December 2016
TheStructuralEngineer
Volume 94 | Issue 12
The flagship publication of The Institution of Structural Engineers
ETIHAD STADIUM EXPANSION PART BACKPROPPING OF FLAT SLABS POSTLOSS REVIEWS PROFILE: VICTORIA JANSSENS BAMBOO DESIGN VALUES
ENGINEERING CLARITY
Structural glass design and the journey towards tow ards purity of expression
www.thestructuralengineer.org
Contents
PAGE STRUCTURAL STRUCTURAL AWARDS
TheStructuralEngineer December 2016
PAGE ETIHAD STADIUM EXPANSION
3
PAGE PROFILE: PROFILE: VICTORIA JANSSENS
TheStructuralEngineer Volume 94 | Issue 12
Upfront
Features
Opinion
5
Editorial
14
47
Profile: Victoria Janssens
6
Institution news: The world world of the structural structural engineer
Viewpoint: Structural technician – rev C
Institution Instituti on news: Structural Awards 2016
Project focus
50
8
52
Book review: The BIM Manager’s Handbook
10
Institution Instituti on news:
24
53
Book review: Designing Tall Buildings
Institution Instituti on transfer list: 7 November 2016
Two more titles released in Essential Knowledge
54
Verulam
Milne Medal Lecture: Engineering clarity
Expansion of the Etihad Stadium, Manchester. Part 2: Construction
Professional guidance
Series 12
Institution Instituti on news:
Institution to offer specialist diplomas in offshore and seismic engineering
Enter the Excellence in Structura Structurall Engineering Education Award 2017
Poster prizes awarded for Undergraduate Research Grant Scheme
Research Award winner reports on CL CLT T research
Research Panel sets new themes and topics
32
Enginee r’s Guide to PI Claims. Part 11: Post-loss Engineer’s reviews and lessons learned
34
Managing Health & Safety Risks No. 57: Hazards from ground movement
36
Confidential Reporting on Structural Safety (CROSS)
Technical 38
Temporary Works Toolkit. Toolkit. Part 4: An introduction to backpropping of flat slabs
42
Structural use of bamboo. Part 3: Design values
At the back back 58
Diary dates
60
Spotlight on Structures
61
And finally…
62
Products & Services
64
Services Directory
65 TheStructuralEngineerJobs
Front cover: Apple cover: Apple IFC, Shanghai / Eckersley O’Callaghan The Structural Engineer PESIDENT Alan Crossman CEng, FIStructE, FICE, MCIWEM CHIEF EXECUTIVE Martin Powell EDITOIAL HEAD OF PUBLISHING Lee Baldwin MANAGING EDITOR Robin Jones t: +44 (0) 20 7201 9822 e:
[email protected] [email protected] g EDITOIAL ASSISTANT Ian Farmer t: +44 (0) 20 7201 9121 e: ian.farmer@istruc
[email protected] te.org
www.thestructuralengineer. www.thes tructuralengineer.org org ADVETISING
EDITOIAL ADVISOY GOUP
DISPLAY SALES Jemma Denn t: +44 (0) 20 7880 6206 e:
[email protected] [email protected] o.uk
Will Arnold MIStructE Allan Mann FIStructE Don McQuillan FIStructE McQuillan FIStructE Chris O’Regan FIStructE O’Regan FIStructE Angus Palmer MIStructE Simon Pitchers MIStructE
ECUITMENT SALES Paul Wade t: +44 (0) 20 7880 6212 e:
[email protected] DESIGN SENIO DESIGNE Andrew Stanford
Price (2017 subscription) Institutional: £410 (incl. e-archive, p&p and VAT) Personal: £125 (incl. p&p) Personal (Student Member): £40 (incl. p&p) Single copies: £35 (incl. p&p)
PODUCTION PODUCTION EXECUTIVE achel Young
Printed by Warners Midlands plc The Maltings, Manor Lane Bourne, Lincolnshire PE10 9PH United Kingdom
© The Institution of Structural Engineers. All non-member authors are required to sign the Institution’s ‘Licence to publish’ form. Authors who are members of the Institution meet our requirements under the Institution’s egulation 10.2 and therefore do not need to sign the ‘Licence to publish’ form. Copyright for the layout and design of articles resides with the Institution while the copyright of the material remains with the author(s). All material published in The Structural Engineer carries carries the copyright of the Institution, but the intellectual rights of the authors are acknowledged. The Institution of Structural Engineers International HQ 47–58 Bastwick Street London EC1V 3PS United Kingdom t: +44 (0)20 7235 4535 e:
[email protected] The Institution of Structural Engineers Incorporated by oyal Charter Charity egistered in England and Wales number 233392 and in Scotland number SC038263
Presidential Inaugural Address 2017 Ian Firth BSc MSc DIC CEng FREng FIStructE FICE FConsE on nssE sE on Support The Institution of Structural Engineers rs in rs in welcoming Ian Firth as our 97th President at o our our ou ur prestigious Presidential Inauguration. Date
Thursday 12 January 2016
Time
17:30 for 18:00 start
Venue
The Institution of Structural Engineers rs rs International HQ 47-58 Bastwick Street London EC1V 3PS
Price
Free Annual
recognised as one of the world’s leading bridge designers.
Institution Events
www.thestructuralengineer.org
Upfront
TheStructuralEngineer
Editorial
December 2016
5
Upfront An A n “award-wi winn nnin ing g” is issu sue e Robin Jones Jones Managing Editor
As 2016 draws to a close, we can reflect on what has been a tumultuous year, notable for the Brexit vote in the UK and Donald Trump’s Trump ’s recent victory in the US presidential election. It remains to be seen what the economic consequences of these events will be, but the Brexit vote continues to fire up many members with a dislike of the Eurocodes (page 54). 54). This month’ month’s s letters to Verulam do, however,, also include some more measured views. however At the Institution, the end of the t he year means, of course, the Structural Awards, which were held on 11 November in London. Back in February, President Alan Crossman mused on the “art of the possible” in his inaugural address, and there can be no better epithet for this year’s winning projects. Congratulations to all who received an award and, above all, to Fast + Epp for their achievement in winning the Supreme Award for Structural
Medal Lecture, James O’Callaghan of Eckersley O’Callaghan takes readers on a journey through his career in structural glass design and the evolution of this material (page 14). 14). We’ve We’v e already completed one series of articles arti cles this year (the Conservation compendium ended in June) and December sees the Engineer’s Guide to PI Claims draw to a close with a look at post-loss reviews and the lessons engineers can learn from claims made against them (page 32). 32). I’d like to thank t hank Griffi Gri ffiths & Armour Ar mour for another excellent series. Don’t forget that you can find both these series and many others – including includi ng the Institution’s Technical Guidance Notes – on our new series webpage at www.istructe.org/ tsemaster/article-series.. tsemaster/article-series Another of these series is the Temporary Works Toolkit , which continues in Technical this month with the first of a two-part article
Engineering Excellence for the Grandview Heights Aquatic Center in Canada. You can read about all the winning projects on page 8, 8, but we’re particularly pleased to feature one of them in Project focus (page 24).. This month’s article completes the description of Manchester’s 24) Etihad Stadium expansion – which won the Award for Sports or Leisure Structures. Authors from Severfield and Laing Lai ng O’Rourke describe the construction challenges, particularly relating to the temporary works required for erection of the new roof. Our Feature this month is also by a former winner of the Institution’s Supreme Supreme Award. In a paper based on his 2016 2 016 Milne
discussing backpropping of flat slabs (page 38). 38). We also feature the latest article in our mini-series on structural use of bamboo: part 3 gives design values for this material (page 42). 42). In Opinion, we profile globetrotting Irish engineer Victoria Janssens (page 47) and 47) and structural technician Balazs Trojak opines on the future of his profession (page 50). 50). At the back, we have our regular Diary dates (page 58), 58), Spotlight on Structures (page 60) and 60) and And finally… (page 61) sections. 61) sections. And that just leaves me to wish all readers season’s greetings and the very best for the New Year. Until January… when we plan to bring you yet another new series!
The Structural Engineer provides structural engineers and related professionals worldwide with technical information on practice, design, development, education and training associated with the profession of structural engineering, and offers a forum for discussion on these matters promotes the learned society role of the Institution by publishing peer-reviewed content which advances the science and art of structural engineering provides members and non-members worldwide with Institution and industry related news provides a medium for relevant advertising
The Institution has over 27 000 members in over 100 countries around the world is the only qualifying body in the world concerned solely with the theory and practice of structural engineering through its Chartered members is an internationally recognised source of expertise and information concerning all issues that involve structural engineering and public safety within the built environment supports and protects the profession of structural engineering by upholding professional standards and to act as an international voice on behalf of structural engineers
The Structural Engineer (ISSN (ISSN 1466-5123) is published by IStructE Ltd, a wholly owned subsidiary of The Institution of Structural Engineers. It is available both in print and online.
Contributions published in The Structural Engineer are published on the understanding that the author/s is/are solely responsible for the statements made, for the opinions expressed and/or for the accuracy of the contents. Publication does not imply that any statement or opinion expressed by the author/s reflects the views of the Institution of Structural Engineers’ Board; Council; committees; members or employees. No liability is accepted by such persons or by the Institution for any loss or damage, whether caused through reliance on any statement, opinion or omission (textual or otherwise) in The Structural Engineer , or otherwise.
6
TheStructuralEngineer December 2016
Upfront Institution news
The world of the structural engineer Martin Powell Chief Executive The Institution of Structural Engineers
“But the world of the structural engineer cannot be thus defined – it would vary with each individual, and they vary widely, as a glance at this audience au dience will show. sh ow. The structural engine engineer er can ca n only be an abstraction, a figment of the imagination im agination.” .” Ove Arup Maitland Lecture, 1969
as they commence their journey towards chartered professional membership. Two well-subscribed well-subscrib ed events brimming with the vibrancy of learning from the experiences of experienced professionals and with the excitement that this Institution is benefiting from the engagement of a new generation of engineers, having witnessed two consecutive years of 9% growth in Graduate membership.
Learning from the past In my regular quarterly articles for The Structural Engineer , much emphasis is always placed on highlighting some of the Institution’s recent achievements and
working hard to embrace the changing needs of a diverse membership and yet, at the same time, pausing to reflect whether the basic needs of professional structural
Shortly afterwards I had the pleasure of a private viewing at London’s Victoria & Albert Museum of an inspirational retrospective exhibition on the life and
pending plans. With over 27 000 members and many others who are interested in our activities, the Institution’s Trustee Board and staff are constantly mindful of finding ways to improve communications, whether it be with those who are actively engaged with its activities around the world or those who prefer a more passive association. The rise of social media and digital communications in recent years has seen a remarkable increase in numbers interacting with us, although we know for many, the printed word is still the preferred medium. Perhaps more than ever before in the history of the Institution, these different channels of outreach are providing members with more options to personalise the nature of the relationship they wish to have with their professional body. With this in mind, and perhaps appropriately for an end-of-year article, my focus this month is more reflective than promotional. promotion al. Reflective on an Institution
engineers have in fact altered much at all!
work of Ove Arup, which attracted nearly 70 000 people during its showing. Arup delivered the Institution’s Maitland Lecture in 1969 and it is recorded in The Structural Engineer 1 (available online to Institution members). I commend it to you, for it articulates issues and challenges of the day that remain equally relevan relevantt to those facing the profession and to the structural engineer in the current era – the role of the structural engineer and their collaborative engagement in multidisciplinary teams; new technological demands; off-site construction and the challenges of repetition and mass production; design deficiencies; a modern movement and the interest of young people in new ideas; the creative engineer; system engineering and the role of the engineer in society. There may be changes in the nuance, but nevertheless there is a tremendous resemblance resemblanc e in that today’s senior and junior e ngineers share sha re many simil ar
Passing on experience Recently we held a joint event with the Royal Institute of British Architects (RIBA), with some 400 in attendance learning about the world’s offi cially sle nderest tall tower – the British Airways i360 observation tower in Brighton on the English south coast. It is the world’s first “vertical cable car” and was designed, engineered, manufactured and promoted by the same team responsible for the London Eye. John Roberts, a former President of this Institution, was heavily involved in both projects and one of the event’s speakers. John is one of our most experienced and senior members, and the parallel I draw is with another event that took place at the same time and just a few miles away at our own Institution HQ. Our building was packed with young Graduate Members meeting up with President Alan Crossman
www.thestructuralengineer.org 7
pressures and issues to those experienced during the late 1960s.
Supporting tomorrow’s engineers At this time of year, the President and I spend a considerab considerable le time personally signing letters and certificates. The number of members celebrating 50 years in membership of their Institution is astonishing – not least because many remain active in support of Institution activities. In parallel, hundreds of new membership certificates have been signed ahead of forthcoming presentation ceremonies. Throughout the Institution world, we are witnessing resurgence in young member groups and, with it, mentoring and support is being freely offered by senior members. And here, I suspect, is one of the key differences between the Institution of 50 years ago and
mentoring and support that was afforded to our senior members when they were in the formative stages of their career. The provision and concept of the modern institution as a “professional home for life” and a place to receive support, encouragement encouragem ent and opportunities for lifelong learning must become enshrined as a fundamental element in our development plans. With it comes an opportunity, beyond the direct products and services offered by the Institution, for senior members to give back to the profes profession sion in support of tomorrow’s engineers. Many already do, and find it richly rewarding. It is the hallmark of a caring professional body.
wish to see improve. We can be delighted at the growth of our graduate cohort and their keenness to become actively involved with their Institution. My thanks, as always, go to the many members who have contributed to the vibrancy of the Institution over the past year in so many ways. If you are one of those whose relationship is currently more at arm’s length, then on behalf of the Board I extend an open invitation to become involved. We have come a long way since Arup delivered his Maitland Lecture in 1969 and, whether the challenges of today are different or similar, there seems little doubt that we will be able to move mountains if we develop in tandem.
An invitation to participate As 2017 approaches, we have a full programme of development activity signed off by the Board – more of which I will
Reference 1
today. The anecdotal evidence today is of increased business pressure making it increasingly increasi ngly diffi cult for our o ur young professionals to receive the employer
report onain my next however, article early year. As reflective, thenext voting statistics for Council and Vice-Presidents continue to be low and represent a level of engagement that the Board would dearly
Arup O. (1969) ‘Maitland Lecture: The world of the structural engineer’, The Structural Engineer , 47 (1), pp. 3–12
Demag double girder V-type crane Following the launch of the Demag single girder V-type crane, we have introduced double girder models to our product range. The double girder V-type crane is available with load capacities of up to 50 t and spans of up to 35 m, as standard, with longer girder lengths available upon request.
deadweight reduced by an Girder average of 17%
Precise positioning of sensitive loads
tt 0 5 5 o t t U p
Easily adapted to building geometry
Precise crab runways and torsion free
crane girders
Girder design creates a brighter
environment and improved line of sight, promoting workplace safety
Tel: 01295 676100 Email:
[email protected] Email:
[email protected] om Web: www.demagc Web: www.demagcranes.co.uk ranes.co.uk
Less deadweight. Increased capacity.
8
TheStructuralEngineer
Upfront
D e c e m b e r 2 01 6
Institution news
Structural Awards 2016: taking structural engineering to new heights The winners of The Structural Awards 2016 were announced on 11 November during a ceremony held at The Brewery in London. Over 380 people attended the event, which was hosted by BBC presenter Clive Myrie.
On the night, the Institution presented its ultimate accolade – The Supreme Award for Structural Engineering Excellence – to the Grandview Heights Aquatic Center in Surrey, Canada, engineered by Fast + Epp. The Center boasts the world’s most slender, long-span timber catenary roof. The undulating roof shape reduces the amount of air to be heated and
The new home for Oxford University’s School of Government features highquality exposed concrete throughout. Its unusual form, established through a series of stacked, off-set cylindrical and square volumes, creates a variety of different spaces. The whole building is designed to encourage openness and communication.
of alternating radial and circumferential trusses.
dehumidified, cutting operational costs, while ingenious steel tube columns in the facade serve a double function: resisting wind loads and acting as ventilator ducts. The Awards judges said: “We were struck by the undulating roof, which elegantly balances structural form with building use and celebrates the expressed materials. The adoption of timber in catenary permitted a structural depth of just 300mm for a 55m span – a design which defies convention and demanded design excellence.” For full details of this year’s winners and shortlisted entries, visit www. structuralawards.org.. structuralawards.org
Award forQuay Pedestrian Elizabeth BridgeBridges (Perth, Australia) Arup Elizabeth Quay is part of a bold plan to revitalise central Perth. This striking 22m high cable-stayed bridge is the project’s centrepiece. The design benefited from the use of a range of digital tools.
included span of therou first-floor joists, thethe sag8m in th e gallery nd the octagonal hall, and partial failure of a large timber truss.
Awards Aw ards winners
geometry and load paths, while providing continued rain protection to fans. Eightyfive per cent of materials used for the expansion were locally procured.
Supreme Award for Structural Engineering Excellence & Award for Community or Resident Residential ial Structures Grandview Heights Aquatic Centre (Surrey, Canada) Fast + Epp Award for Sustainability 5 Broadgate (London, UK) BuroHappold Housing the European trading operations of Swiss bank, UBS, this 13-storey building is the largest s ingle let offi ce space in Europe. The structure is a steel frame with concrete floors on profiled metal decking, founded on a 1.75m thick reinforced-concrete raft. Award for Education or Healthcare Structures Blavatnik School of Government (Oxford, UK) Pell Frischmann
Award for Sports or Leisure Structures Etihad Stadium Expansion (Manchester, UK) BuroHappold Engineering The project to expand Manchester City Football Club’s stadium with a new South Stand saw engineers required to modify an existing cable-net roof with complex
Award for Structural Heritage Mount Stewart House (County Down, Northern Ireland) Mann Williams This fine house was in need of a thorough overhaul. Significant structural problems
Award for Infrastructure or Transportation Structures Transformation of Birmingham New Street Station (Birmingham, UK) Atkins/AKTII Birmingham New Street Station was officially re-opened re-op ened by the Queen in November 2015 after a five-year, £750M transformation. The new roof comprises an EFTE inflated cushion system supported off curved steel tubular arch beams, which in turn are supported off two dramatic wishbone truss arches.
Award for Small Projects Formby Helical Stair (Formby, UK) Webb Yates Engineers A breath-taking, two-storey stone staircase that springs from one landing and sweeps unsupported through 320° to the next. The total weight of French Combe Brune limestone making up the stairs is approximately 6.6t.
Award for Arts or Entertainment Structures Stavros Niarchos Foundation Cultural Centre (Athens, Greece) Expedition Engineering & OMETE A new home for the Greek National Library and National Opera, the Centre features a number of engineering innovations. A super-slender, lightweight ferrocement canopy roof is raised on slender columns over the whole building, and carries a huge solar panel array.
Award for Small Practices Expo2015 Hive (Milan, Italy & London, UK) Simmonds Studio A highly complex sculptural structure that was the centrepiece of the UK Pavilion at the Milan Expo 2015. The Hive consists of 60 000 unique aluminium parts, formed in a structural system of 31 stacked layers
Award for Commercial or Retail Structures Torre BBVA Bancomer (Mexico City, Mexico) Arup The Latin American HQ of the bank, BBVA Bancomer, and the tallest completed building in Mexico. The architecture clearly expresses the engineering of the
www.thestructuralengineer.org 9
5 Broadgate
Grandview Heights Aquatic Center Center
P M U J
R E T E P
Blavatnik School of Government
A M E
Elizabeth Quay Bridge
E I D D E
Etihad Stadium Expansion
D L O P P A H O R U B
P U R A
Formby Helical Stair
Transformation of Birmingham Transformation New Street Station
Expo2015 Hive
L I A R K R O W T E N W O R C + N O T F U H
Torre BBVA Bancomer
Mount Stewart House
structure. Engineers designed for Mexico City’s low-frequency earthquakes by placing the structural frame on the exterior of the envelope. This eccentrically braced megaframe acts as an external protective skeleton, carrying all the building’s lateral wind and seismic loads.
Stavros Niarchos Foundation Cultural Centre
2017 Awards
Next year will see the 50th anniversary of The Structural Awards, with entries opening in January. Don’t miss your chance to participate in this celebration of the profession’s achievements. Visit www. structuralawards.org for structuralawards.org for more information.
S O B M Y L O R E Y S I G R O I Y
N O T R
O G K R A M
10
TheStructuralEngineer
Upfront
December 2016
Institution news
Institution transfer list: 7 November 2016 The Membership Committee on 7 November 2016 confirmed that
EASTON, Marc David FOSTER, Lisa
the followingwith were transferred in accordance the Institution’s Regulations:
FRANCIS, Alexander Alexand er FUNG, Ho Nicholas Hon GAJANTHAN, Vethana Vethanathan than GALLOWAY, GALLOWA Y, Matt hew GOMES, Alexandre Jose GRANT, William John HARLEY, Thomas HARRISON, Garry Lee HIGGINSON, Ryan HIGH, Rebecca Marie HOLLIS, Ed HUANG, Yuhan JOB, Daniel KALLENAHALLII THIMMAIH, Manjunatha KALLENAHALL KOCLEGA, Monika KOZLOWSKA, Anna Elzbieta KWOK, Ting Sang LAU, Chau Ming LEA-WILSON, Simon Peter LEIGHTON, Thomas Ridgway LEUNG, Ki Lim LIE, Ka Ming
TRANSFERS Associate-Member to Member (6) ANDREWS, Mark BRADLEY, Daniel Philip IZADI, Golnaz LOMPERI, Sanna Maria Alexia PAIN, Malcolm Wyndham RAFFERTY, Damian James Graduate to Member (94) ABBERTON, Stephen James ADEKOLA, Adedayo ANANTHARAM, Seetharam ASGHAR, Ali ATKINSON, Adam AUSTIN, Christopher BALL, Eleanor BEKAR, Bedir BENNETT, Robert BETTS, Rachel BIGNELL, Thomas Duncan BOTFIELD, Tim BRACEY, Ian Robert BRINDLE, Paul Michael BROWNE, Stuart Nicholas CHAN, Kam Cheong CHAN, Tak Kei Edward CHIU, Kar-him CHONG, Hon Meng CHRISTOFI, Christopher CLAYTON, Patrick CONDON, Rory Edward CREED, Oliver DAMIAN, Tiberiu Alexandru DAVIDSON, Steven Thomas
MATHEW, SamuelPaul Thomas MATTHEWMAN, MATTHEWS, Christopher Patrick Twells MCDONALD, Lee Anthony NICKELL, Catherine Ruth NICOLIN, Rossella ODENDAAL, Russel PATEL, Khalid PEMBERTON, Tom Alan PERIKLEOUS,, Ioannis PERIKLEOUS PETROV, Kiril Mihaylov PHAM, Duc Chuyen PHILLIPS, Seamus Augustus PHILLIPS, Wayne PLUTECKI, Jan Waldemar POON, Ngai Hang PRADHAN, Tikeshwar Nath QUINN, Graeme William Thomas RAVEZZANI, Maria Chiara
RICE, Andrew Stuart RIDDLE, Olivia Yvette RIGBY, Christina SHAO, Chunhui SINGH, Savitree SMITH, Adam SMITH, Andrew David STRIDE, Maia Gabrielle SUMNER, Kevin David SUN, Andrew Alexander THEEPAN, Nirmalendran TSUI, Ka Shing TUNGATE, Michael James TURPIN, Leigh WALKER, James WHITFIELD, Ben WILKINSON, Gavin James WONG, Fat Tim WONG, Wing Shuen Phoebe WU, Shumin WYATT, Michael Philip YANG, Wenbin YIM, Kei Yung YIP, Ying Ho ZENG, Sheng ZHAO, Rui
Technician to Associate-Member (1) WILSON, Adam
Graduate to Associate-Member (11) BLENKINSOP, Ross CROSNIER, Matthieu Pierre Jean FEGAN, Jeffrey Rowland HILL, Jonathan James HOUGHTON, John Anthony KUAN, Wai Kin MADHAVASUBRAMANIAN, Rajan MITCHELL, Peter OJJERRO, Eric ROBERTS, Benjamin Edward XUE, Zhiping
Two more titles released in
Essen Es sentia tiall Kno Knowle wledge dge Ser Series ies The Institution has published two further titles within the Essential Knowledge Series: No.11. Triangulated structures and No.17. Dynamics. Text No.11 provides an introduction to the most important aspects of triangulated structures. These are widely used and can provide stiff structures with very little structural material. As they are formed from many interconnecting parts, a knowledge of several aspects of modelling, analysis and design is needed to be able to understand their structural behaviour. Text No.17 examines structural dynamics – the study of how structures respond to loads that vary rapidly with time. Examples range from footfall forces on footbridges and
office floors, to severe se vere environmental environmenta l loads such as earthquakes and extreme winds. The key phenomenon which causes problems is resonance, whereby large amplifications of motion occur when the frequency (i.e. oscillation rate) of a load coincides with the natural frequency of the loaded structure. This introduction to the subject, focusing on linear elastic structures, explains how to calculate or estimate the key dynamic properties of simple structures, and outlines the principles used by finite-element programs in analysing the dynamics of more complex structures. The Essential Knowledge Series breaks down key fundamentals of structural
engineering into concise, accessible, peer-reviewed study texts, delivering an invaluable resource for engineering students around the world. Every text is free to Student and Academic Members of the Institution. A total of 20 texts will be published in the Series, with new titles added each month. View currently available titles at www.istructe. org/essential-knowledge .
New Lighter Load Thermal Break Fabreeka-TIM® LT is a new lighter load thermal break material for non structural applications
Applications for Fabreeka-TIM LT Series Parapets, soffits, roof to wall transitions
Steel stud exterior walls
Masonry ties
Fabreeka-TIM FabreekaTIM LT15 material is designed for f or 1,500 psi loading loa ding and Fabreeka-TIM Fabreeka-TIM LT5 material is designed for 500 psi loading. Both provide better thermal insulation than vinyl and plastics, reduce corrosion between dissimilar metal elements and both are made from recycled materials, which help to achieve LEED credits.
Concrete and precast joints and accessories
Metal building framing
Below grade to above grade transitions
Cladding attachment support clips for Z-girts, C-channels, Hat channels used in:
- Curtain walls, rain screens, metal wall panels, veneer walls, louvres
The original Fabreeka-TIM Fabreeka-TIM material is a trusted thermal break solution specified by building professional everywhere. Manufactured from a fibreglass-r fibreglass-reinforced einforced laminate composite, it is a thermally efficient, energy-saving product that prevents thermal bridging in structural connections. Now with Fabreeka-TIM LT LT, lighter load applications can also benefit from reduced thermal bridging and improved energy efficiency. efficiency.
For more information about the benefits of Fabreekaabreeka-TIM TIM LT or to get your copy of our latest catalogue, contact ACE Fabreeka UK on 01942 727440 or email: email:
[email protected] ACE Fabreeka UK . Unit 404 Easter Park Haydock Lane Haydock WA1 WA11 1 9TH T +44 (0)1942 - 727440 . F +44 (0)1942 - 717273 717273 . www.ace-fabreeka.co.uk
12
TheStructuralEngineer
Upfront
December 2016
Industr y news
Institution to offer specialist diplomas in offshore and seismic engineering The Institution of Structural Engineers will offer two new technical qualifications from 2017. The new “specialist diplomas” will test candidates’ competence in the topics of offshore structural engineering and seismic engineering. The diplomas are not associated with routes to Institution membership, so either examination may be sat by both Institution members and non-members. Candidates who have several years of experience practising in these specialist areas are invited to apply to sit the examinations. Each diploma will demonstrate a high level of competence in the specialist areas, carrying the authority and credibility of a professional engineering institution with a reputation for high standards and rigorous examinations. The Institution is offering the new qualifications to address increased specialisation within the structural engineering profession and the need for individuals to demonstrate competence in these areas to current or potential employers, clients and regional authorities. The first examinations will take place alongside the Chartered Membership Examination in January 2017, at centres around the world. Each examination lasts for threeand-a-half hours and costs £200 to enter. Registration for the new examinations closes on Friday 16 December 2016. Learn more about the Specialist Diploma in Offshore Structural Engineering at www. istructe.org/membership/examination/ specialist-diploma-in-offshore-structuralengineer.. engineer Learn more about the Specialist Diploma in Seismic Engineering at www.istructe.org/ membership/examination/specialist-diplomain-seismic-engineering . To enter either examination, request an entry form from the Institution’s Examinations Manager via
[email protected] [email protected]..
Enter the Excellence in Structural Engineering Education Award 2017 The Institution’s Excellence in Structural Engineering Education Award 2017 2017,, presented to university academics who demonstrate outstanding commitment to innovative i nnovative teaching philosophies and techniques, is now open for entries. Submissions close on 24 March 2017.
Award winners will be invited to the People and Papers Awards in London, scheduled for 8 June 2017. Selected Awards Awards will also be featured at the Academics’ Conference on 14 September and may be considered for publication in The Structural Engineer . Submissions may cover any aspect of the learning and/or teaching of structural behaviour on any Bachelor’s or taught Master’s course. More information about the Award is available at www.istructe.org/eventsand-awards/people-and-papers-awar and-awards/ people-and-papers-awards/ ds/ excellence-in-structural-engineeringeducation/how-to-apply.. education/how-to-apply You can read the 2016 winning w inning entry on “Experiments in learning design”, by Tim Stratford Stratfor d of the University of Edinburgh, in the August issue of The Structural Engineer .
Poster prizes awarded for Undergraduate Research Grant Scheme The best posters from the Institution’s 2015/16 Undergraduate Research Grant Scheme have been awarded prizes. As part of the Grant Scheme, four universities were awarded £800 each to fund projects undertaken by students as part of undergraduate studies. Each grantwinning entry was then required to produce a poster and executive summary detailing their findings at the end of the funded project. Prizes for the best posters have been awarded as follows: 1st prize: Lukas Grekavicius and Jack Hughes of the University of Leeds won £125 each for
their poster showing the findings from their research: “Novel morphologies of aluminium cross-sections through structural topology optimisation techniques” . Joint 2nd prize: Paul Zhu of Imperial College London and Tanapa Bumrungtrakul of the University of Loughborough were jointly awarded second prize for their posters and received £75 each. Paul researched “Structural performance of robotically-fabricated mechanical joints for folded timber structures” . Tanapa investigated “Stress-wave based methods for non-destructive testing” .
Find out more about the Undergraduate Research Grant Scheme at www.istructe. org/education/scholarships-grants-andbursaries/undergraduate-research-grants.. bursaries/undergraduate-research-grants
Research Award winner reports on CLT research The winner of the Institution’s 2014 Research Award, Dr Christian Malaga Chuquitaype, has published the results of his research into the “Lateral response of cross-laminated timber panels pan els” ” . Dr Malaga, from Imperial College London, worked with Ramboll to develop a fundamental understanding of how cross-laminated timber (CLT) panels respond to lateral loads from extreme actions such as earthquakes and strong winds – an important resource that could help structural engineers design taller timber buildings. Dr Malaga’s report is available at www. istructe.org/getattachment/research-award/ Previous-Research-Award-holders-(1)/IStructEResearch-Award-2014-Final-Report.pdf.. Research-Award-2014-Final-Report.pdf The Research Award is the largest offered by the Institution, offering grants of £6000 to support high-quali high-quality ty research in structural engineering. The Award collaboration collabor ation between industry andencourages academia, supporting innovative research ideas, and the development of further strands of ongoing research. The Research Award is presented by the Institution’s Research Fund.
Research Panel sets new themes and topics The Institution’s Research Panel Panel has identified two new themes within the Industry Focused Research Challenge: “Solutions for developing countries” and “Designing for resilience”. Both apply across all the Institution’s research funding schemes, and grant applications on these themes will be given priority. Further topics for research were also identified by industry at the 2016 Young Researchers’ Conference. Representatives from Robert Bird Group, Waterman Group, Flint & Neill Ltd and Ramboll presented a number of topics requiring research (such as parametric design and floor damping in buildings) buildings).. These are now displayed online for the benefit of: academics who may be looking for ideas for student projects; and those who wish to engage in discussion about particular research needs. You can view a webinar outlining these research needs at https://istructe.hosted. panopto.com/Panopto/Pages/Viewer. aspx?id=260112e7-89d7-4149-afebfb971d16503e.. fb971d16503e More information on themes and topics and be found on the Institution’s Research page at www.istructe.org/resources-centre/technicaltopic-areas/research.. topic-areas/research
www.thestructuralengineer.org
TheStructuralEngineer December 2016
Features
13
Articles with a broad scope often accompanying a significant Institution award or event.
14 Engineering clarity
In a paper based on his 2016 IABSE Milne Medal Lecture, James O’Callaghan reflects on his career as an engineer and, in particular, his interest in the art of structural glass design – a field in which he is widely acknowledged as an authority. James illustrates the evolution of glass as a structural material over the last 20 years and considers its future in an industry in dustry increasingly increasin gly focused on energy energ y efficiency. The Milne Medal is awarded annually to an individual engineer for excellence in structural design, both in the overall concept and in the attention to detail in their work, and is named in recognition of the late Bob Milne, who served for many years as the Honorary Secretary of the IABSE British Group.
14
TheStructuralEngineer
Feature
December 2016
Milne Medal
Engineering clarity E L P P A
James O’Callaghan BEng, CEng, MIStructE, MHKIE MHKIE Director, Eckersley O’Callaghan, London, UK
Synopsis
Introduction
In a paper based on his 2016 IABSE Milne Medal Lecture, James O’Callaghan reflects on his career as an engineer and, in particular, his interest in the art of structural glass design – a field in which he is widely acknowledged as an authority. James illustrates the evolution of glass as a structural material over the last 20 years and considers its future in an industry increasingly focused on energy energ y efficien ciency. cy. The Milne Medal is awarded annually to an individual engineer for excellence in structural design, both in the overall concept and in the attention to detail in their work, and is named in recognition of the late Bob Milne, who served for many years as the Honorary Secretary of the IABSE British Group.
Clarity of thought and expression are considered the ultimate aspiration for many designers. The realisation of iconic structures often belies not only the complexity of the engineering, but also the commitment of the engineer. This paper explores the theme of clarity through my experiences of working with glass – how it was developed into a structural material; how it has innovated; how it is utilised in the building envelope; and where the next challenges lie in the face of energy-related headwinds. It is also a chance to reflect ct on the complex process of innovation which has advanced the application of glass s technology over a relatively short period of time. I have been fascinated ted by glass for my entire career reer as an engineer. I share this is fascination with millions, ns, whether they realise itt or not, because the material forms the backbone of our
S T C E T I H C R A Y L O Ñ I V L E A F A R
1 Figure Tokyo Yurakucho Canopy, Japan (1996)
2 2 Figure Samsung Jong-Ro Tower, Seoul, South Korea (1999)
S T C E T I H C R A Y L O Ñ I V L E A F A R
www.thestructuralengineer.org 15
S T C E T I H C R A Y L O Ñ I V L E A F A R
3 Figure David L. Lawrence Convention Center, Pittsburgh, USA (2002)
5 Figure Staircase, Apple SoHo, New York, USA (2002)
E L P P A
built environment. It is the fundamental gateway for light into our habitats. The qualities of glass are relatively unique – in particular, its transparency. However, it is the material properties, such as its purely elastic behaviour, which offer the potential of structural use in specific ways.
Beginnings I joined Dewhurst Macfarlane and Partners (DMP) in 1995 – it was here that my interest in architecture developed, along with my exposure to the art of structural glass design. Tim Macfarlane was an early pioneer of this specialist field and it was under his tutelage that I began to understand the possibilities that the material offered. Tim was an inspiration to me. We owe much to his curiosity in how glass might be considered as a viable structural material. He invested time to develop new ideas for connections, testing the material to understand its behaviour, and even researching archived engineering data to
4 4 Figure Detail of cable,
facade for Rafael Viñoly’s new Samsung Headquarters building (Figure 2). 2). This was a large, complex project using innovative connection technology extrapolated
2004) (Figures 3 and 4) was 4) was incredibly inspiring; this was a very challenging time in my career when the responsibility was great on relatively young shoulders
build up a body of knowledge for how it could work as structure. Tim’s early glass projects, such as the glass extension to Keats Grove in London with Rick Mather and the Tokyo Yurakucho Canopy (Figure 1) with 1) with Rafael Viñoly, represented significant steps in assembling glass elements into threedimensional shapes using engineered structural connections. These were developed by borrowing from connection details commonly used in other materials, such as timber. Starting without the constraints of codes released a certain freedom to develop ideas, to imagine glass in more ambitious ways and to test where the boundaries might be. However, today’s use of glass has matured such that there is now a need for a coordinated code to ensure that the industry designs robust structures around the world. In 1997, I was based in Seoul with DMP to work on a significant structural glass
from the engineering of the Yurakucho Canopy. There was no precedent in Korea for the design and therefore the process of developing buildable details with the specialist contractor was very educational. All parts were bespoke and, with no initial concepts of how to make them, I was exposed to the very fundamentals of fabrication through machinery. I realised how innovations in materials evolve – they are as much a part of the ability to make as they are of the ability to design. The success of the Samsung building led to an opportunity to work in New York on several significant projects for Rafael Viñoly, w hile establishing an offi ce for DMP in the city. Working in close collaboration with a high-profile architect on projects such as the David L. Lawrence Convention Center in Pittsburgh (Winner of the In stitution’s Supreme Award for Structural Engineering Excellence in
and yet invaluable experience to develop my confidence as an engineer.
S T C E T I H C R A Y L O Ñ I V L E A F A R
David L. Lawrence Convention Center
N A H G A L L A C ’ O Y E L S R E K C E
6 6 Figure Glass tread to wall connection showing insert, Apple SoHo
Details It was in my formative years working on ground-breaking projects that I found purpose in details. Everything is a construction of details and I find the process of refining them deeply rewarding. Questioning every millimetre of material, to justify its addition or omission, striving towards the most efficient assembly ass embly whi ch accommo dates the forces it must endure – nothing more and nothing less. The best structures really pull at your heartstrings because the details release the concept. This is what I mean by “engineering clarity”. Those that leave you feeling underwhelmed tend to have details that let them down. The design of details is often left too late, or left to less interested parties, with inelegant
16
TheStructuralEngineer
Feature
December 2016
Milne Medal
N A H G A L L A C ’ O Y E L S R E K C E
solutions polluting the overall concept. Concept and detail, wrongly considered to be sequential activities, must be given equal attention throughout development to achieve designs which are wellengineered. There is a level of intuition to this, which comes with experience.
7 7 Figure Stair tread broken in testing supporting load
Partnerships In early 2004, I returned to the UK and formed the engineering consultancy Eckersley O’Callaghan (EOC) with Brian Eckersley.. We had known each other Eckersley from earlier days at DMP and found ourselves looking for our next step. Backed by our combined relationships in the UK and USA, we set up in Islington, London, and steadily grew the practice over the following 12 years. We both share a love of architecture and how structural engineering can best enhance it. This continues to be the motivation for everything that our practice does today. A part of our success has been due to
8 8 Figure Staircase, Apple Osaka, Japan (2004)
E L P P A
our long-term partnership with Apple – we have played a central role in engineering the feature glass elements in their iconic retail stores since we established. Apple’s commitment to continuously innovating towards perfect clarity has truly stimulated the industry. As a result, glass technology has exponentially advanced over a
relatively short period of time. I was first introduced to Apple through the architects Bohlin Cywinski Jackson (BCJ) in 2001 to work on the flagship store in SoHo, New York, having been working on a glass project with the same architects architect s for Corning Inc. The design was to be symmetrical with product zones on
Figure 9 Staircase, Apple Sanlitun, Beijing, China (2008)
N A H G A L L A C ’ O Y E L S R E K C E
10 Figure Staircase hanging insert detail, Apple Sanlitun
N A H G A L L A C ’ O Y E L S R E K C E
either side of a central stair. Stairs take up significant space and therefore this one had to be as light or as transparent as possible. In an early meeting with Apple CEO, Steve Jobs, we agreed that an all glass stair would be the best approach. We developed the concept of glass walls (supported on the structural floor) with glass treads spanning between. The lateral stability of the stair was provided by internal glass fins (Figure 5). 5). While the structural concept for both the stair and a related bridge was relatively simple, the load requirements and expected traffic signifi cantly exceeded the domestic glass staircases that had been built at the time. The SoHo stair incorporated an “insert connection”, made possible through an understanding of the relatively new interlayer SentryGlas® (Figure 6). 6). SentryGlas proved pivotal in the
www.thestructuralengineer.org 17
N A H G A L L A C ’ O Y E L S R E K C E
12 12 Figure Close up of insert laminated fitting, Apple Hamburg (2011)
development of structural glass projects because of its specific properties. Developed by DuPont as a solution to hurricane-prooff glazing, this interlayer hurricane-proo polymer had greater stiffness and bond strength than those used historically, including polyvinyl butyral (PVB). Both these properties made it attractive for structural glazing because of the added composite action between glass layers; and, importantly, the post-breakage behaviour was far superior (Figure 7). 7). The shear bond and flow characteristics also opened the possibility of evenly laminating a metallic object into the glass. Testing at the University of Munich led to some very promising results, indicating that a pull out load of 50kN was typical with a 50mm radius insert. We found that similar thermal characteristics between glass and insert were important to relieve stress during lamination. The material chosen was titanium for this very reason. Having established that an insert would be a viable approach to connecting glass, a detail was developed to connect a glass tread to a vertical glass wall. The detail allowed for relatively straightforward tread replacement in case of breakage. The connection was successfully rolled out on many stairs in Apple stores over the next five years, up to around 2010. The versatility of the connection detail also allowed it to be used on glass bridges and circular glass stairs, such as for the store in Osaka (Figure 8). 8).
11 11 Figure Staircase, Apple Hamburg, Germany (2011)
up usable store space below (Figures 9 and 10). 10). Our next step was to refine the tread connection further such that both parts of the connection could be inserts – the part within the supporting glass wall and that within the tread – thus preserving all glass surfaces.
the pull-out force could be accommodated (Figures 11 and 12). 12). It relied on Seele’s expertise in tolerance management and lamination quality for longevity. In 2013, the connections continued to evolve through the projects we had recently completed with Foster + Partners. By enhancing our understanding of its
We worked with Seele and Sedak GmbH, the fabrication developers of insert lamination, to develop a detail in 2010 for a stair in Hamburg. The circular insert embedded within the supporting glass substrate relied on a flange to ensure that
performance, we refined the detail further, resulting in a linear profiled connection for Apple Westlake in Hangzhou, China (Figure 13). 13).
Size mattered
Development It has always been important in our approach that we strive to evolve our concepts. For example, a detail was developed for a store in Beijing to connect a hanging rod directly to an insert in the central layer of a glass stringer. This concept enabled the stair to float, freeing
13 Figure Linear insert laminated fitting, Apple Westlake, Hangzhou, China (2013)
G N U O Y L E G I N
Our focus on engineering connections connections to be as effi cient and e legant as p ossible is because our eyes read them more than the glass itself. The success of a glass structure is, in my opinion, a function of the elegance of its connectivity. The natural progression for clarity was to reduce the number of fittings. We felt the way to do this was to increase the size of the glass. The first project to probe this concept was the first Fifth Avenue glass cube in New York, where glass would be showcased as structure and facade in one (Figure 14). 14). The challenge was to realise the 10m glass fins as monolithic elements. At the time, the infrastructure in jumbo glass production was limited to 6m by float
N A H G A L L A C ’ O Y E L S R E K C E
18
TheStructuralEngineer
Feature
December 2016
Milne Medal
14 Figure Apple Fifth
16 Figure Apple George
Avenue, New York, USA (2006)
Street, Sydney, Australia (2006)
N A H G A L L A C ’ O Y E L S R E K C E
15 15 Figure Spliced lamination concept
N A H G A L L A C ’ O Y E L S R E K C E
E L P P A
lines, autoclaves and post-processing. There was simply no demand for larger elements. Working with Seele and Bischoff Glass Technologies (BGT), we developed a concept called “spliced lamination” (Figure 15),, again inspired by timber construction. 15)
to realising innovation in our industry. Knowledge alone can only take us so far. The supersized autoclaves were eventually accompanied by larger tempering furnaces and longer panels off the float lines. Spliced lamination was rendered an interim solution. The logistics of transporting
complex than making the glass itself. We needed the whole supply chain to recognise the benefit of investing. We have embraced a central role in the process of navigating the interplay between the industry’s players. The evolution in tempering technology
This involved 6m and 4m layers of glass that were cut, tempered and laminated in a staggered manner such that the joints between elements did not align. The engineering theory was sound but, in practice, it needed an autoclave large enough to bond the three layers into a single 10m glass element. BGT identified an aircraft wing manufacturer with an autoclave longer than 10m, which was used overnight (downtime for wing production) to laminate the glass fins. This was a very successful approach because it allowed the concept of much larger glass panels to flourish. Seele subsequently ordered a large autoclave which could laminate panels up to 14m
and installing the large glass would later be resolved – these were perhaps more
came through the design of a glass cylinder entrance pavilion for a store
17 17 Figure Apple Boylston Street, Boston, USA (2008)
× 3.2m, though relying on the spliced technique as tempering technology still limited the size to 8m. With the freedom of larger format glass, we embarked on more ambitious designs which looked to embrace this innovation. There are two projects that marked this step: the first, at the Apple Store on George Street in Sydney, required 14m × 3m panels braced by glass fins (Figure 16); 16); the second, at Boylston Street, Boston, used 12m glass fins cantileve cantilevering ring from the building to create a glass box on the front of the concrete building frame (Figure 17). 17). Spliced laminated glass reduced the number of joints, the amount of silicone and the number of fittings. The increased clarity in these projects was evident and represented another big step forwards.
Progressing industry My experience is that forming partnerships between designers and makers is key
E L P P A
www.thestructuralengineer.org 19
19 Figure Apple IFC Shanghai, China (2010)
18 Figure Curved glass coming out of tempering furnace (2010)
N A H G A L L A C ’ O Y E L S R E K C E
in Shanghai. Beyond the challenges of resolving complex wind pressure patterns on the structure, we focused on how to make the panels in full height 12.5m pieces with a radius of 5m. Furthermore, it was important that the glass was fabricated in China and built with local labour. I was dispatched to China to investigate the capabilities of various glass fabricators around the country. After many meetings, we came across a firm called Beijing North Glass (BNG) which had modest fabrication equipment and approaches, but demonstrated a deep enthusiasm and, in time, an appreciation for what we wanted to achieve. It was clear that they had never been asked for quality over economy. Adjusting to a quality priority mentality was perhaps the most significant change they had to make. BNG committed to developing a new tempering furnace for 14m curved panels. The furnace was delivered six months
had negotiated supply of 14m sheets (10mm thick) with the float lines in China, allowing the panels to be laminated without “splices” – another step towards transparency had been made. The resulting panels for the Shanghai store were 12.5m × 2.6m with a radius of 5m, each of them being a laminate of three 10mm heat-strengthened glass sheets with no horizontal joints or glass splices (Figures 18 and 19). 19). Since then, the furnaces have grown larger still and have spread to Europe. There are currently several 18m tempering
demand, but the infrastructure to support large-format glass has been established and is available from more than one source globally.
later in Beijing and the first tests were very successful. In the meantime, BNG
furnaces in China and a number over 14m in Europe. It remains a relatively small
described earlier in this paper (Fig. 14). 14). The project would enable us to collate the
20 20 Figure Comparison
E L P P A
Towards cl arity I have been very lucky in my career as an engineer for a number of reasons, but perhaps the greatest opportunity came from the decision to reconstruct the Fifth Avenue Apple Store Glass Cube to coincide with a refurbishment in 2011. The original was constructed in 2006 and
a) 2006 design
b) 2011 design
106 panels 20 columns 35 beams 164 glass units 250 primary fittings
15 panels 8 columns 2 beams 28 glass units 40 primary fittings
of Apple Fifth Avenue designs in 2006 and 2011, New York, USA
E L P P A
20
TheStructuralEngineer December 2016
Feature Milne Medal
21 21 Figure Apple Zorlu, Istanbul, Turkey (2014)
"Glass has a big part in our future, but it is facing headwinds. Its use in buildings is being challenged by the need for better energy efficiency"
E L P P A
advances made in technology and fabrication in the five years since. We worked with BCJ to reimagine the same glass enclosure using large-format glazing and insert-fitting developments. Through this exercise, the number of glass panels was reduced from 90 to 15 and, consequently,, the number of fittings also consequently significantly reduced. We engineered an innovative connection fully embedded within the glass panels and supporting glass fins, thus preserving the reflectivity of the glass
offered the chance to rebuild a structure and it is even rarer if the reasons for doing so are positive. What would you do differently with hindsight and what you know now? The reengineered Cube demonstrates a marked increase in transparency compared to its predecessor. I believe it is an important statement about the power of innovation and the opportunity it affords the built environment (Figure 20). 20). It is impossible to mention every milestone in our adventures in glass over the years in
surfaces entirely. It is a rare thing for an engineer to be
this paper. We have engineered over 200 projects with Apple to date, and many for
22 Figure Project Y
other clients – we have approached every one as a chance to improve on what we have achieved before. Apple Zorlu (Figure 21) in 21) in Istanbul (with Foster + Partners) was just another step in that journey for us, though it was a welcome honour when it was awarded the Institution’s Supreme Award for Excellence in Structural Engineering in 2014 in recognition of its purity. The solution seems impossibly simple, comprising five panels – four glass walls (10m wide × 3m tall) with a thin carbon fibrereinforced reinforce d plastic (CFRP) roof. The elegance belies the complexity of the engineering and all the precedents that have gone before it. This paradox might be exclusive exclusive to working in glass.
Collaboration
Our achievements have derived from a culture
N A H G A L L A C ’ O Y E L S R E K C E
23 Figure EOC.Freigist Eyewear collection
N N A M H C S T E R K K N A R F
www.thestructuralengineer.org 21
N A H G A L L A C ’ O Y E L S R E K C E
24 24 Figure Solar gain analysis
we compromise by rationing light into our buildings. Glass therefore needs to evolve, as does architecture, to fully participate in the dialogue ahead, rather than be at the heart of a conflict. Our practice is now equally focused on the technology and innovations associated
of collaboration and engagement with our partners. We have ventured broadly for challenges (and their solutions), yet always looked closely at all the details. For example, we had the opportunity to assist a client in realising their superyacht in 2007 (Figure 22).. We worked with Philippe Starck and 22) Feadship in Amsterdam to apply the technical knowledge of structural glazing to maximise the transparency of the large open pavilion spaces planned for the yacht. Through its success, the project is established as a precedent that has since openly influenced the design of many superyachts today, an area that we continue to support. I have also had the chance to design a range of eyewear with German manufacturer
we were asked to deconstruct the ideas of eyewear and rebuild them. With my colleague, Lisa Rammig, we questioned all the typical details of frames with a view to simplifying them. The range includes frames in aluminium and titanium – the latter avoids hinges by benefiting from the inherent flexibility and strength of the material. For me, it was an exercise exerc ise of returning to the principles I had learnt through years of practice and reapplying them in a new context.
Glass has a big part in our future, but it is facing headwinds. Its use in buildings is being challenged by the need for better energy efficiency (Figure 24). 24). Rightly or
with dynamic control of energy through the glass, as it is on its future as a structural material. Examples of this would be our research, development and partnerships with technologists Corning and Merck (Figure 25),, exploring how their ideas can have a 25) meaningful influence in architecture through helping to manage the envelope interface. We have a responsibility within our industry to respond to these challenges, to accelerate our research. The call for innovation in the industry is never greater; to evolve the technology that allows glass and its associated systems to react to solar gain and thermal heat loss; to become intelligent. We have proved that we can innovate. We must now redouble our efforts and
Eschenbach (Figure 23). 23). Without any preconceived knowledge of the product,
wrongly, glass will always be the easy target. However,, we must not lose sight of what However
refocus our priorities. Size mattered, now energy governs.
Energy now governs
25 Figure Dynamic glass technology by Merck
K C R E M
R T O P P U S I S C S www.steel-sci.com
Design, Eurocodes, Expertise and Best Practice Steel construction knowledge and support provided to you by SCI
Advisory
Training
Publications
This service provides fast,
independent, authoritative advice
keep engineers updated with the
on all aspects of the use of steel
latest developments within steel
in construction. Questions are
design and equip them to design
team of experts.
of steel construction.
For further details contact
discounts on important publications. @SCIsteel
steel-construction-institute
+44 (0)1344 636525 visit our shop
http://www.steel-sci.com
www.thestructuralengineer.org
TheStructuralEngineer
23
December 2016
Project focus
Peer-reviewed papers focusing on the structural engineering challenges faced during the design and build stages of a construction project.
24 Expansion of of the Etihad Stadium,
Manchester. Part 2: Construction
The Etihad Stadium was initially constructed for the Manchester Commonwealth Games of 2002, with the original stadium comprising reinforced-concrete r einforced-concrete terrace structures that supported a lightweight cablestayed roof. The stadium underwent a planned conversion following the games to become the 48 000seat home of Manchester City Football Club. It opened in August 2003 in time for the first home game of the season, before offi cially becoming becom ing the Etihad Stadium Stadi um in 2008. In 2012, following unprecedented growth and development, the club took the decision to expand the stadium to a capacity of 55 000. In contrast to the previous conversion, the design and construction teams had to extend one end of the stadium without compromising the structural integrity of the roof to the remaining three stands. Part 1 of this paper described the engineering design led by BuroHappold Engineering. Part 2 covers the challenges faced by the fabrication and construction teams (Laing O’Rourke and Severfield). The paper will describe the inventive techniques developed to resolve these challenges, including the temporary temporary works for erection of the roof. roof.
Part 2
24
TheStructuralEngineer December 2016
Project focus Etihad Stadium expansion
Expansion of the Etihad Stadium, Manchester. Part 2: Construction
2016 Winner: Award for Sports or Leisure Structures
Paul Hulme BEng (Hons), CEng, FICE, FICE, Associate Director, Severfield, UK John Calland BSc, Construction Manager, Severfield, UK Tony Hunt BSc (Hons), Project Director, Laing O’Rourke, UK A. Baynton Baynto n Project Engineer, Laing O’Rourke, UK
Synopsis
The Etihad Stadium was initially constructed for the Manchester Commonwealth Games of 2002, with the original stadium comprising reinforced-concre reinforced-concrete te terrace structures that supported a lightweight cable-stayed roof. The stadium underwent a planned conversion following the games to become the 48 000-seat home of Manchester City Football Club. It opened in August 2003 in time for the first home game of the season, before offi cially becoming bec oming the th e Etihad Stadium in 2008. In 2012, following unprecedented growth and developme development, nt, the club took the decision to expand the stadium to a capacity of 55 000. In contrast to the previous conversion, the design and construction teams had to extend one end of the stadium without compromising the structural integrity of the roof to the remaining three stands. Part 1 of this paper described the engineering design led by BuroHappold Engineering1. Part 2 covers the challenges faced by the fabrication and construction teams (Laing O’Rourke and Severfield) Severfield)..
These relate to the programme sequence and construction methodology, and resulted from the key objectives of: completion of the works for the start of the 2015/16 season • maintaining a roof over spectators • no seat loss on match days during the football season • minimal disruption to the stadium operations
• Phase 3: Advance works (first close season)
including cutting back existing roof • Phase 4: Main construction works including steel frame, precast terrace and roof • Phase 5: Completion works (second close season) including removal of existing roof
•
The paper will describe the inventive techniques developed to resolve these challenges, including the temporary works for erection of the roof. Introduction Construction within the existing stadium while it remained in use posed many challenges. The programme was developed around events scheduled at the stadium: all Manchester City Football Club home matches; first team prematch training; One Direction pop concerts in 2014; and the Rugby League Magic Week Weekend end in 2014. The programme was broken into five distinct phases focused on the crucial closeseason periods: • Phase 1: Enabling works including service
diversions out of the footprint • Phase 2: Substructure works including piling and pile caps
Space restrictions do not allow us to describe all of the challenges and solutions in detail; for general descriptions of the whole project, the reader is referred to Hunt et al .2 This paper describes the most important innovative construction solutions associated with Phases 3, 4 and 5, and mostly concerns roof works. The temporary works for erection of the new roof were particularly complex and were described by a Severfield employee as follows: “Install the new roof rafters onto temporary props, supported by a new bowl structure, supported by a new column through the existing bowl from a MEWP on a temporary works platform that is supported on an existing roof that is temporarily supported on a new column and the existing bowl”.
Key challenges of working in existing stadium The objectives all presented challenges associated with working in the existing stadium. However, critical challenges were: net during • working around the existing cable net construction, maintaining its integrity and avoiding damage • access: for deconstruction deconstruction of existing existing structures and installation of new structures, and also man access for operators to key locations
www.thestructuralengineer.org 25
tower cranes provided lifting coverage to the whole site. The availability of Select Plant’s record-breaking record-br eaking CTL 1600 crane – the largest of its type in the UK, capable of lifting 20t at a 70m radius – allowed components such as the rafters to be lifted in a single piece. This speeded up construction, as well as
E K R U O R ’ O G N I A L
1 1 Figure Protection frame around existing cable ring
significantly need2). componentsreducing at heightthe (Figure 2)to . splice Although the tower cranes could be used for much of the installation, the risk study looking at the existing cable-net layout highlighted that a large portion of the new structure was located beneath the backstay cables of the existing roof. roof. Using the tower cranes to lift these components would have meant feeding through the cables. Instead, the structure underneath the backstay cables was installed using mobile cranes beneath the cables. Unfortunately,, due to the proximity of the new Unfortunately terrace to the cables, it was necessary to feed the rakers and precast units through the net. This required a carefully planned operation at low wind speeds. Interim roof The imperative to retain spectator covering during the build also had a major impact, as the new terrace structure clashed with the existing roof. roof. The design solution for the entire process2 focused on modifications to the existing roof, enabling the removal of just enoug enough h of the exist existing ing roof roof structu structure re and fabric to create an “interim roof”. This facilitated construction of a portion of the new stand to release new hospitality spaces, while maintaining an acceptable environment for the fans in the mid and lower tiers of the existing South Stand. (The process is described in more detail further on.)
2 Figure Lifting of whole 60m long new roof rafter
E K R U O R ’ O G N I A L
development of of the interim roof solution solution
•
Cable-protection works One major risk was of damage to the existing cable net during construction, most likely accidental damage during lifting operations. A design study concluded that, while it would be possible to remove and replace any one of the radial cables, any damage to the main tension ring could result in major disruption,
even requiring replacement of the whole roof. To minimise this risk, protection frames were designed and installed around the tension ring before any other activities took place (Figure 1). 1). Cranage and installation of structure
In order to retain the integrity of the playing surface during the works, the whole of the build needed to be undertaken from outside of the ground. To facilitate this, three large
D L O P P A H O R U B
Part 2
26
TheStructuralEngineer
Project focus
December 2016
Etihad Stadium expansion
3 Figure Sequence of operations to establish interim roof works
a) Installation of new interim inclined V-struts into existing structure with MEWP on “tea trolley” across existing terrace
E K R U O R ’ O G N I A L
b) Jacking operations to inner V-struts
D L O P P A H O R U B
d) Interim roof after load transfer (matches continued during works) these
c) Existing roof following removal of rear part after load transfer for interim roof, allowing new terrace construction behind to proceed
Access during interim roof works Access was a major issue. For the modification works to the existing roof in order to create the interim roof, access to the underside of the roof was required above the current terracing, including seating. Programme impacts precluded a full scaffold system being installed and removed during the close season. The final solution was to develop a moveable platform that could support the weight and dynamic effects of a mobile elevating work platform (MEWP) operating on it. This became affectionately known as the “tea trolley”.
D L O P P A H O R U B
for each match. The major disruptive works – modification and subsequent removal of the existing roof – were planned for the close season, when the windows of opportunity were longer.
Creation of interim roof The reasoning behind the interim roof, and its design and sequencing, were explained in Part 1 of this article1. The nature of the sequencing activities on site to realise this process are shown in Figure 3. 3.
Temporary corner cor ner roof Developing programme strategy The first challenge was to programme the works around the client’s goals and the impact of these. The site works were planned to take place over a 15-month period that, in football terminology,, included two close (summer) and terminology one full (winter) seasons. The works needed to be carefully planned around the time slots in the close season and between matches; all works needed to cease and the ground be made ready to accept the public in time
Although spectator covering was required on match days across the whole roof, the interim roof solution was not possible in the corner bays. These bays were within the zone of the new corner roof space frame, which would eventually transition from the new main South Stand roof into the existing East and West Stand roofs. In order to provide access for the installation of steel members, which were required for both permanent and temporary works (Figure 4), 4), the corner bays had to have
D L O P P A H O R U B
a covering that could be removed. The solution in these bays was to completely remove the existing roof and install a new deployable covering. The temporary roof would need to be sympathetic to the design behaviour of the original roof so as to accommodate movement of the two portions of existing roof to each side, while at the same time avoiding transfer of unwanted forces from one side to the other. It was initially proposed that the temporary roof would take the form of a steel frame with temporary sheeting. This would be installed to a geometry that would allow the new permanent corner roof to be installed while the temporary roof remained in place. However, However, following further optioneering, a scaffolding contractor was appointed to propose how the roof might be formed utilising a sheeted scaffold solution (Figure 5). 5). While it was reasonably simple to determine that the basic structure would work across the span, complexities arose in configuring the connections onto and around the existing rafters. The connections needed to adequately
www.thestructuralengineer.org 27
deal with movement, but also ensure that the existing rafters could accommodate the loads and forces imposed by the temporary roof. This was made rather more complicated by the fact that the existing roof to one side was now in the interim state; therefore, its normal mode of movement was slightly different and certainly sensitive. Differential vertical and lateral more movements of the rafters would mean that the gap which the temporary roof was covering could vary. The team worked together to develop solutions, with BuroHappold advising on the nature of the existing structure and proposing the generic structural framing approach, and Laing O’Rourke and the scaffold specialist configuring the necessary connection detailing. It was determined that the connections would need to consist of a knee joint at one end, which would be allowed to articulate about the point on which it bears onto the rafter. At the opposite end, the connection would again be allowed to articulate at the rafter, but this time it would also need to be pinned at the top in order to ensure that any lateral movement could take place without being resisted. These governing design principles are shown in Figure 6. 6. The final connection designs on the
E K R U O R ’ O G N I A L
side of the rafter, which was now acting as a spine beam. Lateral movement could still be resisted by the addition of a socket fixed to the top and articulation art iculation was still afforded around this. Connection designs on the pinned side of the roof are shown in Figure 8. 8. Again, there
knee-joint side of the roof are shown in Figure 7. 7. The spacing of the unit beams did not necessarily conform to the spacing of the old purlins, and thus there were challenges in providing local supports of suffi cient strength streng th at the existing existi ng rafters. At some locations, where the existing rafters contained internal diaphragm stiffeners, load was directed on to the rafter via the adjacent existing cleat. With these cleats no longer taking vertical loads from the now removed
were twoof conditions the local strength the rafter:depending truss loadsonwere either transmitted through to the spine beam via puncheons; or they were directed straight onto the rafter via a full box tie. Resistance to lateral movement was avoided through the introduction of pinned joints (swivel couplers) at the top of the rafter and at the bottom of the unit beam. The temporary roof was purposely designed for limited snow and wind loadings in order to limit the weights and designs of the roof scaffold elements and connections. This also assisted cranage, handling and justification of the existing steelwork for the temporary condition. This was all achieved by using a removable sheeting system. The
purlins, it was relatively easier for the new loads to be justified. At other locations, where vertical load couldn’t be transferred directly onto the top of the existing rafters, this was dealt with by way of a puncheon connected to another unit beam fixed to the
sides of each sheet were contained within tracks which allowed them to be drawn through from one end, meaning they could be opened or closed as required. Weather conditions were monitored on a daily basis so that the sheets could be removed in the
4 4 Figure Corner roof partially removed to allow installation of lower MEWP support platform
6 6 Figure Indicative diagram of 5 5 Figure Extract of initial proposal for temporary roof showing typical section with lightweight aluminium unit beams spanning between existing roof rafters
temporary roof load-path system showing pin-based single knee-joint portal to accommodate main roof movements
See detail, Figure 8
See detail, Figure 7
Part 2
28
TheStructuralEngineer December 2016
Project focus Etihad Stadium expansion
7 7 Figure Connection designs of temporary
8 8 Figure Connection designs of temporary
scaffold roof at knee-joint side of roof
scaffold roof at pinned side of roof
event of snow or wind speeds forecasted to be in excess of 56mph. Following satisfactory completion of the design for the temporary roof, the framing was installed first followed by the sheeting (Figure 9). 9).
9 9 Figure Temporary corner roof
Construction of new central roofs
For the installation of the roof rafter sections, an MEWP was located in a specially designed trackway that was installed on the existing roof (which was in its interim condition). This provided access to the connection points of the rafters, temporary roof supports and purlins. The roof rafters needed to be supported until the permanent mast-and-stay tension system was effective. Temporary Temporary props, supported from the terrace rakers, were provided to support the individual rafters. These were
E K R U O R ’ O G N I A L
www.thestructuralengineer.org 29
D L O P P A H O R U B
D L E I F R E V E S
11 11 Figure Photo taken on edge of central roof portion showing new roof rafters being
10 10 Figure New roof rafters being installed on temporary props on new terrace
installed on temporary props on new terrace with new roof installed over existing roof (old corner roof has been removed)
(MEWP on its track on cut-back interim roof can be seen to right)
E K R U O R ’ O G N I A L
D L O P P A H O R U B
12 12 Figure Erection of corner roof space frame
restrained laterally by a series of guy wires (Figures 10 and 11). 11). The upper and lower struts of the mast/ stay assemblies were installed using temporary wires to hold them in position until the tie bars were installed. The tie bars of the new forestays and backstays, which are up to 60m long, were installed using a lifting beam that provided support at 6m centres along the length of the bar. The support was provided by a nylon strop wrapped around the bar. Once again, access was an issue, this time to release the supports once the tie bars were installed. To overcome this issue, a remote release devise that could be activated from one end was developed. Once the tie bars had been installed, the roof needed to be lifted off its props and the load transferred into the permanent tension system. This was achieved by tensioning the tie bars at the connection point to the main structure using a jacking frame.
13 13 Figure Deconstruction of interim roof (note yellow gantry on top of interim roof)
The transfer was carried out in two stages: one for each half of the roof. This was to avoid any built-in arching stresses. Following the load transfers, the two halves of the roof were connected together.
Construction of new corner roofs The corners of the roof were structurally independent of both the new and existing roofs, and a space frame type structure was chosen (see Part 1 for design details 1). The main challenge in the construction was to build them around the existing tension ring which was located above the existing roof but below the new roof. This resulted in the tension ring passing through the corner roofs. To achieve this, the roofs were preassembled into large units on the ground and installed around the cable net. In order to optimise the preassembly, a common boom member in the truss was split into
two so that it could be incorporated into the preassembled sections and then bolted together in the air (Figure 12). 12).
Removal of existing roof On completion of the new roof, the major challenge left was to take down and remove the existing roof. As the new roof had been constructed above the existing roof, the only way that cranes could be utilised was to position them on the playing surface, using a specialist crane mat pitch protection system to minimise damage to the ground. However, However, enough time had to be allowed following removal of the protective mat for the grass to grow back before the start of the football season. The only way to achieve that was to develop a methodology that allowed the removal of large sections of roof that could then be laid on the playing surface, cut up and removed from site. Removal piece
Part 2
TheStructuralEngineer December 2016
30
Project focus Etihad Stadium expansion
by piece would have taken too long and presented some very interesting access challenges. Unfortunately, the proximity of the new roof to the existing roof precluded a crane from lifting a large section out directly. di rectly. The design of the existing roof relied on pairs of
the football season. While the design and construction challenges were appreciable in themselves, the request by the club to provide continued rain protection over the existing stand provided a significant further challenge. Of particular interest are the solutions found
Project credits
rafters, braced together in plan. This paired unit formed a conveniently large section to lift out. A methodology was developed that involved lowering off the front end of the roof, using the temporary support at the rear to pivot about. This increased the available headroom above the existing roof to allow a large mobile crane to pick up the unit and move it onto the playing surface, where it could be cut up and transported off site (Figure 13). 13). This method resulted in a five-week time saving to the critical close-season activities.
Piling: Van Elle and Expanded Project management: Christal Cost consultant: Turner and Townsend Wind tunnel testing: RWDI
The main construction challenges arose from key objectives of the rapid programme,
to this challenge: the interim roof and the delivery of the detail design solutions through jacking, numerous numerous load transfers transfers and effective effective underpinning of the existing clad cable-net roof with new columns. The project was awarded a Steel Design Award for 2015 and the Institution of Structural Engineers Award for Sports or Leisure Structures for 2016. Such awards recognise aspects of technical excellence, but it is important to realise that project success is achieved through all parties pulling together with common purpose, as happened for this project. In addition to the collaboration of the design and construction teams, the authors express their appreciation for the dynamic, proactive and enthusiastic
which required completion of the works by the start of the 2015/16 season and minimal disruption to the Etihad Stadium’s operations, including no seat loss on match days during
leadership offered to the project by Manchester City Football Club, particularly from Jon Stemp, Ed Dalton, Danny Wilson and Pete Bradshaw.
Conclusions and acknowl acknowledgements edgements
Client: Manchester City Football Club Architect: Populous Structural, civil, geotechnical, fire and facade engineer: BuroHappold Engineering Main contractor: Laing O’Rourke Steelwork contractor: Severfield Temporary corner roof: Allied Scaffolding Ltd
References 1
McCormick F. and Pottinger A. (2016) ‘Expansion of the Etihad Stadium, Manchester. Part 1: Design’, The Structural Engineer , 94 (11), pp. 22–30
2
Bush A., McCormick F. and Hulme P. (In press) ‘Etihad Stadium Expansion: Design and Construction’, Proc. ICE Civ. Eng.
Sir Arnold Waters Medal The Sir Arnold Waters Medal is open to presentations that have won a Regional Group award in the session.
To be eligible for consideration, all authors of a presentation must be members (any grade) of the Institution, and the presentation must be submitted to HQ by the Regional Group. The Judging Panel will consider: Value to the profession as a contributio contributionn to the art and science of structural engineering Clarity and presentation Extent of the author’s responsibility for the work described
Entries for 2017
•
•
•
•
Presentations must be submitted to the panel secretary by the Regional Group Chair/Secretary by 28 February 2017 The submission may take the form of a written paper, an electronic presentation (e.g. PowerPoint), or any other suitable method
•
Further information on entries can be found at www.istruc www.istructe.org/Arnold-Waters te.org/Arnold-Waters
Sir Arnold Waters VC VC 1886–1981 President: 1933–34 and 1943–44
The only person to have been Institution President twice, Sir Arnold Waters was awarded the Victoria Cross for an act of bravery in completing the construction of a bridge during the second Battle of the Sambre near Ors in France in 1918. Registered with the Charity Commission for England and Wales No. 233392 and in Scotland No. SC038263
www.thestructuralengineer.org
TheStructuralEngineer December 2016
31
Professional guidance Articles that provide information and advice on everyday matters affecting the practising structural engineer.
32 Engineer’s Guide to PI Claims. 11: Post-loss reviews and lessonsPart learned 34 Managing 34 Managing Health & Safety Risks No. 57: Hazards from ground movement 36 Confidential 36 Confidential Reporting on Structural Safety (CROSS)
Part 11
32
TheStructuralEngineer
Professional guidance
December 2016
PI claims
Engineer’s Guide to PI Claims. Part 11: Post-loss Po st-loss reviews reviews and lessons learned learned We conclude the series on PI claims from Gr Griffi iffith ths s& Armour with Armour with a look at what engineers can gain from a post-loss review.
Since January, our series has traced the life of a fictional professional indemnity (PI) claim against an engineer, considering last month some of the issues which should be taken into account in negotiating settlement agreements. That would normally be the final step in bringing the dispute to a close, followed by a transfer of any settlement funds from the relevant party and/or their insurers. At this point, everyone usually breathes a sigh of relief – a weight has been lifted from the engineers’ shoulders and they can now concentrate on their next project. But in most cases it would be a mistake simply to close the file, put it down to experience and carry on.
Implications for policy renewal If the claim has cost the PI insurers any significant sum of money, then it will feature in any renewal negotiations between the engineers’ brokers and the insurer’s underwriters. In extreme cases, underwriters might decline to offer renewal terms at all. A more common response is for underwriters to impose an additional premium, an increased excess and/or additional terms and conditions relating to any areas of perceived higher risk.
claims are so high in value that insurers will simply never recoup their losses, even with an extended period of increased premium contributions. For that reason, something further is now often required beyond a tough negotiation around premium levels. PI underwriters typically look for constructive feedback at management level from firms
broker in the form of a post-loss review. This should be a candid, retrospective look at precisely what it was that went wrong, how similar occurrences can be prevented in future and, crucially, how to evidence this to insurers. In our final article, therefore, we give examples of the sort of themes that engineers in this position might t ypically
But in current market that conditions, underwriters recognise there are limits to how much additional premium or self-insured retention can realistically be imposed on engineers without forcing them to shop around for alternative options. In addition, some construction PI
of engineers who have had claims, asking: “what did yousignificant learn from the experience and what will you do differently in future?” Engineers might find that a diffi cult question to answer unless some appropriate guidance is offered from a
explore. Theto impetus be provided by the need satisfymight PI underwriters in the short term, but if undertaken in the right way, the exercise should produce meaningful longer-term benefits for the practice’s stakeholders, including its owners, staff and clients.
www.thestructuralengineer.org 33
Technical standards One of the obvious ways of dem onstrating something positive to insurers is to show
in preventing spurious claims from arising (because there should be less room for dispute over, for example, whe re
project if, after that conversation, you still feel uncomfortable. Similarly, claims often arise out of cases
that you have addressed any areas of technical weakness in your work that might have been highlighted in an expert’s report, even if those shortcomings were not in fact causative of loss in the final analysis. Anything that you can do to show that you are managing the risk of si milar perceived shortcomings in future will be well received by underwriters, whether it is a record of technical training for staff, some form of enhanced checking regime, an audit or peer-review process, or a greater degree of supervision over less experienced staff. Following a significant claim, it might also be appropriate to put together a presentation for your staff so as to
your services began and ended) and in mitigating loss when liability attaches. It can be useful to review the clai m in this context. Could a different form of agreement have prevented the dispute altogether, or could it have placed the defence team in a better positi on to negotiate a favourable settlement? Underwriters might be interested to understand who within the practice has responsibility for negotiating agreements and how they go about it . What are their absolute minimum non-negotiable requirements? Can they give any examples of how their policie s in this regard have improved following the claim, or can they cite any instances of having walked away
where the engineers have accepted a project which was not a good match for their skills and experience. In both cases, it can be useful to set out for underwriters an account of how your practice goes about selecting the projects in which you become involved. Can you give any examples of work that you have turned down or where you have decided not to enquire further? How often do you say “no” and why? Who within all but the smallest of firms has the final say on which instructions you will accept? What criteria do they employ? This could be a positive statement to underwriters about where you feel your technical and organisational strengths lie
increase awareness of how errors can arise and what the effects can b e. Your brokers may be willing to assist you with this and it can help to create a healthy culture in which your staff lea rn from one another’s experiences.
from work because satisfactory contact terms could not be agreed?
and why, despite now having a significant claim on your record, you should still be regarded as a good risk.
File management It may be that your engineeri ng work was essentially flawles s, but that it was diffi cult to defend the claim for other reasons. Perhaps there was a lack of documentary evidence showing that you had indeed warned your client about the risks of proceeding wi th a lowercost alternative – in which case, can you demonstrate that all staff now understand the importance of committing all client advice into writing and maintaining a comprehensive file recording all such exchange s? Does your offi ce have a polic y of random audits at regular intervals so that you can check the general condition in which files are being maintained, and in particular check that these procedures are being followed? Underwriters are we ll aware of the value of documentary evidence in defending claims, a theme which has been the subject of some emphasis in this series. Being able to demonstrate a few simple issues of good housekeeping may well go a long way towards demonstrating what they want to see.
Contract review The majority of claims against engineers are made in contract rather than in negligence. Underwriters are well aware of the value of a well-drafted agreement
Project selection criteria Conclusion
A recurring theme in claims against engineers is that they often arise out of projects which were simply never going to be successful and which, with hindsight, the engineer would never have agreed to take on. Warning signs are often identified by the engineers at an early stage, but for one reason or another (commercial pressures, sanguine hopes of improvement or an unwillingness to upset the client) they feel that they must continue with the project only to regret this at a later date. The tipping point is usually the formation of a contract between an engineer and its client. Once that agreement has been formed, whether in writing or otherwise, the engineer is bound to see the project through to completion and there will be no quick exit route if things turn sour. If your claim arose out of one such project, what might you do differently in future? It may be that you can demonstrate to underwriters that you now have a system in place which encourages your staff to flag up early warning signs, such as an unrealistic budget or programme, contractors taking on projects wide of their experience, or simply aggressive
lea ding independent indepe ndent Griffi ths & Armour is a leading and privately owned UK insurance broker
personalities who willdoesn’t refuse go to to listen to reason if something plan. These risks should be identified prior to formal acceptance of the client’s instructions, so that you can consider having a frank conversation with your client and even withdrawing from the
and risk management adviser. further information, scan the QR codeFor or visit www.griffi www.gr iffithsandar thsandarmour.com mour.com.. Griffiths & Armour Ar mour is authorised and regulated by the Financial Conduct Authority.
Whether initiated by questions from underwriters or not, post-loss reviews should be embraced by engineers who have faced claims as an opportunity to learn from the experience and to produce something positive out of the negative. The review process may be more or less formal depending on the circumstances of the loss and the profile of the firm. Some form of documented output will nearly always be advisable as the best means of distilling the issues and producing relevant action points. The tangible document will also be of value for policy renewal purposes. It is hoped that this article gives a feel for how an engineer might go about the process. It need not be particularly complicated or time consuming if it is suitably focused. And finally, as is often the case with risk-management exercises, do remember never to be afraid of stating the obvious.
34
TheStructuralEngineer
Professional gu guidance
December 2016
Health and safety
Managing Health & Safe Safety ty Risks The Aberfan disaster claimed 144 Figure 1
lives in south Wales
No. 57: Hazards 57: Hazards from ground movement
Any risk assessment consists of three parts: identifying hazards; assessing the probability of occurrence; and considering the consequences. Historically, some of the worst failures have occurred when the hazard was unforeseen and the consequences severe. Normal foundation design consists of checking the bearing capacity of whatever is provided, but the possibility of losing foundations altogether is to be feared. This can occur through general ground movement. Recently the UK has commemorated the 50th anniversary of the Aberfan disaster (south Wales) in which a whole mining spoil tip moved, engulfing housing and a school 1. In total, 116 schoolchildr schoolchildren en and 28 adults were killed, buried by the soil. The tip was unstable (partly because material had been dumped on flowing water) and the potential for movement had been ignored (Figure 1). 1).
Scour Less dramatic failures occur by bridge scour and, in recent years, several bridges have been washed away in floods. A notable example was a bri dge in Workington (Cumbria, UK) which was swept away in a storm (2009) with a policeman still on it2. The danger is perhaps exacerbated as predicting how scour may undermine foundations is not a precise art and scour development is not easy to identify by surface inspection alone. The Workington failure also demonstrates a breaking of one fundamental structural safety attribute: that structures should display adequate warning of developing collapse3. There have been many other examples of building damage caused by flooding around their foundations; one example occurred
Y T T E G
slip occurred after torrential rain)5. With more houses being squeezed onto less appropriate sites in the UK, the hazards from the surrounding areas need to be considered, including how potential ground movement might be triggered by a severe storm.
common, not least on railway cuttings. The consequences consequ ences range from traffi c disruption disrupti on to derailment. Landslips also occur in other circumstances. In 2013, a woman died when a landslide engulfed her house in Cornwall, burying her while asleep (the
Sink holes Structures have also been affected by sink holes opening up, in some cases allowing whole dwellings to collapse into the void. Such holes might develop from old mine shafts, from groundwater flow or from leaking sewers. Dramatic cases occur with regularity6,7. In 2016, a large sink hole (5m × 3m) developed in the new carriageway of the A1 near Newcastle 8. Also in 2016, a car fell into a sinkhole in Greenwich, London9. In Manchester in 2015, a spectacular hole developed within the Mancunian Way urban motorway. It cost £6M and a year’s work to rectify the hole, which had apparently been created 10
in 2014away in Newcastle when surrounding flood watersthe swept all the ground piled foundations below a block of flats. The block had to be demolished 4.
Landslips Landslips along embankments are
Y T T E G
2 2 Figure 15m deep A sink hole caused considerable damage in Fukuoka, Japan, in November 2016
by leaks from a 100-year-old sewerwhat . It takes little imagination to envisage might have happened if any of these holes had developed under a bridge pier. The danger of leaking pipes was recently seen dramatically in Florence, Italy 11, while Figure 2 shows an urban sink hole that formed in
www.thestructuralengineer.org
35
Fukuoka, Japan, in November 2016.
REFERENCES: 1) Wikipedia (2016) Aberfan d isaster [Online] Available at: https:// en.wikipedia.org/wiki/Aberfan_disaster (Accessed: November 2016) 2) BBC News (2009) Witness describes Workington bridge collapse [Online] Available at: http:/ http://news.bbc.co.uk/1/hi/uk/8371834.stm /news.bbc.co.uk/1/hi/uk/8371834.stm (Accessed: November 2016) 3) Institution of Structural Engineers (2016) ‘Managing Health & Safety Risks No. 55: Attributes of structural safety’, The Structural
as she slept’ in Looe [Online] Available at: www. bbc.co.uk/news/uk-england-cornwall-37899252 (Accessed: November 2016) 6) CCTV News (2016) Police offi cer dive rts traffic around in China before a sink hole opens up [Online] Available at: www.youtube.com/ watch?v=_wS-6KXSmg0 watch?v=_wS-6KX Smg0 (Accessed: November 2016) 7) Science alert (2016) This gigantic sinkhole in Ottawa just took out a 4-lane road [Online] Available at: www.sciencealert.co www.sciencealert.com/gig m/giganticanticsinkhole-in-canada-s-capital-ottawa-mayhave-been-caused-by-quick-clay have-been-caused-by -quick-clay (Accessed: November 2016) 8) BBC News (2016) ‘Large sinkhole’ closes busy A1 in Gateshead [Online] [Online] Available at: www. bbc.co.uk/news/uk-england-tyne-36633416 (Accessed: November 2016) 9) The Telegraph (2016) Greenwich sinkhole may have ‘serious impact’ on house prices, say experts [Online] Available at: www.tele www.telegraph.co.uk/ graph.co.uk/ news/2016/05/12/car-falls-down-sinkhole-ingreenwich/ (Accessed: November 2016) 10) Manchester Evening News (2016) Mancunian Way hole [Online] Available at: www. manchestereveningnews.co.uk/all-about/ mancunian-way-hole mancunian-way -hole (Accessed: November 2016)
Engineer, 94 (10), pp. 34–35 4) ITV News (2014) Newburn flats to be demolished [Online] [Online] Available at: www.itv. com/news/tyne-tees/topic/newburn-flats/ (Accessed: November 2016) 5) BBC News (2016) Landslide ‘buried woman
11) The Guardian (2016) Off-street parking: Florence road collapse sinks row of cars [Online] Available at: www.theguardian.com/world/2016/ may/25/florence-road-collapse-sinks-row-ofcars-ponte-vecchio-street-italy cars-ponte-vecchio-s treet-italy (Accessed: November 2016)
have been identified • make sure all underground services have been identified: consider their age and potential for failure and the potential consequences • consider the sensitivity of the design to foundation disturbance and make sure the
Poor design Most of the failures described here were linked to “natural events”, but gross failu res have also been triggered by carelessness or poor design. Excavating in front of foundations is problematical; cases are known of wall foundations kicking in when basement floor slabs have been removed; or of portal frame columns moving when holes have been dug next to their foundations, apparently in ignorance of the fact that the pad foundations resist both vertical load and lateral thrust. If services are run in front of retaining walls, it is self evident that they may, in time, be accessed for repair, potentially removing ground providing resistance to forwards movement of the wall.
structure is “robust”
This guidance note has been prepared by the Institution of Structural Engineers’ Health and Safety Panel.
Safety lessons The safety lessons for designers are to:
• consider all local hazards with potential to affect the structure • consider how gross movement might be triggered by severe weather • make sure all potential underground voids
Call for papers
The Structural Engineer Engineer
36
TheStructuralEngineer
Professional guidance
December 2016
CROSS newslett newsletter er
Confidential Reporting on Structural Safety (CROSS) In this article, we summarise CROSS newsletter No. 44 from Structural-Safety Structural-Safety.. CROSS is keen to receive reports about damage caused by weather events and a new section of the website has been opened for the purpose – Weather damage. This is a long-term project sponsored by the UK Department of Communities and Local Government to help determine whether the Buildings Regulations might need to be amended. In addition, of course, we continue to need reports about concerns, or possible failures, or failure events. They are sent by consulting engineers, contractors, owners and operators of large infrastructure groups, local authority building controllers, and others. After processing to remove names and identification details, they are reviewed by our panel of experts who provide comments that can help others to learn from these experiences. Reports and comments are published on the website and many are included in these newsletters, which are freely available and widely read. There is still much work to do by identifying risks during design, construction and operation, and using these to create a safer environment for the public and for those in the industry – so please contribute. The success of the CROSS programme depends on receiving reports, and individuals and firms are encouraged to participate by sending concerns in confidence to Structural-Safety at www.structural-safety.org/confidentialreporting/submit-report/.. reporting/submit-report/ In this issue, however, the high standard of reports continues, with concerns about: crane base bolts, inadequate bracing in a design, more on the sudden hole in a piling
when supposedly Grade 10.9 high-strength holding bolts failed on a crane base. Sixteen bolts, which had been pre-tensioned in the standard way, all failed within four days. This was found to be a brittle failure failure and because the bolts were prestressed, they failed in a manner which released energy, resulting in the bolt heads being ejected up to 4m above the lifting frame. It is believed the failure was due to delayed hydrogen embrittlement, which can be caused in the manufacturing manufacturing process.
Inadequate structural design at school
On review of a design for a school extension, a reporter noted several major issues including an almost total lack of vertical bracing throughout the extension, and a total lack of roof bracing in the hall. The design was carried out internally by the local authority which was responsible for the school, yet it appeared to the reporter to have been carried out by inexperienced engineers with lack of adequate or competent checking. These concerns were raised with the contractor, who then relayed them to the local authority and modifications were made.
Sudden hole in piling mat (2) This is further information about Report 566 “Sudden Hole in Piling Mat”, which was published in the April 2016 Newsletter. The report at that stage was not conclusive about the cause of the hole and does not reflect the conclusions of later investigation investigation.. The report has therefore been updated.
safety critical surface at the top of an 8m high embankment. This occurred over a distance of some 25m directly above a length of rockfill shear key being installed at the embankment toe (Figure 1) 1). Had there been a failure of the embankment the consequences could have been severe.
Responsibilities for hybrid concrete construction There was a report about a problem during the construction of a hybrid concrete overbridge. A substantial precast element, weighing over 10t, had been placed in position and used as part of the shuttering for an in situ pour. During the pour, the element was pushed out of alignment by the pressure of wet concrete and there was a substantial spillage onto an operating area below.. It was subsequently established that below the designer and construction team did not adequately review the proposed design to agree upon the construction sequence, including any limitations of the proposed permanent works design to resist temporary loads.
Wind damage damage to roof with with PV PV panels panels A reporter has a house which was built in 2011 and had solar panels installed on the roof flush with the tiling. Later the same year she had external PV panels fitted. During a heavy storm, a big area of roof tiles blew down. The reporter suspects that the solar panels have caused local wind turbulence and caused loads in exces excess s of the roof design load.
Fixing systems for gravestones Embankment slip Vertical movement movement was observed on the
This report is about the safety of pins used to hold headstones in place. There is a standard pin which is widely used in the monumental masonry industry but which, when tested independently, failed when gravestones were pushed from behind or from the front.
Comments
mat, an embankment slip, hybrid concrete construction, wind damage to a roof with photovoltaic (PV) panels, and the safe fixing of gravestones.
Further details and comments these reports from the CROSS panelon can be found online at www.structural-safety.org .
Receive the newsletter Failure of Grade 10.9 bolts There was a high potential for collapse
Figure 1 1 n through embankment Cross-section Cross-sectio
Readers can register to receive the CROSS newsletters at www.structural-safety.org .
www.thestructuralengineer.org
TheStructuralEngineer December 2016
37
Technical Articles that are technical in nature; focusing on methods of analysis, material properties and aspects of design of structures.
38 Temporary Works Toolkit. Part 4: An introduction intr oduction to backpropping of flat slabs slabs 42 Structural use of bamboo. Part 3: Design values
Part 4
38
TheStructuralEngineer December 2016
Technical Temporary Works Toolkit
Temporary Works Toolkit Part 4: 4: An introduction introduction to backpropping of flat slabs
The Temporary Works Toolkit is a series of articles aimed primarily at assisting the permanent works designer with temporary works issues. Buildability Buildabil ity – sometimes referred referr ed to now as “construction method engineering” – is not a new concept and one always recognised as vital to the realisation r ealisation of one’s ideas; it ought to be at the forefront of an engineer’s mind. www.twforum.org.uk www.twforum.org .uk
Eur. Ing. Peter Pallett BSc, CEng, FICE, FCS Above Ground Temporary Works Consultant, Pallett TemporaryWorks Ltd.
Introduction Backpropping of concrete slabs during construction is a subject often misunderstood in the industry. Regrettably, many permanent works designers (PWDs) still consider the subject as “not relevant and a contractor’s issue”. This article explains the theory and background to backpropping and gives advice on the methods recommended to be adopted for backpropping calculations. It looks at the physics involved and how engineers and designers can mitigate damage to concrete slabs during construction. A second article, giving worked examples, with solutions to reduce overloading flat slabs during construction, will follow in the January issue. The client and the PWD have legal responsibilities to ensure that a structure can transfer any loads from backpropping. The Construction (Design and Management) Regulations 2015 (CDM 2015) legal guidance (L153)1 has very specific requirements for designers to control temporary works. The law alsodesign states…that a structure “be of such as to withstandhas anyto foreseeable loads which may be imposed on it” (CDM 2015 Reg. 19(2a))1. Backpropping during construction is a totally foreseeable load on the structure. Hence, designers have to consider backpropping and understand
The mechanics of how loads transfer through slabs is basic physics: within elastic limits the deflection of a slab is proportional to the
proportional, each slab would effectively be taking 50% of the applied load. This is not correct, because the props will themselves be elastic members and need to shorten as they take load. So, if you have the same two identical floor slabs, but now separated by elastic props (Figure 1b), 1b), as the load is applied to the top slab, the props have to physically shorten in order to transfer load to the lower slab. The upper slab must now deflect more than the lower slab as the distance apart is reducing. Thus, distribution of load will not be even – resulting in more load applied to the upper slab. The theory predicts an approximate 70:30% split of the loads. When the three-dimensional deflected shape of a slab is considered, the movement of the various members and their method of support becomes complex. The simple assumptions discussed so far take no account of the different physical stiffness of the completed floor slabs. Older floors are stiffer than newly constructed
total applied load on the slab – to carry load it needs to deflect. So, if you have two identical floor slabs separated by rigid (non-elastic) props (Figure 1a), 1a), applying a load to the top slab would cause both slabs to deflect by the same amount. Hence, as load/deflection is
ones; hence, they have differentisdeflection properties. Further, no account taken of the different stiffness of the backprops – aluminium members being less stiff than steel props. Another aspect of load transfer is whether or not the backprops have been inserted with some residual load, i.e. as
the mechanics of load transfer during construction of their designed structure. To quote a senior and respected engineer on whether concrete slabs get overstressed during construction: “It’s not a question of whether they crack, but by how much they crack!” The issue is really quite simple: nearly all modern buildings are designed for imposed loads that represent only a small proportion of the total design load. Many commercial buildings have a ratio of imposed load to self-weight of 1:2.5, and apartment buildings often less at 1:3.5. Hence, the self-weight of the next slab to be constructed cannot be taken on the recently completed slab, and the construction loads need to be distributed to lower, already completed, floor slabs. This transfer of load is known as “backpropping”.
The physics
www.thestructuralengineer.org
39
1 1 Figure Floor slabs separated by props
than two two levels levels was unnecessary, as the load just didn’t didn’t get distributed distributed to the the lowest lowest level. The detailed research was written up for industry use by the Concrete Structures Group in CS140: Guide to Flat Slab Formwork and Falsework 3. Early striking stri king of soffi t formwork and
while striking the falsework to that slab, a designer has no idea where the weight of the slab and any imposed load is being supported. Is it transferred to the building’s columns/walls? Is it carried by the reprops? Is it distributed between various supports? There have been major collapses of such
falsework was a key issue and the research introduced a new method of considering early striking of slabs. Research was also published on a more accurate method of predicting the concrete strength required – based on determination of crack width, as opposed to earlier methods based on a simple ratio of loads4–6.
structures with props “left in place” without an understanding of how much load was being transferred and to where! It is therefore an important rule of thumb in backpropping calculations that the formwork/ falsework to a recently cast slab be struck completely; the new slab is allowed to take up its instantaneous deflection under selfweight, and only then has a designer the confidence that the floor self-weight is now being transferred directly to the permanent supports of the columns/walls, etc. Hence, any loads transferred through this floor from construction of higher floors will all be “additional loading” to that already on the slab. This rule of thumb does not not preclude preclude the
a) Rigid props
Methodology If you leave propping in under a slab that has just been cast, such as installing installing “reprops “reprops””
b) Elastic props
pre-tensioned props which would push the floor above upwards, decreasing its load, while at the same time increasing the load into the lower floor. The nomenclature usually
"It is an important
used for backpropping relating to the varying stiffness is shown in Figure 2. 2.
Research In the 1990s, industry concerns were formulated into a research project, culminating in full-scale trials at the European Concrete Building Project (ECBP) which were completed in 1998. The research, led by Prof. Andrew Beeby, University of Leeds, was published in 2000 in a Building Research Establishment Report (BR 394 Task 4) 2. It demonstrated that it is the supporting slab below the falsework that takes the majority of the load when backpropping. It further confirmed that backpropping through more
2 2 Figure Diagrammatic representation of backpropping
Stiffness
rule of thumb in backpropping calculations that the formwork/ falsework to a recently cast slab be struck completely"
One level of backpropping
use of, say, two sets of formwork/falsework without any backpropping being used. This is a common technique used in developing countries as sets of equipment leapfrog up the building. The Concrete Society’s formwork Worked Example 77 highlights the limits of such a technique and illustrates the significant role of the PWD in accepting that loads greater than designed are being applied regularly during construction. Consider the general arrangement of construction of a concrete slab, with its i ts soffit formwork and grid of supporting falsework legs standing on the previously cast floor. When the fresh concrete is placed, does the load distributed into the supporting slab
Load
Slab to be cast
wp
Falsework Supporting slab (1)
Ss1
Backprops
Sb
Lower slab (2)
Ss2
Backprops (when fitted)
S
wb1
w
b
Lower slab (3)
b2
Ss3 Any preload to props is
PP
Two levels of backpropping
Part 4
40
TheStructuralEngineer
Technical
December 2016
Temporary Works Toolkit
act as a distributed load, or as individual point loads from each of the falsework legs? Further, the grid of backprops below the supporting slab, transferring load to lower floors, will rarely be at the same centres as
be used in calculations for assessing assessing the amount of backpropping necessary. Worked examples of backpropping calculations using Method 1, including “What if?” scenarios, are published in the
predict the load transfer transfer,, knowing the stiffness of the slabs and the stiffness of the backpropping. It considers deflection of the system in two dimensions only. Refer to CS1403 for more detailed
the falsework legs (only about a third of the load is transferred); hence, the concrete supporting slab will also have an influence on load transfer. Thinking in three dimensions complicates backpropping calculations still further. It is more usual for designers to simplify the approach and regard the applied loads from the formwork/falsework as a distributed load applied to the supporting slab. There are four methods by which designers can complete backpropping calculations.
separate booklet with the Concrete Society formwork guide7. The percentages of load transmitted through lower supports for a falsework cast with no backpropping, with one level backpropped, and then with two levels of backpropping, are shown in Table 1. 1. The table assumes elastic backprops and, where there are two levels of backpropping, that they are identical, i.e. exactly above each other on the floor plan. It is important to state that the distributed load applied on the existing floor slabs is additional to the load already supported by the floor at the time considered. Designers will be aware that this method gives loads in backpropping significantly less than
information on this method.
Method 1 Based on the University of Leeds research 2, this method (also reproduced in Clause
19.3.4 of BS 59758 and in Section 5.4.2.3 of the Concrete Society formwork guide 9) uses a simple assumption about the percentage of load transferred through the supporting slab(s). The method is generally conservative, and recommendations on percentages for either one or two levels of backpropping are given. This is the method most likely to
previously assumed for rigid backprops. The corollary being that more load is required to be carried by the supporting slab with the realistic assumption of elastic backprops.
Method 3 This method, using simplified equations, is given in detail in CS1403 and Section 5.4.2.5 of the Concrete Society formwork guide9. The equation for two levels of inserted backprops is reproduced below; it assumes that the slabs have been struck individually, and have taken up their deflected shape, prior to installation of the backpropping. The analysis assumes that the structure is in two dimensions only, only, and that to calculate the loads in backpropping the slabs will be at least twice the stiffness of any backpropping introduced. This makes and (see Fig. 2) 2) For two levels of backprops, as shown on the right hand side of Fig. 2: 2:
Load in top backprops is (1)
Method 2 This method uses the equations established by the University of Leeds research2 to
Load in lower backprops is Table 1: Method 1 percentage of load transfer for flat slabs less than 350mm thick
Location
Load
No backprops fitted
One level of backprops On slab
New slab cast on falsework
wp
Supporting slab Backprops
wb1
Lower slab (2) Backprops Lower slab (3)
wb2
100%
In prop
100% 100%
100%
70% wp
None
–
–
30% wp
None –
On slab
In prop
100%
100%
– 30% 30 % wp
100% 65%wp
–
– 35% wp
23% wp
–
None
–
12% wp
–
12% wp
–
–
Notes:
1) Assumes all floors are of of similar construction and have similar stiffness at time considered 2) Assumes lower and supporting slabs have been struck and have taken up their deflected shape and are carrying their own weight 3) The distribution is that percentage of the applied load onto the supporting slab. Each floor slab will also have to carry its own self weight and any imposed construction loads already on the floor 4) Determination of the characteristic strength of the slabs to carry the applied loads is not considered 5) All floors are suspended floors and Method 1 slabs are flat slabs
(2)
Two levels of backprops Method 4
This method is a more accurate determination by using a three-dimensional representation of the equations in Method 2. It introduces introdu ces deflection deflect ion coeffi cients and allows for the location of the slab and its deflected shape. Edge panels will behave differently to internal panels of the slab, etc. The calculation is presented as an Excel® spreadsheet on a CD-ROM with CS140 3. The spreadsheet allows selection of interior panels, edge panels, corner panels or panels supported on four sides by walls/ beams. The stiffness of the concrete slabs and backpropping can be varied, and props can be preloaded. The output gives gi ves a “loading factor”, a “cracking factor” and an deflection If all arefor less“effective than unity, then thefactor”. limits are safe striking. If any factor is greater than unity, then reference must be made to the PWD – the philosophy of loading a slab to above its design service load is extensively discussed in Annex E of CS1403.
www.thestructuralengineer.org
41
With one level level of backpropping backpropping
loads, once the arrangement of the falsework and the backpropping is known, is to use the CS140 spreadsheet3.
erection has commenced before installing the backprops, the supporting slab will already be supporting this construction load. The load in the two levels of backprops Wb1 and Wb2 may be estimated from Method
The previously cast floor slab is now the supporting slab for the next level of construction, as shown on the left-hand side of Fig. 2. 2.
With two levels levels of backpropping backpropping
The temporary works coordinator (TWC) will need to establish whether the supporting supporti ng slab has suffi cient capacity capa city at its very early age to support the self-weight of the temporary works and possibly some imposed construction operations load at the time considered. As the supporting slab matures, its capacity should increase up to its design service load capacity. Note that the supporting slab should always be considered to take the weight of the formwork and falsework for the next slab. This overcomes the onerous requirement to place the backprops in position before formwork can be moved vertically up the building. The intention should be to install the backpropping at the earliest available
Three previously cast floor slabs are now the supports for the new slab, with the most recently cast slab being the critical supporting slab, as shown on the right-hand side of Fig. 2. 2. The TWC will need to first establish whether this supporting su pporting slab sla b has sufficient “spare capacity” at its very early age to support the self-weight of the temporary works and some imposed construction operations load at the time considered. As the supporting slab matures, its capacity should increase up to its design service load capacity. The supporting slab should always be considered to take the weight of the formwork and falsework for the next slab. This overcomes the onerous requirement
1, Table 1, 1, Method 3 (using Equations 1 and 2), or be calculated using another method, obviously requiring knowledge of the relative stiffness; the accurate method to predict the loads being to use the Method 4 CS140 spreadsheet 3. The load imposed on the supporting slab (1) will be the difference Wp – Wb1. This loading often governs the speed of construction at this critical stage. The TWC must ensure that both the supporting slab (1) and the lower slabs (2) and (3) have each ea ch gained suffi su fficient strength strengt h before casting the new slab.
opportunity. The load in the backprops Wb1 may be estimated from Method 1 (Table 1), 1), or be calculated using a simplified Method 3 equation. The additional load imposed on the supporting slab will be the difference Wp – Wb1. This loading is often critical and can govern the speed of construction. The TWC must ensure that both the supporting slab and the lower slab (2) have gained ga ined suffi cient strength before casting the new slab. The more accurate method to predict the
to place the backprops in position before formwork can be moved vertically up the building. In the backpropping calculations for construction of the new slab, the temporary works designer (TWD) will need to establish the total load during construction Wp. This will include the self-weight of the new slab, but with no super imposed construction load. The self-weight of the falsework and formwork may not necessarily be carried through to the backprops, because if
be aware of the implications of specifying design loads, and understand the effects on their slabs during construction caused by load transfer transfers s between floors through backprops. It highlights the coordination needed between the PWD, the TWD and the TWC to ensure safe construction. A second article, to be published in January 2017, will discuss the research results, give a worked example, and demonstrate demonstra te how to reduce overloading of flat slabs during construction.
Conclusion The conclusion from this paper is that all PWDs, as competent designers, need to
References
1
Health and Safety Executive (2015) L153: Managing health and safety in construction: Construction (Design and Management) Regulations 2015 – Guidance on Regulations,, Sudbury, UK: HSE Books Regulations
2
Beeby A.W. (2000) BR 394: A radical redesign of the in situ concrete frame process, Task 4: Early striking of formwork and forces in backprops, backprops , London, UK: University of Leeds and Building Research Establishment Ltd
3
Concrete Structures Group (2003) CS140: Guide to flat slab formwork and falsework , Crowthorne, UK: Concrete Society (Guide includes backpropping Excel spreadsheet on CD-ROM)
5
British Cement Association (2001) Best practice guide No. 4 for in situ concrete frame buildings: Early striking and improved backpropping (BCA backpropping (BCA ref. 97.505), Crowthorne, UK: BCA
6
Beeby A.W. A.W. (2001) ‘Criteria for the loading of slabs sla bs during construction’, Proc. ICE – Struct. Build .,., 146 (2), pp. 195–202
7
Concrete Society (2012) CS169: Formwork – a guide to good practice (3rd practice (3rd ed.). Worked Examples, Examples, Camberley,, UK: Concrete Society Camberley
8
British Standards Institution (2011) BS5975: 2008+A1:2011 Code of practice for temporary works procedures and the permissible stress design of
4
British Cement Association (2000) Best practice guide No. 1 for in situ concrete frame buildings: Early age strength assessment of concrete on site site (BCA ref. 97.503), Crowthorne, UK: BCA
falsework , London, UK: BSI
9
Concrete Society (2012) CS030: Formwork – a guide to good practice (3rd practice (3rd ed.), Camberley, UK: Concrete Society
Part 3
42
TheStructuralEngineer December 2016
Technical Structural use of bamboo
Structural use of bamboo Part 3: Design values Sebastian Kaminski MEng Kaminski MEng (Hons), ACGI, CEng, MIStructE, Senior MIStructE, Senior Structural Engineer, Arup Advanced Technology + Research, London, UK; Member of INBAR Task Force – Bamboo Construction Andrew Lawrence Lawr ence MA (Cantab), CEng, MICE, MIStructE, Associate MIStructE, Associate Director, Arup Advanced Technology + Research, London, UK; Member of INBAR Task Force – Bamboo Construction David Trujillo Trujillo MSc, DIC, CEng, MIStructE, Senior MIStructE, Senior Lecturer, Coventry University, UK; Chair of INBAR Task Force – Bamboo Construction Ian Feltham Feltham MA, CEng, MICE, MIStructE, Director and Fellow, Arup Advanced Technology + Research, London, UK Luis Felipe Felipe López López MSc, CEng, MIStructE, Head MIStructE, Head of Engineering Department, Base Bahay Foundation, the Philippines; Member of Colombian Earthquake Engineering Association (AIS) Synopsis
Bamboo is a strong, fast growing and sustainable material, having been used structurally for thousands of years in many parts of the world. In In modern times, it has the potential to be an aesthetically pleasing and lowcost alternative to more conventional materials, such as timber, as demonstrated by some visually impressive recent structures. This five-part technical series, aimed at both developed- and developing-world contexts, will bring together current knowledge and best practice on the structural use of bamboo, covering: • an introduction to bamboo (part 1) • durability and preservation (part 2) • design values (part 3) • element design equations (part 4) • connections (part 5)
believed to be the most up-to-date guide available for determining design values for bamboo elements.
Nomenclature
f c,0,i = characteristic compressive strength parallel to fibre (N/mm2)
f i,0.05 = fifth percentile value of strength results from test data (N/mm2)
f i,k = characteristic value of population (N/mm2)
f m,i = characteristic flexural strength strength about any axis (N/mm2)
f t,0,i = characteristic tensile strength parallel to fibre (N/mm2)
f v,i = characteristic shear strength about any axis (N/mm2)
k mod = service class and load duration factor
k sys = system strength factor X i,d = design strength (N/mm2) m = mean value of test data nc = number of culms connected
together to form one element
This third article proposes: strengths and other properties for
nt = number of tests (minimum 12,
the scheme designfor of any bamboo species; a method calculating characteristic strength values from test data; and a method for calculating design values of strengths for limit state design. It is
sγ
recommended ≥20)
M
= standard deviation of test data = material factor of safety
C mois = moisture content correction factor
C lab = laboratory test condition factor
Introduction Bamboo typically has a strength similar to high-grade (e.g. D40) hardwood. Testing for strength will in most cases be required before detailed design, as little reliable published data is available. Some tests are more important than others, e.g. flexure, shear and tension perpendicular to fibre are more important than compression and tension parallel, since in most structures it is rare for bamboo elements to be loaded close to their failure in the latter two modes. For very simple structures, it may be possible to use conservativ conservative e design values without any testing. The methods proposed in this article have been developed based on ISO 22156:2004 Bambo o – Structural design desig n ,1 ISO 22157-1:2005 Bamboo – Determination of physical and mechanical properties 2,3 , NSR-10: Colombian code for seismically resistant construction. G12: Structures of timber and Guadua angustifolia Kunth bamboo 4 , EN 384:1995 Structura l timber. Determination of characteristic values of mechanical properties and density 5 and EN 1995-1-1:2004 Eurocode 5: Design of timber structures6. The methods should be used in conjunction with the Eurocode suite of codes. Where there is any ambiguity, refer to EN 1995-1-1 and use good-practice timber design theory. The values proposed assume a rigorous process of testing the bamboo to obtain the test data, and that bamboo selected is of appropriate condition and quality for construction, as outlined in part 1 of this series7. This article is divided into four sections:
www.thestructuralengineer.org
43
Alternatively, for samples of 20 or more specimens, the data can be ranked and the value corresponding to the nth term in the rank may be used as the fifth percentile. The nth term would be determined as: total sample/20. For elements in axial compression only,
Table 1: Moisture content correction factor C mois , as function of moisture content at time of testing Moisture content (MC) (%) MC ≤ 12
Flexure
Shear
1.0
1.0
12 < MC ≤ 18 MC > 18
Tension parallel to fibre
Compressi on Compression parallel to fibre
1.0
1.0
Interpolate between above and below below 1.2
1.2
• Calculation of characteristic strength values from test data • Suggested characteristic strengths for any bamboo at scheme design stage • Calculation of design values • Other values for design
Calculation of characteristic strength values from tes values testt data data Introduction The following method can be used to calculate characteristic strength values for design from test data derived in accordance with ISO 221572,3. This standard includes tests to determine strengths in compression and tension parallel to the fibres, and also strengths in flexure and shear. The sample used for testing must be fully representative of the variability of the material that is proposed to be used for the actual structure. This variability should include origin, age, position along the culm, etc. The minimum sample size stated in the standard is 12; however, in the authors’ opinion, a larger sample size is probably required considering the many sources of variability. In addition, if budgets are limited it is generally better to focus resources on conducting more bending and shear tests than tension and compression tests, since buildings constructed from bamboo are more likely to be highly stressed in the former modes compared with the latter. The number should also take into consideration how well understood and studied a given species is, as well as the available budget. Additionally, it should be noted that the larger the sample size, the less “punished” the design values will be (Equations 1 and 2). 2). The method described here adjusts the test data to 12% moisture content (MC), and also includes adjustment factors for laboratory test conditions. To use the strengths for design, the characteristic values must then be factored by the modification factors given in the section on “Calculation of design values”. These may be conservative, as test data is limited. The mod factor adjusts the strength for servicek class and load duration. The k mod factor for Service Class 1 and 2 corresponds to an MC in the material corresponding to a temperature of 20°C and the relative humidity of the surrounding air only exceeding 85% for a few weeks per year. This is applicable to all air-
1.2
where an element is formed from four or more culms connected together such that they equally share the load (e.g. a column), the characteristic value of strength for a whole population f i,k can be determined from:
1.2
conditioned spaces and most indoor/outdoor covered areas with normal humidity6. Service Class 3 corresponds to climatic conditions exceeding 1 and 2. As outlined in part 2 of this series8, bamboo should not be used outside exposed to water or rain; therefore, Service Class 3 assumes that the bamboo is under cover and protected from direct rain/water, but in a very humid environment with a relative humidity >85%. This scenario only exists in some tropical countries. Bamboo must be treated if in this environment, otherwise it is liable to rot.
(3)
This modification takes Eqs. 1 and 2 and 2 and divides s by , which is essentially using standard statistical theory to say that the characteristic value of a number of samples selected from a population is likely to be greater than the characteristic value of a single sample. Alternatively, EN 1990:2002 Annex D9 can be used, adjusting for C mois mois and C lab lab as above.
Determining the characteristic strength The characteristic value of strength for a whole population f i,k can be determined from the following equation (based on ISO 221561 and NSR G124):
Moisture content correction C mois Like timber, bamboo exhibits an increase in strength as it dries below the fibre saturation point. Therefore, it is important to consider the MC of both test specimens and members that will constitute permanent parts of a structure. Ideally, tests would be carried out at a MC similar to that which the bamboo will experience in service, which in most cases will be “dry”. However, if this is not the case, the
(1)
f i,0.05 can be calculated as follows: where f (2)
Table 2: L aboratory test condition factor C lab
Flexure
0.7
Shear
Tension
Compression Compressio n
parallel to fibre parallel
parallel to fibre
0.5
0.5
0.7
Table 3: Characteristic strengths f i,k for design of dry*, mature † bamboo, free of visual defects (splits, decay, etc.) and assuming a 10 minute test load (N/mm2) Flexure f m,k (N/mm2) Colombiangrown Guadua angustifolia Kunth For scheme design, all species C24 softwood (for comparison)
Shear f v,k (N/mm2)
Tension parallel Compression to fibre parallel to fibre 2 f t,0,k (N/mm ) f c,0,k (N/mm2)
35–50
3–5
40
20
30
2
40
20
24
2.5
14
22
* At 12% moisture content † Within “mature” age range for that particular species – normally 3–5 years
Part 3
44
TheStructuralEngineer
Technical
December 2016
Structural use of bamboo
Table 4: Service class and load duration factor k mod Service Class
Permanent (self-weight)
Long term (storage, imposed)
Medium term (imposed)
Short term (construction)
Instantaneous (wind, seismic)
that the strengths are in the correct form. For example, it is commonly quoted that “bamboo is stronger than steel”, which is misleading and can lead to bamboo being used in a structure when it is in fact inappropriate.
1
0.6
0.65
0.75
0.8
1.05
Calculation of design values
2 3*
0.6 0.4
0.65 0.45
0.75 0.55
0.8 0.6
1.05 0.75
Design strengths The design value X i,d of a strength property shall be calculated as follows:
*As outlined in part 2 of this series 8, bamboo should not be used outside exposed to water or rain; therefore, Service Class 3 assumes that the bamboo is under cover and protected from direct rain/water, rain/water, but in a very humid environment with a relative humidity >85%. This scenario only exists in some tropical countries. Bamboo must be treated if in this environment, as otherwise it is liable to rot in the high humidity
Table 5: Material factor of safety γ
M
Flexure
1.5
Shear
Tension parallel to fibre 1.5
Compression parallel to fibre
1.5
test data should be normalised to 12% MC by applying a correction factor C mois , dependent on the MC of the bamboo at the time of the test. Suggested values are shown in Table 1 – these values are based on NSR G124 and EN 3845. Using “green” (unseasoned) bamboo for construction should be avoided at all cost. Green bamboo is cheaper and carpenters will tend to push for it because it is much easier to work than dry bamboo; however, as the bamboo dries and shrinks, it is likely to split, weakening it and causing the connections to fail. Laboratory test conditions conditions C lab The relationship between experimental procedures and the strength exhibited by full-scale specimens is poorly understood for bamboo. It is likely that test pieces contain fewer defects than full-scale specimens, and therefore the International Organization for Standardization (ISO) and the Colombian Earthquake Engineering Association (NSR) recommend the use of factors to reduce experimental results. A laboratory test condition factor C lab should therefore be applied to the characteristic values to represent the variability of the actual culm. Suggested values are provided in Table 2 – 2 – these values are adapted from NSR G124 and ISO 221561. This correction follows similar
1.5
for Colombian-grown Guadua angustifolia Kunth – this is based on NSR G12 4 and Lozano10. For detailed design, testing would normally need to be undertaken to validate the values in Table 3. 3. However, they are intended to be conservative and so for simple structures (low rise, low occupancy and low stresses) it may be possible to use these design values without any testing, depending on local regulations. Where bamboo is sourced from a single consistent source, a large amount of testing is undertaken, and testing and selection are rigorous, it is possible that better characteristic strengths could be achieved. Note that some widely available published data on bamboo strengths are misleading, as the form of the strength is not immediately obvious (e.g. characteristic, ultimate, average, design, allowable). Testing methodologies affect the interpretation of results too, hence the recommendation to adhere to ISO standards. Strengths do vary between bamboo species; however, it is unlikely that they would be significantly different from those presented in Table 3. If published strengths are found to be widely different from these, then care should be taken to ensure
(4)
Modification factors Service class and load-duration factor k mod The stresses in Table 3 are 3 are normalised to Service Classes 1 and 2 and 5–15-minute loading conditions, as is typical for most laboratory tests, and hence must be corrected for both service class and duration of load. Suggested values are given in Table 4 based 4 based on EN 1995-1-16, and are in broad agreement with NSR G124 and ISO 221561. As with timber design, the duration of load for a particular load combination depends on the lowest duration load in that combination. System strength factor k sys Where four or more elements of the same stiffness are connected to a continuous load distribution system (such as is the case with floor joists, rafters, purlins and trusses) and, in addition, either: • the continuous load distribution system is capable of redistribution of loads, or • the elements are no further than 0.6m apart, the load distribution members are continuous over at least two spans and any joints are staggered
then it is suggested that the allowable stresses provided in Table 3 are 3 are modified by a system strength factor k sys of 1.1. This is based on NSR G124 and EN 19956 1-11 cl. 6.6. k sys should only be applied if the 1characteristic stress obtained is as per Eq. 1 1 and not Eq. 3. 3. Factor of safety γ M A factor of safety must be applied to the characteristic values to bring them to a
Table 6: Typical moduli of elasticity E for for bamboo at 12% and 19% moisture content
5
theory to timber, as laid out in EN 384 .
Suggested characteristic strengths for any bamboo at scheme design stage Table 3 proposes 3 proposes characteristic strengths for any bamboo species normalised to 12% MC. Detailed published test data are only available
Moisture content (%)
Average modulus Average mo dulus E 0.5 (N/mm2)
5th percentile modulus E 0.05 (N/mm2)
12
10 000–17 000
7500–13 000
19
8500–15 000
6700–8000
Detailed published test data are only available
www.thestructuralengineer.org
45
standard probability of being exceeded of about 0.1% (1/1000)6 by applying a material factor of safety for limit state design. Suggested factors of safety are provided in Table 5 – 5 – these values are based on NSR G124 and ISO 221561, and are more conservative conservativ e than the values in EN 19951-16. However, “grading” of bamboo, when undertaken, is not as rigorous as it is for timber in the European market (see part 1 of this series7).
Other values for design Young’s modulus and deflection Bamboo is not very stiff, and therefore deflection, especially flexural deflection, will often govern. Deflection checks should be conducted using standard elastic engineering formulae. Table 6 proposes 6 proposes a range of typical moduli of elasticity E at at 12% and 19% MC. The lower values are based on NSR G124, while the upper values are based on other experimental data – the difference is believed to be a lack of test data coupled
with slippage of bamboo connections, which is poorly understood. The authors believe the higher values are more appropriate for deflection purposes, while the lower values of the fifth percentile should be used for Euler buckling checks (with a further appropriate safety factor required – to be described in detail in a subsequent article in this series). Separate allowance should always be made for connection slip. Some people believe creep to be negligible (3–5% of the elastic deformation) 11; however, recent research suggests it could be as high as 50% of the initial deflection – but limited research has been conducted on this topic. Note that the values presented in Table 6 are 6 are typical values and, like strength, there is likely to be a wide variation in stiffness depending on species, origin, distance from the ground, etc. Ductility in earthquakes As discussed in part 1 of this series7, like timber, bamboo elements possess several brittle failure modes. As such, an appropriate behaviour factor for a bamboo structure should in most cases be q = 1.5 and Eurocode 8 should be followed as for timber structures12. Where failure is confined to connections which use steel nails for which the failure mode is a plastic hinge forming in the nail (i.e. modes b, d, e, g, h, k, m, Figure 8.3, steel-to-
properties for the scheme design of any bamboo species, a method of determining characteristic strength values from test data, and a method for calculating design values of strengths for limit state design. Significantly more research is still required for all species of bamboo to provide more accurate design
References
1
International Organization for Standardization (ISO) (2004) ISO 22156:2004 Bamboo – Structural design, design, Geneva, Switzerland: ISO
2
International Organization for Standardization (ISO) (2004) ISO 221571:2005 Bamboo – Determination of physical and mechanical properties . 1:2005 Part 1: Requirements, Requirements, Geneva, Switzerland: ISO
3
International Organization for Standardization (ISO) (2004) ISO/TR 22157-2:2004 Bamboo – Determination of physical and mechanical 22157-2:2004 properties. Part 2: Laboratory manual , Geneva, Switzerland: ISO
4
Asociación Colombiana de Ingeniería Sísmica (AIS) (2010) NSR10: Reglamento Colombiano de construcción sismo resistente. Titulo G: Estructuras de madera y estructuras de guadua [NSR-1 [NSR-10: 0: Colombian code for seismically resistant construction. G12 : Structures of timber and Guadua angustifolia Kunth bamboo], bamboo], Bogota, Colombia: AIS
5
European Committee for Standardization (CEN) (1995) EN 384:1995 Structural timber. Determination of characteristic values of mechanical properties and density , Brussels, Belgium: CEN
6
European Committee for Standardization (CEN) (2014) EN 1995-11:2004+A2:2014 1:2004+A2:201 4 Eurocode 5: Design of timber structures. Part 1-1: General. Common rules and rules for buildings, buildings , Brussels, Belgium: CEN
7
Kaminski S., Lawrence A. and Trujillo D. (2016) ‘Structural use of bamboo. Part 1: Introduction to bamboo’, The Structural Engineer , 94
(8), pp. 40–43
8
Kaminski S., Lawrence A., Trujillo D. and King C. (2016) ‘Structural use of bamboo. Part 2: Durability and preservation’, The Structural Engineer , 94 (10), pp. 38–43
9
European Committee for Standardization (CEN) (2002) EN 1990:2002 Basis of structural design, design, Brussels, Belgium: CEN
10
Lozano J. (2010) Validación de la guadua angustifolia an gustifolia como material estructural para diseño por el método de los esfuerzos admisibles admisibles [Validation of Guadua angustifolia as a structural material for design by the method of allowable stresses], Bogota, Colombia: Universidad Nacional de Colombia sede Bogotá
11
Janssen J.J.A. (2000) Technical Report 20: Designing and Building with Bamboo, Bamboo, Beijing, China: INBAR
12
European Committee for Standardization (CEN) (2013) EN 1998-1:2004+A1:2013 1998-1:20 04+A1:2013 Eurocode 8: Design of Structures for Earthquake Resistance. Part 1: General rules, seismic actions and rules for buildings, buildings, Brussels, Belgium: CEN
6
bamboo connections ) and rigorous capacity design/overstren design/ overstrength gth principles are applied, it is possible that more global ductility can be achieved; however, however, little test data exists.
Summary
values and coeffi c oefficients – current cu rrent values are therefore likely to be conservative. In time, bamboo will be as well understood as timber is today, but we have some way to go before that happens. The next article in the series will cover element design equations.
This article proposes strengths and other
www.thestructuralengineer.org
46
TheStructuralEngineer December 2016
Opinion Letters or longer articles written from a personal perspective, on topics of current interest that offer a particular opinion and often encourage further discussion and/or debate.
47 Pr Profile: ofile: Victoria Janssens Jans sens
50 Viewpoi 50 Viewpoint: nt: Structural technicia technician n – re rev vC 52 Book review: The BIM Manager’s Handbook 53 Book 53 Book review: Designing Tall Buildings 54 Verulam 54
www.thestructuralengineer.org
Opinion
TheStructuralEngineer
Victoria Janssens
December 2016
47
Profile
Irish engineer Victoria Janssens has Janssens has recently applied her talents in Hong H ong Kong on the Zaha Hadid-designed hotel tower at the City of Dreams, Macau, and on the Mercedes-Benz Stadium in Atlanta – all thanks to a decision to risk working overseas. She talks to Jackie Whitelaw .
Figure 1 Ornidale
Block, Vancouver
The word that sums up the current theme of
Victoria Janssens’ career is “connections”. The 31-year-old is working as a Senior Structural Engineer Engineer for BuroHappold in Hong Kong, where she has been focusing on the design of steel connections for the new Zaha Hadid-designed hotel tower in the City of Dreams leisure and entertainment complex in Macau. Also in the professional arena, she is now providing construction-stage construction-stage design support for the members and connections forming the curvaceous, free-form roof of what will be one of the world’s largest underground rail stations. Located at West Kowloon in Hong Kong, this will serve as the terminus for the high-speed rail link to mainland China. And on the personal front, it was a connection that opened the door to the job in Hong Kong and the huge, high-profile, namemaking projects that are available to work on from the island.
Human connections There’s nothing sinister about the latter. When Janssens wanted to move out to Hong Kong to work in 2014, she did the very sensible thing of asking a contact. This was someone she had kept in touch with from earlier work experience with BuroHappold in Leeds, who was herself now working in Hong Kong. Through her she
S T C E T I H C R A H + B
was – and here Janssens is. That experience has reinforced her instinct that building and maintaining a good network is as important to an engineer’s career as building great structures, particularly if you want to do a bit of globetrotting. “If you have the right experience, contacts can provide that bit of extra help, which can be particularly useful if you want to work overseas,” says the Irish woman. “Construction is a tightknit industry and it is important to develop and maintain a good network. It also helps when you need advice, in that you can pick up the telephone and ask questions. “You “Y ou also learn a lot from talking to different people; construction is an evolving industry and you will get left behind if you lock yourself away in front of a computer. We need to interact with
before the move east, in 2012, she and her engineer partner had wanted to work abroad and had upped sticks from Dublin and moved west to Vancouver in Canada. “I’d always wanted to travel and work somewhere else in the world,” she says, “and I had always been attracted to North America. My partner and I had previously spent some time travelling in the States but decided Canada would be an easier place to get a visa. We settled on Vancouver because of the temperate climate on the west coast and its similar feel to San Francisco – a city that we both loved. “But it was very ve ry difficult to get g et a job before befo re arriving in Canada. Like many other expats, we got open work visas and went.” The first few months were pretty
and learn from other engineers, architects and construction professionals.”
challenging, she remembers. “It was hard to get work. I spent two months sending applications and hearing nothing back. But then it all happened! I was called for an interview with a local firm, Wicke Herfst Maver Structural Engineers, had an interview with
Taking a chance Janssens has learned from experience how hard it can be to get a foot in the door in a new
found out whether the consultant was hiring. It
one of the founding partners and found myself
market with no contacts. Two and a half years
48
TheStructuralEngineer
Opinion
December 2016
Victoria Janssens
“In the UK and many other places, the steel fabricator would typically design the steel connections, but in Hong Kong it is more common for the structural engineer to take on this role – particularly when dealing with
2 Figure Fifth tower of City of Dreams, Macau
S T C E T I H C R A D I D A H A H A Z
S A I D E P I L I F
employed. “WHM is a relatively young company – it celebrated its seventh birthday while I was there – and was an exciting, dynamic working environment. With about 20 people in the office, I was thrown th rown in at the deep end and was given a lot of responsibility early on.” Janssens worked on a variety of projects, from architecturally challenging single-family homes to large mixed-use developments. If there was a favourite, it was the redevelopment of an Edwardian commercial building which required the retention of the original brick façade, but demolition and replacement of the structure behind with a new six-storey six-st orey office block bloc k (Figure 1). 1). “I led the development of the wood-concrete composite floor system for the new building, intended to reflect the original structure with the underside of the ceiling as exposed wood and a polished concrete floor on top. “Unfortunately, the floor system ran into difficulties with the local building buildin g department. Concrete became more cost-effective, even if only marginally so, and the new building was redesigned as a reinforced-concrete structure after I left. This was still a very interesting project and full of challenges, such as addressing the interface with the adjacent structures and detailing the system to tie back the existing facade to the new structure.
on the dramatic structures being designed in Hong Kong. The fifth tower of City of Dreams (Figure 2) 2) was Janssens’ first BuroHappold project at the Hong Hon g Kong office, described by the consultant as ‘the most challenging large-scale steelwork of its kind to ever be accomplished’. “It’s a wonderful expression of architecture, a 40-storey structure encased by a striking steel exoskeleton,” Janssens says. “The steel exoskeleton works together with the pair of concrete lift cores to form a dual system resisting lateral loads. I was responsible for designing the connections for the internal steel framing, most notably for the floor system which shared the loads between the lateral force-resisting systems. “I was designing for shears and bending, but also for large axial forces, which meant conventional steel connections could not be used in many locations. There were about 12 000 connections in total with limited repetition; I spent a full year designing them.” From never having done connections before, Janssens is now a developing expert. And in her next role for BuroHappold she provided construction-stage support for the steel members and connections of the West Kowloon Terminus station roof (Figure 3). 3).
Cutting-edge research Janssens has been fascinated by steel buildings for a long time. After her engineering degree at Trinity College Dublin (which, as for so many structural engineers, had been preceded by a brief spell studying architecture before she found that not to be the right challenge for her skills), Janssens opted to study for a PhD. The decision was in part thanks to some prescient advice from a practising structural engineer. “In 2007 I was in the final year of my degree and applying for graduate positions as well as considering a PhD. At one point, a potential employer pulled me aside and wisely mentioned that if I could secure the funding for a PhD, I should take up the opportunity. I decided to take the advice and, as the economic diffi culties unfolded over the coming c oming months, I was very fortunate to have a secure job for thr three ee years years rese research arching ing the pro progres gressive sive collapse of steel buildings.” The work put her at the cutting edge of structural steel research, following closely on from the publication of numerous reports and guidelines after the collapse of the World Trade Center towers on 9/11. “The Structural Eurocodes have changed the approach to robustness for high-risk structures and I was involved in European research to establish a risk-based framework 3 3 Figure West Kowloon Terminus, Hong Kong
Vancouver is in a seismic region, which adds a lot of complexity to the structural design. I learned a lot.”
Steelconnections After two-and-a-half years, it was time for a
complex geometry. “It has been a steep but enjoyable learning curve, developing the knowledge to deal with the interaction of different actions and achieving the required release conditions, while ensuring the connection could be safely fabricated and provided the necessary construction tolerances. Working at this level of detail has been invaluable experience and has changed the way I think about a structure.”
S A D E
change of scene and an opportunity to work
A
www.thestructuralengineer.org
for assessing the robustness of structures like stadia and high-rise buildings. “I was involved in developing guidance on quantifying the consequences of structural failure in terms of potential loss of life, as well as the economic costs. This was very much a first effort at collecting information more commonly used in the insurance profession and has since garnered a lot of interest in the academic community.”
Making a name Steel, it would seem, is in her blood. She has recently returned from a five-month spell in New York working on the retractable roof of the Mercedes-Benz Stadium – the new home for the NFL’s Atlanta Falcons (Figure 4). 4). “The BuroHappold Buro Happold New York office was looking for help with the design of the roof steelwork and I happily volunteered to help out. The stadium features an iconic retractable roof made up of eight petals which open like the aperture of a camera. This was a great project to be part of,” Janssens says. So, what next? For the moment Janssens says she is in a job she loves in a place she loves and is handling any homesickness
M U I D A T S Z N E B S E D E C R E M
4 Figure Mercedes-Benz Stadium, Atlanta
through the media of Skype and FaceTime. “I’ve thought that I might return to academia but I think that may be further down the line, if at all. What is most important to me now is that I continue learning and enjoying what I do. At the same time I would like to establish a name for myself through working on iconic structures and pushing the limits of structural engineering.”
She would recommend a bit of globetrotting to everyone as a way of developing their career and themselves. “I’ve grown a lot working in different places and with different individuals from different cultures. It’s good to step outside of your comfort zone. You learn a lot and it’s a great way to improve yourself both personally and professionally,” she says.
If you are aged 28 years or under, you are invited to enter the Kenneth Ke nneth Severn Award 2017. To enter, enter, please answer the following question, set by 2017 Institution President, Ian Firth:
HOW SHOULD STRUCTURAL ENGINEERS BALANCE SAFETY AND SERVICEABILITY REQUIREMENTS REQUIREMENT S WITH A HUMAN DESIRE FOR ELEGANCE AND BEAUTY? Our health and well-being is affected by our environment. The appearance and character of the built environment around us strongly affects how we feel, and structural designers should be concerned with creating elegance and beauty as well as ensuring safety and serviceability. Describe the contribution of structural engineers towards creating an elegant, attractive and appropriately humancentred built environment, and suggest what changes in their education and professional development might enable them to do this more effectively. Answers should should be in the form of a written paper (max. 1500 words) and may include relevant imagery that supplements the text. The judges will be looking for originality, value to the structural engineering profession and clarity of presentation. Please submit your entry online at: www.istructe.org/kenneth-severn-award.
2017
The closing date for entries is 31 January 2017.
The winner will receive: The prestigious Kenneth Severn Diploma A cash prize of £500 Have their paper considered for publication in The Structural Engineer rs oof ag Entrants must be 28 years agee or or un under und der on 1 January 2017. Entry iss NOT restricted to members of the Institution.
Ian Firth ru BSc MSc DIC CEng FREng FIStructE ruct ctEE FICE FI E FConsE FI F on onsE sE Institution President 2017
Registered with the Charity Commission for England and Wales No. 233392 and in Scotland No. SC038263
50
TheStructuralEngineer
Opinion
December 2016
Tomorrow’s technicians
Viiewpoint V
In a rallying cry to the profession, Balazs Trojak rojak explores explores the changing role of structural technicians and looks forward to a bright future that is theirs to shape.
Structural technician – rev C “The future is already here, it’s just unevenly distributed.” William Gibson We humans don’t particularly like change. We like the stability of our cave, our hunting ground, the familiar faces around the warmth of the fire. As much as we love constants, we have learnt an enduring phenomenon: the world keeps changing and the only constant is change itself. To deal with this, we adapt and change ourselves even if only for the sake of keeping “everything else” exactly the same as before. This is not something you or I can escape. A quick glimpse back at your professional life reveals as much. Ask yourself this: when you started out, how many revisions did you do to a typical drawing before it became “as-built”? And what is that number today? You don’t need convincing.
Proclaiming our value I am a structural technician by experience with little initial academic background. I studied and picked it up along the way, like most of my friends and colleagues. We have changed ourselves and grown with the job. Technicians are an admirable but strange bunch, who are still afraid to call themselves professional. We are somehow convinced that we are on the fringes of structural engineering, failing to realise the ultimate value of our work. Our product is delightful, clear and elegant, but also frail; have you seen a drawing drawn by an engineer? Let’s finally admit that being an engineering technician is a vocation in its own right. It’s not a job, it’s not a career; it’s a vocation that is a vital part of the structural engineering
routes to being a technician, but technical knowhow is on a par with engineering knowledge. I know some conservative engineers who still think technicians are wannabe or failed engineers. Or that the first step of being an engineer is being a techie. Think again, that time has long passed. What we do today is extremely complex and good technicians possess a spectacular variety of skills (Box 1). 1).
Changing with the times As the industry progresses, the range of tasks we carry out broadens by the day. We have adapted and continue to grow into specialisms. Most of us are now in roles that didn’t exist 10 years ago: BIM coordinator, BIM author, information manager, interface manager, BIM technician, the list goes on. This trend will continue. As the value of data becomes more widely recognised, we are spending more and more time creating, managing, exchanging and measuring data. Not to mention presentation of that data. As you know, data is not information – turning data into something tangible, readable and understandable by
"TECHNICIANS ARE AN ADMIRABLE ADMI RABLE BUT STRANGE BUNCH, WHO ARE STILL ST ILL AFRAID AF RAID TO CALL THEMSELVES PROFESSIONAL"
humans (i.e. information) is the technician’s art and craft. Our responsibility will continue to grow because we are best able to deal with the associated risks. Remember, in BIM Level 2 the model and the contained information is the deliverable; drawings are secondary (CIC BIM Protocol). The future holds many more challenges, but with them many opportunities. There will always be something new, something disruptive, but we’ll keep up; this is what we do. We learn new abilities and we adapt. If you find yourself constantly in an old-school environment – tracing mark-ups and being micromanaged – run. You won’t be developing your skills and are missing the greatest perk of any job. No amount of salary can compensate for that.
Taking time to develop The best technicians spend as much time on their professional development as engineers do, because there is no single set way to reach any particular target. Today’s methods are tomorrow’s commercial failures. Each day we need to relay engineering intent to all other professions and laypersons by appropriate media in the most effective manner. Continued professional development is key to this and the learning never stops; ask any engineer. Technology Technology changes, legislation changes, work culture changes, scope changes. To keep up with change we must devote time to our own development. I learned to draw on paper, but much
profession. Yes, there are no clear academic
as I took pride in my technical font, the
www.thestructuralengineer.org
51
computer had replaced my skill. I got over it and now accept that I’ll have to unlearn a great many more skills, but I’ll keep going and learning new ones. Much of this learning you can do at work, but doing it at home is doing your future a
Shaping our future
real favour. The more you put in, the more you’ll get out. Once you accept the fact that one cannot know everything about the complex systems we use today, everyone else will have to accept it too (including your engineer breathing down your neck), but we have to try. Take the time to look up how a formula works in Excel® (five minutes) or how a new plugin might greatly enhance the capabilities of your BIM software (30 minutes). This will make you more efficient, s o the tim e invested pales pa les into insignificance.. Learn how your models will insignificance be used downstream. Learn where your data is going. Find out what the end goal is for your firm on all projects and offer alternative delivery options. Take pride in your work and don’t ask permission, because most engineers don’t know where their profession is heading. To quote Harriet Minter: “Proceed until apprehende apprehended!” d!”
of reach. To To get it is a lot simpler than most imagine; all you need is a little commitment. Life will be easier afterwards. Colleagues, the future of technicians is bright, but only if we invent it for ourselves! The only limits are our own imagination and drive to abandon the status quo and break forward.
Once you have a minimal amount of skill, start showing your initiative. This is the best way to gain respect and credit. Now you are moving forward. The Institution of Structural Engineers’ Technician Technician accreditation is not out
Be an innovator, an explorer, learn about new technologies, discover new methods. Grasp the opportunities. The future of the structural technician’s profession will be what we make of it.
Author Auth or biograph biography y Balazs Trojak BSc, TIStructE, EngTech Balazs is a BIM consultant with 20 years’ experience as a structural technician. He advises a growing number of structural engineers in BIM adoption and Revit training. Contact: paraforms.co.uk
Box 1: The modern technician’s skillset Technical skills: •
•
•
•
•
•
•
•
Digital skillset Data management Software BIM Physics Statistics Engineering Pragmatism
Interpersonal skills: •
•
•
•
•
•
Art skills:
Written, verbal and drawn communication Listening Negotiating Problem solving Decision making Assertion
•
•
•
•
Making sense of complexity Focusing information Presentation Visual appeal and so on
ADVANCED STRUCTURAL ENGINEERING SOFTW SOFT WARE Structural Engineering problems require software that can deliver robust solutions for a wide range of project types. GSA is a comprehensive design and analysis package for buildings, bridges, tensile structures and much more. This intuitive software is feature rich and has been used the world over to aid the design of many award winning structures. For accurate results, delivered
Download your free 30-day trial from our site today
oasys-software.com
+ 44 44 (0 (0 ) 1 91 91 23 23 8 7 55 55 9
o as as ys ys @a @a ru ru p. p.c om om
Oasys Software
@Oasys_Software
Th eOasysSoftware
52
TheStructuralEngineer
Opinion
December 2016
Book review
eview This new handbook offers a good grounding in the practicalities of BIM, says Laura Norris, Norris, thanks to its structured approach, with good, solid advice gleaned from industry experts working in the field on a daily basis.
The BIM Manager’s Handbook: Guidance for Professionals in Architecture, Engineering and Construction Author: Dominik Holzer Publisher: Wiley Price: £29.99 (hardcover); £26.99 (E-book) ISBN: 978-1-118-98242-6
The BIM Manager’s Handbook is is the latest review of an emerging and diverse job role that is steadily becoming crucial in leading engineering and architectural firms. The book seeks to demystify the misconceptions about Building Information Modelling (BIM) and analyse the opportunities associated with BIM management. Published in 2016, the information contained within is current and gathered from the experience of some of the world’s top BIM managers. Initially, the book provides a candid look at the rise of BIM in today’s construction industry. It also delves into BIM best practice. The first chapter strikes a familiar cord when it discusses examples and common misunderstandings that lead to “bad BIM”. It introduces terms such as “pseudo BIM” and the dreaded “overmo “overmodelling”, delling”, recommending that the BIM manager’s role should be to initially recognise these BIM falsehoods and redefine their data management in order to make fuller use of collaborations. Not a simple or quick task by any standard. Holzer goes on to discuss benchmarking
Perhaps the first highlight on a personal note is in Chapter 2, calling on BIM managers to be the facilitators of change and the people who need to inspire progression. This chapter consists of concise, well-laid-out guidance concerning the key aspects of resistance to implementation in the workplace. It also proposes practical steps that can be taken to overcome such issues. BIM technology, software and hardware are covered in Chapter 3. Consideration is given to BIM in the cloud and the need for collaboration in real time. It reviews the tools and technology needed to achieve coherent BIM, focusing on the different types of products on the market to inform BIM managers on the technological aspects of their role. Although it is crucial for practices to discuss the technological setup behind BIM and the interfaces required for successful sharing of data, this chapter is possibly the best-known aspect of BIM. Interestingly, Interestingl y, the last few pages of this chapter summarise BIM technology trends, looking to the future. If they are realised, these trends will streamline the construction process and,
BIM with policies, key performance indicators (KPIs) and how to measure the day-to-day performances. He includes some interesting metrics from industry experts, rating the foremost themes which they recommend to achieve that successful BIM ideal and, perhaps
eventually, the facilities management process. eventually, In my opinion, the chapter on BIM support infrastructure is by far the most valuable; it deals with setting up the background administration documents that accompany the BIM process. Industry standards and support
point for reviewing the employer’s information requirements (EIRs), creating unique company standards and in-house CAD standards. It also covers a range of crucial, often unclear, requirements for a company offering BIM, fundamental tips on BIM execution plans and BIM placement, discussions on BIM capability statements, specified documents and also BIM library management. For a company new to BIM, or even a company which desires to streamline its existing BIM infrastructur i nfrastructure, e, this section is by the most enlightening and considers items that are essential before a consultant can begin offering BIM Level 2 to a client. The final chapter is an interesting discussion on how to optimise your BIM efforts. It includes steps that a BIM manager can take to excel, how they can gain “Expert Status”, implementing innovation and boosting your firm’s BIM capabilities. All topics are directly answered by the global panel of BIM experts, giving the lowdown on what industry experts truly think about these topics. In conclusion, this handbook provides a good grounding in the practicalities of BIM – not just the data flow, but the support infrastructure, CAD standards and documentation required by a practice looking to pursue higher level BIM. While not the ultimate reference handbook, the book provides a general overview and structured approach, with good, solid advice gleaned from industry experts working in this field on a day-to-day basis.
Laura Norris MEng, CEng, MIStructE Laura is a structural engineer, working as a consultant engineer for the past 11 years. After passing her Chartered Membership Exam in 2012 she moved to London and joined Price & Myers. Laura has since worked on multiple BIM Level 2 projects, often working from the early RIBA stages to completion.
more importantly, achieve client satisfaction.
documents are considered here as a starting
www.thestructuralengineer.org
Opinion
TheStructuralEngineer
Book review
December 2016
53
eview Bob Lang finds Lang finds this to be an intriguing and informativ informative e text on the design of tall buildings and is particularly drawn to the structural details from real-life projects projects which demonstrate the consequences of engineers’ decisions.
Designing Tall Buildings: Structure as Architecture (2nd ed.) Author: Mark Sarkisian Author: Mark Publisher: Routledge Publisher: Routledge Price: £110.00 Price: £110.00 (hardback); £31.99 (paperback) ISBN: 978-1-138-88670-4 ISBN: 978-1-138-88670-4
The most cursory rummage around rummage around your local bookshop will reveal two types of book in this field. One, a technical text, perhaps focusing on analysis, heavily numerate and particular. The second, more graphic in nature, perhaps aimed at setting an agenda more than solving absolute problems. Seldom, it seems, do these two aspects sit side by side in a single source. Why should this be? One answer is that it requires an author of considerable skill, judgement and experience to produce it. Mark Sarkisian displays all of these assets, in abundance, in this, his latest book. Here, practical design advice and design references sit side by side with creative conjecture. Those faced with tall-building design as a profession will recognise immediately what Sarkisian has to say and understand the background to his chosen topics. Those not so employed will find an intriguing, eminently readable text. All will benefit and be informed. The opening chapter concentrates on the history of tall-building design and construction; setting the scene and providing a basis for critical thinking when presented with what
wealth of information, guidance and advice to practitioners. All presented in a clear and logical form. There are a number of particularly strong sections in the book, mainly discussing antiseismic design of tall buildings. For example, a critical, personal appraisal of performancebased design is given, shedding light on the consequences of the post-event condition of structures. Also, the engineering challenges of appropriating ductility in tall buildings are reasoned and described well; highly creative structural systems which relieve the structure of unwanted force in an extrem extreme e condition. The evolution of structural form is dealt with, aided by real examples of well-known structures whose form is explained. Often, these are forms which have been developed so as to minimise the forces experienced by a structure, due to a combination of wind, seismicity and settlement under self-weight. Factual data are presented, drawn from some of the world’s tallest buildings. Useful target deflections and material data are given. Further,, the important Further i mportant issue of damping is
follows. The final chapter concentrates on the future, giving consideration to the environmentt and the application of genetic environmen algorithms to define form. The section on the idiosyncrasies of bamboo, the strength and stiffness it displays, is particularly interesting.
considered and how it might be quantified – all presented as a practitioner’s guide. Useful as this is, more could have been said to champion the instrumentation of our buildings. Suggesting how we might generate hard data, to calibrate our analytical assessments of
A section of the book is dedicated to describing alternative structural forms which are chosen as a function of building height. There is a reassuring clarity to what is presented, with a solid supporting logic. As there has to be, there are a number of constants populating the models which suggest a transition through core and moment frame through to explicit tube and multi-tube forms; all real and relevant. Of particular interest is the description of structures which separate the ductile system from the gravity system, yet still have architectural presence when aligned with solid engineering principles. Finally,, what sets this work apart are Finally structural details. Details which are drawn from jobs that have (or are) being built; detai details ls which which graphically demonstrate the consequences of decisions made by the engineer. Details which give credibility to a concept that would otherwise be just a credible structural diagram. When an engineer can survive the rigours and complexity of the construction process, yet still feel free to exer exercise cise their imagination, it requires courage and competence. We see both demonstrated in this book. Yes, there are editorial questions; would a larger format be appropriate? Could some repeated elements of text be edited out? But I have said little to detract from this fine piece of work which articulates the issues confronting us, day to day, in a manner that is neither pompous nor demeaning. Perhaps just one question remains – since when has structure not been architecture?
Robert Lang FICE, FIStructE Bob Lang is a Director of Arup. He has wide experience of multidisciplinary engineering and a particular interest in the design and construction of tall buildings. projects include BBVARecent Bancomer in Mexico City (opened February 2016) and two towers, Project Atrio in Bogota, presently under construction. He was a plenary speaker at the Council for Tall Buildings and Urban Habitat Conference in London (2013).
Sandwiched between these chapters is a
building performance and presumed damping.
54
TheStructuralEngineer
Opinion
December 2016
Letters
Ve V erulam
Send letters to… All contributions to Verulam should be submitted via email to:
[email protected]
Contributions may be edited on the grounds of style and/or length by the Institution's publishing department.
Topics of importance openly discussed
Eurocodes: is there a middle way? Our wave of letters on the Eurocodes from disgruntled readers continues unabated. It seems there is fresh
that Eurocodes offer has limited real usage; saving, for example, a few kilogrammes of steel can often be irrelevant in the grand scheme. When engineers say they are using Eurocodes, this can often be nothing cleverer than clicking the box in the software for design to Eurocode rather than the British Standard. If the different design output from each is then reviewed, to the older experienced engineer, engineer, one will be familiar and the other little more than gobbledegook. Importantly,, as has been stated by others, Importantly a critical factor is that the supervising engineer may often not be familiar with w ith Eurocodes. In the real world of that supervising engineer, engineer, and despite the best of ideals for Continuing Professional Development (CPD), running a business and modern project pressures never permit the time for learning, understanding and remembering radically new design codes. So I would support the idea for some form of comprehensive “concise manual”, cutting out such academic niceties as secondary load reduction factors. We need to recognise what the average design engineer actually needs to avoid fundamental errors and to allow him or her to sleep peacefully. I think the Institution needs to take note.
We can close this topic off with a summing up from Barry Haseltine, who has vast practical experience and is also leader of the UK delegation to Technical Committee 250 “Structural Eurocodes” (TC250):
I read with interest the Verulam comments of November 2016. I would not overly defend the old British Standards; they were documents of their time and rather a muddle of different approaches. But they certainly worked and did the job intended. I also guess they were developed with very limited financial support and certainly not with 30 years of development time.
I fully agree with John French French’s ’s comments (October 2016) about investigating the reinstatementt of British Standards. I have reinstatemen yet to have a discussion with a practising engineer who has anything good to say about Eurocodes. In fact, most practising engineers will freely admit that whenever possible they will still opt to design to British Standards
You have experienced, recently, an increase in the number of contributions from members concerning the Eurocodes, after the Brexit vote. In the Brexit situation, there is plenty of room for confusion, given that the whole process is unfamiliar to the UK, but there are some basic facts of which, I’m afraid, many of your contributors seem to be unaware. The Eurocodes have been drafted by CEN, the Comité European de Normalisation, based in Brussels. CEN is an organisation composed of European National Standards Bodies (NSBs); there are 33 member bodies from the EU and the European Free Trade Trade Association (EFTA). (EFT A). For the UK, the NSB is the BSI, for Germany – DIN, for France – Afnor, etc. NSBs have to abide by the rules of CEN, which include a requirement to publish, without any changes of any sort, all Standards approved through CEN’s procedures; procedures; CEN itself does not publish anything. CEN is not a part of, nor even linked to, the European Commission/ EFTA, EFT A, but it does sometimes receive funding from the Commission/EFTA for specific work. In the case of the Eurocodes, TC250 TC250 has the responsibility to draft the documents, which are subjected to a rigorous process of commenting, consultation and voting before being made available by CEN to be published in the various countries where there is an NSB. Generally, the NSB must publish a CEN standard and withdraw any national conflicting ones in a very short time; but, because of the scale of the Eurocodes, special provisions
The Eurocodes no doubt have all the possible finesse available as knowledge has improved. My contention though is that for possibly 80% (or even more) of our design using codes, what is important to many is accomplishing adequate rather
unless forced to do otherwise. Does this not say something about these ridiculously complicated, and frankly unnecessary unnecessary,, documents that have been foisted upon the profession? Go on – ask the membership! The answer
were made for them, which culminated in the withdrawal of national ones by the end of March 2010. The BSI has made it clear that it wishes to continue to be a member of CEN after Brexit; clearly, clearly, the UK would be seriously
impetus following Mr Trump’sThe winfirst in the US Presiden Presidential tial election. is from Gordon Stamper: This is my first letter to Verulam since becoming chartered in November 1986. I’ve just read the Novem November ber 2016 2016 letter letter from Andrew Dawber: “this needs to go to a vote”. I remember the Institution having a members’ vote in the 1970s on whether to stay with the permissible stress code approach or change to limit state. I voted for the former, as did the significant majority. The rest is history history… … Brexit result = the people are fed up and have spoken. US Presidential election = the people are fed up and have spoken. Two out of three wasn’t bad (but three out of three would have been better – for proper engineers, working for real, live clients).
The second, perhaps more measured approach, is from Philip Benson:
The third is from Ian Whitlam:
than refined design. The academic finesse
may surprise you – but it will not surprise me.
disadvantaged if British Standards were to
www.thestructuralengineer.org
55
diverge from European ones, as we would not be able to sell into Europe, so there should not be any dispute over the BSI remaining at the CEN table. Assuming that the BSI does so remain, it would continue to be bound by the rules covering drafting and implementation of CEN Standards, including that the Eurocodes
ought to be made and modern codes make it easy to fulfil that obligation.
must continue to be the only codes published by the BSI for the relevant aspects of structures. So to be clear, the EU/EFTA does not produce or publish the Eurocodes; Britain leaving the EU does not affect the work of CEN and the commitment of this country’s NSB, the BSI, to publish Eurocodes to the exclusion exclus ion of other codes of practice. Thus, comments about taking back design codes into the UK, holding votes in the Institution, etc., are irrelevant and unhelpful to those who accept the rules as they are and work with w ith them.
two sides to the coin
Well, that just about sums it up. In response to Mr Benson, it might be forgotten that the Institution has actually published simplified design manuals for using the Eurocodes. Perhaps the Institution Institution’s ’s technical committees will now take heed of grassroots pleas and see what more can be done to update and publicise these? Maybe more guidance can be offered on how to use the Eurocodes without refinement? There is no point in using advanced technology for its own sake. As Mr Benson implies, our prime duty is to ensure structures are safe and that does not take refinement. Whether the design is skinned to the bone (or even should be) is a matter between the engineer and their client.
Complexity and choice Verulam’s point about quality of design is illustrated below, where Steve Lieske thanks us for publishing his letter in November: Thank you for printing my “Eurocodes rant”. Can I point out that the second paragraph concerned a totally different topic – steel connection details (“The devil’s in the detail”, October 2016). And in this regard, seriously, what are “execution classes”? And lastly, well said to Andrew Dawber! Well, execution classes give you, the designer,, the choice of top-quality designer fabrication versus “good enough”. Don’t
Professionalism:
The second is from Keith Laidlaw, who has obviously been around for some time: I read Richard Kemp’s strong views and would
Next we have two further responses to Richard Kemp Kemp’s ’s letter, “The devil’s in the detail”. First, David Dibb-Fuller writes: I read with interest Mr Kemp’s criticism of the “professionalism “profession alism from structural and chartered structural engineers”. I started work in the early 1960s as a trainee draughtsman with Cleveland Bridge and Engineering. We had a large design and drawing offi ce populated populat ed by detailers. structu ralThe structural engineers and very experienced information we worked from was sparse to say the least, but the expertise embedded in the design offi ce was such that detailed det ailed design des ign was not compromised. We did all the setting out (general arrangement) drawings from the architect’s information, then proceeded with connection design and, finally finally,, detailing. Later in my career I was the Technical Director at Conder Southern, where I managed the design desig n and drawing drawi ng office. We were most effective when we had to do the whole design and were least effective when presented with all the information Mr Kemp complains about not receiving. Experienced steelwork designers save
like to make a few comments “from the other side of the fence”, as a consultant structural engineer with some 36 years’ experience. I cannot agree with the general criticism of our lack of professionalism. All engineers that I have worked with have always displayed exemplary levels of professionalism. However, we all have to work within the confines of ever-decreasing fee scales and I think that is what Richard is conflating with professionalism when he makes his criticism. Perhaps Building Information Modelling (BIM) may get us back to the days of the ACE fee scale, but with modern technology. That may make a difference to most of the things Richard comments upon. But that depends upon the take-up of BIM by our clients; mostly contractors, of course, these days. With a few notable exceptions, my experience is that the general take-up of BIM by contractors is not looking good. I am sure some of Richard’s observations may be fair comments. There are good and less good in every profession. I won’t go into each item, but I would just respond to a couple of points to give a flavour of how some of his comments are viewed “from the other side”. It is, and has always been, common practice for the majority of connections to be designed by the fabricator, except where there is a specific engineering or architectural requirement. I didn’t realise this
clients money by producing the most costeffective framing solutions tailored to the whole steelwork process: design, detailing, fabricating and erecting. So instead of complaining, Mr Kemp should celebrate the opportunities presented by what he calls lack of information. I have some sympathy, however, with Mr Kemp’s comments about approvals. Trying to get approval from some so me is extremely diffi cult and should be better tied up within the contract. But on the other hand, I have acted as an expert witness in a number of cases where the engineer was never provided with any information to approve and which resulted in whole or partial collapse of steelwork during
when I first started andproject, I designed the connections on work my first only all to be asked by the steel fabricator if he could do something different that better suited their own fabricating process. As a result I had wasted an awful lot of time. I won’t repeat what my Senior Engineer said to me at the time, but it was drummed into me 36 years ago that we don’t design connections unless there is very good reason to do so! Engineers have in my experience never “approved” subcontractor drawings. Again, it was drummed into me in my early years that we only ever “review and comment”; there are good reasons for this – both legal and related to professional indemnity insurance – which I am sure others who are far better qualified
erection. Is there a way out of this sad situation? Well, it’s a case of having to work together, of having to communicate better, and of educating clients and project managers to realise the risks involved, both financially and in terms of
legally can expand upon. Richard has obviously had individual poor experiences, but it is not my experience of structural engineers. As I have described above, there may be perfectly valid reasons why some engineers are not meeting
complain about complexity, it’s a choice that
Richard’s expectations, as those expectations
health and safety.
56
TheStructuralEngineer
Opinion
December 2016
Letters
may be very different when viewed “from the other side of the fence” through a consultant’s appointment document. I made reference earlier to BIM and how this could improve the situation if it were fully embraced by all; I fully believe this would be the case. If it were, then there might be no “other
structures for which “advanced design” is appropriate; there are others where it is a misplaced effort. We need the tools to deal with all situations.
though Verulam and papers I’ve written for The Structural Engineer , particularly on marketing and public relations. I was fortunate in being able to study business as a postgraduate at the London School of Economics under Professor Sir Arnold Plant, who was particularly keen on
side”, but I suspect that is a few bridges too far at this stage. The irony here is that the few parties who are positively embracing BIM are in fact consultant structural engineers and steel fabricators; so perhaps Richard and I are not that far apart?
Professionalism: business and marketing skills
engineers acquiring business skills. As far as I’m aware, not many engineers have studied business skills or economics in the past, so this new development at the Institution is to be warmly welcomed, and will help to promote both our members and the profession. Hopefully it’ll give our members the confidence to make sure that “everybody who should know does know about their successes and achievements”. Editorial coverage in the national, regional, local and construction industry press, including radio and TV where possible, should help them to do this, and it’s usually free. Every practice and company is unique according to the skills and experience of the people involved, so this should help to set them apart from their competitors. I’m delighted to see that after many years of lobbying through our outstanding Institution publication, we are at last beginning to get to grips with learning how to promote ourselves.
There might be a common theme here in the debate on codes and the debate on professionalism. Our duty is to keep structures safe: everyone agrees. Beyond that, “professionalism” requires us to work to our best advantage within the industry as it has grown up, to be clear where responsibilities lie, and to use the skillset of the entire industry to our best advantage, as between concept stage and site construction. Design is not just about producing calculations to a code: it is a far more complex task balancing material use, functionality and programme. There are
We end on a positive note with the Institution being praised for efforts to help us all in our “professionalism”. Undeterred by Brexit, our regular French correspondent, David Brett, writes: Many congratulations to the Institution for launching a number of new CPD courses which will help to improve the business skills of our members, e.g. “Bid Winning Skills”, “Business Skills for Engineers”, “Creative Thinking and Entrepreneurship”, “Moving into Engineering Management”. I’ve been promoting this idea for many years
New Specialist Diploma Offshore Structural Engineering Using your knowledge you will be asked to prepare a design appraisal with sketches, recommend the best solution, and design calculations to establish the form and size of all elements.
Date
Cost
Duration
Test centres
06/01/16
£200
3.5 hours
Worldwide
Further details available at www.istructe.org/Offshore-Exam Registration closes on 16 December 2016.
www.thestructuralengineer.org
TheStructuralEngineer December 2016
A At t the back The home of diary dates, updates on Institution services and other miscellanea, plus products, services and jobs.
58 Diary 58 Diary dates 60 Spotlight 60 Spotlight on Structures 61 And finally… 61 62 Products 62 Products & Services 64 Services 64 Services Directory 65 TheStructuralEngineerJobs 65 TheStructuralEngineerJobs
57
58
TheStructuralEngineer
At the back
December 2016
Diary dates
Unless otherwise stated, technical meetings start at 18:00 with refreshments from 17:30 - they are free of charge to attend, unless stated otherwise. Registration
Diary dates Note that more current information may be available from the Institution website: www.istructe.org/events-and-awards
MEETINGS AT HQ 47–58 Bastwick Street, London EC1V 3PS, UK
Thursday 1 December Dynamic wind effects on slender towers
Kamran Moazami and Ender Ozkan 17:30 for 18:00
Booking: www.istructe. org/events/hq/2016/ cpd-course-appliedvibration-serviceability
Monday 16/23/30 January + Monday 6 February (afternoons only) The Drawing Gym for
for evening technical meetings is required via
[email protected] History Study Group meetings start at 18:00 with refreshments from 17:30. Registration is not required for History Study Group meetings except for the Annual business meeting held in January.
Regional Group Committee members should submit details of forthcoming events to:
[email protected]
Monday 23 January Bid Winning Skills
Tuesday 6 December Luxcrete
Annual General Meeting/ President’s visit
Robin Lines Cost: £275 + VAT (Members); £350 + VAT (non-members) 10:00–17:30 Booking: www.istructe.org/ events/hq/2017/cpd-coursebid-winning-skills
Ian Edwards
Alan Crossman Park Farm Hotel, Hethersett, Norwich NR9 3DL 18:00: AGM 19:15: Short presentation by the President
Wednesday 8–Thursday
Bill Harvey
9 February The Drawing Gym for Engineers (two-day course)
Thursday 16 February Sutherland History Lecture – A decade in the life of the Clifton Suspension Bridge
Tuesday 10 January Annual Meeting
Tuesday 7 February Arched viaducts
Monday 6 February
CPD COURSES Held at HQ unless otherwise stated
Thursday 1–Friday 2 December Understanding Structural Behaviour (London) Dr David Brohn Cost: £450.00 + VAT (Members); £585.00 + VAT (non-members) 10:00–17:00 Booking: www.eventbrite. co.uk/e/understandingstructural-behaviour-tickets26100670809?ref=ebtnebtc
Thursday 8 December Applied Vibration Serviceability Prof. Aleksandar Pavic & Prof. Paul Reynolds Cost: £275 + VAT (Members)
Engineers (two-day course) Trevor Flynn 14:00–17:00 Cost: £450 + VAT (Members); £585 + VAT (non-members) Booking: www.istructe. org/events/hq/2017/ cpd-course-drawing-gym(four-afternoons)
Trevor Flynn 10:00–17:30 Cost: £450 + VAT (Members); £585 + VAT (non-members) Booking: www.istructe.org/ events/hq/2017/drawinggym
Thursday 12 January Bid Winning Skills (Edinburgh)
Thursday 23 March Bid Winning Skills
Robin Lines Harley Haddow, 124–125 Princes St, Edinburgh
Robin Lines Cost: £275 + VAT (Members); £350 + VAT (non-members)
EH2 4AD Cost: £275 + VAT (Members); £350 + VAT (non-members) 10:00–17:30 Booking: www.istructe.org/ events/hq/2017/cpd-course-
10:00–17:30 Booking: www.istructe.org/ events/hq/2017/cpd-coursebid-winning-skills-(2)
An Offshore Engineering Challenge
John Rees, Aogan Mulcahy and Robert Mackean
Matthew Byatt The All Saints Hotel (formerly the Suffolk Golf Hotel & Spa), Fornham St Genevieve, Bury St Edmunds IP28 6JQ 18:30
Tuesday 21 March The structure of the Georgian London house
Secretary: Paul Wilson (tel: 01603 614 834; email:
[email protected])
Paul Bell
Tuesday 25 April Sir John Wolfe Barry: Tower Bridge to the BSI – engineering pathways
Northern Counties (Tyneside)
Nick von Behr
Deep basement design (TBC)
REGIONAL GROUPS
Crowne Plaza Hotel, Stephenson Quarter, Forth Banks, Newcastle upon Tyne NE1 3SA
East Anglia HISTORY STUDY
Tuesday 6 December
09:30–16:30
bid-winning-skills-(1)
GROUP
Monday 5 December
17:45 for 18:15
www.thestructuralengineer.org
59
Tuesday 10 January AGM followed by Maintaining Transport Structures (TBC)
Teesside University, Middlesbrough TS1 3BA 17:45 for 18:15
Zayed Road, al Bashra, Mall of Emirates, Dubai 19:00–21:00
Secretary: Farhad Homayoun Shad (email: Fhs29074@
Crowne Plaza Hotel,
Tuesday 21 February
Stephenson Quarter, Forth Banks, Newcastle upon Tyne NE1 3SA 17:45 for 18:15
Polyhalite – the new industry for Teesside (Joint meeting with ICE and IChemE)
Tuesday 7 February Seismic Reinforcement of Historic Masonry Structures
Speaker: TBC Stephenson Building, Teesside University, Middlesbrough TS1 3BA 17:45 for 18:15
Marco Corradi Crowne Plaza Hotel, Stephenson Quarter, Forth Banks, Newcastle upon Tyne NE1 3SA 17:45 for 18:15
Secretary: Trevor Little (tel: 0191 226 1234; email:
[email protected])
UAE Northern Counties (Teesside)
Tuesday 13 December
Tuesday 13 December The Kelpies
Inauguration of the 2017 Chairman and successful CM Exam candidate celebration
Tim Burton Stephenson Building,
Sheraton Dubai Mall of the Emirates Hotel, Sheikh
gmail.com)
Bradford BD7 1DP 18:00 for 18:30
Yorkshire Monday 12 December Seismic-resistant design of connections with the use of perforated beams Dr Konstantinos Tsavdaridis
Wales Tuesday 13 December arcoBridge – lowcost FRP bridges for mainstream applications
The University of Leeds, Leeds LS2 9JT 18:00 for 18:30 Details: Detail s: j.f.carr@sheffi j.f.carr@ sheffi eld. ac.uk
Secretary: Nick Buxton (email:
[email protected])
INTERNATIONAL CONFERENCES
Vancouver, Canada
Ian Wise and Nikesh Rajamanie Cardiff University Engineering Department, Trevithick Lecture Theatre, The Parade, Cardiff CF24 3AA 17:30 for 18:00 Contact: Pierre Grigorian
Wednesday 18 January Chairman’s Address
(email:
[email protected])
The Role of the Expert Witness Witness
Secretary: Tim Bennett (email: tim.bennett@arup. com)
Brian Clancy John Stanley Bell LT, Richmond Building, Bradford University, Richmond Road,
David Richardson Lecture Theatre A, School of Civil Engineering, Leeds University, Leeds LS2 9JT 18:00 for 18:30
Wednesday 15 February
Tuesday 19–Saturday 23 September 39th IABSE Symposium 2017: Engineering the future (Joint IABSE and SEABC symposium) The Westin Bayshore Hotel and Conference Center, 1601 Bayshore Drive, Vancouver BC V6G 2V4, Canada Details: www.iabse.org/ Vancouver2017
New Specialist Diploma Seismic Engineering Using your knowledge of seismic design you will be asked to prepare a design appraisal with appropriate sketches, and to carry out design checks on key members of the proposed scheme.
Date
Cost
Duration
Test centres
06/01/16
£200
3.5 hours
Worldwide
Further details available at www.istructe.org/Seismic-Exam Registration closes on 16 December 2016.
60
TheStructuralEngineer December 2016
At the back Spotlight on Structures
Spotlight on In this section we shine a spotlight on papers recently published in Structures – the Research Journal of The Institution of Structural Engineers. Structures is
a collaboration between the Institution and Elsevier, publishing internationally-leading research across the full breadth of structural engineering which will benefit from wide readership by academics and practitioners. Access to Structures is free to Institution members (excluding Student members) as one of their membership benefits, with access provided via the “My account” section of the Institution website. The journal is available online at: www.structuresjournal.org
Volume 8, Part 2 The latest issue of Structures Structures,, has recently been published online. This is a special issue presenting papers from the Eighth International Conference on Advances in Steel Structures (ICASS’2015), held in Lisbon, Portugal on 21–24 July 2015. The Guest Editors for the issue were: • Dinar Camotim, Instituto Superior Técnico, Universidade de Lisboa, Portugal • Rodrigo Gonçalves, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal • Nuno Silvestre, Instituto Superior Técnico, Universidade de Lisboa, Portugal • Pedro B. Dinis, Instituto Superior Técnico, Universidade de Lisboa, Portugal
Editors’ highlights The Guest Editors have selected the following highlights which may be of particular interest to members: On the Safety of the European Stability Design Rules for Steel Members Luís Simões da Silva, Trayana Tankova and Liliana Marques http://dx.doi.org/10.1016/j.istruc.2016.07.004 Seismic Response and Engineering of Cold-formed Steel Framed Buildings B.W. Schafer, D. Ayhan, J. Leng et al. http://dx.doi.org/10.1016/j.istruc.2016.05.009 Design of Concrete Filled Tubular Beamcolumns with High Strength Steel and Concrete J.Y. Richard Liew, Mingxiang Xiong and Dexin Xiong http://dx.doi.org/10.1016/j.istruc.2016.05.005
Full issue
Wenyu Liu, Kim J.R. Rasmussen and Hao Zhang http://dx.doi.org/10.1016/j.istruc.2016.06.002 Comparison of seismic design provisions for buckling restrained braced frames in Canada, United States, Chile, and New Zealand R. Tremblay, M. Dehghani, L. Fahnestock, R. Herrera, M. Canales, C. Clifton and Z. Hamid http://dx.doi.org/10.1016/j.istruc.2016.06.004 Stressed Skin Effect on the Elastic Buckling of Pitched Roof Portal Frames Zs. Nagy, Nagy, A. Pop, I. Mois and R. Ballok http://dx.doi.org/10.1016/j.istruc.2016.05.001 Shakedown Behavior of a Continuous Steel Bridge Girder Strengthened With Post-Installed Post-Insta lled Shear Connectors Kerry Kreitman, Amir Reza Ghiami Azad, Michael Engelhardt, Todd Helwig and Eric Williamson
http://dx.doi.org/10.1016/j.istruc.2016.06.001 The Post-buckled Failure of Steel Plate Shear Webs With Centrally Located Circular Cut-outs J. Loughlan and N. Hussain http://dx.doi.org/10.1016/j.istruc.2016.05.010 Spherical Dome Buckling With Edge Ring Support J. Michael Rotter, Greig Mackenzie and Martin Lee http://dx.doi.org/10.1016/j.istruc.2016.05.008 Distortional Influence of Pallet Rack Uprights Subject to Combined Compression and Bending J. Bonada, M.M. Pastor, F. Roure and
M. Casafont http://dx.doi.org/10.1016/j.istruc.2016.05.007
The issue also contains the following articles: Systems Reliability for 3D Steel Frames
Koiter Asymptotic Analysis of Thin-walled Cold-formed Steel Uprights Pallet Racks V. Ungureanu, Ungureanu, A. Madeo, G. Zagari, G. Zucco,
D. Dubina and R. Zinno http://dx.doi.org/10.1016/j.istruc.2016.04.006 Dynamic Time-history Elastic Analysis of Steel Frames Using One Element per Member Si-Wei Liu, Rui Bai and Siu-Lai Chan http://dx.doi.org/10.1016/j.istruc.2016.05.006 Highlights • Dynamic time-history elastic elastic analysis by one-element-per-member model is proposed • Geometric nonlinearity allowing allowing large deflections and deformations are considered • The curved arbitrarily-located-hinge (ALH) (ALH) beam-column element is employed • Direct time-integration method via Newmark’s algorithm is utilized • A significant saving in the computational expense is achieved Fracture Toughness of G450 Sheet Steels at Ambient Temperature Subjected to Tension Cao Hung Pham, Dang Khoa Phan, Minh Toan Huynh and Gregory J. Hancock http://dx.doi.org/10.1016/j.istruc.2016.05.012 Response of CFS Sheathed Shear Walls Matteo Accorti, Nadia Baldassino, Riccardo Zandonini, Federica Scavazza Scavazza and Colin Colin A. Rogers http://dx.doi.org/10.1016/j.istruc.2016.07.002 Highlights • Study of light steel steel residential building in seismic areas • Experimental investigation investigation of performance performance of walls under gravity and lateral loads • Influence of the bracing bracing system and of the sheathing under monotonic and cyclic lateral
loads • Analytical methods for for determining the elastic stiffness and strength of sheathed panels • Deformation capacities and energy dissipation confirm adequacy for low and
Subject to Gravity Loads
medium seismic areas
www.thestructuralengineer.org
At the back
TheStructuralEngineer
And finally. fina lly.....
December 2016
61
The place to test your knowledge and problem-solving ability. If you would like to submit a quiz or problem, contact
[email protected]
And finally... finally...
This month we bring you a question from the Institution’ Institution’s s Structural Behaviour Course on deflected shapes. The answer will be published in January. Question
Choose the correct deflected shape under the load shown.
A
B
C
D
The Structural Behaviour Course is available at www.istructe.org/resources-centre/structural-behaviour and is free to Student Members of the Institution.
Answers to November’s quiz All diagonals in the crane structure (pin-jointed (pin-jointed truss) shown are at 45 degrees. What is the force in member AB?
The correct answer is B 141kN Take a sectional cut through AB, then simply resolve forces, i.e. the force equals 100 / sin(45).
PRODUCTS & SERVICES
Telephone: +44 (0)20 7880 7633
62
Email:
[email protected] k
TheStructuralEngineer December 2016
Working Workin g with wit h Eurocode Eur ocodes? s? You’re You’re not still doing it like this, are you? To use Eurocodes you need to research and cross-refer cross-reference ence them with various separate documents, including: the National Annexes, Execution Execution Standards and NonContradictory Complementary Complementary Information (NCCI). But not just once, you will need to reference forwards, backwards and forwards again, within, across and between documents. But there is another way - Eurocodes PLUS digitizes all 1 5 000 pages of the Eurocodes, making them more accessible and easier to understand, helping you reduce the time and cost of implementation. Find out how Eurocodes PLUS can help you clear your desk. Further information: BSI Group (web: www.bsigroup.com/eurocodesplus)
Engineering group begins operation under one brand COWI in the UK, operating as one combined company from 1 January 2017, brings together an engineering group providing specialist civil and structural engineering services, particularly within bridge, tunnel and marine infrastructure. Flint & Neill has been part of COWI since 2008 and has benefited from the financial position and greater opportunities of a larger company. Flint & Neill and also Donaldson Associates will continue unchanged, but now combined they can collaborate more effectively as part of the COWI Group. The move reflects COWI’s continued investment in the UK and will allow closer collaboration with COWI around the world. COWI will operate in the UK from offi ces ces in London, Bristol, Derby, Uttoxeter, Uttoxeter, Glasgow and York. The office in Hong Kong will continue to be managed from the UK. Further information: COWI Group (web: www.cowi.com and www.flintneill. www.flintneill.com) com)
Colour-coded studs and tracks Kingspan Steel Building Solutions has introduced colour coding to its steel framing systems to simplify site installation for contractors. Available nationwide, the new coding is designed to reduce time on site and the potential for errors. All studs, tracks and design drawings are now colour-coded according to steel gauge, making it easier to understand openings, parapets and other complex detailing, and locate and install different sections when working with design drawings. Further information: Kingspan SBS (web: www.kingspanpan www.kingspanpanels.co.uk/ els.co.uk/steel-building-solutions steel-building-solutions/news/ /news/colour colour coded studs)
3D software cuts through the decision making processes Reinforcing steel fabricator Midland Steel chose Trimble’s Tekla Tekla software as its 3D modelling software to enable it to overhaul its design processes, which has resulted in condensed project schedules, improved efficiencies on site and ultimately reduced costs. One project alone saved the company approximately £250,000 to £300,000, equating to around 40% of steel by weight. In the initial stages of a project, Midland Steel reviews an engineer’s 2D drawings before converting them into a 3D model using Tekla Structures. The model is then submitted to the engineer and the contractor for overview. The information in the 3D model facilitates changes in design, highlightsand anymake possible errors and difficulties arising in thecontained construction. Tekla BIMsight viewerany allows both parties to comment suggestions before submitting it back to Midland Steel. In addition, labour intensive processes, such as formwork and reinforcement, can be addressed, planned and subsequently improved using the 3D model, also reducing costs considerably.
Further information: Trimble Tekla (web: www.tekla.com/uk )
PRODUCTS & SERVICES Telephone: +44 (0) 20 7880 7633
www.thestructuralengineer.org
Email:
[email protected]. uk
TheStructuralEngineer
63
December 2016
Structural Concrete Alliance announces 2016 award winners The Structural Concrete Alliance has announced CCL (GB) Ltd as the winner of the 2016 Structural Concrete Alliance Award for Repair and Refurbishment for its upgrading and strengthening work at National Grid PLC’s Isle of Grain site near Rochester, Kent. Second place was awarded to Sika Ltd for its restoration of Poplar Baths in London, while third place went to Volkerlaser for its refurbishment and strengthening of the Woodhouse Tunnel in Leeds. Further information: Structural Concrete Alliance (email: admin@structuralconcr
[email protected]; etealliance.org;web: www.structuralconcr www.structuralconcretealliance.org.uk; etealliance.org.uk; tel: +44 (0)1420 471619)
Load analysis software soft ware now compatible with more mo re design de sign codes A new release of Oasys AdSec is compatible with Indian IRC and Canadian CSA standards as well as Eurocodes. Release 8.4 also includes an improved interface and now enables engineers to edit and query models from within graphics. Additional material models are built in to the new release and standard curves are provided as templates. Sections made from concrete, steel or fibre-reinforced fibre-reinforced polymer (FRP) or any combination of these c an be tackled. AdSec can still be used in conjunction with Oasys Pile, ALP and Frew software. Further information: Oasys Software (web: www.oasys-software.com)
Bristol footbridge gets anti-slip surface Bristol’s Primrose Bridge has been given a new anti-slip surface from Polydeck as part of its latest refurbishment. South Gloucestershire Council discovered that the footbridge would require more than a surface patch repair to bring it up to current safety standards. The council contacted local company Polydeck, which recommended the application of GRIPFAST NT Slurry, a three part, anti-slip wearing course and waterproofing membrane, designed for use on steel, concrete and aluminium substrates. After removing the existing surfaceaggregate before applying a primer, Polydeck applied the GRIPFAST Slurrymechanically before dressing the surface with a 1-3mm and finally conducting a thorough sweep to remove any excess. GRIPFAST NT Slurry has a typical design life of 20 years. Further information: Polydeck (tel: +44 (0) 1934 863678; web: www.polydeck.co.uk)
Framing solution for complex development Unite’s latest development in Coventry, a curved, complex shaped building, required a bespoke solution. An addition problem was the confined site access. voestalpine Metsec plc and its Metframe system was chosen as a solution to the design criteria. Furthermore, with off-site manufacture of the panels this would help streamline the build process and reduce activity on the busy, restricted site. Far Gosford Street, ‘Gosford Gate’, will be home to 286 students and combines studio living spaces with communal study, social and utility areas. Main contractor Bowmer & Kirkland required a number of bespoke elements for the the building’s complex design. These were met using Metsec’s Metframe system and essential engineered designs, produced by the Metsec team, were employed to construct the upper levels of the building. Specific requirements of the project, particularly the difficult curved wall and corners of the building, involved close collaboration. The framing was delivered in the correct erection sequence for a streamlined installation process by installer Mansell Finishes, which installed the panelled system. This cuts down the activity movements on the restricted site, avoids waste and helps to reduce the project’s overall environmental impact. Further information: Metsec
(web: www.metsec.com; Twitter: @MetsecUK; facebook.com/MetsecUK)
SERVICES DIRECTORY
Telephone: +44 (0) 20 7880 7633 Email: greg.lee@redacti ve.co.uk
64
TheStructuralEngineer December 2016
ANALYSIS & DESIGN
STRUCTURAL DESIGN & CAD DRAWING
TONY DOYLE ASSOCIATES LTD COMPUTER AIDED DESIGN & DRAWING
A u t o C A D D r a u g h t i n g S e r v i c e s ANALYSIS & DESIGN
STRAP software for analysis and design of cold formed, concrete, steel and pre & post-tensioned structures.
Fine GEO5 geotechincal software for
We are a team of professional technicians with of ces in the UK ces and Ireland providing an ef cient, cient, on-demand service for our clients
- RC Detailing Specialists - Structural Drawing GA s & Details
soil structure interaction, earth pressure, sheeting slope & pilestability, design.
- Bespoke Drawings for all Applications -
Trial downloads at www.sigma-x.net UK: +44 (0) 203 603 1442 Ireland: +353 (0) 86 85 45 425 www.sigma-x.net
Tel: 01934 808468 www.tonydoyleassociates.co.uk
SOFTWARE
E N
L H
I
EN 1990, EN 1991, EN 1993, EN 1994, EN 1995, BS5502-22, BS5950, BS5268, BS6399 UB, UC, RSJ, UBP, HF-CHS, HF-SHS, HF-RHS, CF-CHS, CF-SHS, CF-RHS, RSA, TEE, 2-RSC, 2-RSA, PFC, 2-PFC , ASB, SFB, UB/PFC (Gantry Girders) , Custom, rolled, welded, S235, S275, S355, S420, S450, S460, Custom, Class 1, Class 2, Class 3, Class 4 (slender)… E sy t se pro n pr f ssi na nall s ft ftwa wa e - fa fas st co pr pre ehen hensi si e r s lts lts.. G t th j b on !
F ee 8 d y t ial av ava aila le f
all a ll o
of war are e!
WANT TO WA AD A DVERTISE YOUR PRODUCTS YO PRODUCTS & SERVICES SERVICES? ?
Download from: www.quiksoft.co.uk email
[email protected] or call 08456 250 280
REINFORCED CONCRETE DETAILING
R.C. Detailing Specialists Established 1980 Extensive experience Proven reliability Large capacity Paul Benham Ltd
Civil & Structural Engineering Draughting Service
[email protected] www.paulbenhams.co.uk 01273 730956
ADVICE AND INFORMATION
Contact Greg Lee on Lee on 020 7880 7633 7633 or email
[email protected] 50 years of
independent practical concrete know-how – just a phone call away.
01276 607140
TheeStructuralEngineer Th The flagship publication of The Institution of Structur Structural al Engineers
Register to receive latest jobs by email - visit www.thestructuralengineer.org/jobs.
TheeStructuralEngineerJobs Th Telephone 020 7880 6212
Email
[email protected]
Trusted recruitment advisors bringing candidates and organisations together to build outstanding careers. Associate Director | Bristol Associate Director | Central London seeking an Associate Director with a wealth of structural design experience and a proven track record of strong business development and client management skills, whose CV demonstrates a career of successful project delivery across a broad sector base.
Senior Structural Engineer (rail bias) | Central London Chartered engineer sought by global leader, experienced in rail building design. Responsibilities; design calculations and reports ensuring compliance with relevant standards and Network Rail GRIP process. Previous exposure to London Underground schemes would be an advantage.
Structural Engineer | Central Leeds, West Yorkshire | £30k to £38k Prestigious consultancy is seeking negotiable an Associate Director who has experience managing staff at all the company to existing and prospective clients and winning new business. Excellent and rare opportunity to join this blue chip company working on some of the most renowned and major international projects in London.
Our client has recently secured a large framework within the Healthcare sector. Engineer required with technical judgement and resourcefulness in the planning, design and construction stage of projects. Role will consist of checking all drawings, calculations & coordinating design with other disciplines.
Senior Structural Engineer Cardiff | £44k to £48k
Associate, Structures | Manchester | £60k to £65k
Wonderful opportunity for a
An ambitious Chartered Structural Engineer required to head a small team working collaboratively with the infrastructure and energy teams. Demonstrable building structures experience in the UK with good client facing skills.
structural engineer at senior level looking to join a successful company. Your role will be to help establish and grow the engineer who has a solid buildings structures design background.
Find more jobs online at conradconsultin conradconsulting.co.uk g.co.uk For more information please contact
[email protected] Or, for a confidential chat, call us 8am to 8pm on 020 3159 5387
TheeStructuralEngineerJobs Th Telephone 020 7880 6212
Register to receive latest jobs by email - visit www.thestructuralengineer.org/jobs.
Email
[email protected]
Jobs London | Dublin | Soa We require: •
Senior Structural Engineers to Director Level • Graduate Design Engineers • Revit/CAD Engineers and Technicians
Chartered Structural or Civil Engineer North Finchley, London
Structural Engineering Technician Dorchester,, Dorset Dorchester
Graduate Engineer – Civils & Structures Dover, Kent
These jobs and plenty more at jobs.the jobs .thestru structur cturalen alengine gineer.org er.org
Continuing Professional Development
Upcoming Courses Bid Winning Skills 12 Jan 2017 (Edinburgh) and 23 Jan 2017 (London) This course focuses on improving conversion rates when bidding for projects.
The Drawing Gym for Engineers 16 Jan - 6 Feb 2017 (Monday afternoons or available as a two day course) This course motivates you to communicate effectively using a broad set of
What’s it worth… building effective relationships in business (2 days) - In collaboration with The University of Bath 17-18 Jan 2017 This course develops the skills that are critical for maximising effective relationships across a variety of projects with key stakeholders.
Designing with Glass as a Structural Material 19 Jan 2017 The aim of this workshop is to focus on the design and detailing of structural glass elements.
skills for in the design process. Practical work will be supplemented with
Book now at istructe.org/trainingcourses
www.thestructuralengineer.org
Structural Design/ Project Engineer Central London London Ref: 51122 51122 Up to £45,000 + Benefits
knowledge based recruitment in structural engineering consultancy
BLAVATNIK SCHOOL OF GOVERNMENT
W
Farringdon-based 10-strong niche consultancy has a requirement for a Structural Design/Project Design/Proje ct Engineer to join the expanding practice as it continues to win new work and accolades. Candidates will need to be a Graduate member of IStructE and/or ICE, have a MEng/MSc and will need to have gained good design skills in the common materials in UK consultancy.
JTI HEADQUARTER HEADQUARTERS S
FORMBY HELICAL STAIR
Structural Project Engineer
W
Central London London Ref: 51133 Up to £50,000 + Benefits Design-focused niche consultanc Design-focused consultancy y based PELL FRISCHMANN at London Bridge has a requirement for a Structural Project Engineer to join their rapidly expanding London studio. Candidates will need Chartered Structural to be near-Chartered with IStructE and/or (Forensic) Engineer ICE, have a MEng/MSc and must have gained good design and projectWest Sussex Ref: 51087 running skills in another niche or Up to £60,000 + Benefits premier design-focused Forensic Structural Engineers based in West London consultancy. Sussex has a requirement for a Chartered Structural (Forensic) (Forensic) Engineer to join its expanding BOMNONG L’OR CENTRE
practice working on a wide range of projects. Candidates will need to be Chartered with IStructE and/or ICE, have a MEng/MSc from a top 10 university and have excellent analytical design skills combined with good communication and client-facing skills.
SOM
Technical Director/ Associate Surrey Ref: 51119 Up to £90,000 + Benefits WEBB YATES ENGINEERS SNFCC W
Large premier multi-discipline consultancy has a requirement for a Technical Director (or aspiring Associate+) to join the expanding mid-Surrey ofce. Candidates will need to be Chartered with IStructE and/or ICE and must have extensive structural engineering design, project and team-running experience as a minimum and at more senior level be skilled at servicing warm clients.
COBALT PLACE
Senior Structural Engineer Central London London Ref: 51101 Up to £52,500 + Benefits Large consultancy that specialises in forensic engineering and expert witness engineering has a requirement for a Senior Structural Engineer to join one one of its its teams teams working working on a wide range of UK and international projects. Candidates will need to be Chartered or/near with IStructE and must have excellent analytical
STRUCTUREMODE
EXPEDITION & OMETE
Civil Infrastructure Engineers
Associate Structural Engineer
London & The South-East Up to £70,000 + Benefits
Central London London Ref: 51116 51116 Up to £62,500 + Benefits
WDT has around 15 roles for Civil Infrastructure Infrastruct ure Engineers up to AssociateDirector level with a wide range of premier, niche and mainstream consultancies. Candidates will need to be a member of ICE (grad+) and (as a minimum) good design skills in roads and drainage design and at more senior level good project and team-running experience in civil infrastructure and associated works.
Design-focused niche consultancy based in Design-focused Central (South) London has a requirement for an Associate-level Structural Engineer to join the expanding business. Candidates will need to be Chartered with IStructE and/or ICE, and will have worked in premier and/or niche London consultancy as well as being capable of directing a team and coordinating & dialoguing with external consultants consultants..
WALSH V&A EUROPE 1600-1815 GALLERIES
STRUCTURAL AWARDS
WINNERS 2016
For the sixth year running we were a proud sponsor of The Structural Awards by IStructE and this year we sponsored the “Award for Community or Residential Structures”. Structures ”. Well done to all the winners and see featured iconic projects by some of this year’s successful nominees and clients of Walker Dendle Technical Recruitment.
Walker Dendle Technical Recruitment would like to congratulate Expedition, Pell Frischmann and Webb Yates on their winning projects featured with a W in their categories at the Structural Awards 2016 on Friday 11 November. For the 10th year running we had a table for the night with guests from Bradbrook Consulting, Conisbee, Engenuiti, GLaSS, Heyne Tillett Steel, Milk Structures, Sinclair Johnston
ECKERSLEY O’CALLAGHAN
24 Greville Street Farringdon London
design skills gained in specialist or mainstream UK structural engineering consultancy.
THE CUBE
ENGENUITI
T 020 3457 0797 E
[email protected]
L A C I N H C E T E L D N E D R E K L A W F O S T N E I L C D N A S E E N I M O N L U F S S E C C U S S ’ R A E Y S I H T F O E M O S Y B S T C E J O R P C I N O C I E R A D E R U T A E F
EC1N 8SS
and Walsh.
uualker alkerdendle dendle.co.uk .co.uk
Structural-Safety works with the professions, industry and government on safety matters concerned with the design, construction and use of building and civil engineering structures.
We provide an impartial expert resource to share and to learn from the experiences of others.
You can participate You part icipate by reporting concerns, in condence, to the website. Reports are anonymous and de-identied before being published. Reports can also lead to Alerts which inuence the safety of existing and new structures. Visit the website to register for Newsletters and Alerts and to view the database of reports. reports .
www.structural-safety.org CROSS Condential
reporting on structural safety |
SCOSS Standing
Committee on structural safety
Sponsored by
