported in one piece and lifted into position by a pneumatic

each bridge. BALUSTRADE

The main trusses also serve as balustrades and are pan-

crane. The steel received no further treatment and the blank metal contrasts

elled with perforated sheet aluminium, anodised and painted in a shade of

attractively with the turquoise-blue of the balustrade panels.

turquoise-blue.

BUILDING COSTS

were only ~ € 80 000 per bridge.

Figs. 3.8a, b The two bridges near Hammelburg are bolted structures

with small components (see joints of the lateral trusses) but were lifted into position in one piece; bridge end with aluminium sliding plate.

3.8

Hammelburg, Germany: two truss footbridges over the River Saale

87

View

LW

Plan

Substructure

Planking

Cross section

Abutment

Sliding plate

Handrail bearing Planking

Fig. 3.8c View, plan, cross section and abutment detail.

3

Girder bridges

88

3.9

Gelsenkirchen / Essen, Germany: steel fans support footbridge over road and stream

Client: Local government association of the Ruhr district (KVR) and “Ruhr Grün” e. V., Essen Planning: Prof. Frei Otto, Munich Galvanisation: Rietbergwerke GmbH & Co. KG, Rietberg

Cross section

Fan bar Deck plate

Transverse bar LOCATION

Mechtenberg Hügel is a 90 m hill on the border between Gelsenkir-

chen and Essen and is part of a 3 km2 landscape park planned by the regional association of the Ruhr district “Green Ruhr” which is likely to become exemplary for the renaturalisation of industrial wasteland. In 2003 a filigree footbridge was built at the foot of the hill over the B 227 Hattinger Straße and the Leither Bach stream to link Gelsenkirchen-Ückendorf and GelsenkirchenRotthausen. This cycle and footbridge is ~130 m long and has an effective width of 3.4 m. It consists of 10 auxiliary spans of 9.6 m each and a main span

Detail 1

Detail 2

of 30.4 m over the two-lane road.

Transverse bar connection

Fan bar connection

THE LOAD BEARING SYSTEM

is that of a continuous girder, in this case with

11 spans.

Fig. 3.9a Total length of 130 m, 11 spans, 3.4 m effective width.

A footbridge north of Essen. (See also photo pp 70/71.) Fig. 3.9b Cross section with details of connections.

3.9

Gelsenkirchen / Essen, Germany: steel fans support footbridge over road and stream

THE GALVANISED SUPERSTRUCTURE

is built of 180 t (3800 metres total bar

89

THE PEDESTRIAN DECK

is in the form of galvanised cassettes, 10 mm in depth,

length) of S 355 round steel, 70 mm in diameter and divided into bars 2 to 3 m

which rest on the transverse bars already mentioned. All parts received the best corrosion protection

in length. The bars are arranged in fan shapes and clamped longitudinally and

CORROSION PROTECTION

crosswise. The fan shape is created by bars radiating out from the foot of the

available at present. Node connections, bolts and the 180 t of round steel bars

support, crossing a network of longitudinal and transverse bars. The bars come

were hot-dip galvanised to a thickness of at least 230 μm.

together at the foot of the fan in a heavy duty steel gusset plate. They are con-

FOUNDATIONS

nected with drop forged clamps, in principle like those used in scaffolding but

med into the relatively unstable ground and connected at the top to form stable

which were developed especially for this use. They consist of two halves which

block foundations. (See also photos on pp 70/71.)

are welded together (sometimes using spacers) a certain distance apart and at a certain angle enabling them to be friction locked at any node. The bridge has more than 1300 of these node connections with over 10 000 bolts.

Fig. 3.9c Gusset plate at foot of fan.

Almost 1100 piles with diameters of 0.6 to 0.8 m were ram-

3.9

Gelsenkirchen / Essen, Germany: steel fans support footbridge over road and stream

90

View







Plan

Fig. 3.9d The main span over the road B 227 is 30.40 m long. Fig. 3.9e Span over Leither Bach stream. Fig. 3.9f View and plan of the main span.

3.10

Overview: Bad Kissingen, Germany: two cycle and footbridges, curved on plan

91

3.10 Overview: Bad Kissingen, Germany: two cycle and footbridges, curved on plan

Client: Water management department of Bad Kissingen Design: Dr.-Ing. Dietrich Renner, Solnhofen

The town centre of the German spa Bad Kissingen was inundated

Both bridges have a maximum gradient of 5.5 % and are therefore suitable for

by the worst floods for over a hundred years when the River Fränkische Saale

wheelchair users; stairs are unnecessary. The transverse camber for drainage

LOCATION

burst its banks on 3 / 4 January 2003. Dykes and walls were finally built to

of rainwater is generally 2 %. Ambulances or other emergency vehicles may

protect the town in 2006 / 07. The water management authorities also repla-

use the bridge, whereby a temporary increase of tension in the load bearing

ced two footbridges that had contributed to the disaster by causing a back-up

structure is acceptable. (with the exception of the portal arch of the Schweizerhaus

of water by new bridges with greater spans and lengths and positioned above

ALL SUPPORTS

high water level. Normal water level in Bad Kissingen is 197 m a.s.l. while

bridge) are slender rigid columns of seamless hot-rolled round hollow section

flood levels can reach ~201 m a.s.l.

(ø 508 mm, wall thickness 20 mm; filled with concrete) with cross-shaped

THE BRIDGES DIFFER

in the form of their torsionally stiff main girders: the

heads. All abutments are fixed points. Expansion joints were not necessary be-

girder of the Luitpold bridge is of heavy calibre round hollow section with a

cause both bridges are able to expand or contract into the outer or inner curve

25 m span, while the Schweizerhaus bridge has a trapezoidal box girder and

in response to changes in temperature. All components were prefabricated in

a span length of up to 17 m.

the usual way and coated for corrosion protection. This cut construction time

THE BRIDGES ARE THE SAME,

however, in respect of their load bearing system

and capacity, steel structure and gradient: Both are designed for a uniformly distributed load of 5.0 kN/m2 caused by cyclists and pedestrians with an additional point load of 40 kN for unusual load cases such as a cleaning vehicle, ambulance or other vehicle. This is in accordance with the demands to be found in professional literature (for example [3, 5]). Both are continuous girder deck bridges supported over five points with welded plate girders, an effective width of 3.25 m and a total length of around 100 m. They are both curved on plan with radii of 90 m and 70 / 80 m. S 355 steel was mainly used.

Fig. 3.10 The flood of the century: Bad Kissingen close to the Luitpold bridge

in 2003.

on site to a minimum – an important factor for a tourist centre and spa.

3

Girder bridges

92

3.10.1 Bad Kissingen: Luitpold footbridge as a girder bridge with a tubular spine over river Saale

Client: Water management department of Bad Kissingen Design: Dr.-Ing. Dietrich Renner, Solnhofen Structural planning: Dipl.-Ing. Volker Wettmann, Munich Steel construction: STS Stahltechnik GmbH, Regensburg Detail planning: Dipl.-Ing. Manuela von Rüdt, Osterzell

LOCATION

The Luitpold footbridge rises along a curve with a radius of 70 m

from 202 m above sea level at the pump rooms and promenade to a height

THE BRIDGE IS SUPPORTED

by rigid columns (B – F) of round hollow section

(ø 508 mm × 20 mm) made of S 355 steel. Their capitals are designed to ena-

of 202.6 m over the river and a newly created island; it then descends

ble slight movement in the direction of the outer curves when the structure

along a counter-rotational curve with an 80 m radius to the Luitpold building

expands or contracts as temperatures change. Virtually no constraint stress

200 m a.s.l.

occurs and expansion joints were not necessary. The abutments were first

Section lengths: (18.5 + 15.4 + 17.0 + 17.6 + 25.0 + 11.5) m = 105.0 m;

built with pin-ended supports in sleeve foundations, one of which was turned

width 3.25 m.

into a fixed bearing after erection.

Section masses: (15.0 + 12.5 + 13.5 + 13.5 + 20.0 + 9.0) t = 83.5 t. THE STEEL SUPERSTRUCTURE

of the Luitpold Bridge consists of a main

CORROSION PROTECTION

is the same as for the Schweizerhaus footbridge

(Section 3.10.2) but the deck is grey (DB 703). One wonders whether a livelier

girder H in the form of a heavy calibre hot-rolled round hollow section

choice of colour might not have been more suitable for a thriving spa.

(ø 457 mm × 17.5 and 14.2 mm; S 355 steel). A perforated plate L (S 235;

ERECTION

began on the river bank near the historical Luitpold baths with the

thickness 20 mm, height 200 mm) is welded onto the top of the main girder,

assembly and welding of four of the bridge sections with a total length of

bisecting the perpendicular, whereby the “holes” are intended to lighten its

68.5 m and 55 t in weight. At the end of March 2006 preparations were being

appearance. The bridge panel D (S 235 plate, 14 mm thickness), the actual

made to lift the fifth and sixth sections (the former above the river, the latter

pedestrian deck, is welded onto this plate and is a part of the load bearing

near the pump rooms) into position when floods inundated the building site.

system. The bridge panel is covered with a 6 mm coarse pale grey, coating B

The bridge was finally completed in May 2006.

for slip resistance. The deck is stiffened by transverse girders Q (8 mm steel plate) placed at intervals of ~470 mm. Pedestrians are protected by a low kerb with water spouts and by a balustrade G, 1.25 m in height, with double posts of galvanised flat steel which are bolted to every fifth transverse girder Q. Between the posts there are nine rows of 18/8 stainless steel wire cable and an upper chord of round hollow section (48.3 mm ø). There is a handrail of 18/10 (V4A) stainless steel round hollow section, 42.4 mm ø, fitted at hip height for handicapped bridge users and a second handrail at the top of the balustrade.

Fig. 3.10.1a The Luitpold footbridge was built higher up the river bank

than its predecessor and it is longer and elegantly curved. Heavy flooding in 2007 did not threaten the new bridge. The height of the new flood barrier in the foreground of the picture can be raised further by the attachment of a mobile steel and aluminium wall.

3.10.1

Bad Kissingen: Luitpold footbridge as a girder bridge with a tubular spine over river Saale

93

View

MHW

Luitpold baths

Pump rooms

Isometry

Cross section

Site plan

er rri ba

Floo d

Island

to Pump rooms

Fig. 3.10.1b View, isometry, cross section and site plan of the Luitpold bridge.

Luitpold baths

3

Girder bridges

94

3.10.2 Bad Kissingen, Schweizerhaus footbridge: a trapezoidal box girder bridge

Client: Water management department Bad Kissingen Design: Dr.-Ing. Dietrich Renner, Solnhofen Structural planning: Dipl.-Ing. Volker Wettmann, Munich Steel construction: STS Stahltechnik GmbH, Regensburg Detail planning: Dipl.-Ing. Manuela von Rüdt, Osterzell

LOCATION

The Schweizerhaus footbridge sweeps elegantly over the wide

water meadow in a smooth curve with a constant radius of 90 m. The bridge deck appears to be horizontal (202.1 m a.s.l.) but in fact rises by ~1 m to its highest point at the portal arch. There are six spans: (13.8 + 17.0 + 17.0 + 17.0 + 17.0 + 15.7) m = 97.5 m. Its effective width is 3.25 m. THE LOAD BEARING SYSTEM

is that of a deck bridge as a continuous girder

over five support points. The columns E 1, 2, 3, and 5 (numbered downstream from the north-east) are tubular steel supports fixed in foundation sleeves. The support point P 4 (downstream and to the south) is a fixed portal arch across the river. The bridge is suspended beneath the vertex of the arch on a transverse girder between two suspension bars (M42 Besista). THE STEEL SUPERSTRUCTURE

consists of a main girder H in the form of an

unnoticeably asymmetric 60° / 120° trapezoidal box with a lateral height of The steel structure was coated with four layers:

535 mm to the mountainside in the north-east and 515 mm towards the valley

CORROSION PROTECTION

in the south. The top flange is 1500 mm wide and the bottom flange 940 mm.

priming (at the steel works) of 70 μm zinc dust paint, followed by two inter-

The sides and the deck plate D are of S 355 steel, 14 mm thick, but the floor

mediate coatings of mica-iron paint, each 80 μm, and by a top coating of

plate is cut from 16 mm S 355 steel. The deck is stiffened by transverse

80 μm mica-iron in a shade of blue-green (DB 501).

girders Q of steel plate, 8 mm thick, at intervals of ~470 mm. Every fourth

ERECTION

transverse girder has an extension at each side, to which the balustrades G

This was followed by three weeks of down time due to floods caused by mel-

(height 1.25 m) are bolted. The double posts of the balustrades are of flat steel.

ting snow.

The portal arch was transported in two parts and welded on site.

Between them there are eight rows of horizontal M 12 round steel bars with

Beginning on 2 April 2006 and working from the south abutment at Schwei-

V-bracing and a top chord (ø = 48.3 mm, galvanised). The handrail is of 18/10

zerhaus, a 200 t crane set up the support E 5 and the pylon arch P and then

V4A stainless steel, 42.4 mm in diameter. The pedestrian deck was covered

positioned the deck section 5/4. This was followed by meticulous lifting,

with a white-grey, 6 mm thick, slip-resistant coating.

aligning and measuring of the north-east columns and bridge panels, ending

THE FOUR FIXED COLUMNS E

are of round hollow section (ø 508 × 20 mm,

on 19 April 2006. Rod-shaped luminaires fitted at knee height on every fourth

S 355 steel, filled with concrete) and are 4.5 to 5.35 m high; of this, a length

ILLUMINATION

of ~1.3 m is concreted into sleeve foundations. The sleeve foundations them-

balustrade post illuminate the deck for pedestrians and cyclists.

selves are rigidly fixed with at least one pile. THE PORTAL ARCH

with a span of 27.3 m, consists of two panels of S 355 steel,

each 40 mm thick, welded together at intervals with spacer plates. The lower ends of the arch have a box cross section filled with concrete as protection against possible impact loads such as collision of ice floes. The box section is 600 mm wide at its foundation height of 500 mm and the arch tapers towards the vertex – for lighter weight and a more elegant appearance.

Fig. 3.10.2a The portal arch stands 27.3 m wide and >10 m high over the bridge deck and River Saale. Fig. 3.10.2b The Schweizerhaus footbridge is architecturally in contrast to the Café-Restaurant Schweizerhaus. The photo shows relatively low flooding in March 2007.

3.10.2

Bad Kissingen, Schweizerhaus footbridge: a trapezoidal box girder bridge

95

View

MHW

Isometry

Cross section

Site plan

ay rw ai t S

Fig. 3.10.2c View, isometry, cross section and site plan.

3

Girder bridges

96

3.11 Bad Kissingen, Germany: galvanised, bolted footbridge over ring road B 278

Client: State of Bavaria, road construction authorities and Town of Bad Kissingen Design: Dipl.-Ing. (FH) Horst Arand, Bad Kissingen Steel construction: FMS Fränkischer Maschinen- und Stahlbau GmbH, Gochsheim

Like many other spas, Bad Kissingen banished traffic from the inner

main girders and connected with the inner row of posts. All balustrade posts

town onto ring roads such as the B 287 north-east ring. The east ring was

and handrails are of stainless steel 18 / 10 hollow round section, 76 mm ø.

LOCATION

recently widened from two to four lanes and provided with a 22.3 m span

There are panels of corrugated wire mesh between the posts. The deck pa-

footbridge for spa visitors and local residents. Its effective width is 3 m. The

nel was coated with epoxy resin with corundum grit for slip resistance. The

idea of a reinforced concrete structure was dismissed right from the start not

balustrades have planting boxes for flowers etc. and can be hung with flags

only because of the critical location of the bridge in a cutting, in a bend and

and banners to greet brides, grooms and other guests as they pass under the

at a junction, where formwork and falsework would have been a dangerous

bridge.

obstruction for motorists during the erection stage, but also because a mas-

CORROSION PROTECTION

sive bridge girder would have blocked the view over the town once the bridge

engineer and the steel works commissioned with the prefabrication of the

Hot-dip galvanisation had been planned. The design

was in service (Fig. 3.11a). Apart from this, a prefabricated bridge was needed

superstructure discovered that the bridge deck, 22.30 m × 3.50 m × 0.62 m,

because it had to be built as quickly as possible in the winter, the “off” season

was much larger than the melt pools of European galvanisation plants. This

for spas, with as little interruption to traffic as possible (only half an hour was

seemed to put galvanisation out of the question. What was more, the engi-

needed). The road construction authorities, who would later be responsible for

neers were afraid that the zinc would not flow into the narrow gap between

bridge maintenance, insisted on hot-dip galvanisation for the superstructure

the deck panel and the main girders and also that the main girders, which

and were even prepared to pay any additional costs this might incur.

were to be bent cold without pre-warming, would lose their prescribed arch of

is that of a girder on two supports: the fixed

220 m radius when subjected to the temperature of around 450 °C in the zinc

bearing is in the south-east support wall while the sliding bearing is in the em-

bath (deformation as a result of the release of internal bending stress). The

bankment of the north-west abutment. The superstructure arches at a radius

superstructure was therefore redesigned to enable galvanisation to take place

THE LOAD BEARING SYSTEM

of 220 m so that the rise at mid bridge is 220 mm.

as originally planned.

is a longitudinally divided, bolted girder

The deck was cut in half transversely and each part separately galvanised.

frame of four main girders, each 22.3 m long with a web height of 0.6 m, in

The parts were then bolted to the main girders (instead of welding them as

a parallel arrangement 1.1 m apart. They consist of two HEB 600 sectional

originally planned). The main girder grid was also divided, not along the highly

THE GALVANISED SUPERSTRUCTURE

steel girders on the longitudinal axis flanked by two U 600s at the sides of the

stressed transverse axis (as had been done with earlier German bridges in

bridge. The four main girders are connected by eight IPE 360 transverse gir-

Bonn, Hamm and Flieden near Fulda) but on the longitudinal axis, which is

ders at intervals of 3.15 m, whereby the transverse girders are attached with

generally free from dead weight forces. The main girders of U and T 600 sec-

8 × 6 end plates 360 × 170 × 15 mm and 8 × 4 M 16 / 10.9 bolts. Two deck

tional steel presented no problems during galvanisation and were later bolted

panels, each 20 mm thick, 3.50 m wide and 11.15 m long are fitted onto the

to the eight three-part transverse girders with end plates to form the girder

frame with countersunk bolts. An edge plate 20 mm thick but only 300 m wide

grid as planned. The bridge received two coats of blue paint to further increase

was bolted along the edge of the deck to carry the posts of the balustrades. A

the maintenance intervals; it has been in service for 12 years now and shows

second outer row of posts is bolted directly onto the web of the U 600 outer

no sign of corrosion.

Fig. 3.11a The footbridge over the east ring road in Bad Kissingen had to be erected in one weekend and receive the best possible protection against corrosion. A prefabricated, hot-dip galvanised structure was therefore chosen.

3.11

Bad Kissingen, Germany: galvanised, bolted footbridge over ring road B 278

View

Ansicht

97

22,30 m

Plan

Cross section

0,60 m

1,25 m

Querschnitt

1,20 m

1,10 m 3,50 m

Fig. 3.11b View, plan and cross section.

1,20 m

3

Girder bridges

98

3.12 Rietberg, Germany: a flame red, rigid frame footbridge over a new lake

Client: Landesgartenschau Rietberg-Park 2008 GmbH, Rietberg Design: Professor Eberhard Fiebig, Kassel Steel construction: Heinrich Lamparter Stahlbau GmbH & Co. KG,

Kassel, Kaufungen Photos, sponsor: Seppeler Holding & Verwaltungs GmbH & Co. KG,

Rietberg Source: “kontakte”, magazine of Seppeler Holding. 2007, [58]

and 2008, [59]

LOCATION

The little town of Rietberg with its historical timbered houses was

THE SUPERSTRUCTURE

is built entirely of S 355 steel and consists of two

the location of the Garden Show of North Rhine Westphalia in 2008. A new lake

main trusses each with upper and lower chords of rectangular hollow sec-

was created in the shape of a figure eight with a footbridge over the narrower

tion, 300 × 100 × 8.8 mm, rigidly connected by vertical posts of rectangu-

section in the middle.

lar hollow section, 100 × 100 × 6.3 mm. These trusses are connected

The bridge was hot-dip galvanised and coated in flame red. It was a generous

under the pedestrian deck by transverse girders, also of rectangular hol-

donation by a local company specialising in surface protection to its home

low section, 250 × 100 × 8.8 mm, braced by diagonals of angle section,

town of Rietberg and designed by the well-known steel sculptor Professor

L 150 × 50 × 8 mm. The pedestrian deck lies on the transverse girders and

Eberhard Fiebig, Kassel. He considered various options and came to the con-

consists of a grid of hot-dip galvanised steel plates with a spherical emboss-

clusion that a load bearing structure under the pedestrian deck was out of the

ment. This stiffens the plate and at the same time provides a slip resistant

question because more than half of it would be under water. A suspension or

surface for pedestrians.

cable-stayed bridge with pylons or as an arch over the pedestrian deck would

SLIDING BEARINGS

not have blended into the landscape because the bridge is only one metre

of the bridge; two more are located at the “Café” end of the bridge and there

above water level at the banks of the lake. He decided on a straight structure

is a fixed bearing at the other end.

Two transversely fixed sliding bearings support the middle

light fittings are built into the posts of the main trus-

without ramps in the form of a two-span bridge (16.08 m + 23.30 m), i.e. a

LOW CONSUMPTION LED

total length of almost 40 m, a constant effective width of 2.80 m and a dead

ses and thus are protected against vandalism.

load of approx. 25 t. THE LOAD BEARING SYSTEM

is that of a continuous girder over two intenti-

onally asymmetric openings in the form of a Vierendeel girder (named after Arthur Vierendeel, 1852 – 1942). Balustrades were unnecessary because of the trough cross section.

Fig. 3.12a The filigree rigid frame footbridge for cyclists and pedestrians fits perfectly into the landscape.

3.12

Rietberg, Germany: a flame red, rigid frame footbridge over a new lake

99

$"

View

!$"

!$"

!$"

"$%

View from below(Verbandsebene) Untersicht

View from above Draufsicht

217

½ Cross section (at middle pier)

$!

$"

Cross section (bearing)

$%

#

$

Detail Q (embossed plate)



#

!

Fig. 3.12b Views and cross sections.

!

3

Girder bridges

100

3.13 Bochum, Germany: girder bridge with tubular spine over industrial railway

Client / project management: Local government association of

the Ruhr district (KVR) and “Ruhr Grün” e. V., Essen Design: Wörzberger Ingenieure GmbH, Rösrath near Cologne Steel construction: Heinrich Rohlfing GmbH,

Stemwede-Niedermehnen Inspection engineer: Prof. em. Dr.-Ing. E. h. mult. Stefan Polónyi, Cologne

Detail

LOCATION

The local government association of the Ruhr district and the

regional association “Green Ruhr”, transformed sections of the path of the former industrial railway line from Grimberg Harbour on the Rhine-Herne canal in Gelsenkirchen to the Centenary Hall of the Steel Works in Bochum (Bochumer Verein / Krupp), into a theme cycle path North Rhine Westphalia Industrial Culture / Nature. It follows embankments up to 15 m in height and crosses other former industrial railway lines and German Rail tracks in Bochum-Stahlhausen, where an unusual cycle and pedestrian bridge, opened on 1 May 2003, now connects several abandoned railway lines to create a network of cycle routes. The bridge is S-shaped on plan and slightly inclined. It is approx. 60 m long along the middle axis with a 6 % gradient and an effective

Cross section

width of 3 m (to accommodate cyclists). THE LOAD BEARING SYSTEM

is that of a torsionally stiff continuous girder on

three pairs of pin-ended supports in an S-shaped spatial curve, as local conditions required. THE STEEL SUPERSTRUCTURE

consists of a spine of heavy calibre round

hollow section, selected because it is ideally suited to resisting the torsional moments arising from the spatial curve in the path of the bridge. This main girder H (610 ø × 16 mm) carries the transverse girders Q of 15 mm heavy plate onto which the deck panel D (20 mm) is welded. A clamping trestle E, designed to reflect the shape of the transverse girders, fixes the “reptilian” spine of the main girder H with anchor bolts into the concrete abutment. Both the abutment and the three A-shaped pairs of bearing supports B, C, D of round hollow section (244.5 ø × 10 mm) needed firm foundations (on small

Fig. 3.13a The footbridge is S-shaped on plan. Perspective. Fig. 3.13b Detail and cross section.

3.13

Bochum, Germany: girder bridge with tubular spine over industrial railway

View

Plan

GEWI piles) because of the general problem of land subsidence in the area and because the embankment, built of mining rubble in around 1900, has not yet come to rest. THE BEARINGS

are neoprene pads with the exception of one fixed point.

THE OVERHEAD POWER LINES

of the railway (15 kV, 16.7 Hz) are protected by

a steel frame with glass panes. THE BALUSTRADES

are 1.2 m high and meticulously designed. The handrail

(60 mm ø), the frames (25 mm ø) and the vertical bars (10 mm ø) are of tubular chrome-nickel steel 18/8; the flat posts (70 mm × 20 mm) are of constructional steel. ERECTION

The footbridge was divided into four sections and lifted into position.

Isometry

Fig. 3.13c View, plan and isometry. Fig. 3.13d View from below with steel / glass frame each side to protect

the overhead power lines of the railway.

101

3

Girder bridges

102

3.14 Zurich, Switzerland: 500 m footbridge with spiral box girder arms over junction

Client: City of Zurich, Switzerland Architect: Werner Stücheli, Dipl.-Arch. BSA, Zurich Engineer: Max Walt, Dipl.-Ing. ETH, Zurich Steel construction: Zschokke Bau AG, Zurich

LOCATION

Buchegg Platz is a major junction for regional, national and inter-

Site plan

national traffic approaching from Winterthur and Zürich-Kloten airport. It lies on a hill ~2 km to the north of Zürich main station. Long-distance road traffic crosses underground in a ring road tunnel. Bus and trolley lines and a north – south tramline cross over-ground and also have reversing loops here. Local car traffic is directed around the periphery. A cycle and footbridge, with a total length of almost 500 m, extends over Buchegg Platz. It has four “arms”, is spatially curved both on plan and in the

N

elevation and designed not only to provide pedestrians and cyclists with safe access in all directions but also to fulfil the aesthetic demands of an inner city environment. The famous Swiss precision triumphed again and produced a significant example of the art of structural engineering. The reinforced concrete cylinder of the elevator tower is the fixed point of the bridge and is flanked by two spiral stairways of steel. The bridge arms radiate from this point like the spokes of a wheel, except that they are not straight like spokes but jauntily curved. They all have a constant outer width of 3.4 m and an effective width of 3.0 m with the following radii and lengths: Bridge arm

Radius R

Length L

middle – west

132.69 m

105.03 m

middle – east

132.69 m

100.30 m

east – west

205.33 m

middle – south

63.42 m

79.80 m

middle – north

76.16 m

110.35 m

north – south

190.15 m

access north

66.00 m

Total

461.48 m

Fig. 3.14a Four bridge arms radiate from the middle tower which

also has a circular bench and a “hat brim” as weather protection. Fig. 3.14b Site plan.

3.14

Zurich, Switzerland: 500 m footbridge with spiral box girder arms over junction

103

Longitudinal section

Underpass

THE LOAD BEARING SYSTEM

is in each case that of a curved continuous com-

Cross section

posite girder over 19 + 4 spans with lengths of 13 to 28 m as a deck bridge on composite supports. is basically a welded steel box girder with

with cross stiffening not only at the support columns. The steel box girder of

0,95 m

a trapezoidal cross section of 0.5 m / 1.5 m in width and 0.75 m in height,

1,20 m

THE STEEL SUPERSTRUCTURE

3,00 m

varying wall thickness is connected to the pedestrian deck with head bolts for

1%

1%

shear resistance. The deck itself is 140 mm thick and was cast on site and 0,75 m

covered with a ~24 mm protective and sealing coating of mastic asphalt. It has a ~1 % cross gradient to a gully in the middle of the deck. The balustrades are between 0.95 and 1.05 m in height. THE SUPPORT COLUMNS

are welded steel box girders with a rectangular cross

0,50

section of ~0.4 × 0.8 m and heights of 5 to 6 m. They are rigidly fixed at the top and bottom and their sleeve foundations are generally on four concrete piles. THE BRIDGE GIRDER

rests on pin-ended supports in the abutments, for longi-

tudinal movement combined with torsional resistance. ERECTION

began at the elevator and stairway tower which was prepared with

a sleeve of steel plate onto which the X-shaped centre part of the bridge was welded and temporarily held by four supports. Erection continued from the middle outwards in two opposite directions. A mobile crane placed new sections onto the brackets of the box girders already in position and onto the following support columns. The prefabricated sections, each approx. 20 m long, were welded onto the column heads.

Fig. 3.14c Longitudinal section and typical cross section.

0,75 m

0,50

0,50

0,50

0,75 m

3

Girder bridges

104

3.15 Gelsenkirchen-Horst, Germany: bridge on tubular “serpentine” support over hollow

Client: Local government association of the Ruhr district (KVR) and “Ruhr Grün” e. V., Essen Planner: PASD Feldmeier · Wrede Architects BDA · Town planners SRL, Hagen Structural planning: IPP Prof. Polónyi + Partner GmbH, Cologne Source: Stefan Polónyi, Wolfgang Walochnik: Die Fußgängerbrücken der BUGA ’97. 1997, [38]

LOCATION

The Nordstern coal mine in Gelsenkirchen-Horst on the Rhine-

THE STEEL SUPERSTRUCTURE

consists of a girder grid of two parallel main

Herne canal and the Emschertal railway closed in 1992. Part of it was rebuilt

girders of HEB 260 steel section 1.83 m apart topped by HEA 100 transverse

as a modern industrial estate and the rest became the site of the 1997 German

girders alternating with two U 100s, all at intervals of 0.75 m. This orthogonal

Federal Garden Show. A footbridge was built to cross a hollow 120 m wide

grid is cross braced with flat steel bars. The bridge rests on a support made of

and 5 m deep in the north-east part of the grounds to provide pedestrians

hollow round sectional steel (216 mm ø × 22.5 mm) which twists and turns

with access from the Garden Show grounds to the old cooling tower, which

in three dimensions and is painted bright red. The pedestrian deck is of close-

had been partly preserved as an industrial monument and arts venue. The

meshed 30 mm × 10 mm grating. is rigidly fixed at the abutments and to individual

bridge is approx. 117 m long and has an effective width of 3.5 m.

THE SERPENTINE SUPPORT

The planning for this bridge began at the same time as the design of the arch

reinforced concrete foundations at each point where it touches the ground.

bridge at the abandoned coal mine in nearby Castrop-Rauxel (see Section 4.5),

The original plan was to shape the support in a tube bending facility using

where a spatial curve constructed of tubular steel had been suggested as

inductive heat. The company responsible decided, however, to weld the struc-

the load bearing structure. This had received general acclaim because of its

ture together from single (flat) curved and straight sections which were turned

unusual and intricate design and it was therefore adopted as the basis for the

accordingly. The finished form nevertheless has the smooth flow of a single,

footbridge in Gelsenkirchen-Horst.

spatially curved tube.

THE LOAD BEARING SYSTEM

is that of a continuous straight girder, supported

by an unusual line of twisting serpentine supports.

Fig. 3.15a Footbridge on “serpentine” support for the German Federal Garden Show in Gelsenkirchen-Horst.

3.15

Gelsenkirchen-Horst, Germany: bridge on tubular “serpentine” support over hollow

View

117,00 m

Plan

Cross section

Tube

Detail

2,5 mm

Fig. 3.15b View, plan, cross section and detail. Fig. 3.15c From below: the “serpentine” support.

105

Arch bridges

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

4

Arch bridges

108

4.1

Basle Border Triangle: arch bridge over the Rhine – a world record footbridge

Client: Town of Weil; Communauté de Communes des Trois Frontières CC3F Huningue Design and planning: Planning association LAP/FA/Weil am Rhein GbR; Feichtinger Architectes, Paris, Vienna; Leonhardt, Andrä and Partner, Consultant Engineers VBI, Berlin, Stuttgart Construction: Max Bögl GmbH & Co. KG, Neumarkt Sources: Wolfgang Strobl, Imre Kovacs, Hans-Peter Andrä, Uwe Häberle: Eine Fußgängerbrücke mit 230 m Spannweite über den Rhein. 2007, [39]; Wolfgang Strobl: Geh- und Radwegbrücke zwischen Weil und Huningue. 2006, [40]; Starke Verbindung. Faszination Stahl. Heft 13, 2007, [41]; Clementine van Rooden, Uwe Häberle: Fußverbindung. 2007, [42]; Elegante Bögen – Filigrane Tragwerke: MSH-Profile im progressiven Brückenbau. 2007, [43]; Town of Weil am Rhein: Brücken verbinden – Des Ponts qui unissent. 2007, [44]

LOCATION

The Rhine footbridge between Weil (Germany) and Huningue

(France) 200 m downstream from the Basle suburb of Klein-Hüningen (Switzerland) was opened in mid 2007 as the longest spanned arch cycle and footbridge in the world. The aim in building the bridge was to improve infrastructure in the heavily industrialised northern district of Basle. At the same time, however, the bridge was intended as a symbol for the deep alliance between the neighbouring countries as it crosses the great river in a single arch. The bridge was carefully designed and positioned to preserve the line of vision between the coaxial approach paths and roads, Hauptstraße in Weil and Rue de France in Huningue and the historical tower of the former garrison town. For this reason the bridge was placed close to the visual axis and designed with an asymmetric cross section. The rise of the arch was reduced to the limit of what engineering can achieve, giving the structure elegance and at the same time a tension and excitement. The challenge faced by the engineers is almost palpable: the span is 230 m in length with a rise of only 14.5 m and a total height of 25 m. The total length over the river is 248 m with an effective width of 5.5 m at mid-span and 7.0 m at the bridge heads. The “Passerelle des Trois Pays” was floated into position in its entirety (>1000 t) in a spectacular manoeuvre in November 2006. THE LOAD BEARING SYSTEM

is that of an arch bridge (deck bridge) whose

arch derives from a quadratic parabola, with the quarter points raised by 0.4 m for reasons of stability, so that the configuration is a polynomial of the fourth degree. The orthotropic (stiffened) deck panel of steel plate, 10 mm thick, ties the horizontal thrust of the arch (Langer girder principle), whereby a part of the thrust is deflected to the abutments and transferred into the ground.

Fig. 4.1a The “border triangle” connects Germany and Switzerland

with France; eastern side, Weil am Rhein – torsionally rigid but longitudinally sliding bearing. Fig. 4.1b View towards the historic tower of Huningue on the west bank. (See also pp 106/107.)

4.1

Basle Border Triangle: arch bridge over the Rhine

THE STEEL SUPERSTRUCTURE

109

The bridge has twin arches. The northern arch

WIND LOADS

were a vital consideration in the dimensioning of the slender

is perpendicular and consists of two hexagonal box girders, 900 mm high and

structure.The hexagonal cross sections were more problematic than the tubular

589 mm wide, of S 355 J2G3 steel plate in thicknesses of 15 and 50 mm.

cross sections because of their higher c-values. In general, however, the wind

The northern longitudinal girder is also a hexagonal box, 600 mm high and

loads are significantly lower than those given in the report of the German DIN

434 mm wide. The southern arch, however, is inclined towards the northern

Code 101 [5]. The inspection engineer endorsed the decision to analyse wind

arch by 16° from the perpendicular and is made of hot-rolled hollow round

loads for an assumed traffic height of 1.8 m in accordance with E-DIN 1055-4.

section with an outer diameter of 609 mm and 36 mm wall thickness. The

THE LOAD CASE

“traffic on one side only” was also significant for structural

southern longitudinal girder is of hollow round section with a 325 mm diam-

analysis and dimensioning. The forces were calculated taking into consider-

eter and 25 mm wall thickness. The uniqueness and elegance of the bridge is

ation the different states of erection and the forms of the bridge components.

largely due to this asymmetry of its cross section.

The latter was a highly complex spatial form because of the asymmetry of the

BEARINGS

The original plan had been to use fixed bearings for all the bases

cross section. are surface foundations with sheet piling. Ground

of the arch. This idea was discarded after analysis of temperature constraints.

THE ARCH FOUNDATIONS

Nevertheless, it was imperative to brace the structure against wind loads be-

anchors were used to secure the tension stays at the bridge heads.

cause of the softness of its system.

ASSEMBLY, ERECTION

The arch bases on the Weil side were built in the form of a torsionally stiff but

downstream and floated to its final location in a spectacular manoeuvre which

The main structure was welded together at a site 3 km

longitudinally sliding V-shaped shaft.

drew a huge crowd of spectators. The waterway was closed to traffic for less

The torsionally rigid and non-sliding arch bearing on the Huningue bank was

than a day.

achieved using two spherical bearings for the “strong” north arch and three

Following preassembly, cranes were used to position the structure on pon-

spherical bearings for the “soft” southern arch.

toons which were then floated into position. The bridge was placed on auxiliary

The intersection between the southern arch and the deck girder is a cast com-

presses and the tension stays connected. The pontoons were then lowered

ponent almost 5 m in length. The connection between the twin hexagonal gir-

and removed, the bearings were concreted and finally other separately pre-

ders of the northern arch and the hexagonal deck girder is also of cast steel

fabricated sections such as the approach ramps, balustrades, drainage and

but built from several individual component parts.

illumination were fitted.

Cross section

Fig. 4.1c The bridge crosses the Rhine from Huningue

on the west bank to Weil am Rhein on the east bank. Fig. 4.1d Hexagonal cross section of the northern arch.

Huningue

Plan

View

9,30

Rhin

France

Arch span length

Navigation channel

Rhein

Deutschland

8,6 m over NHW NHW

24,5 m over NHW

Frontie r

9,30

Rheincafé

Ramp

Hauptstraße

4.1 Basle Border Triangle: arch bridge over the Rhine 110

Fig. 4.1e View and plan of the bridge near Basle, Switzerland.

4.2

Overview: Gelsenkirchen, German Federal Garden Show: three arch bridges

111

4.2

Overview: Gelsenkirchen, German Federal Garden Show: three arch bridges

Client: Local government association of the Ruhr district (KVR) and “Ruhr Grün” e. V., Essen Planner: PASD Feldmeier · Wrede Architects BDA · Town planners SRL, Hagen Structural planning: IPP Prof. Polónyi + Partner GmbH, Cologne Source: Stefan Polónyi, Wolfgang Walochnik: Die Fußgängerbrücken der BUGA ’97. 1997, [38]

There are numerous steel arch bridges in the Ruhr, the largest

The level of the deck was defined by the clearance needed for ships plus the

industrial area in Europe, but several new variations were built for the German

construction height of the load bearing structure. The load bearing structure

Federal Garden Show BUGA in 1997: arch footbridges made of tubular steel,

therefore had to be above the deck to avoid creating an additional gradient for

or rather of round hollow profile as a steel construction element. Three such

pedestrians.

bridges were built close together in Gelsenkirchen: Emscher Ost bridge, the

The configuration of the cable bracing and the form of the arch were designed

LOCATION

bridge over the new Färsenbruch Straße and the double arch bridge over the

to avoid any significant bending stress to the arches.

Rhein-Herne Canal.

THE THREE ARCH BRIDGES

are the result of all these considerations and can

All three bridges have bearing arches which do not lie co-

also be regarded as steel sculptures in the landscape, even though their main

axially to the axis of the path but instead cross the path at a sharp angle, i.e.

function is clearly defined as the bridging of waterways or streets for pedest-

they cross from one side of the path to the other side on the opposite bank.

rians and cyclists.

CONSTRUCTION

This was necessary first to maintain the given directions of the path network, second to provide virtually unlimited clearance above the deck and third to keep span lengths over the road or river, and therefore costs, to a minimum.

Fig. 4.2 Aerial view of the grounds of the 1997 Federal Garden Show in Gelsenkirchen with River Emscher and Rhine-Herne Canal (www.bundesgartenschau.de).

4

Arch bridges

112

4.2.1 Gelsenkirchen, Germany: double arch bridge over the Rhine-Herne Canal

Cross section at transverse girder

Ø

the double arch bridge over the Rhine-Herne Canal is the largest of the three

The expansion path needed for the deck construction was calculated at ± 7 cm in the longitudinal and ± 5 cm in the transverse direction on the south bank.

arch bridges built for the Federal German Garden Show in Gelsenkirchen. It is

The arches were attached to their foundations with HV bolts.

also wider than the other two with an effective width of 5.5 m. It is capable

STRUCTURAL ANALYSIS

of carrying a low-speed maintenance vehicle of maximum 30 t in weight. The

the BASTA programme, which was developed by the planning office to ana-

LOCATION

With an arch span length of 79 m and a total deck length of 109.3 m

All calculations were based on a spatial frame using

bridge lies in the approach path to the South Entrance of the garden show.

lyse steel structures according to the linear-elastic theory. Sliding and fixed

The path continues over the lattice girder bridge Emscher-Mitte over the River

bearings were simulated at the feet of the arches. The superstructure was assumed to be fixed at one abutment and sliding at the other.

Emscher. LOAD BEARING SYSTEM

The two tubular arches stand parallel, 31.8 m apart

The system was first analysed according to the first-order theory for all imag-

and at right angles to the axis of the canal (shortest span) the deck crosses the

inable load case combinations. The decisive combinations were then tested

canal at an angle of 51°. The characteristic asymmetric arch was the result

with second-order theory. This confirmed the stability of the arches: as expec-

of the requirement that the curve of the arch should be at the point where

ted they were effectively secured against lateral displacement by the spatial

the hanger bars are attached to the bridge deck. The highest point of each

bracing. The second-order theory analysis provided a realistic assessment of

arch is the point where it crosses the axis of the deck. The arches are of hol-

the stiffness of the bracing bars. The longitudinal stiffness of these compo-

low round sectional steel (ø 1120 mm; 40 mm thick in the straight sections

nents is dependent on their prestressing and the sag resulting from their own

and ø 1120 mm; 25 mm thick in the curved sections). The hangers are round

dead weight. Some of the hanger bars are relatively flatly inclined and here it

bars, 50 mm in diameter. The transverse girders are of hollow round section

is vital to limit the sag, not only for technical reasons but also because sagging

(ø 406.4 mm; 25 mm thick). The pedestrian and cycle deck is an orthotropic

bars would detract from the appearance of the bridge. This was tested using

plate made of S 355 steel. Two longitudinal girders of wide flange sectional

different prestressing and load combinations; the results displayed on the mo-

steel (HEB 600) carry 28 transverse girders (HEA 340 rolled section) at inter-

nitor were an excellent basis for assessment. In addition to this, prestressing

vals of 2.75 m. The deck panel is 12 mm thick and stiffened with trapezoidal

was adjusted to assure that no load combination would cause compression

longitudinal ribs (6 mm thickness). The deck was treated with epoxy resin with

in the bars. This adjustment was a long and iterative procedure because any

quartz grit for slip resistance.

change in the prestressing of one hanger leads to changes in the prestressing

THE BEARINGS

for the superstructure are four 200 × 400 mm neoprene pads.

of adjacent hangers and in the dynamics of the superstructure as a whole.

The fixed and sliding bearing points are arranged to enable the superstructure to expand and contract without constraint when temperatures change. In case the bearings need to be renewed at some point, niches for hydraulic presses have been provided directly adjacent to the bearings.

Fig. 4.2.1a The nine pairs of hangers on each of the two arches are

features of the bridge in Gelsenkirchen. Seen from certain angles – such as in this photo – the arches appear to cross. They are in fact parallel – as the drawing confirms. Fig. 4.2.1b Dimensions: two 79 m arch span, 109.3 m pedestrian deck and a 51° angle between the axes of arch and deck.

4.2.1

Gelsenkirchen, Germany: double arch bridge over the Rhine-Herne Canal

113

Rohrbogen Arch (Anschnitt) (section)

Plan

Ø

51°

5,5 m

79 ,0 0

m

31 ,8 0

m

Rh ei nHe rn eKa na l

Bridge length

FURTHER ANALYSES

Structural analysis was followed by oscillation tests. The

ERECTION

The two arches, each with a total mass of 115 t, were prefabricated

bridge was first investigated in respect of its sensitivity to pedestrian traffic

in five segments per arch and welded together on the bank of the canal.

and marching groups. The BASTA programme provides a time-history analysis.

On Saturday, 24 August 1996, the first arch, i.e. the western arch, was lifted

This is an incremental calculation along the time axis by which the results of

by two floating cranes assisted by one mobile crane on land. After ensuring

the calculation of the previous time increment are used as the preconditions

that the load was evenly distributed, the cranes were floated synchronously

for the next time increment. The assumed load in each case is the load ordin-

the 50 m to the place of erection, and the arch was set on its abutments. There

ate appearing in the load – time function for the increment under analysis. This

it was fixed and adjusted with four steel cables. Finally the HV bolts were

is then included in the equation. The load – time function was assumed for a

tightened in the rosettes of the bearings.

defined flow of pedestrian traffic.

The second arch was placed in position by the same method on the following

The bridge displayed very high oscillation speeds and amplitudes for this load.

day. Erection of the arches was completed in only one weekend, as is usual for

Two effective remedies were chosen: the deck was changed to an orthotropic

steel bridges; the canal was closed to shipping for only two hours. The 112 m

plate and the inclination of the hangers was reduced.

deck weighing 200 t was fitted the following weekend. The floating cranes

This was followed by additional dynamic analysis to ascertain the best pos-

lifted it onto a pontoon carrying three rows of stacked steel containers to

itioning of any mass dampers that might be required.

achieve the necessary height of approx. 1 m above the abutments. The

The testers went on to simulate fluttering vibrations under wind load (which

60 × 10 m pontoon was then floated into position and hydraulically lowered,

had caused the spectacular collapse of the Tacoma Bridge in the State of

placing the bridge plate onto the abutments. Finally the hanger bars were in-

Washington / USA in 1940). This last test confirmed the bridge over the Rhine-

stalled and prestressed.

Herne canal would not be susceptible to wind load.

AWARD

Fig. 4.2.1c Plan and arch section of the double arch bridge in Gelsenkirchen.

The bridge received the Renault Traffic Design Award in 1997.

4

Arch bridges

114

4.2.2 Gelsenkirchen, Germany: arch bridge over Färsenbruch Road LOCATION

Färsenbruch / Lehrhofebruch Road, formerly Terneden Straße in

Gelsenkirchen is a motorway approach road south-east of the German Federal Garden Show ground. The arch bridge over Färsenbruch road is the pedestrian connection to the suburb of Gelsenkirchen-Hessler and was effectively a landmark for the main entrance of the 1997 Garden Show and the adjacent landscape park. In elevation it is similar to Emscher-Ost bridge (Section 4.2.3). THE TUBULAR ARCH

of S 355 steel (ø 45.2 mm; wall thickness 20 mm) is po-

sitioned at an angle of 63° to the axis of the road. The span length of the arch is 42 m. It stands on two box-shaped abutment blocks of reinforced concrete at the top of the embankments. The bases of the arch are fixed with HV bolts and steel rosettes. THE DECK PLATE

is at an angle of 39.5° to the axis of the arch and is 42 m

long between its abutments of reinforced concrete. It is 3.8 m wide and constructed as an orthotropic plate; the deck panel is 10 mm thick and the ten longitudinal rib panels are 100 mm thick. There are two main longitudinal girders of HEB 600 wide flange section and 16 auxiliary / transverse girders (HEA 200, all 2.625 m). The deck plate was coated with epoxy resin with quartz grit for slip resistance. The deck is suspended from the arch by bars of round steel (ø 40 mm) attached to transverse girders of hollow round sectional steel (ø 298.5 mm; 16 mm wall thickness). The transverse girders are inserted through the webs of the longitudinal girders. The balustrades are 1.2 m high with handrails of V2A steel and 10 horizontal strands of stainless steel wire cable. BEARINGS

Four neoprene bearings (200 × 250 mm) were selected for the

superstructure. The fixed and sliding points are arranged to allow the superstructure to respond to temperature changes without restraint. Niches have been provided at the abutments for the insertion of hydraulic presses when the bearings are changed. The expansion path was calculated at + 3690 mm / – 248 mm. ERECTION

Two mobile cranes were used to erect the arch. Some of the ten-

sion bars were prestressed after suspension of the deck to ensure that it formed a horizontal plane due to its own dead weight.

Fig. 4.2.2a The footbridge over the motorway approach road at Nordstern

park in Gelsenkirchen has four pairs of hangers and forms an angle of 39.5° between deck and arch. Fig. 4.2.2b Attachment of hanger to transverse girder.

4.2.3

Gelsenkirchen, Germany: arch bridge over River Emscher

4.2.3 Gelsenkirchen, Germany: arch bridge over River Emscher

THE RED TUBULAR ARCH

of S 355 steel stands at right angles to the axis of

the river and has a span length of 40 m, a diameter of 508 mm and a wall thickness of 30 mm. It stands on two abutments of reinforced concrete which transfer their load into the ground through shallow foundations. The feet of the arch are attached to steel rosettes with HV bolts. THE DECK

is at an angle of 19° to the axis of the arch, its width is 3.52 m and

it is 46.15 m long between the abutments. It is an orthotropic plate of rolled sectional steel: two main longitudinal girders (HEB 600) 3 m apart; HEA 140 transverse girders with a deck panel, 10 mm thick. The deck is coated with epoxy resin with quartz grit for slip resistance. The deck is suspended from the arch by five pairs of round steel bars (ø 40 mm) connected to transverse tubes (ø 406.4 mm, 10 mm thick).

Fig. 4.2.3 The footbridge over the River Emscher in Gelsenkirchen: 40 m arch span, 46.15 m pedestrian deck, an angle of 19° between the axes of arch and deck.

115

4

Arch bridges

116

4.3

Dessau, Germany: arch bridge with curved deck over the River Mulde

Client: Town of Dessau Design: Prof. em. Stefan Polónyi Structural Engineering, Cologne

with kister scheithauer gross architekten und stadtplaner GmbH, Cologne Structural planning: IPP Prof. Polónyi + Partner GmbH, Cologne Source: Stefan Polónyi: Begehbarer Raum. Die Tiergartenbrücke über die Mulde in Dessau. 2002, [45]

LOCATION

The 100 m wide River Mulde and a multi-lane road separate the

Tiergarten landscape park from Dessau town centre with its historic castle and grounds (Johannbau). The former wooden footbridge was replaced by a steel pedestrian and cycle bridge in 2000 when the landscape park and river bank were redesigned and modernised. The town of Dessau received money for this project from the EXPO 2000 fund. If the bridge had only been intended as a connection, it could have been built as a simple straight bridge and would have been better positioned elsewhere. It is, however, an essential part of a walking route that meanders through the landscape and therefore it was decided that the bridge should curve to continue and reflect this path. Water levels in the Mulde vary considerably and it is a very fast-flowing river. The riverbed is flat and therefore suitable for the construction of piers, but Dessau wanted a bridge that would not interfere with the flow of the river. The bridge was also to be a landmark but at the same time fit into the silhouette of the town without appearing dominant. This was another argument against a bridge with piers. Path bridges can be supported on piers or from pylons or they can be suspended from arches. The planning team opted for an arch with hangers as the main load bearing component. (They selected a bridge type first built in Castrop Rauxel, then used for bridges at the German Federal Garden Show in Gelsenkirchen and further developed for the IBA international building exhibition at Emscher Park in Oberhausen.) A path now meanders from the town centre to Tiergarten park over the new curving Mulde bridge (r = 105 m) with a span of 107.65 m. The box girder deck is suspended on round steel bars from an arch of tubular steel inclined at an angle of 17° off the perpendicular. The hangers enclose the deck, creating a spatial entity through which the pedestrian can walk, and they are also a delightful sight when crossing the bridge.

Fig. 4.3a Aerial view: a footbridge as part of a meandering path system. Fig. 4.3b The steel arch and deck arched in opposite directions to form

a spatial entity through which the pedestrian crosses the River Mulde in Dessau.

4.3

View

Dessau, Germany: arch bridge with curved deck over the River Mulde

117

Ansicht

107,65 m

Plan

Grundriss Mulde-River

Mulde - Fluss

r = 105 m

The box girder of the deck is similar in appearance

This means that deformations as a result of changing temperatures alter the

to the wing of an aircraft with a slightly convex bottom plate. (This type of heavy

radius of the deck. This alters the angle of the deck at the abutment by only

STEEL SUPERSTRUCTURE

plate is now rolled in widths of 4 m, which became the determining factor for

0.24° or a difference in side length of only 13 mm. This is simply covered by

the width of the bridge. The original design had been for two parallel plates;

a strip of sliding plate. is of hollow round section with an outer diameter of 812.8 mm and

the curve on plan was formed with a polygon with a side length of 2 m.) The

THE ARCH

4 m plate meant that far fewer welding joints were needed but a polygon with

wall thicknesses of between 14.2 and 50 mm. It is rigidly fixed at both ends.

a side length of 6 m had to be accepted. The transverse bulkheads are located

At first the plan had been for a hinged bearing, but analysis showed that the

in the corners of the polygon and cantilever out alternately on the concave and

structure would then be too soft and susceptible to oscillation. The torsional

convex side of the deck. The length of the cantilever is calculated to prevent

fixing of the deck and rigid fixing of the arch give the bridge the necessary sta-

the hangers from cutting into the profile of the bridge. The hangers are fitted

bility. The deck is suspended from the arch and thereby stabilises it. The arch

to the ends of the cantilevers with bolts and threaded fork ends. The box girder

sections are welded together at the bulkheads. The bulkhead plates extend

is also stiffened by three longitudinal bulkheads of appropriate thickness. The

downwards out of the cross section of the arch and each has one hole at which

deck is fixed against sliding at both ends; at the same time it can turn around

the hangers are attached.

bolts in its normal axis while remaining torsionally stiff.

Bild 4.3c View and plan of the walking bridge in Dessau.

4

Arch bridges

118

4.4

Oberhausen, Germany: arch bridge over main road B 223

Concept: Dipl.-Ing. Thomas Knabben, Pulheim Design: IPP Prof. Polónyi + Partner GmbH, Cologne Steel construction: Märkische Montagerealisierung und

Metallverarbeitung GmbH, Schwedt; MONT Stahl-Rohr-MaschinenMontage GmbH, Szolnok / Ungarn; Fenne Baugesellschaft mbH, Gladbeck

LOCATION

A cycle and pedestrian bridge with (only) one main girder and a

freely suspended deck crosses the four traffic lanes of the B 223 Mülheimer Straße between the old city and the new centre of Oberhausen. It was opened in 2001. At a height of 6 m above ground level, the bridge connects the second floor of the technology centre for environmental protection (TZU) with the Kaisergarten landscape park and the adjacent industrial estate, both of which were built on a former pithead. The bridge stands next to the former water tower of the Gutehoffnung steelworks, which is listed as an industrial monument and, like the tower, has become a landmark in Oberhausen. Access to the bridge is via stairways from the pavements each side of the road. Short ramps at the TZU building lead to an elevator which enables disabled people to use the bridge. The bridge is part of a pedestrian route, defined by town planners, which follows a wide curve to Oberhausen castle. The arch stands at right angles to the road while the bridge deck and the TZU building form a small section of the curving path. LOAD BEARING SYSTEM

The bridge is a further development of the “serpen-

tine tube” first built in Castrop-Rauxel and implements some of the knowledge gained in the construction of the Garden Show bridges in Gelsenkirchen (see Sections 4.2 and 4.5). It was designed as a load-bearing round hollow girder (tube) in the form of a free spatial curve, whereby the deck is suspended from the high arch at the eastern end and supported on two smaller arches in the west. Unfortunately, for reasons of economy, this elegant solution had to be shortened and replaced by a longer embankment. The tubular spine is rigidly fixed in an abutment at the other side. STEEL STRUCTURE

The tubular arch is 508 mm in diameter and stands in a

vertical plane at an acute angle to the axis of the deck. It has a span length of 32 m over the road and 2 × 18 m in the west. THE DECK

is a box girder, 2.8 m wide, of 6 mm steel plate in the form of the

wing of an aircraft, whereby the lower plate is convexly curved. The horizontal top plate is coated with epoxy resin with quartz sand for slip resistance. The box girder is stiffened by transverse bulkheads at intervals of 1.6 m and longitudinal and transverse ribs 0.4 m apart. In the suspended bridge section curved transverse girders of round hollow section, ø 300 mm, under the box girder are cantilevered at each side to provide anchorage for the hangers. Cable connections are welded on at each end of the transverse girders. The cable is inserted through the connection then adjusted and fixed at the bottom

Fig. 4.4a A tubular arch supports the footbridge over Mülheimer Straße

in Oberhausen. Fig. 4.4b The arch has a pronounced curve; the deck curves gently. Fig. 4.4c Views, plan, cross section.

4.4

Oberhausen, Germany: arch bridge over main road B 223

119

View from north

with counter plates and nuts. Labour-intensive sealing of the points of penet-

View from west

ration was therefore unnecessary. THE HANGERS

are in a particular configuration: their axes meet at an imagina-

ry point above the arch and normal to the plane of the arch, which provides the necessary clearance. The curve of the arch was calculated in accordance with the support line of the hangers, giving it a dynamic appearance. The ø 50 mm hangers are fixed in the arch in the same way as to the transverse girders; the openings at the top of the arch were covered with steel lids. THE TWO STAIRWAYS

provide lateral support for the load bearing structure

and their curved hollow round section, 270 mm in diameter, reflects the shape of the arch. The steps are mounted on two parallel tubes which also support the bridge deck and are analogous to the transverse girders to which the hangers are attached.

Cross section

ONLY MINIMUM FOUNDATIONS

were possible because of the utility pipes

in the ground under the pavements. Two foundations connected by tension

Effective width

cables were used to provide sufficient counterweight to the horizontal thrust of the stairway tubes. THE BALUSTRADES AND ILLUMINATION

of this footbridge are meticulously Deck plate Floor plate

designed. SURFACE PROTECTION

The parabolic arch is painted red (like many of the

main load bearing elements of new bridges in the Ruhr district); in contrast, the stairways are painted blue. ERECTION

Plan

was with a mobile crane.

Deck plate width

4

Arch bridges

120

4.5

Castrop-Rauxel, Germany: serpentine arch footbridge over main road B 226

Client: State Development Organisation LEG NRW, Dortmund Planning: LEG North Rhine Westphalia (Architect Peter Freudenthal,

Dortmund) with Stefan Polónyi, Cologne Structural Planning: IPP Prof. Polónyi + Partner GmbH, Cologne Steel construction: E. Rüter GmbH, Dortmund Source: Wolfgang Walochnik: Tragendes Stahlrohr – Rohrkunst?

1995, 1997 [46]

LOCATION

The grounds of the disused Erin coal mine near the centre of Cas-

trop-Rauxel were transformed into a park in 1997, preserving the shaft tower

A BRIDGE WAS NEEDED

with a span of 31.5 m, or at least 27 m, with traffic

clearance of at least 4.7 m. At the same time the town planners wanted the

as an industrial monument. A footbridge was needed to connect Erin Park with

deck to be as thin as possible, to keep the number of steps up to the bridge

the town centre. The bridge begins at a shopping centre in the east, continuing

to a minimum, which meant that the load bearing structure had to be above

along the axis of the mall, and then crosses a four-lane ring road with a centre

the deck. The bridge was therefore to be suspended from an arch or a pylon.

strip (the “old city” ring road, B 226). It then leads over a grassed area to end in

Finally, a free spatial curve was selected that soars in a high arch over the

the west at the edge of the park as a viewing platform. Two short side bridges

ring road and snakes around the structure before going to earth in the park.

(simple girder grids) connect the footbridge with an adjacent office building

This serpent carries a deck with a curved bottom plate, similar to the wing

(VEW) and a service centre (DieZ). An angled stairway leads down into the park

of an aircraft in cross section, which it partly supports and in some places

at the western end. DESIGN HISTORY

A workshop was held at which the architect and plan-

penetrates. THE STEEL SUPERSTRUCTURE

consists of a torsionally stiff box girder, 400 mm

ner was asked how he would visualise this footbridge. In reply he sketched

high, 4.8 m wide and 93 m long, with an arced cross section. The girder is

about 20 bridges arranged according to material and bridge type. A sketch

stiffened along its entire length by longitudinal bulkheads and transverse bulk-

featuring a tubular sculpture received general acclaim because the steel tube

heads at the support points. It is of welded steel plate, generally 10 mm thick.

is synonymous with the surrounding industrial landscape. The client’s own

The superstructure is supported by a tubular “serpent”, 609.6 mm in diameter

architect took this one step further by “snaking” the load bearing tubular sec-

with a wall thickness of ~22 mm, which was inductively heated and hot bent.

tion through, above and around the deck of the bridge, like a gigantic mythical

The superstructure is suspended from the arch in the long span over the ring

creature. The original design of Erin Park had placed a small lake at the end of

road. The round bars of the hangers pass through the arch in sleeves and are

the bridge. The bridge planners then had the idea of continuing the ends of the

bolted on the other side at the top of the arch. The sleeves were then grouted

arches underground and having one of them rise dramatically out of the wa-

for corrosion protection.

ters like the Loch Ness monster. This plan, unfortunately, had to be abandoned

In the western section of the bridge, leading to Erin Park, the superstructure

for reasons of economy.

lies on arches, again of round hollow section, but in this case on two arches

Fig. 4.5a A futuristic footbridge in the form of a giant serpent connects the town centre of Castrop-Rauxel with a park on the grounds of a former mine.

4.5

Castrop-Rauxel, Germany: serpentine arch footbridge over main road B 226

121

Perspective

◀ West to Erin Park

East to town centre ▶

because the main tubular spine divides into two tubes which converge into one and then divide again. At one point one of the tubes winds itself audaciously around the deck. FOUNDATIONS

The supports stand on individual shallow foundations. The

ground consists of compacted recycling material. THE HORIZONTAL FIXED POINTS

are approximately at mid bridge, which can

expand and contract towards each end in response to temperature changes. The supports at the outer bearings slide longitudinally (in slotted holes). The four middle foundations are horizontally connected to counterbalance the horizontal thrust. The “serpent” is rigidly fixed to these foundations.

Isometry

◀ West to Erin Park

East to town centre ▶

B 226

Fig. 4.5b Perspective and isometry: the girder of the arch divides

into two in the middle and at the ends of the bridge. Fig. 4.5c The tubular arch supports, penetrates and winds itself

around the deck. Some local people call the bridge “the sick worm”.

4

Arch bridges

122

4.6

Munich, Germany: tubular arch bridge “zur Wies’n” over Bayer Straße

Client: Bayerische Hausbau Projektentwicklung GmbH, Munich Structural planning: Dipl.-Ing. Christoph Ackermann,

Consultant for Structural Engineering, Munich Architecture: Ackermann and Partner, Architects BDA, Munich Materials specialist: high-tensile steel and glass balustrades:

Prof. Dr.-Ing. Ömer Bucak, Munich Construction, assembly: Maurer Söhne GmbH & Co. KG, Munich Sources: Ömer Bucak: Brücke über die Bayerstraße München.

2005, [47]; Christoph Ackermann: Brückenbauen mit neuen Werkstoffen: Die Fußgängerbrücke über die Bayerstraße in München. 2005, [48]

LOCATION

The cycle and footbridge between the grounds (“Wies’n”) of the

Oktoberfest and the European Patent Office and Hackerbrücke station in Munich is known as the “Wies’n” bridge. It is 40 m long with a span of 38 m and an effective width of 4 m. Its gentle arch (with a rise of only 2.16 m) crosses four traffic lanes and two tram lines without intermediate support over a busy main road, Bayer Straße, in Munich’s inner city. THE LOAD BEARING SYSTEM

is an arch with two hinges as a hybrid structure,

formed by the combination of an upper arched girder of reinforced concrete, 200 mm thick, (the deck) and a lower frame (bottom chords with diagonals and posts) of round hollow section, 219 mm in diameter, of high-tensile S 699 fine-grained structural steel. The arch frames are a hyperbolic approximation of the thrust line and transfer the even loads as compression into the abutment blocks. The bottom chords, diagonals and posts are rigidly welded together and connected to the reinforced concrete slab with hinged eye bars. THE FRAME STRUCTURE

The original plan was to use S 355 (St 52) steel, as

normally chosen for bridge building, whereby the quantity of steel needed was calculated at ~35.5 t. The engineering firm in charge of the project investi-

Cross section

gated and later opted for an alternative using S 690 high-tensile fine-grained structural steel and requiring only 18 t, half the quantity of the original design. This had two advantages: erection costs were lower because of easier hand-

4,00 m

ling on site and because welding joints are much smaller in tubular sections than in solid material.

Fig. 4.6a A filigree footbridge of high-tensile steel over Bayer Straße

in Munich. The steel arch weighs only 18 t in S 690 compared with 36 t in St 52. The bridge was lifted onto its abutments – precision work by two large mobile cranes operating in a very confined space. Fig. 4.6b View from below. Fig. 4.6c Cross section.

4.6

Munich, Germany: tubular arch bridge “zur Wies’n” over Bayer Straße

123

View

38,00 m

The German Institute for Building Technology had not yet issued a general approval for S 690 steel; it was therefore necessary to have the concept approved by the building authorities on the basis of an expert appraisal by the materials specialist Professor Dr.-Ing. Ömer Bucak at the Laboratory for Steel and Light Metal Engineering of the Technical University in Munich. He investigated nodes for high-tensile steel structures which were then calculated in accordance with the Eurocode 3 EN 1993 Part 1-8. ASSEMBLY

The bridge was prefabricated in two sections which were welded

together at an assembly site using precision-built falsework. The deck slab was cast in formwork which again had to be correct to a millimetre. Tension rods were attached to the bridge ends to stabilise the structure for transport to the erection site. Bayer Straße was closed for only one day while the superstructure, 40 m in length and weighing 110 t, was lifted into position. BALUSTRADES

with stainless steel handrails and glass panelling were fitted

despite the vandalism prevalent in Munich.

Fig. 4.6d View. Fig. 4.6e The bridge was lifted into position in one piece with minimum

disturbance to traffic – the advantage of steel bridges.

4

Arch bridges

124

4.7

Bensheim, Germany: middle deck arch bridge of composite structure over road

Client: Town of Bensheim; Hessen State Office for Roads and Traffic, Wiesbaden Architect, photos: Heinz Frassine, Bensheim Steel structure design: Schlaich, Bergermann & Partner, Consultant Engineers, Stuttgart Steel construction: Jaeschke & Preuss Baugesellschaft mbH, Duisburg (no longer in existance)

LOCATION

The B 47 to Worms and the B 3 Darmstadt – Karlsruhe in Bensheim

run parallel until the B 47 turns off and enters an underpass under the railway to the south of Bensheim station. This junction lies in a cutting crossed by a graceful cycle and footbridge opened in 2006. The bridge is 30.3 m long with an effective width of 2.5 m. Access to the bridge is via three stairways and three ramps. THE LOAD BEARING SYSTEM

is that of a compression arch suspended deck

bridge with a cycle and pedestrian deck at a level approximately one third of the height of the twin arches. The deck is a composite steel structure, 200 mm thick. The minimalised main girders of U 240 section provide a frame for the deck slab and hold the balustrades. THE STEEL ARCHES

have a linear length of ~35 m and a rise of ~6 m. They

are ~4 m apart at the crown and 5 m apart at their fixed bearings in the walls of the cutting. The arches are of hollow round S 355 sectional steel, 193.7 mm in diameter, with a constant wall thickness of 8.8 mm. Spotlights at the bases of the arches illluminate the chords of the bridge from below. T 240 transverse girders are suspended from each of seven pairs of hangers in the form of round steel bars. The deck lies on the transverse girders. The arches are stiffened against each other by three cross members. THE BALUSTRADES

consist of metal bars and are unusually high (1.8 m) to

protect cyclists. Pedestrians are provided with a handrail at hip height.

Fig. 4.7a An arch bridge takes pedestrians and cyclists over a two-level road near Bensheim station. Fig. 4.7b View in the west direction (railway).

4.7

Bensheim, Germany: middle deck arch bridge of composite structure over road

125

View

2%

30,30 m

2,20 m

Plan

1,20 m

3,60 m

0,30

3,20 m

0,20 0,24

T 2,50 m 3,00 m

4,70 m

Cross section

Worms

Karlsruhe

Fig. 4.7c View, plan and cross section. Fig. 4.7d View from the city in the direction of the station.

Darmstadt

4

Arch bridges

126

4.8

Osnabrück, Germany: arch footbridge over River Hase

Client: Town of Osnabrück Structural design: IPP Prof. Polónyi + Partner GmbH, Cologne

LOCATION

The River Hase meanders through Osnabrück flowing under two

open footbridges, each with spans of approx. 16 m and effective widths of 3.1 m and 2.2 m. The two bridges have different load bearing systems: 1. A cable-stayed bridge in Öwer de Hase (see Section 2.13), 2. An arch bridge over a landing stage in Herrenteich Straße. THE STEEL SUPERSTRUCTURE

of the latter consists of two arched girders B

of hollow round section (193.7 × 8.8 mm). The five main transverse girders Q have the same cross section as the arch girders and are positioned approximately at the quarter points of the superstructure. There are further secondary transverse girders. The second and fourth main transverse girders are diagonally braced from the centre of the arch by round bars, 50 mm in diameter. Two main longitudinal girders H (IPE 400) of S 355 steel lie on the transverse girders. THE ABUTMENTS

are also galvanised (cast steel).

THE BALUSTRADES

The panelling of the balustrades is attractively designed

with slanting bars. Planting boxes for flowers can be hung from the balustrades.

Fig. 4.8a Arch bridge over the River Hase in Osnabrück. Fig. 4.8b Arch abutment and bearing for a main longitudinal girder.

4.8

Osnabrück, Germany: arch footbridge over River Hase

View

River

Plan

Planking

Cross section

Fig. 4.8c View, plan and cross section.

127

4

Arch bridges

128

4.9

Sindelfingen, Germany: an arch footbridge leaps into a multi-storey car park

Client: Daimler-Chrysler AG, Werk II, Sindelfingen Design: Renzo Piano Building Workshop, Genoa, Italy Steel construction: Greschbach GmbH & Co. KG, Herbolzheim

LOCATION

Symmetry is soothing – or is it simply tedious? The asymmetry of

this footbridge from ground level at Daimler Gate in Sindelfingen into the upper

THE BALUSTRADES

are of tubular 18/8 chrome-nickel stainless steel (KHP),

55 mm in diameter, with rows of horizontal rails, also of hollow round section

floor of the staff car park makes it appear to be leaping over the entrance road

and 40 mm in diameter.

to the Daimler Chrysler (Mercedes-Benz) works. The bridge is 36 m long with

CONSTRUCTION, ASSEMBLY

an opening width of 30 m and an effective width of 2.3 m. Traffic clearance

ally 7.90 m long. Three sections for the works entrance side and two sections

is 5 m up to a maximum of 5.82 m at the highest point. The bridge was

for the car park side were welded together at the steel works before galvani-

completed in the summer of 2000.

sation. During erection the arch segments were put into position and welded

THE LOAD BEARING SYSTEM

The arches were produced in five sections, gener-

is that of an arch bridge with a suspended deck.

together on site. The arches are entirely built of S 355 steel with the excep-

of this bridge consists of a pair of arches of

tion of the footplates, which are of St 37-2. Apart from the balustrades, all

THE STEEL SUPERSTRUCTURE

hollow round sectional steel, 38.8 m in length and 508 mm in outer diameter

steel components were hot-dip galvanised, in spite of the risk of deformation

with a wall thickness of 17.5 mm, bent to a curve with a radius of 34.85 m

through the release of bending or welding stress, thereby receiving the most

and a rise of 6.1 m. Nineteen transverse girders of IPE 140 sectional steel are

long-lasting and therefore economical surface protection. Two coats of Duplex

suspended from the arches by 2 × 19 hangers of stainless steel wire cable.

corrosion protection in silver grey were added for decoration.

The transverse girders are integrated into the pedestrian deck of concrete, which was cast on site and coated for slip resistance.

View

Daimler Gate 16

Fig. 4.9a An asymmetric footbridge appears to leap into the staff car park at the Daimler-Chrysler Mercedes-Benz works in Sindelfingen. Fig. 4.9b View of the arch with a span of 35 m and outer tube diameter of 508 mm.

4.10

Overview: three arch footbridges in Southeast Asia

129

4.10 Overview: three arch footbridges in Southeast Asia

Singapore

Client: Government of Singapore, Ministry of National Development (MND), Public Works Div. Design: President Lim Peng Hong, BEng, MSc, DIC, PEng

Kim Seng Park

k-K Jia

Mo

ral

i Qua on erts ngapore River Si

Pulau-Saigon Bridge velock Rd.

Ha

eau enc

Singapore River View

Alkaff Bridge Cle m

Robertson Bridge

-Av e.

Rob

Grand Copthorne

Waterfront Plaza

Exp

d.

nR

ulta

dS

e ham

Ce nt

im-

Str .

y.

Jiak Kim Bridge

Clemenceau Bridge Me

rch

an

tR

d.

Singapore, an island 137 km north of the equator between the

The bridges presented here are built from hollow round section and demon-

Pacific and Indian oceans, is a city state with almost 4 million inhabitants. In

strate the advantage of hot-rolled tubular steel as a product available with

LOCATION

competition with Hong Kong, it is a main hub for passenger and goods trans-

various wall thicknesses for every diameter.

port and a centre for business, finance and communications in the Far East.

All bridges in Singapore are open bridges for public use. Covered or enclosed

The Lion City owes its existence and, in recent years, its burgeoning economy

connecting bridges for private or business use are rarely needed in the tropical

to Sir Stamford Raffles, who recognised the advantages of this key location

heat of the city except, possibly, as parts of air-conditioned shopping malls.

and founded a British settlement at the wide tidal estuary of the Singapore

CORROSION PROTECTION

is generally achieved by multiple coating (other

River in 1819. Within a short time the banks were lined with offices and

than for stainless steel components). Long-lasting hot-dip galvanisation would

warehouses and the huts of the coolies, mostly Chinese building and dock

probably have been better for the hot and humid climate of Singapore.

workers. This old town went into a decline around 1950, after a new deep

Many thanks to Mr Lim Peng Hong, President of the Civil & Structural Engineer-

water dock was built outside the city centre, and many old buildings were

ing Division of the Ministry of National Development, Public Works Division, for

demolished. Since the 1980s, however, the charm of the river estuary, the old

allowing me to interview him on several occasions.

warehouses and even China Town has been rediscovered and the area has been extensively redeveloped. Grand hotels and luxury condominions have been built and attractive promenades line the river banks. Since 2000, three unusual footbridges have been built across the Singapore River. MAJOR DEVELOPMENTS IN STEEL BRIDGE CONSTRUCTION

over the past two

centuries can be seen here concentrated on a stretch of the Singapore River only 5 km long. There are beam bridges, bar-stayed beam bridges, arch, truss, lattice girder, rigid frame and chain bridges. The only bridge type not represented is the “true” suspension bridge because the spans required so far have not been wide enough to warrant such a structure.

Fig. 4.10 Overall view of bridges over the Singapore River. (Drawing: Peter Palm, Berlin)

4

Arch bridges

130

4.10.1 Singapore: concave-convex rigid frame bridge (Alkaff Bridge)

Client: Government of Singapore, Ministry of National Development (MND), Public Works Div. Design: President Lim Peng Hong, BEng, MSc, DIC, PEng Steel construction: Precise Development Pte Ltd, Singapore Sources: Lim Peng Hong; BEng, MSc, DIC, PEng. MIES: Bridges in Singapore. 1980, [55]; Idelberger, Klaus: Stege nach Maß für jede Spannweite, jeden Zweck. 1980, [56]

LOCATION

This footbridge owes its shape more to the desire of the architect

THE STEEL SUPERSTRUCTURE

comprises the pair of symmetric Vierendeel

to make a statement than to aspects of structural analysis. It is reminiscent of

girders mentioned above (girder frames with rigid corner connections) with

a “tongkang”, a traditional river boat in Singapore (not to be confused with the

upper chords O and and bottom chords U of hollow round section, 508 mm

seaworthy sailing junk). The Alkaff Bridge crosses the Singapore River close to

in diameter, and 11 posts P of hollow round section, 508 or 457.2 mm in

Clemenceau Bridge in a gentle bow with a span length of 57 m and an effect-

diameter. Wall thicknesses are 35 or 28 mm. Thirteen cross members con-

ive width of 4 m, connecting shops and restaurants on the north-west bank

nect the bottom chords. The girder grid of the deck arches in the opposite

with elegant condominions on the opposite bank.

direction to the Vierendeel girders and has main girders and traverse girders

consists of a pair of mirror-symmetric rigid

of a similar calibre plus a secondary structure bearing the paving of the deck,

frames (Vierendeel girders) that curve inwards along the length of the frame

consisting of bricks set in concrete. The loads of the upper and bottom chords

THE LOAD BEARING SYSTEM

and upwards at each end. The girder grid of the deck curves upwards against

are transferred to two support trestles S. The balustrades have posts of hollow

the frames. This complex structure rests at each end on a trestle of similar

round section, ø 76.5 mm, and are panelled with bars of hollow round section

tubular construction.

48.5 mm in diameter. CORROSION PROTECTION

A multi-layer coating was considered adequate in

spite of the prevailing industrial and maritime atmosphere.

Fig. 4.10.1a A footbridge with a span length of 57 m connects shops and restaurants with condominions (right). The silhouette and cross section are reminiscent of the “tongkang”, a traditional river boat that used to be poled upstream.

4.10.1

Singapore: concave-convex rigid frame bridge (Alkaff Bridge)

131

View 57,00 m 12 x 4,10 m = 49,20 m

3,90 m

3,90 m

O P

S

U 2,20 m 0,00 m

View from above

Draufsicht

U

S

O

U

Plan

Grundriss F U H H U

T

K

K

K

Querschnitt

K

K

Ansicht View of bridgehead

Cross section

Brückenkopf O

O

P

P

U

2%

T

Fig. 4.10.1b View, view from above, plan, cross section and view of the

bridgehead of the boat-shaped Alkaff Bridge over Singapore River.

U

4

Arch bridges

132

4.10.2 Singapore: an asymmetric, divided arch supports a straight bridge (Robertson Bridge)

Client: Government of Singapore, Ministry of National Development (MND), Public Works Division Design: President Lim Peng Hong, BEng, MSc, DIC, PEng Steel construction: Hon Construction Pte Ltd, Singapore

LOCATION

An unconventional bridge, completed in March 2000, was con-

structed about 500 m downstream from where the Alexandra Canal joins Singapore River. It connects warehouses and offices on the north bank (Robertson Quai) with three hotels on the south-south-west bank: Grand Copthorne, Grand Palace and Singapore River View. Its average span length is 48.20 m. The pedestrian deck is 6.2 m wide in the middle of the bridge and 4 m at the abutments. THE LOAD BEARING SYSTEM

features an arch steeply bowed to the north and

falling in a gentle curve to the south. It divides into two towards each end of the bridge. The slightly arched girder grid of the deck is supported on six pairs of inclined hangers. THE STEEL SUPERSTRUCTURE

consists of an asymmetric arch B with a

maximum height of 11.23 m. The crown of the arch is a single box girder (1100 × 950 mm to 1500 × 1250 mm) which divides into two “legs” (660 mm × 440 mm × 26 mm) stably connected together with cross members T of hollow round section, ø 355 mm × 32 mm, at the bearings and hanger points. Six

Cross section

hangers H (solid bars, ø 75 mm) with varying lengths and inclinations support six main transverse girders (round hollow section, ø 500 mm × 32 mm) which carry four lines of longitudinal girders L (round hollow section ø 457 mm × 32 mm) stiffened to form a slightly convex pedestrian deck with a deck panel of trapezoidal sheet metal covered by a top layer of concrete, 125 mm thick. THE BALUSTRADES

are 1 m high, perpendicular and angled inwards by 42.3°

at the top. The double posts are made of stainless steel plate, 75 mm × 2 mm. The handrails are of tubular stainless steel (ø 75 mm). The five horizontal strands are cables with a diameter of 6 mm. CONCEALED LIGHTING

is installed along the length of the bridge behind the

kerbs. The deck is illuminated by lighting at the points where the arch divides. THE FOUR BEARINGS

Pedestrian deck Concrete

on the south bank are fixed bearings; on the north bank

there are concealed pot bearings with neoprene pads. The bridge also responds to expansion and contraction due to temperature changes through the

4,28 to 6,34 m

arch and the convex deck. Fig. 4.10.2a The Robertson Bridge with a span of nearly 50 m connects warehouses and offices on the north bank with modern grand hotels on the south-south-west bank (left) of the Singapore River. Fig. 4.10.2b The hangers with cross member, north bank. Fig. 4.10.2c Cross section.

4.10.2

Singapore: an asymmetric, divided arch supports a straight bridge (Robertson Bridge)

133

View

Hä

4×L

B

6×Q

View from above Bridge deck

0,66

Concrete slab

Hä

T Hä

Walled river bank

6×Q

T

B

Plan, load bearing structure

4,40

4,40 4,40

4,74

2,02

4× L

2,27 2,02

T

N

Fig. 4.10.2d View, view from above and plan of Robertson Bridge.

6×Q

B

T

4

Arch bridges

134

4.10.3 Singapore: a curved bridge panel supported by a symmetric arch (Jiak Kim Bridge)

Client: Government of Singapore, Ministry of National Development (MND), Public Works Division Design: President Lim Peng Hong, BEng, MSc, DIC, PEng Steel construction: Chin Leong Construction Pte Ltd, Singapore

LOCATION

The footbridge is a continuation of Jiak Kim Street over Singapore

River and was ceremonially opened by the Prime Minister of Singapore. The symmetry and elegance of its architecture is more striking than its span length of 40.6 m and effective width of 3.5 m, which is, however, adequate for the relatively low volume of cycle and pedestrian traffic. THE LOAD BEARING SYSTEM

is similar to that of the “horseshoe” footbridge

over the Rhine-Main Canal near Kehl (Schlaich, Bergermann & Partner). The deck of the bridge in Singapore arches slightly and is curved on plan. It is supported by an arch inclined at 56.4° to the horizontal with nine inclined bar hangers. THE STEEL SUPERSTRUCTURE

consists of a symmetric but eccentric arch B

(hollow round section, ø 508 mm × 50 mm), with a rise of 8.7 m above the transverse axis of the bridge and inclined over the deck. The main girders HT (hollow round section ø 508 mm × 50 mm) are arranged laterally, pushed out from the axis of the bridge. Four equidistant auxiliary girders N (hollow round section, ø 246 mm) are combined with nine transverse girders Q (hollow round section, ø 355.6 mm × 25 mm) to form a butt-welded grid as a load bearing component. This grid supports a pedestrian deck G, covered by a 125 mm layer of concrete with a 2 % camber from the centre. Nine stainless steel hangers H connect the arch with the main girder. THE BALUSTRADES

are of stainless steel with hollow posts, 1 m in height and

with a cross section of 200 × 50 mm at the handrail and 200 × 200 mm at the base. The handrails are of hollow round section, 100 mm in diameter. The five horizontal bars are 20 mm in diameter. BEARINGS

There are fixed and movable bearings at each end of the bridge:

fixed on the inner curve and movable on the outer curve. ILLUMINATION

The guttering at the sides of the deck is fitted with strip lighting.

The arch is lit by a line of spotlights installed in the deck exactly in its vertical projection. All luminaires are therefore effectively protected against vandalism. The illuminated bridge is one of the highlights of night time riverboat excursions through Singapore.

Fig. 4.10.3a A footbridge with an arch inclined over the deck and

span length of 40.6 m over Singapore River. Fig. 4.10.3b The balustrades have the same inclination as the arch.

4.10.3

View

Singapore: a curved bridge panel supported by a symmetric arch (Jiak Kim Bridge)


    
  

135

 



    



   



   


  

View from above

   













 





 



  

 

 









 

 

 

  

Details 

  

 

  



 

 

 









 

 

 



Fig. 4.10.3c View, view from above, cross section and details.





 





 



  

Cross section

4

Arch bridges

136

4.11 Melbourne, Australia: arch bridge, horizontally and vertically angled (Flinders Bridge)

Client: Municipal Administration, Melbourne Architects: Cocks Carmichael Whitford Pty Ltd, Melbourne Structural analysis: Irwin Johnston & Partners Engineers Pty Ltd,

Melbourne

LOCATION

The Yarra River flows through Melbourne, a deep water port and

capital of the south Australian State of Victoria with 3.2 million inhabitants, on its way to the Pacific Ocean. An unusual footbridge was opened in 1991 on a part of the river where rapids had once separated salt and fresh water, enabling settlements to be established upstream of this point. The bridge includes a café platform C on the southern pierhead beneath the deck. The two auxiliary spans are ~30 m long and are at right angles to the banks. The ~45 m main span is turned ~15° towards the bank, providing room for a viewing platform above the northern pier. The main span is raised slightly in the middle, which emphasises the impression of crossing a great river. The effective width is 5 m to accommodate the streams of pedestrians and cyclist between Flinders Street Station on the north bank and the attractive promenades and shops on the south bank. Melbourne competes with Sydney for the title of “Most beautiful town in Australia”. THE LOAD BEARING SYSTEM

is that of an arch bridge, whereby the deck is

supported by a single and distinctive triangular hanger. The deck continues over two auxiliary spans. THE STEEL SUPERSTRUCTURE

consists of the arch girder B, a box girder with a

700 mm × 700 mm cross section, an auxiliary girder (150 mm × 150 mm) to stabilise the main arch and the single hanger H, which is triangular in shape and whose girders are also triangular in cross section (700 mm × 700 mm). The grid of the deck has two main box girders H (1750 mm × 500 mm × 30 mm), two lateral girders K, similar to U 220 and several transverse girders, approximately HEA 260 with tapered ends. On top of this there are seven longitudinal beams of squared timber and top planking arranged with gaps between the planks. The balustrades have wooden handrails. The two auxiliary spans have wide-flange main girders similar to HEB 400 instead of the box girder used in the main span.

Fig. 4.11a A footbridge across the Yarra River with a main span of 45 m connects the promenades and shops on the south bank with Flinders Street Station on the north bank. Fig. 4.11b View from the south bank with the café under the deck in the foreground and the city of Melbourne in the background.

4.11

Melbourne, Australia: arch bridge, horizontally and vertically angled (Flinders Bridge)

137

View B

Box girder arch

Hanger H

C

Viewing platform

Café

S

N

Plan

et Offs

C 00 30,

m

th Wid

r

ive

of r

00 30,

m

Café 15°

mp Ra

South

North

Details

0,20

0,15

Cross section at hanger

K H

Fig. 4.11c View, plan, cross section and details.

H

4

Arch bridges

138

4.12 Hong Kong: arch bridge, horizontally and vertically curved over airport approach road

Client: Cathay Pacific Airways Ltd; Chek Lap Kok International Airport; Project Manager: John Dowes, Hong Kong Structural planning: Harris & Sutherland (Far East) Ltd, Hong Kong

LOCATION

Cathay Pacific Airways (CX) erected a footbridge with a glass roof on

the main island Lantau at the edge of the new Chek Lap Kok airport in 1999. It crosses a four-lane approach road to the taxiway, linking Cathay Pacific’s new headquarters with a car park and warehouse. Passengers can also use the bridge. The bridge rests on two columns that also serve as elevator, escalator and stairway towers. The main span is approx. 40 m in length with an effective width of approx. 3 m and provides elevated access to the car park (PH) at one end and a stairway and escalator down to CX headquarters at the other. THE LOAD BEARING SYSTEM

is that of an arch bridge. The arch B has a radius

of 25 m. The deck G is slightly arched but also curved on plan with a radius of 114 m. Nineteen hanger bars connect the arch with the eccentric main girder of the deck. THE STEEL SUPERSTRUCTURE

consists of the arch of hollow round section

(ø 508 mm × 16 mm) inclined 23.63° outwards off the perpendicular with 19 hangers H of welded rectangular section whose shafts taper from 47 × 16 mm at the foot to 25 × 16 mm at the top. Two main deck girders G of hollow round section (ø 650 mm × 16 mm), curved with an average radius of 114 m, are connected to a stiff box girder with deck and floor plates. Nineteen roof girders radiate from a tension boom Z of hollow round section (approx. 200 mm in diameter) positioned at a height about half way up the arch. The roof is glazed with silicate glass with dot shading. Spacers of hollow round section are fitted between the hangers and the glass of the balustrade panels. ILLUMINATION

Spotlights are bolted under the main deck girders.

THE BALUSTRADES

have stainless steel posts with glass panels.

Fig. 4.12a The arch girder of this footbridge at Hong Kong airport is inclined

outwards (whereas the arch of the Singapore bridge is inclined inwards over the deck, see Section 4.10.3). Fig. 4.12b The footbridge over the busy airport approach road at Chek Lap Kok airport connects the headquarters of Cathay Pacific Airways with a warehouse.

4.12

Hong Kong: arch bridge, horizontally and vertically curved over airport approach road

139

View

Ansicht

B

H 5,25 m

CX HQ

G

PH

View from above

Draufsicht Escalator

G PH

B Elevator

Elevator

Stairway

N

Stairway

Escalator

Cross section

Querschnitt

Variable Hight

B

D

Z

1,00 m

4°

66,37 °

G

Fig. 4.12c View, view from above view and cross section.

G

CX HQ

Enclosed skywalks CHARACTERISTICS

Footbridges can be important features of urban land-

scapes. Bridges between buildings normally require neither access stairways

THE CROSS SECTIONS

include virtually all closed geometric shapes: ellipses,

ovals, circles, double circles and polygon forms from triangles to octagons.

nor approach ramps but are usually fitted with roofs or are fully enclosed, often

Rectangular cross sections are, of course, predominant because it is generally

using silicate or acrylic glass, polycarbonate or sheet steel.

more economical to use regular straight and flat materials to enclose the

for skywalks is generally based on an assumed load

skywalk than specially designed curved elements. Enclosed walkways

of 5 kN/m², or often less, although structures of this kind frequently carry

between buildings protect their users from weather and noise and also provide

some kind of installation, such as a moving pathway etc. They rarely have to

additional escape routes in case of emergency.

STRUCTURAL ANALYSIS

cope with vehicles. ALL LOAD BEARING SYSTEMS

HEIGHT ABOVE GROUND LEVEL

common in large-scale bridges can be used for

Although skywalks are generally positioned at

a height allowing clearance for trucks or other vehicles, such as trams, there

skywalks, such as (the somewhat archaic) chain bridges, cable or bar-stayed

are some exceptions, for example in Oakland on San Francisco Bay where two

girder bridges, single or multi-span continuous girder bridges, truss, arch or

19-storey office towers, 95 m high, were linked at the 13th and 14th floors in

spatial frame bridges. Only the “true” suspension bridge would not normally

1995. This enclosed, two-storey skyway has a span length of around 50 m and

be used to connect buildings because the distance to be spanned is not usually

was built at a height of 52 – 60 m above ground level.

long enough to justify the expenditure. The bridges presented in this chapter

The Petronas Towers were opened in the Malaysian capital of Kuala Lumpur

are arranged according to their load bearing systems in the sequence men-

in 1995. With a height of 452 m, the 88-storey structures were the world’s

tioned above. This does not represent any kind of value judgment.

highest multi-storey buildings in 1998. They are connected at the 41st and 42nd floors by an enclosed two-storey skyway some 60 m in length (see Section 5.1).

The World of Footbridges. From the Utilitarian to the Spectacular. First Edition. Klaus Idelberger. © 2011 Ernst & Sohn GmbH & Co. KG. Published by Ernst & Sohn GmbH & Co. KG.

5

Enclosed skywalks

142

5.1

Kuala Lumpur, Malaysia: “Skybridge” at the 41st floor

Sources: Leonard Joseph with Klaus Idelberger (translation):

Das Petronas Büroturmpaar in Kuala Lumpur. [51]; Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

The Petronas Twin Towers in the Malaysian capital of Kuala Lumpur

were completed in 1998 and were at that time the highest office towers in the world with total height of 451.9 m and 88 floors. They are visible from a distance of 25 km and the Skybridge is certainly their most eye-catching feature. It serves three purposes: 1. Firstly, it is an architectural highlight, a “gateway” to the city and a symbol of power for the state-owned oil concern Petronas. 2. The Skybridge shortens routes for pedestrians between the towers by providing an alternative crossing. This also reduces the number of elevators needed, increasing the available office area to 436 000 m2. 3. It provides additional escape routes, both upwards and downwards. THE ERECTION

of the Skybridge 183 m above ground level was pure artistry

(see source).

Fig. 5.1a The Petronas Twin Towers can be seen from a distance of 25 km. Fig. 5.1b View with skeleton columns.

5.2.1

Berlin, Germany: suspended rigid frame bridge with suspension cables over Seller Straße

143

5.2 Enclosed suspension bridges 5.2.1 Berlin, Germany: suspended rigid frame bridge with suspension cables over Seller Straße Client: Bayer Schering Pharma AG, Berlin; Building Dept. Dipl.-Ing. Architect Alfons Hiergeist Planning: Beuker & Partner GbR, Architects and Town Planners, Düsseldorf Structural planning: Polónyi und Fink GmbH, Structural Engineers, Cologne Steel construction: SOMMER Fassadensysteme · Stahlbau · Sicherheitstechnik GmbH & Co. KG, Döhlau

LOCATION

An enclosed bridge with a span length of 39 m connects a new

Cross section

administration building with an older office block in Wedding, a district in Berlin. THE LOAD BEARING SYSTEM

consists of two rigid frame girders (Vierendeel),

each suspended within the frame by a polygonal cable anchored at the ends of the upper chord. The upper and lower chords of each frame are cross braced with bars of flat steel. The Vierendeel trusses have a second bottom chord

STEEL SUPERSTRUCTURE

The upper chords are of HEA 400 sectional steel,

2,60 m

supporting a second deck for conduits beneath the pedestrian deck. The two main trusses have slightly different heights to give the roof a gradient. the bottom chords and transverse girders are of HEB 200 wide-flange sectional steel. The posts are also of HEB 200 wide-flange section with cantilever arms of HEA 120 welded on at the sides at varying heights. These cantilever arms lie on the suspension cables. The suspension cables are each made of two steel wire cables with a diameter of 51 mm. The tension force is introduced through deflectors. The cables are clamped at the deflection points. THE ABUTMENTS

are the outer wall of the new building on one side and two

supports on a single foundation on the other.

Fig. 5.2.1a A footbridge crosses a wide boulevard at the Berlin headquarters

of Bayer Schering Pharma AG. Fig. 5.2.1b View and cross section.

View 13,40 m

8,10 m

4,76 m

0,00 m

8 × 4,76 = 38,08 m 39,00 m

5

Enclosed skywalks

144

5.2.2 Bietigheim, Germany: a box-shaped footbridge connects two furniture stores

Client: Hofmeister GmbH, Furniture Store, Bietigheim-Bissingen Design, photos: Dipl.-Ing. Hans Noller, Architect, Bietigheim-Bissingen Structural planning: Schlaich, Bergermann & Partner,

Consultant Engineers, Stuttgart Steel construction: Gebr. Wöhr GmbH & Co. KG, Aalen-Unterkosten Source: Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

Bietigheim is a small town north of Stuttgart. In 1995 / 96 a well-

BEARINGS

The skywalk lies on fixed bearings on the side with the new build-

known furniture retailer built an enclosed footbridge over Post Straße to con-

ing and on longitudinally sliding bearings on the other side.

nect an existing showroom with a new furniture retail market on the other

THE PYLON PORTALS

side of a main road. This box-shaped skywalk is 16.5 m + 31.8 m + 16.5 m

with cross bars of the same material. The pylon heads are decoratively shaped.

= 64.8 m long and 2.64 m wide. The glass/steel structure has enhanced the

The portals are cross braced in the perpendicular by round steel bars of 30 mm

approach to Bietigheim from the north-east by effectively creating a modern

diameter.

and attractive “gate” to the town. The simple bridge is more than just a safe

THE SKYWALK

are bolted structures of HEB 240 sectional steel St 52-3

is enclosed with single glazing at each side. The panes are

and inexpensive connection between two buildings: bridge users can stand

fitted linearly at the top and bottom and held in position with clamping rails.

and look out over Bietigheim forest on one side and over the lively town on

The roof is of laminated safety glass that is linearly supported at the top ridge and at clamping points at the roof edges. There is a conduit under the ridge for

the other. is that of a chain bridge i.e. the original form of

cables and a pneumatic tube (for “tube mail”) to network the new facility with

the suspension bridge. Long span lengths in bridges (and halls) are usually

the older building. The deck is a trapezoidal plate with a top layer of concrete

achieved nowadays by suspending the bridge deck (or the roof of the hall) on

and a floor covering.

THE LOAD BEARING SYSTEM

All steel parts were hot-dip galvanised in accord-

steel wire cables from pylons (or columns). Before the invention of steel wire

CORROSION PROTECTION

cables, suspension bridges were built with chains made of bars with eyes at

ance with the German Code DIN 50976 (which applied in Germany until 1999

each end. Chains of this type freely fall in lines in which y = ½ (e x + e –x). Even

but has now been replaced by DIN EN ISO 1461) with a zinc coating of at

today, chain bridges can be an economical alternative in special circumstan-

least 85 μm. When the steel for the bridge was selected, it was important to

ces, when – as in Bietigheim – the chains are anchored in the bottom chords

consider the effects of its Si content on the galvanisation process, particularly

at each side of the bridge. This is a particularly effective solution when longi-

in the case of S 355, because the client wanted a completely even surface.

tudinal forces are short-circuited in the bridge panel by the bars of the lower

All external surfaces received an additional double top coating with a thick-

chord so that the abutments in the buildings at each end of the bridge remain

ness of 2 × 60 = 120 μm. The surfaces between cables and clamps were zinc

almost free from longitudinal forces. The bars of the lower chord are mainly

sprayed without an additional coating to increase friction.

subjected to compression.

ASSEMBLY

THE GALVANISED STEEL SUPERSTRUCTURE

is built as a rigid frame in the

The components were preassembled and erected on site in only a

few days. The structure cost approx. € 400 000.

transverse cross section. As the deck panel of trapezoidal plate does not itself have a stiffening effect, 16 cross braces made of round steel bars were fitted beneath the pedestrian deck. The glazed side walls of the skywalk are fitted with diagonal bars, effectively a stiffening truss, to counteract uneven loads.

Fig. 5.2.2a Suspension chains, cross braced pylons and the galvanised surfaces are some of the interesting features of this structure in Bietigheim near Stuttgart.

5.2.2

Bietigheim, Germany: a box-shaped footbridge connects two furniture stores

View from south

Cross section

View from below

Fig. 5.2.2b View from south, view from below and cross section. Fig. 5.2.2c The skywalk seen from below.

145

5

Enclosed skywalks

146

5.2.3 Fulda, Germany: glass walls and roof for a box bridge with chain suspension

Client: Sparkasse Fulda Architects: Reith and Wehner, Fulda Structural planning: Dipl.-Ing. Sturmius Feuerstein VBI, Structural

Analysis, Petersberg, and Dipl.-Ing. Reiner Schabel, Structural Planning and Building Physics, Künzell Steel construction: Octatube, Delft, Netherlands Façade: Josef Gartner GmbH, Gundelfingen

LOCATION

A skywalk was built in Fulda in 2001 to connect an art nouveau

building known as “Zur Schwartzen Raab”, originally a coal weighing and

BEARINGS

The bridge rests on pin-headed columns on a cross girder of re-

inforced concrete at the old building and on roller bearings on a main girder

trading station and now a bank administration, with a modern banking facility.

of hollow round section, ø 219.1 mm × 11 mm, on the side leading into the

The enclosed bridge over Ohmstraße continues as an open bridge through

new building.

the adjacent glass hall of the bank to the listed buildings of the Buttermarkt.

THE PEDESTRIAN DECK

consists of an 80 mm trapezoidal plate between two

The bridge has a span length of 13.02 m, an effective width of 1.2 m and is

steel T-sections. The surface of the deck is covered in grooved oak planks with

2.33 m high from floor to ceiling with 6 m clearance for traffic on the road

a thickness of around 40 mm. There is a cavity for cables etc. under the planks. Lighting is installed in the deck.

below. LOAD BEARING SYSTEM

The box-shaped bridge is supported by two frames

GLAZING

The bridge is glazed with panes of laminated safety glass (VSG

(top and bottom chords of round hollow section, ø 82.5 mm, posts of round

1860 × 2400 mm), which are fixed to the primary wall structure with six small

hollow section, ø 63.5 mm), and by chain suspensions (round bars of stainless

cardan joints fitted to rods. Four cardan joints were sufficient for the panes of

steel, ø 24 mm) at each side. The chains are not rigidly fixed to the posts and

the roof, which is not designed to be walked on.

therefore fall in lines in which y = ½ (e x + e –x). This is the original form of

AIR CONDITIONING

the suspension bridge and it was used for long spans until steel wire cables

Windows near the doors at each end provide adequate ventilation.

were developed. Nowadays it is an aesthetic and also economical building

ERECTION

was not necessary because of the low volume of the bridge.

of the component parts began with the bearing supports and the

method in special cases, such as here in Fulda, when it is possible to anchor

load bearing structure for the sides, floor and roof. This was followed by the

chains to posts and chords.

fitting of glass panes and the wooden deck.

THE GALVANISED STEEL SUPERSTRUCTURE

consists of the frame trusses

mentioned above and a pair of longitudinal floor girders (rectangular hollow section 180 / 80 × 5 mm), 1 m apart with transverse girders of square hollow section, 60 × 60 mm.

Fig. 5.2.3a The modern steel and glass skywalk blends with the historic buildings in Fulda’s old town.

5.2.3

Fulda, Germany: glass walls and roof for a box bridge with chain suspension

147

View

Administration View from below

Ohm Straße View from above

Cross section

Lighting

Fig. 5.2.3b View, view from below, view from above and cross section.

Bank

Town

5

Enclosed skywalks

148

5.3 Cable and bar-stayed girder bridges 5.3.1 Munich, Germany: box bridge over underground station and sidings Client: City of Munich Design: Bohn Architects, Munich Structural planning: Seeberger, Friedl and Partner, Munich Steel construction: STS Stahltechnik GmbH, Regensburg Source: Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

The public transport authorities in Munich opened a new above-

ground station in the district of Fröttmaning in 1994. The station includes extensive sidings, almost 80 m in width. An elegant skywalk crosses the sidings at a height of 6 m above ground level to connect the station with a multi-storey car park, a bus station and a new industrial park. The box-shaped girder bridge is enclosed with glass and is 140 m long with a span length of 79.2 m and an effective width of 6 m. Access to the bridge inside the station is with escalators, lifts and stairs and at the other end a branch leads into the car park and a stairway down to ground level. The design of the station complex was the prize-winning entry in a competition. Ten years later the same architects redesigned part of the station, extending the original skywalk by a few metres and adding a further skywalk, when a new platform was built to accommodate passengers to the new Allianz Arena nearby. THE LOAD BEARING SYSTEM

is that of a multi-span continuous girder, cable-

stayed from two H-shaped pylons. THE STEEL SUPERSTRUCTURE

The girder grid of the pedestrian deck is

covered with a layer of concrete 200 mm thick. THE TWO PYLONS

are H-shaped with three cross bars above the skywalk and

a similar cross bar below. THE PEDESTRIAN PASSAGE

wide-flange sectional steel supported by a pair of main girders of HEB 500 sectional steel. CORROSION PROTECTION

All steel parts were galvanised by the duplex pro-

cedure: hot-dip galvanisation, an 80 μm base coat, followed by two coats of has an almost rectangular cross section consis-

two-component epoxy resin mica-iron paint (RAL 9007) each to a thickness of

ting of approx. 50 portal-shaped frames of IPE 160 sectional steel, which are

at least 70 μm. The total thickness of the coating is therefore at least 220 μm.

slightly inclined into the bridge from a height of 1.34 m and bolted to the trans-

Every piece of metalwork was also galvanised. A total of 240 tonnes of steel

verse girders with corner gusset plates. The transverse girders are of HEB 280

were used to build this skywalk.

Fig. 5.3.1a A cable-stayed skywalk crosses sidings to connect

a large car park and an industrial park with Fröttmaning Station in Munich. Fig. 5.3.1b The interior of the skyway is elegant and airy.

Munich, Germany: box bridge over underground station and sidings

Longitudinal section

Cross section

Pylon I

Querschnitt 3,40

Längsschnitt

149

160

140

1,34 1,50

5.3.1

Mitte

Ground anchor

Plan from below

4,80

(Total length)

Details of cable fixation

Fig. 5.3.1c Longitudinal section, plan, cross section, pylon I and details

of cable connections.

5

Enclosed skywalks

150

5.3.2 Overview: Walldorf, SAP, Germany: a “family” of five skywalks

N

Client: SAP Deutschland AG & Co. KG, Walldorf Design: Vorfelder Architekten- und Planungs-Gesellschaft mbH,

Walldorf Steel construction: Otto Rossmanith GmbH & Co. KG,

Heidelberg-Kirchheim

LOCATION

The SAP complex in Walldorf, ~15 km south of Heidelberg on the

B 291 and L 723, contains what is probably one of the highest concentrations of pedestrian bridges between buildings. The world-famous software developer has its headquarters in Walldorf with 16 000 employees working in modern laboratories and offices on a greenfield site. Five skywalks connect the various buildings, generally at the 2nd and 3rd floors, to protect employees from wind and weather as they move around the complex and to save time (see site map).

Skywalks connecting the SAP compay buildings No.

Bridge

from

to

Span / length

Over (road)

A

Cable-stayed

Building 1

Building 3

60 m

Dietmar-Hopp-Allee

Building 1

Building 2

19 m

Footpath and bus-only route from SAP

girder bridge B

Two-storey girder bridge

C

Asymmetric

to neighbouring town Building 2

Car park 1

16 + 7 m

Footpath and verge

Building 3

Building 4 + P 3

12 + 8 m

Robert-Bosch Straße

Building 1

Building 18

87 m long

Over grassland to Star Building

girder bridge D

Single-storey girder bridge

E

Single-storey girder bridge

Fig. 5.3.2 Site map of the five skywalks in the impressive

SAP Walldorf complex. © SAP

A

Walldorf, SAP: a cable-stayed box bridge over main road

151

A

Walldorf, SAP: a cable-stayed box bridge over main road THE CABLE-STAYED BRIDGE A

between Buildings 1 and 3 has a span length

of 60 m and extends over the main road Dietmar-Hopp-Allee (named after the founder of SAP). One of the intentions of SAP and the town of Walldorf in building the bridge was to provide an urban landmark in the form of a “gateway” to the complex. The portal is an A-shaped pylon with cable stays; it is 24 m in height, and the concept was to make the interplay of physical forces in the structure and cables visible and understandable to the observer. The buildings are connected at the third floor. THE PEDESTRIAN “TUBE”

is a composite steel structure. The main girders

are of standard HEA 650 high-web section, 4.1 m apart, with L 200 angle brackets to supporting a reinforced concrete slab of 140 mm thickness. The main girders are penetrated every 7.5 m and connected to transverse girders of square hollow section, 260 × 260 × 11 mm. These transverse girders extend in cantilever sections, 1.14 m long, at each side of the bridge with the cable attachments for the 2 × 9 stays at each end. The slightly gabled frames of the tube are welded onto the main girders. They are made of hollow

Cross section

rectangular section, 160 × 90 × 5.6 mm, 2.9 m in height and 4.1 m wide and Frame

are the supporting structure for the walls of insulated glass and the insulated roof panel of steel plate. Of the 2 × 50 windows, 2 × 24 can be tilted and turned. All windows are of 28 mm insulated glass with an insulating value of k = 1.3 W/m2 K. THE PYLON COLUMNS

are fixed in concrete pedestals and are built of hollow

round S 355 sectional steel with an outer diameter of 508 mm and 20 mm wall thickness. THE CABLE ATTACHMENTS

on the pylon are distinctive precision-milled parts

specially designed for this bridge. The stainless steel wire cables for the harp consisting of 4 + 1 + 4 pairs of cables were manufactured by Pfeifer, Memmingen.

Cross section pylon

View

Gradient approx. 1 %

Total length

Fig. 5.3.2 Aa The skywalk between Buildings 1 and 3 at SAP is a “gateway” to the complex. Fig. 5.3.2 Ab Cross section, view and pylon cross section.

5

Enclosed skywalks

152

B

Walldorf, SAP: two-storey girder box bridge THE TWO-STOREY GIRDER BRIDGE B

between Buildings 1 and 2 has a span

length of 19.2 m and connects the 2nd and 4th floors. It crosses a cycle and pedestrian path and a bus-only lane in the direction of the neighbouring town of Wiesloch. The main girders are 4 m apart, with a span of 4 × 4.80 m = 19.2 m between the support portals and a total length of 6 × 4.80 m = 28.8 m. The two portals are of heavy calibre hollow round section, 508 × 20 mm, sheathed in steel plate and positioned 1 m away from the pedestrian “box” as a precaution in case of fire. The portal columns extend beyond the upper storey as a design feature of the bridge. The cross beams are of wide flange steel section. Portals were necessary because it was not possible to analyse how the buildings would react to the additional load of the bridge. The bridge deck contains a cable conduit large enough to accommodate any additional cables that might become necessary in the future. GLAZING

is with insulated glass panes identical in principle to those in the

cable-stayed bridge described in 5.3.2 A.

View

4,80 m

19,20 m

4,80 m

28,80 m

4,00 m

4,50 m

5,40 m

Plan

Fig. 5.3.2 Ba The skywalk between Buildings 1 and 2 at SAP. Fig. 5.3.2 Bb View and plan.

C

Walldorf, SAP: girder box bridge

C

Walldorf, SAP: girder box bridge

153

THE ASYMMETRIC GIRDER BRIDGE C

between Building 2 and car park P 1 is

16.1 + 7.5 m long and crosses a path and grass verge. Like the cable-stayed bridge, it is of composite structure with HEA 500 main girders and transverse girders of HEA 180 with a layer of concrete ~110 mm thick. The main girders support frames with posts of hollow rectangular section 200 × 100 × 10 mm, connected with cross beams of hollow rectangular section 250 × 150 × 10 mm. The insulated glass panes are point mounted. The relatively short supporting portal is constructed of hollow round section with a diameter of 355.6 mm and a wall thickness of 12.5 mm. The cross beam is of HEB 340 wide flange section. The other end of the bridge rests on brackets in the wall of a new car park. GLAZING

This was the last skywalk to be built and is virtually fully glazed.

The panes are point mounted and appear to be without frames. The silicone joints are barely visible. A safety handrail of hollow rectangular section, 149 × 80 × 6.5 mm is fitted at a height of 1.1 m. THE SUPPORT STRUCTURE

was “piece” galvanised against corrosion. The roof

was made of “strip” galvanised 18/76 sheet steel, i.e. a material continuously drawn through a hot-dip galvanisation bath. Additional coatings of paint were not considered necessary or in keeping with the rural environment.

View

Plan Building 2 car park 1

Fig. 5.3.2 Ca The skywalk between SAP Building 2 and the car park P 1 over a foot path and grass verge. Fig. 5.3.2 Cb View and plan.

5

Enclosed skywalks

154

D

Walldorf, SAP: girder box bridge THE SINGLE-STOREY GIRDER BRIDGE D

over Robert-Bosch Straße between

Buildings 3 and 4 leading on to the car park P 3 is 12 + 8 m long. It is supported on portals for the same reason as the two-storey bridge B. The support columns extend beyond the bridge, emphasising the symmetry of its architecture. They are built of hollow round sectional steel with an outer diameter of 355.6 mm and have two cross beams. The steel components were galvanised and again left unpainted. Unfortunately, no further details were available.

View

4,00 m

12,00 m

4,00 m

20,00 m

Fig. 5.3.2 Da The skywalk between SAP Buildings 3 and 4. Fig. 5.3.2 Db View.

E

Walldorf, SAP: truss bridge, angled on plan

155

E

Walldorf, SAP: truss bridge, angled on plan THE SINGLE-STOREY TRUSS BRIDGE E

over grassed areas between Building 1

and the Star Building is 87.5 m long with spans of (25 m + 12.5 m + 25 m) after which it turns at a angle and continues in an additional section, 25 m long. The main trusses are located outside the pedestrian tube and have upper and bottom chords of wide flange HEB 240 section, struts, zigzag diagonals and transverse girders of HEB 200 section. The supports are of hollow round section, 323.9 × 10 mm with cross bracing of round bars (Besista M 52) and side stairways of HEB 220, 2 ½ flights with stringers of IPE 200 (dimensions estimated by author without drawings). All stairways at SAP are of impressive formal simplicity and all are hot-dip galvanised for long-lasting protection against corrosion.

View Construction joint

Star Building

Construction joint

Building 1

View from above

Emergency Stairway

Fig. 5.3.2 Ea The skywalk between Buildings 1 and the Star Building 18 crosses grassed areas and a road. It is angled towards the axis of one “ray” of the star. Fig. 5.3.2 Eb View and view from above.

Emergency Stairway

5

Enclosed skywalks

156

5.3.3 Poplar, London: cable-stayed tubular bridge over road, rail and motorway

Client: London Docklands Development Corporation Architects: ABK Architects, Ahrends, Burton and Koralek, London Structural Engineers: Maunsell Structural Plastics Ltd,

Beckenham, Kent Steel construction: Watson Steel Structures Ltd, Bolton, Lancashire Glazing: EAG English Architectural Glazing Ltd, Mildenhall, Suffolk

LOCATION

The London Docklands Development Corporation LDDC built an

attractive, tubular skywalk between the suburb of Poplar and the North Quay of the former Canary Wharf. The bridge crosses Aspen Way, railway lines and Poplar Station, one of the stops of the partly elevated Docklands Light Railway, DLR. The cable-stayed, enclosed bridge has a total length of 86 m and main spans of 45 m and 35 m. The effective width is 5 m and the tube is approximately 8 m in diameter. There are stairways and elevators both in the middle, serving the station, and at both ends (allowing for future extensions of the bridge to other buildings). THE LOAD BEARING SYSTEM

is that of a deck bridge in the form of a cable-

stayed continuous beam on three supports: a pair of pylons and the abutments at each end. The architects and structural engineers had decided on this form of bridge at an early stage of planning. The deck, however, needed careful consideration. The stiffening girder was originally planned with hinges at the 3 + 3 points of cable attachment. Dynamic analysis of the oscillation behaviour of the structure indicated that a rigid deck was needed and that the pylon

Perspective

columns required two cross beams above and two below the tube. THE SUPERSTRUCTURE

consists of a stiffening girder in the form of a box

girder of steel plate (only 0.7 m high) welded together from two longitudinal I-girders, a flat deck panel with longitudinal stiffening and a concrete covering and a rounded bottom plate. This bottom plate extends beyond the deck panel at each side to form a continuous rainwater gutter. THE STEEL PYLONS

are 37 m high with a constant round hollow cross section

of 0.8 m ø from the foundations to the cable attachment point, after which the columns taper upwards. THE TWO CABLE FANS

lie in perpendicular planes with three cables on each

side of the two pylon columns. Each cable consists of 12 or 17 individual strands instead of a single wire cable with a wide diameter or a heavy calibre bar as commonly used for stayed bridges in the UK.

Fig. 5.3.3a Tubular cable-stayed pedestrian bridge over road and London Poplar station: a cable-stayed bridge with a pair of pylons. Fig. 5.3.3b View of the bridge tube at Poplar Station, seen from the former West India Dock. Fig. 5.3.3c Perspective.

5.3.3

Poplar, London: cable-stayed tubular bridge over road, rail and motorway

157

View

Aspen Way

Docklands Railway

Motorway Motorway

The upper cable anchorage is concentrated at the pylon head and is protected

ELEVATORS AND STAIRWAYS

against the weather by a rhomboidal housing that can be opened for inspec-

planned as provisional arrangements to be replaced by permanent connecting

tion and maintenance. The lower cable anchorage at deck level had to be spe-

paths to buildings to the north and south of the bridge after final completion

cially designed because of the unusual cross section of the bridge: transverse

of the Docklands development. Since nobody knew when this would happen,

girders of hollow round section (with adjustable cable clamps) extend beyond

and because nothing is as long-lasting as a temporary measure, it was finally

the walls of the tube but still remain in keeping with the architecture of the

decided to build permanent steel stairways in a cantilever construction with

bridge when viewed from below.

support columns similar to the pylons at the centre of the bridge.

THE PEDESTRIAN TUBE

is a striking and innovative construction: 76 rounded

frames, 4 m in diameter are placed at intervals of approx. 1.2 m. They are constructed of I-section steel with a varying web height containing oval per-

Cross section

forations for a “light” appearance. Illuminated handrails are attached to the frames. The glazing is secured against failure of a pane or breakage through vandalism by cables on the outside of the tube. THE GLAZING OF THE TUBE

consists of pre-tensioned glass, printed with white

stripes providing protection from bright sunlight. The stripes become narrower from the top downwards to allow free vision at eye level. The glazing panels overlap near the top to allow hot air to be released, while slits at deck level allow fresh air to enter the tube. The upper ventilation is positioned on the east side of the tube because the prevailing wind is from the west. THE ILLLUMINATION

in the handrails was specially designed to cast light

downwards onto the deck and laterally onto the glazing. THE FLOOR COVERING

was chosen for maximum heat reflection and damping

of the noise produced by bridge users walking through the tube. Pylon head with cable entry

Fig. 5.3.3d View, perspective, cross section and pylon head with cable entry.

at each end of the footbridge were originally

5

Enclosed skywalks

158

5.3.4 Ålesund, Norway: a box skywalk becomes a logo for a shopping centre

Client: Amfi Eiendom Aktieselskabet and other owners Operating company: Stormoa Shopping Centre,

Manager Anne Nerbovik, Ålesund, Norway Design, photos: Sandbakk & Pettersen Siv. Architects AS,

Ålesund, Norway Steel construction: Stavsengs Ingenioerfirma AS,

Ålesund, Norway

LOCATION

A box-shaped pedestrian bridge became a logo and a crowd-

Cross section

drawer for a shopping centre east of Ålesund, a pretty town with art nouveau houses in the Geiranger Fjord region in the west of Norway. The area is world famous for its natural beauty. The single-storey bridge connects two-storey 0,50

retail buildings, one of which has an underground car park. It has an elevator at one end and escalators at both ends. The span length is ~38 m and the effective width at mid bridge is 2.1 m with 2.7 m clearance. Building costs in 2000 came to approx. 20 million NOK (around € 2.5 million), but as the present manageress commented: “A lot of money but it finally gave us a pros-

snow load on the roof.

2,90 m

THE STEEL STRUCTURE

is that of a bar-stayed continuous beam 2,70 m

designed for 2.4

kN/m2

consists of HE 220A and 120A longitudinal girders

2.35 m apart. The transverse frames are 3.6 m apart and are built of hollow rectangular section 150 × 100 × 5 mm, coupled at the top corners by longitudinal members of hollow square section, 150, alternating with 100 × 100 × 5 mm. The frames support a handrail, an insulated roof with illumination at mid point, installation conduits and also the outer glass façade with downpipes for roof drainage. The attractive floor of the deck is made of wooden planking on insulation material. THE STEEL STRUCTURE

0,25

2,10 m 2,60 m

0,25

is stayed at the transverse girders (hollow round sec-

tion 133 mm ø) by nine pairs of steel bars (28 mm ø) extending from the pylon head, which itself is rear anchored to a concrete anchor block by a pair of anchor bars (52 mm ø). THE PYLON

has become a landmark because of its vibrant red colour coating

and its eye-catching architecture. The mast head with its cable fans is striking in design; it leans to the south at an angle of 17° off the perpendicular and impresses with its sheer height of 23 m above ground level. Following the line of the bending moment, it tapers to a point above the cable attachment and at the same time braces the escalators to the south. It is a welded rectangular box girder made of steel plate, ~15 mm in thickness.

Fig. 5.3.4a A stylish pylon attracts shoppers to a centre 10 km

east of Ålesund. Fig. 5.3.4b Cross section of the bridge.

3,70 m

perous shopping centre after several changes in ownership.” THE LOAD BEARING SYSTEM

5.3.4

Ålesund, Norway: a box skywalk becomes a logo for a shopping centre

159

View 23,00 m

7,50 m 17°

0,00 m

12,20 m

25,20 m 50,00 m

Plan

Fig. 5.3.4c View and plan of the bridge at a modern shopping centre near Ålesund.

12,60 m

5

Enclosed skywalks

160

5.4 Cable and bar-stayed bridges 5.4.1 Tuttlingen, Germany: bar-stayed, steel-glass box bridge over main road Client: Aesculap AG, Tuttlingen Contractor: Mundus Grundstücks-Vermietungs GmbH, Düsseldorf Design and planning, photo: Dipl.-Ing Günter Herrmann, Architect

BDA, Stuttgart Structural planning: Breinlinger Ingenieure Hoch- und Tiefbau GmbH,

Tuttlingen

LOCATION

Two main roads, the B 14 and B 311 intersect at a roundabout near

to the station in Tuttlingen (~110 km south of Stuttgart). The medical tech-

THE AUXILIARY SPAN

is structurally separate from the main span and con-

sists of a pair of flexible girders (HEA 300, ~10 m long), mostly on concrete

nology concern Aesculap AG had built a modern training centre, the “Aescu-

supports beneath the deck, i.e. a secondary load bearing structure that is in

lapium”, across the road from its headquarters in 1994 / 1995 and in 2004

principle like that of the main span.

connected the two buildings with an enclosed pedestrian bridge. This cros-

THE DECK IS ENCLOSED

in a post (IPE 80) and beam (IPE 220 and U 160)

ses the two roads as a bar-stayed structure of glass and steel with a ~30 m

construction. The glazing is tinted insulated glass approx. 2.5 m × 2.162 m

main span and an auxiliary span of ~11 m which continues as an open gal-

× 80 mm. A travelling platform is used for window cleaning.

lery ~15 m long leading into the Aesculapium. An effective width of 1.7 m was

ASSEMBLY

sufficient because the bridge is not used by the general public.

bled on the ground in their full length of ~40 m and then lifted into position,

The three sections of the main and auxiliary spans were assem-

is that of an under-deck bar-stayed continuous

complete with secondary constructions and full glazing, in a night-time

beam as a trough bridge. The load bearing structure is integrated into the

manoeuvre using a mobile crane. There was, of course, a risk of damage to

THE LOAD BEARING SYSTEM

enclosed section of the bridge, both as a design element but also to keep the

glass panes as a result of elastic deformation of the “box” during lifting. In

height to a minimum and thereby provide maximum clearance for traffic on

fact, the cost of replacing a few damaged panes was correctly considered to

the roads below the bridge.

be far lower than the cost of the extensive safety precautions that would have

THE STEEL SUPERSTRUCTURE

is in two sections: the main span consists of

a pair of main girders at roof level (IPE 400 sectional steel, 30.30 m long and

been needed to glaze the structure on site above a busy road, after lifting and positioning of only the load bearing structure.

2.2 m apart) and two king posts at approx. the third points (square hollow section 100/8) supported by the under-deck stays (two tension eyebars, 36 mm in diameter, Besista System). The pedestrian deck is suspended from the main girders on perpendicular tension bars (IPE 80) in the stayed section of the bridge. The structure is stiffened with wind bracing at roof level (14 × zigzag of HEA 100 alternating with tubular section, 60.3/4 mm and at deck level (2 × 13 cross bracing). The spans end in light, rigid frames that transfer horizontal forces to the bearings (IPE 220 cross beams, HEM 140 masts, built in two halves to facilitate galvanisation and handling and joined with head plates). All steel parts are of S 355 steel. The pedestrian deck and roof are of trapezoidal plate covered in concrete.

Fig. 5.4.1a Bar-stayed bridge over main road in Tuttlingen, with under-deck

bar-stays in main span leading to auxiliary span (right).

5.4.1

Tuttlingen, Germany: bar-stayed, steel-glass box bridge over main road

161

View

Road

Plan, roof

Cross section

Detail 1: diagonal node

Detail 2: connection of tension bars

Fig. 5.4.1b View, plan, cross section and details.

5

Enclosed skywalks

162

5.4.2 Bielefeld, Germany: bar-stayed skywalk from hotel to Civic Hall

Client: Stadthallen-Betriebs-Gesellschaft Bielefeld Design: gmp, by Gerkan, Marg and Partner, Hamburg Source: Klaus Idelberger: Fußwegbrücke in Bielefeld. 1992, [50];

Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

In 1999, the operating company of the Bielefeld civic halls built a

skywalk to connect their civic hall with a hotel, the Bielefelder Hof, directly opposite the main railway station. It is at first floor level and leads from the enlarged hotel foyer over a garden landscape directly into the foyer of the civic hall. The bridge is 54 m long, has traffic clearance of 4.84 m and rises to a maximum height of 11.75 m at the support columns. THE LOAD BEARING SYSTEM

is that of a bar-stayed girder bridge (with a

hinged roof level), in two main spans of 20.25 m and with cantilever sections, 6.75 long, at each end. THE STEEL SUPERSTRUCTURE

basically consists of two trusses horizontally

positioned one above the other and 4.5 m apart. These are connected together by hinged U 160 posts every 6.75 m. At these points the trusses are either directly supported by one of the three pairs of support columns or backanchored by bar stays from the columns. This counterbalanced bar bracing is at the same time the vertical stiffening and secures the structure against lifting through wind action. The horizontal main truss at roof level consists of two IPE 160 girders 1.90 m apart, while the truss at deck level has two IPE 360 m girders supporting HEB 120 girders, also 1.80 m apart. The longitudinal/main girders also form the chords of the horizontal bracing, whereby transverse girders of the same sectional steel (IPE 160 or IPE 360) and 3.375 m apart, function as the posts of the bracing. The upper and lower trusses are cross braced with round steel bars, 20 mm ø, providing horizontal stiffening, for example against wind action. All tension bars in the perpendicular plane are eye bars, some with eccentric plates at the hinge bolt to allow adjustment of the bridge.

Fig. 5.4.2a The civic hall and the hotel Bielefelder Hof were connected by a glazed skywalk to enable guests in evening dress to cross, regardless of the weather. The load bearing structure consists of two horizontal trusses (at heights of 5.20 and 9.70 m) connected by colums every 6.75 m. The colums consist of welded cross sections with four bolted angle irons. Fig. 5.4.2b View from below.

5.4.2

Bielefeld, Germany: bar-stayed skywalk from hotel to Civic Hall

163

View

THE THREE PAIRS OF COLUMS

are 11.62 m high, and the two columns are

4.15 m apart. Each support pair is connected above the pedestrian box by an HEB 160 cross beam – as part of the upper truss – and below the box by an IPE 360 main transverse girder. The supports are stabilised further by diagonals of tension bars, 30 mm in diameter. The supports consist entirely of bolted components. CORROSION PROTECTION

All the above structural components were hot-dip

galvanised for long-lasting, and therefore cost-saving, corrosion protection. The main girders are bolted to avoid damage to the surface caused by welding. THE PEDESTRIAN BOX

is based on a rectangular cross section with an outer

height / width of 4 m / 3.4 m and inner height / width of 3.4 m / 2.95 m. The cubic capacity of the structure is around 750 m3. The box is cut off slightly at the corners of the roof and floor, creating an octagonal cross section. The box is a post and beam structure of extruded section, 1.68 m apart. There are 12 of these grids in the main spans (20.25 m) and four in the cantilever sections (6.75 m). Thermally separate panes of insulating glass are mounted in the post and beam frame (clear glass, k = 2.2 W/m2 K).

Plan

Fig. 5.4.2c View, plan and cross section.

Cross section

5

Enclosed skywalks

164

5.4.3 Manchester: spatial truss tube connecting retail store and shopping centre

Architects: Hodder Associates (Hodder, Williams, Jones, Roberts), Manchester (no longer in operation) Structural engineering and glazing: Arup Group / Façades, London

LOCATION

Manchester United! … on the football field and now by means of a

skywalk linking a retail store and a shopping centre! The metropolitan region of Manchester in north England has over three million inhabitants and is known to sports enthusiasts everywhere because of its famous football clubs. A different kind of union was created when two rival retailers, Marks and Spencer, as a classic store for food and clothing, and the Arndale Shopping Centre, as a large American-style shopping mall, were joined by a “waisted” tube of steel and glass with a span length of ~10 m and ~2 m in width. Instead of firing broadsides at each other, the two flagships are now joined at the second floor level and sail in convoy. THE LOAD BEARING SYSTEM

is a spatial truss of bars and nodes in a triangular

grid system creating a waisted cylinder, i.e. a cylinder that becomes more slender towards mid span. The ingenious configuration of this hyperbolic paraboloid enables the structure to curve spatially towards the middle but nevertheless be constructed using only straight steel bars and flat glass panes. The truss elegantly conceals the small difference in height from Marks and Spencer down to the Arndale Centre and the slight lateral misalignment of the entry points to the two buildings. THE STEEL STRUCTURE

consists of bars of S 355 steel with a maximum length

of ~12 m and 114.3 mm in diameter, directly welded together in a triangular grid. The cylinder is stiffened by two compression rings at the entry points into the buildings and four expanding rings at approximately the fifth points. The glass panels are fitted to the frame with tilt and turn cardan joints and sealed with permanently elastic silicone. THE PEDESTRIAN DECK

consists of wooden planking on slender I-girders

which transfer their load to the rings mentioned above. The lighting and heating are installed below the deck. There are glass balustrades with stainless steel handrails. Natural ventilation was considered sufficient because of the short span.

Fig. 5.4.3a A “waisted” cylinder connects Marks and Spencer with the Arndale Shopping Centre in Manchester. Fig. 5.4.3b Downhill through the cylinder to the Arndale Centre, shoppers fill the skywalk.

5.4.3

Manchester: spatial truss tube connecting retail store and shopping centre

View




Plan

  

Cross section

  

Fig. 5.4.3c View, plan and cross section.

165

5

Enclosed skywalks

166

5.4.4 Berlin-Tempelhof, Germany: skywalk as a cylindrical spatial truss

Client: City of Berlin; Senate Administration for City Development Planning: Betz Architekten Planungsgesellschaft mbH, München Structural planning: IPP Prof. Polónyi + Partner GmbH, Cologne Steel construction: E. Rüter GmbH, Dortmund

(no longer in operation)

LOCATION

Two parallel office blocks belonging to the State Office of Criminal

Investigation in Berlin-Tempelhof were connected at the fourth and fifth floors by a glazed bridge over a courtyard. The structural planners had originally presented ten different proposals in the form of sketches. The design finally chosen was a cylindrical spatial truss supported on bearings at the buildings at each end and in the middle by two crossed cables. These were to be anchored through the massive attics to the roof slabs of reinforced concrete of the buildings at each side. The span length was to be 40 m with an effective width of 1.24 m between the wooden handrails. STEEL SUPERSTRUCTURE

The cylindrical spatial truss consists of eight longi-

tudinal hollow round sections connected by 19 circular frames at intervals of 2 m. The cross section of the circular frames consists of rolled IPE 120 plus round steel bar. The load bearing capacity of the truss is created by coiled octagonal counterbracing attached to the inside of the circular frames. The coils were originally planned as wire cables running along the length of the bridge is a trough made of steel plate with a suitable floor

and clamped to the frames; this plan was rejected in favour of round steel

THE PEDESTRIAN DECK

coils, 15 mm ø, because they were easier to connect. Instead of the original

covering and under floor heating. There is a cable conduit between the deck

cable stays, it was also decided to stay the bridge with 50 mm ø steel bars

panel and the bottom housing of sheet steel. The entire cylinder of the spatial

because they were easier to anchor and more lastingly protected against cor-

truss is covered in stretched Makrolon, fixed from the inside at the sides of the

rosion. The four bar stays are each fixed to a gusset plate beneath the middle

cylinder and below the deck. At the top of the cylinder the Makrolon is fixed

circular frame.

from the outside, with an overlap to form air vents. These are covered with

BEARINGS

The bridge is supported on longitudinally sliding bearings at each

perforated plates of stainless steel to prevent access by insects.

end. The two lower hollow round girders are guided in sleeves in a steel frame.

The bridge was prefabricated in two sections and glazed. The two sections

The angled hangers ensure that the bridge remains horizontal in the longitu-

were put together on site and lifted into position in one piece using a 500 t

dinal plane.

crane standing on the road outside the building. After this the stay bars were attached and anchored.

Fig. 5.4.4a Cylindrical skywalk of the Office of Criminal Investigation

in Berlin-Tempelhof at the former Berlin Airport. Fig. 5.4.4b View along interior of bridge.

5.4.4

Berlin-Tempelhof, Germany: skywalk as a cylindrical spatial truss

167

View

Cross section Ventilation

Ventilation Insect filter

Underfloor heating Lighting

Air inlet

Isometry

Fig. 5.4.4c View, cross section and isometry of the skywalk

in Berlin-Tempelhof.

5

Enclosed skywalks

168

5.4.5 Berlin-Tempelhof, Germany: three-storey, cable-stayed enclosed footbridge

Client: City of Berlin, Police Authorities Planning: Betz Architekten Planungsgesellschaft mbH, Munich Structural planning: Stefan Polónyi Structural Engineering, Cologne Construction: E. Rüter GmbH, Dortmund (no longer in operation)

LOCATION

A three-storey bridge was built to connect a building belonging to

the police authorities in the Berlin district of Tempelhof with a new facility on the other side of the “Bayernring”. The bridge is 1.47 m + 8.82 m + 1.47 m = 11.76 m long with an effective width of ~2 m. The buildings on each side had only a limited capacity to take on new loads. THE TWO PYLONS

are positioned outside the pedestrian decks on one side

of the road and are connected with cross beams to form an H-shape. They are rigidly fixed in a concrete base providing protection from traffic impact and stiffened with diagonal bracing under the bottom pedestrian deck. Three main transverse girders of hollow round sectional steel are fitted under the bottom deck: one in the short span and two in the longer span. These are the attachment points for the cable stays extending from the pylons. There are two supports for each deck which stand on wide base plates supported by transverse girders of hollow round section and are at the same time part of the frame for the glazed façade of the bridge. These supports are connected at ceiling level with transverse members supporting the longitudinal girders for the ceiling panels. Horizontal forces are absorbed by the pylons and the façades of the adjacent buildings. THE FAÇADE

of the bridge is a post and beam construction.

Fig. 5.4.5 A three-storey enclosed footbridge connects

new and old police administration buildings in Berlin-Tempelhof.

5.5.1

Kassel, Germany: girder bridge with triangular cross section connecting factory halls

169

5.5 Girder bridges 5.5.1 Kassel, Germany: girder bridge with triangular cross section connecting factory halls Client: Lokator Grundstücks-Vermietungs-GmbH, Düsseldorf, with VAG GbR Architects: RSE Planungsgesellschaft mbH Architects and Engineers, Kassel Steel construction: Stahlbau Lamparter GmbH, Kaufungen Sources: Klaus Idelberger: Geschlossener Verbindungssteg zwischen Werksgebäuden in Kassel. 1994, [53]; Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

Volkswagen AG built a closed utility and pedestrian bridge between

the entry control point for goods and people and the staff canteen at their

THE PORTALS

are built from IPBl 360 cross beams, two IPB 360 columns with

two or three sets of IPB 140 cross bracing – depending on the height of the

parts centre in Kassel-Baunatal. The bridge is characterised by its long length

portal.

(128 m) and its triangular cross section, which is unusual in Germany but often

CORROSION PROTECTION

The entire steel structure was hot-dip galvanised.

found in France, where it is used for bridges connecting motorway restaurants and in Carrefour shopping centres. THE LOAD BEARING SYSTEM

is a girder with separate sections 6 × 6.81 m =

40.86 m; 8 × 6.81 m = 54.48 m; 5 × ~6.60 m = ~33.00 m. Its total width is 4.50 m and total height 5.80 m. The four superstructures rest on abutments in the adjoining factory halls and on two portal and double portal supports. THE STEEL STRUCTURE

consists of triple chord trusses with a truss width

of 4.16 m and a triangular cross section 5.38 m in height. The grid length is generally 6.81 m. The triple chord trusses consist of hollow round section, 508 mm ø × 11 mm in the upper chord and hollow round section, 323 mm ø × 8.8 mm, in the bottom chords. Stiffening and connecting plates, 20 mm in thickness, are inserted through the chords and welded at the points where they connect with transverse girders, posts and struts. The bottom chords are connected with transverse girders of IPB 200 section, longitudinal stiffening is with IPBI 100 and the posts are IPB 180. The struts are of IPB 140 and are fitted with U-shaped rails for the glass panes. The single glazing consists of 2.27 × 1.00 m panes of rear ventilated, laminated safety glass, 10 mm in thickness. THE PEDESTRIAN DECK

has an effective width of 2.22 m between the simple

balustrades with handrails of hollow round section, 70 mm ø and three lower rails of round steel bar, 20 mm ø, welded to angled steel posts, 2 × L 50/6. A grid of I 120 transverse girders and U 260 section steel is fitted onto the main transverse girders (IPB 200) and covered by a deck panel of trapezoidal plate. The surface of the deck is paved with robust concrete slabs.

Fig. 5.5.1a Enclosed skywalk at VW in Kassel-Baunatal. The cross section

changes from round to triangular along the course of the bridge. Fig. 5.5.1b Cross section (portal).

Cross section (portal)

B G UG OG VG VL

Lighting Balustrade Bottom chord Upper chord Glazing Cable conduit

5

Enclosed skywalks

170

5.5.2 Oslo, Norway: truss bridge with a glass tube on steel frames

Client: Aker Eiendom Aktieselskabet (AG), Oslo Architects: Telje-Torp-Aasen Arkitektkontor Aktieselskabet, Oslo Steel construction: Dr.-Ing. A. Aas-Jakobson Aktieselskabet, Oslo Source: Klaus Idelberger: Fußgängersteg als Glasröhre mit Stahlspanten

in Oslo / Norwegen. 1996, [52]

A wealthy investment and real estate management concern built an

120 × 120 mm, placed at intervals of 1.87 m. The pedestrian deck lies on

attractive skywalk over a four-lane road in Oslo. The bridge connects the Town

this grid and is made of steel plate with an asphalt surface containing corund-

LOCATION

Hall with the Åkerbrygge, four landing stages at the passenger ship terminal,

um grit for slip resistance. This trough cross section is surrounded by three-

and provides access to a new leisure centre created in an abandoned dock-

quarter circular frames of 80 × 80 mm square hollow section, 80 × 80 mm,

land area. The bridge has a span length of nearly 30 m and an effective width

holding the acrylic glazing of the footbridge. The final grid sections at each end

of 2.5 m.

are angled to accommodate the access stairways with 16 + 16 stair treads

THE LOAD BEARING SYSTEM

is that of a single span girder on two supports.

THE STEEL SUPERSTRUCTURE

consists of longitudinal trusses with a height

and intermediate landings. BEARINGS

The bridge rests at an average height of 5 m on a pair of cross-

of 2 m and 2.50 m apart. These include chords of square hollow section,

braced pin-ended bearings of square hollow section, 120 × 120 mm, on the

120 × 120 mm, posts of rectangular hollow section, 120 × 60 mm, and

Town Hall side and on a fixed point in the form of a glazed support tower of

diagonals of rectangular hollow section, 120 × 50 mm. The bottom chords

square hollow section, 150 × 150 mm (with 150 × 50 mm cross bracing) in

are connected by a grid of transverse girders of square hollow section,

the direction of the Åkerbrygge ship terminals.

View from above and cross section

Åkerbrygge

Airport

We s

To wn

ts

ha

tat

ion

ll

Fig. 5.5.2a Bridge with angled access stairway at Oslo Town Hall. Fig. 5.5.2b View from above and cross section.

5.5.3

Hannover, Germany: long double-tube skywalk to exhibition centre and Expo

171

5.5.3 Hannover, Germany: long double-tube skywalk to exhibition centre and Expo

Design: Schulitz + Partner Architects BDA, Braunschweig Structural analysis: RFR, Paris Steel and façade construction: Magnus Müller Pinneberg GmbH,

Delmenhorst Source: Helmut C. Schulitz: Der Skywalk in Hannover. 1999, [49]

LOCATION

Deutsche Messe AG built a skywalk to connect the exhibition

STABILISATION

Two expansion joints divide the structure into three sections.

centre with the railway station Hannover Messe / Laatzen. The bridge crosses

Rigidly fixed supports provide longitudinal stiffening in the middle section of

Münchener Straße and is a double tube at an average height of 6 m above

the bridge. The diagonal bars of the stairways stiffen the outer sections of the

ground level. It is 340 m long with a width of 8.75 m to accommodate path-

bridge. Bracing in the axis of each support stiffens the structure in the trans-

ways and accompanying moving walkways in each direction.

verse direction. All supports, with the exception of the middle supports, are on

SPECIFICATIONS:

hinged bearings in cantilever pedestals.

1. Users of the bridge should have an uninterrupted view of the outside sur-

ENTRANCE AND EXIT

roundings. Massive load bearing components therefore had to be avoided at

ways at each side. Elevators are also located at each end of the bridge. There

façade level.

are emergency stairways, 100 m apart, on the south side of the bridge, each

to the skywalk is via two centre escalators with stair-

2. The bridge should intrude as little as possible on upward vision from street

with two flights of stairs, 1.6 m in width. The structure is thereby divided into

level; this is why a rounded oval shape was selected.

three sections in terms of escape paths. The compressive member in the roof

3. The number of bridge supports should also be kept to a minimum to limit the

area enabled the bridge designers to reduce the dimensions of the secondary

effect on road and pedestrian traffic under the bridge.

load bearing system for the façades and to create a dematerialised structure

THE LOAD BEARING SYSTEM

consists of a suspended pedestrian level with

(curved 40 × 50 mm posts, 4.5 m in height and 2 m apart). consists of two panes of laminated safety glass (VSG

spans of 20, 24 and 28 m, as prescribed by local road and access require-

THE GLAZING

ments. The pedestrian level consists of continuous trusses on column supports,

2.00 m × 2.25 m) in each element of the façade. The curved shape of the

providing additional stiffness to the system.

panes also makes them extremely stiff, enabling thinner panes to be used.

Transverse girders between the main trusses support the

They lie on slender façade sections of solid steel and are secured with point-

two moving walkways. The walkways are cantilever extensions at the sides

mounted steel plates. The façade and deck panels form two overlapping cir-

of the main trusses. The torsional moment resulting from asymmetric load is

cles, i.e. a double tube. The ceiling is covered with panels of expanded metal

STEEL STRUCTURE

transferred through the rigid transverse girders into both trusses and through

which can be opened to gain access to the installations in the roof.

bending into the bridge supports. A compressive member in the form of a

CORROSION PROTECTION

All external components of the steel structure were

quadruple chord truss of tubular and rolled section was introduced at roof level

hot-dip galvanised.

to short circuit horizontal forces likely to cause deformation of the supports.

The “Skywalk in Hannover” won first prize in the 6th competition held by the

The roof consists of trapezoidal plate on rolled section.

German Association of Galvanisers in 1999.

Isometry

Fig. 5.5.3a A double tube 8.75 m wide and 340 m long protects visitors to EXPO 2000 and the Hannover Fair. Skywalk between exhibition centre and railway station. Fig. 5.5.3b Isometry of the steel load bearing structure (see also Fig. 5.5.4e).

5

Enclosed skywalks

172

5.5.4 Dresden, Germany: skywalk for passengers at airport

General planner: Planungsgruppe Blees + Kampmann, Munich Steel construction: Metallbau Schubert, Neukirchen-Adorf Source: Mike Schlaich: Footbridge 2008 Conference in Port. 2008, [1]

LOCATION

From 1990 onwards, flights from and to Dresden increased dramat-

Cross section

ically. A new terminal was constructed by converting a factory hall that had originally been planned as a final assembly facility for an East German wide body passenger jet. The plane was never built [1]. This large new terminal was linked to a new multi-storey car park for 1559 vehicles in 2001. The skywalk is an elliptic tube, 85 m in length, with an effective width of nearly 5 m and an outer width of 6.3 m. It crosses the five-lane airport access road with dropand-go parking bays at an average height of 5 m above ground level. The new pedestrian bridge follows the same course as a pedestrian tunnel, which had to be fitted with concrete caps to distribute the load in the areas of the foundations for the bridge supports. THE LOAD BEARING SYSTEM

is a continuous girder over six pairs of rigid

supports. This girder extends 17.11 m into the terminal and there is a cantilever section, 6.73 m long, leading to the car park at the other end. The bridge supports are positioned at intervals of 17.11 + 8.92 + 14.02 + 12.75 + 12.75 + 12.75 + 6.73 m = 85.03 m. THE SUPERSTRUCTURE

of the skywalk consists of two lateral main trusses

in the form of welded rigid frames (Vierendeel) with a height of 900 mm, constructed from a 15 mm thick web plate with rounded openings and two 20 mm thick flange plates, both of S 355. These longitudinal trusses are a constant 2.55 m apart and coupled by 6 + 27 transverse girders of IPE 200 sectional steel or HEB 200 in S 235 (RSt 37-3). This girder grid is stabilised in the horizontal plane by steel cross bars, 10 mm ø, at the bottom chord level of the main trusses. The bridge is supported on five pairs of rigid supports with hammerhead capitals or in portal form. Capitals, columns and cross beams are of wide flange section, HEB 260, in RSt 37-2. Some are surrounded by reinforced concrete as protection against traffic collision impact. The entire steel structure is hot-dip galvanised for optimum surface protection.

Fig. 5.5.4a The strictly horizontal line of the skywalk in Dresden

penetrates the perpendicular of the façade of the new airport terminal. (Photo: Friedrich Weimer, Dresden) Fig. 5.5.4b Cross section.

5.5.4

Dresden, Germany: skywalk for passengers at airport

Longitudinal section

Plan

THE TUBE OF THE FOOTBRIDGE

as a climatic chamber with natural draught

ventilation consists of 27 arched frames 2.55 m apart and constructed of hollow square section 76.1 × 76.1 × 3.2 mm. The frames are bent to a ¾ ellipse with a radius of 4.56 m at the crown and 2.40 m at the sides. They are protected by a multiple surface coating. The glazing is of shaded glass, VSG 2 × 8 mm, with an intermediate PVB foil, 0.76 mm in thickness and with a G-value of ~0.42. The floor is of ribbed trapezoidal plate, 25 mm high, with a pedestrian surface of stoneware tiles. THE EXPANSION JOINTS

at each end of the bridge are covered with sliding

plates. THE SKYWALK

173

in Dresden is similar to the skywalk in Hannover and a bridge

in the London Docklands (see sections 5.3.3 and 5.5.3).

Isometry

Fig. 5.5.4c Longitudinal section and plan. Fig. 5.5.4d A glass tube connects an airport terminal with

a multi-storey car park in Dresden. See also title photo on page 141. (Photo: Friedrich Weimer, Dresden) Fig. 5.5.e Isometry of load bearing structure.

5

Enclosed skywalks

174

5.5.5 Hildesheim, Germany: truss bridge over Speicher Straße

Client: District of Hildesheim Architects: Bahlo, Köhnke, Stosberg and Partner, Hannover Steel construction, structural analysis: Dipl.-Ing. Dietrich Hilse,

Hildesheim

LOCATION

In 1987, a bridge was built to connect the old headquarters of

the district administration in Hildesheim to a new office building. The bridge crosses Speicher Straße and a parking area. It has a span length of 20.5 m, an inner width of 2.88 m and is built with a 1.26 % gradient towards the new building. There is one intermediate bridge support followed by a secondary span 4.3 m + 0.7 m = 5 m in length. THE LOAD BEARING SYSTEM

of this symmetric bridge is a single span girder

on two abutments in the form of brackets in the adjacent buildings. The trough bridge is supported at the upper chords of the main trusses. The trusses are on the outside of the bridge and contain an inner pedestrian “tube”. A pair of rigid frame trusses (Vierendeel) would have been more expensive here. THE STEEL SUPERSTRUCTURE

has connection joints at the third points and

consists of two upper chords of IPE 240, two bottom chords each with two tension bars, Besista M 20, 2 × 11 posts of IPE 180, 2 × 11 diagonals and bracing using two tension bars, 40 mm in diameter. A SEPARATE PEDESTRIAN TUBE

was fitted between the trusses in the form

of a post and beam structure with insulated glazing of laminated safety glass, 8 mm + 12 mm air space + 8 mm. A wooden handrail protects the glass. The structure has a multiple surface coating for corrosion protection.

Fig. 5.5.5a An enclosed pedestrian bridge connects the old and

new headquarters of the district administration in Hildesheim. Fig. 5.5.5b Main truss.

5.5.5

Hildesheim, Germany: truss bridge over Speicher Straße

View

Plan

Fig. 5.5.5c View and plan.

175

5

Enclosed skywalks

176

5.5.6 Metzingen, Germany: girder bridge with perforated web girders

Client: Town Administration of Metzingen Steel construction: Stahlbau Süssen GmbH, Süssen Glazing: Adolf Merkh Metallbau GmbH, Pfullingen

Cross section

HISTORY

Metzingen’s prosperity is based on the cultivation of fruit and cab-

bage. The 13th century fruit presses and the “old town hall”, built by Duke Christoph von Württemberg as a job creation plan in 1562 / 63 are the pride of the town. The old town hall was burnt to the ground in 1643 during the Thirty Years War and rebuilt in 1668. It was replaced by a new historicised town hall in around 1913. This is now the “old town hall” and was connected to a wing of the “new town hall” by an enclosed pedestrian bridge through which brides and grooms can proceed to the hall of marriage, whatever the weather. THE LOAD BEARING SYSTEM

of this deck bridge is that of a slightly inclined

single-span girder on an abutment in the new building and a supporting portal frame, continuing as a short cantilever section to the old building. THE GALVANISED STEEL SUPERSTRUCTURE

consists of a pair of IPE 400 main

girders with perforated webs (for a “light” appearance) connected to a grid of nine IPE 100 transverse girders. These are covered with wooden planks and a PVC floor surface.

Fig. 5.5.6a View, plan and cross section of the “Wedding Walk” connecting old and new town halls. Fig. 5.5.6b Cross section.

5.5.6

Metzingen, Germany: girder bridge with perforated web girders

View

177

Plan

Perforated girder

THE SUPPORTING PORTAL FRAME

consists of pin-ended columns with hinged

attachment to the main bridge. The portal columns are of HEA 140 and rigidly welded to a cross beam of IPE 270 sectional steel. THE PEDESTRIAN TUBE

is an aluminium post and beam structure consisting

of nine two-hinged frames glazed with insulated laminated safety glass. Separate ventilation and heating were unnecessary and a simple handrail was also considered adequate protection for users. There is a similar bridge with perforated-web main girders in Sulz am Neckar (Section 5.5.7).

Fig. 5.5.6c View and plan of the “Wedding Walk” in Metzingen. Fig. 5.5.6d View through bridge towards new town hall.

5

Enclosed skywalks

178

5.5.7 Sulz am Neckar, Germany: girder bridge with perforated web girders connecting school buildings

Client: Town Administration of Sulz am Neckar Architects, photos: Riehle + Partner, Reutlingen Structural analysis: Plocher Engineering, Sulz am Neckar Steel construction: Walter Kübler, Sulz am Neckar Source: Geschlossene Fußwegbrücken. 2002, [54]

LOCATION

An enclosed footbridge was built to connect a new facility with the

original building of a secondary school in Sulz am Neckar in 1997. The walkway is supported on two columns and is an effective architectural symbol of the connection between old and new. Its light and transparent structure unites the interior of the buildings with the outdoor recreational areas. The bridge is 20 m long and 2.75 m wide. THE LOAD BEARING SYSTEM

of the box bridge is that of a girder on two rigidly

fixed columns, in this case a single-span girder with cantilever sections at each end. THE STEEL SUPERSTRUCTURE

consists of a pair of IPE 550 main girders with

perforated webs and an I 120 longitudinal girder in the axis of the bridge, which is stiffened and secured against tilting with horizontal bracing. TWO RIGIDLY FIXED COLUMNS

of hollow round section, 324 mm in diameter,

with hammerhead capitals, transfer the loads. THE PEDESTRIAN PASSAGE

is a row of two-hinged frames each consisting of

two U 120 steel sections placed back to back and secured by vertical bracing and rods of hollow round section, 40 mm in diameter, at the top corners. A similar bridge with perforated web girders is described in Section 5.5.6. The glazing is laminated safety glass and is fixed to the frame with point mounting of stainless steel. The glazing is fitted on the inside of the frame up to hand-

Fig. 5.5.7a Pupils and teachers at the secondary school in Sulz am Neckar can cross from one building to the next without getting their feet wet. Fig. 5.5.7b Connection of the two-hinge frame of the box with horizontal bracing.

5.5.7

Sulz am Neckar, Germany: girder bridge with perforated web girders connecting school buildings

179

Longitudinal section

Connection with new building

rail level and outside the frame from there to roof level, creating an aperture for ventilation. The ridge of the roof is covered with angled steel section with lateral perforation, serving as ventilation in the summer months and also carrying the light fittings for the passage. The floor is covered with untreated oak planks, 60 mm in thickness, in prefabricated sections laid in the transverse direction. CORROSION PROTECTION

The steel structure was hot-dip galvanised and

therefore received the most durable and, for this reason, most economical surface protection available. THE STRUCTURE

was entered for the 5th competition held by the German

Association of Galvanisers in 1997 and was highly commended by the jury.

Fig. 5.5.7c Longitudinal section.

Connection with old building

5

Enclosed skywalks

180

5.5.8 Leukerbad, Switzerland: a glazed truss bridge for a school centre

Client: Town of Leukerbad, Switzerland Architect: Arnold + Alwin Meichtry, Leukerbad and Susten,

Switzerland

LOCATION

The towns of Leuk and Leukerbad lie in the Rhône valley not far

from Brieg in a branch of the Dala valley. Leukerbad has been a spa since Roman times. The town administration built two new spas, a tennis hall, sports hall and school centre on a confined sloping site, connecting the school and sports hall with an enclosed pedestrian bridge over a wild water tributary of the River Dala. The attractive bridge is approx. 17.5 m long with an outer width of 3.1 m and an inner width of 1.75 m. It is partly hot-dip galvanised. The truss is painted white; the bottom chords and supports are bright red. THE LOAD BEARING SYSTEM

is that of a single-span girder in the form of a

truss continuing as short cantilever sections beyond the two supports. The truss rests on transversely sliding bearings on two rigidly fixed support portals with reinforced concrete pedestals and is guided with “forks” in each of the two adjacent buildings. THE STEEL SUPERSTRUCTURE

consists of two trusses, 3.1 m apart, connec-

ted at the upper chord by 10 and at the bottom chord by 11 transverse posts, forming a tubular structure. The trusses, chords, diagonals, transverse posts and the support portals are all of square hollow section, 180 × 180 × 5 mm. The bracing in the upper chord is of rectangular hollow section, 160 × 80 × 4 mm, like the cross bracing at bottom chord level which consists of ½ + 4 + ½ crosses. THE PEDESTRIAN TUBE

has a rectangular cross section which rounds to an

arch at the top. It is 3.05 m high and 1.85 m wide. It is a post and beam structure with arched ribs of hollow rectangular sectional steel, 80 × 40 mm, holding panes of acrylic glass mounted with aluminium rails. The deck panel is a hot-dip galvanised trapezoidal plate covered with a plywood base for the rubber floor surface. The sides of the tube are secured by robust handrails of folded steel sheet. Heating was not considered necessary because the bridge is only 18 m long and the buildings at each end are both well heated in the winter.

Fig. 5.5.8a The trusses enclose the glazed pedestrian tube. Fig. 5.5.8b An enclosed pedestrian bridge crosses a channelised,

but at times untamed stream in Leukerbad in the Rhône valley.

5.5.8

Leukerbad, Switzerland: a glazed truss bridge for a school centre

181

View

Cross section

S1

S2

1,85 m 3,00 m

3,50 m

10,50 m 17,50 m

View from below

Untersicht

Fig. 5.5.8c View, view from below and cross section.

3,50 m

182

Sources and further literature

Over the decades the author has collected extensive documentation and

[ 21 ] Bögle, A., Cachola Schmal, P., Flagge, I. (Hrsg.): leicht weit – Light

illustrations of footbridges from clients, designers and planners all over the

Structures: Jörg Schlaich – Rudolf Bergermann. München: Prestel Verlag,

world. He has also gathered some information from publications. The photo-

2005.

graphs were taken by the author himself except in cases where a different

[ 22 ] Göppert, K., Kratz, A., Pfoser, Ph.: Entwurf und Konstruktion einer

photographer or publication is named as the source. Both the author and the

S-förmigen Fußgängerbrücke in Bochum. Stahlbau 74 (2005), Heft 2,

publisher have made every effort to identify and name all originators. Please

S.126 –133.

inform us if any have been overlooked.

[ 23 ] Moix, L.: Passerelle sur le Rhône – Ouvrage d’art. Journal de la Construction 72 (1998) 7, 15 Juillet, p. 9 –13.

[ 1 ] Schlaich, M.: Footbridge 2008 Conference in Port. Steel Construction 1

[ 24 ] Pahl, G.: Die neue Rosenaubrücke über die Iller in Kempten. Stahlbau

(2008), No.1, pp. 87– 89.

Nachrichten, Dez. 2007, S.18 – 21.

[ 2 ] Baus, U., Schlaich, M.: Fußgängerbrücken – Konstruktion, Gestalt,

[ 25 ] Idelberger, K.: Offener Steg als Museumszugang bei Kyoto.

Geschichte. Mit Fotografien von Wilfried Dechau. Basel, Boston, Berlin:

Stahlbau 70 (2001), Heft 4, S. 296 – 298.

Birkhäuser Verlag, 2007.

[ 26 ] Agirbas, E., Wienstroer, E., Wilde-Schröter, T.: Neulandbrücke

[ 3 ] Schlaich, M. et al.: Guidelines for the design of footbridges. (Entwurfs-

Leverkusen. Stahlbau 74 (2005), Heft 5, S. 379 – 382.

richtlinien für Fußwegbrücken). fib Fédération Internationale du Beton,

[ 27 ] Slessor, C.: Royal Victoria Dock-Bridge – Transporter of Delight.

Bulletin 32. Lausanne, 2005.

The Architectural Review, May 1999, p. 72 – 74.

[ 4 ] Keil, A.: The design of curved cable-supported footbridges. Second

[ 28 ] See, S.-T., Sesil, D. A.: The Museum Bridge. STRUCTURE, Winter 98,

International Footbridge Conference, Venice, 2005.

pp.19 – 23.

[ 5 ] DIN-Fachbericht 101 Ausgabe März 2003. Einwirkungen auf Brücken.

[ 29 ] Krone, M., Reinke, K.-D.: Neubau des Kaiserstegs über die Spree

Berlin: Beuth-Verlag, 2003.

in Berlin. Stahlbau 77 (2008), Heft 3, S.1–12.

[ 6 ] Bijlaard, B.: Eurocode 3: Design of steel structures – Present status and

[ 30 ] Schierer, G., Schwaab, K.: Markanter Übergang: Die Fuß- und

further developenments. Steel Construction 1 (2008) No.1, pp.16 – 23.

Radwegbrücke in Cham. [Umrisse], Zeitschrift für Baukultur, Heft 3 / 2002,

[ 7 ] Ewert, S.: Brücken. Die Entwicklung der Spannweiten und Systeme.

S. 24 – 25.

Berlin: Ernst & Sohn, 2003.

[ 31 ] Jöllenbeck, M., Wolf, A.: Vier Bauwerke im Kontext: Die „Brücken-

[ 8 ] Dietrich, R. J.: Faszination Brücken – Baukunst, Technik, Geschichte.

familie“ in Walldorf. [Umrisse], Zeitschrift für Baukultur Heft 4 / 2007,

2., erw. Aufl., München: Callwey-Verlag, 2001 (ca. 100 Bauobjekte).

S. 28 – 31.

[ 9 ] Standfuss, F., Naumann, J.: Brücken in Deutschland – für Straßen und

[ 32 ] Neuner, F., Hemmerlein, H.: Fußgängerbrücke mit Aussichtsplattform

Wege. Köln: Dt. Bundes-Verlag / Bundesanzeiger-Verlag, 2006 (Band I), 2007

an der Rodach. Stahlbau 73 (2004), Heft 5, S. 311 – 316.

(Band II), (jeweils 75 Bauobjekte).

[ 33 ] Andrä, H.-P., Burghagen, K., Häberle, U., Svensson, N.: Geh- und Rad-

[ 10 ] Ouvrages Metalliques. Bulletin No. 5 / 2008. OTUA Office Technique

wegbrücke Weil der Stadt. Bauingenieur 82 (2007), S. 341– 345.

pour l’Utilisation de l’Acier, Paris, www.otua.org.

[ 34 ] Andrä, H.-P., Häberle, U.: Am Übergang von Tal und Ort.

[ 11 ] Stahlbrücken. Referenzliste. Stahlbau-Zentrum Schweiz SZS, Zürich.

[Umrisse], Zeitschrift für Baukultur Heft 4 / 2007, S.42 – 45.

[ 12 ] steel doc 2008. Bautendokumentation Stahlbau-Zentrum Schweiz, SZS,

[ 35 ] Mangerig, I., Zapfe, C.: Bewertung des Schwingungsverhaltens

Zürich.

und der Dämpfungseigenschaften der Fußgängerbrücke Gustav-Heinemann-

[ 13 ] Brücken aus Stahl. International Iron and Steel Institute, Brüssel, 1997,

Steg über die Spree in Berlin. München 2006. Gutachterliche Stellungnahme,

Broschüre E 6.

unveröffentlicht.

[ 14 ] Architektur von Stahlbrücken – weltweit. Stahlinformations-Zentrum,

[ 36 ] Zimmer, E.-M., Mündecke, M.: Die Gustav-Heinemann-Brücke

Düsseldorf, Dokumentation 538.

über die Spree im neuen Zentrum Berlins. Stahlbau 75 (2006) Heft 8,

[ 15 ] Idelberger, K., Feige, A.: Fußwegbrücken – 60 Beispiele aus aller Welt.

S. 624 – 632.

4. Aufl., Stahlberatungsstelle Düsseldorf, 1980, Stahl-Merkblatt 443.

[ 37 ] Wörzberger, R.: Begehbare Skulptur zur Erbauung. Die Drachenbrücke

[ 16 ] Graf, B.: Brücken, die die Welt verbinden. München: Prestel Verlag,

in Recklinghausen. [Umrisse], Zeitschrift für Baukultur, Heft 3 / 2008,

2002.

S. 36 – 40.

[ 17 ] Lastfall Fußvolk. deutsche bauzeitung db Nr. 6 / 2001, S.105 – 112.

[ 38 ] Polónyi, St., Walochnik, W.: Die Fußgängerbrücken der BUGA '97.

[ 18 ] Pflisterer, H., Streit, W., Hanrieder, Th.: Rad- und Geh-Wegbrücke über

Bautechnik 74 (1997), Heft 4, S. 215 – 226.

die Iller und die B 19 Neu bei Immenstadt. [Umrisse], Zeitschrift für Baukultur,

[ 39 ] Strobl, W., Kovacs, I., Andrä, H.-P., Häberle, U.: Eine Fußgängerbrücke

Heft 6 / 2006, S. 36 – 43.

mit einer Spannweite von 230 m. Stahlbau 76 (2007), Heft 12, S. 869 – 879.

[ 19 ] Das Rohrbiegewerk der Mannesmannröhren-Werke in Mülheim GmbH.

[ 40 ] Strobl, W.: Geh- und Radwegbrücke zwischen Weil und Huningue.

STIL, Magazin der Salzgitter AG, Nr. 4 / 2007.

Stahlbau-Nachrichten, Heft 1 / 2006, S.11–13.

[ 20 ] Fußgängerbrücke im Innenhafen Duisburg. DETAIL, Heft 8 / 1999,

[ 41 ] Starke Verbindung. Faszination Stahl, Heft 13 / 2007, Stahlinformations-

S.1455 –1457, 1508 (Lighting).

Zentrum, Düsseldorf.

183

[ 42 ] Rooden, C. v., Häberle, U.: Fußverbindung. CH Tec 21, Nr. 41 / 2007, S. 33 – 35. [ 43 ] Elegante Bögen – Filigrane Tragwerke: MSH-Profile im progressiven Brückenbau – Fußgängerbrücke Weil am Rhein. Villeroy & Mannesmann Report Nr. 20, Dezember 2007 (Folge 2). [ 44 ] Stadt Weil am Rhein (Hrsg.): Brücken verbinden – Des Ponts qui unissent. Mit Ville de Huningue / Communauté de Communes des Trois Frontières (CC3F); Eine Dokumentation der Geschichte der Rheinübergänge zwischen Weil & Hüningen. Une documentation de l’histoire de les traversees du Rhin entre Weil & Huningue. Exhibition, 2007. [ 45 ] Polónyi, St.: Begehbarer Raum. Die Tiergartenbrücke über die Mulde in Dessau. [Umrisse], Zeitschrift für Baukultur, Heft 3 / 2002, S. 22 – 23. [ 46 ] Walochnik, W.: Tragendes Stahlrohr – Rohrkunst? Baukultur 1995 / 5, S. 21– 24 und 1997 / 5, S.12 – 15. [ 47 ] Bucak, Ö.: Brücke über die Bayerstraße München. V & M REPORT Nr.15, S. 20 – 23, Vallourec-Mannesmann, 2005. [ 48 ] Ackermann, Ch.: Brückenbauen mit neuen Werkstoffen: Die Fußgängerbrücke über die Bayerstraße in München. Stahlbau 74 (2005), Heft 10, S. 729 – 734. [ 49 ] Schulitz, H. C.: Der Skywalk in Hannover. Bauwelt Heft 8 / 1999, S. 378 – 381. [ 50 ] Idelberger, K.: Fußwegbrücke in Bielefeld. Stahlbau 61 (1992), Heft 3, S. 83 – 84. [ 51 ] Joseph, L. mit Idelberger, K. (Übersetzung): Das Petronas Büroturmpaar in Kuala Lumpur. Unpublished. [ 52 ] Idelberger, K.: Fußgängersteg als Glasröhre mit Stahlspanten in Oslo / Norwegen. Stahlbau 65 (1996), Heft 11, S. 436. [ 53 ] Idelberger, K.: Geschlossener Verbindungssteg zwischen Werksgebäuden in Kassel. Stahlbau 63 (1994), Heft 1, S. 27– 28. [ 54 ] Geschlossene Fußwegbrücken. Feuerverzinken 4/2002 Produktblatt. [ 55 ] Idelberger, K.: Stege nach Maß für jede Spannweite, jeden Zweck. Private press. [ 56 ] Hong; L. P.: Bridges in Singapore. Private press. [ 57 ] Wehrle, J.: Neulandbrücke in Leverkusen. Höchste Präzision in der Fertigung. Stahlbau-Nachrichten 2 / 2005, S. 20 – 21. [ 58 ] Kontakte. Company Newsletter Seppeler Holding, 16 (2007) Nr. 2. [ 59 ] Kontakte. Company Newsletter Seppeler Holding, 17 (2008).