Precast segmental box girder bridges.pdf
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Prof. Dr.-Ing. G. Rombach Technical University of Hamburg-Harburg
Segmental Bridges
Page: 1 INSA Rennes, Feb. 2002
Precast segmental box girder bridges with external prestressing - design and construction Prof. Dr.-Ing. G. Rombach Technical University, Hamburg-Harburg, Germany
Summary Segmental box girder bridges externally post-tensioned are one of the major new developments in bridge engineering in the last years. In contrast to ‘classical’ monolithic constructions a segmental bridge consists of „small“ precast elements stressed together by external tendons (fig. 1). The many advantages of this type of structure like fast and versatile construction, no disruption at ground level, high controlled quality and cost savings have made them the preferred solution for many long elevated highways, especially in South East Asia (see [1], [2]), and bridges. Design and construction of precast segmental hollow box girder bridges will be mentioned in this paper.
1
Introduction
The greatest segmental bridges had been build in South East Asia resp. Bangkok. This region of the world suffers under a big lack of sufficient infrastructure e.g. roads. In the big cities like e.g. Bangkok the traffic nearly collapsed. There is a great need to change this bad situation rapidly. A Master Plan had been developed for the Bangkok region which lead to many big train and highway projects (table 1). Table 1 Projects in Bangkok Name of Project
System
Total length
Constr. Cost Bill. EUR
Hopewell (SRT-CT, BERTS
7 train tracks + 4-lane elevated highway Segmental Constr. 4-lane elevated highway 6-lane elevated highway I-beams
60 km
2,4
13 km
0,08
18,7 km
0,32
6-lane elevated highway Segmental Constr.
39 km
0,85
Bang Na Expressway
6-lane elevated highway Segmental Constr.
54 km +
0,7
Sector C+
4-lane elevated highway Segmental Constr.
appr. 30 km
0,4
SST Ramindra Atrnarong Expressway Second Stage Expressway System
Fig. 1
Segmental bridge under construction
Table 2 Restraints Conditions no space at grade traffic jams flooding bad soil condition short construction time transportation problems cost flexible system
Solution ==> elevated highway ==> precast system ==> segmental hollow box girder
Table 3 Second Stage Expressway System Part I, Sector B INSA-segmart
19.02.2002
Prof. Dr.-Ing. G. Rombach Technical University of Hamburg-Harburg
Segmental Bridges
total length of bridge:
2 x 10 km
total area of bridge deck:
370 000 m
number of spans:
806 (716 segmental ; 90 I beams)
number of segments:
appr. 9000
number of bored piles:
2360
number of driven piles:
10400
number of ramps:
41
at grade roads:
6000 m
office buildings:
8
length of electric cables:
appr. 54 km
construction time:
29 months
total cost:
appr. 325 Mio EUR
Page: 2 INSA Rennes, Feb. 2002
2
2
2 Structural elements of segmental bridges Segmental bridges are mainly built as single span structures to avoid coupling of post tensioning cables. Furthermore in single spans the greatest shear force is not located in the same section as the greatest bending moment. Though the joint between the segment is always closed. A typical span is shown in fig. 2.
45,25m
7,0-15,60m
3,40m 2,40m
Figure 2 Standard span A standard span has a length of appr. 45m. It consists of 14 segments. Dry joints are used in this project (no epoxy glue). No continuous reinforcement is provided across the match cast joints between the segments. Due to the external post tensioning (fig. 3) 3 different segments are needed (fig. 4): ·
Pier segment:
· ·
Deviator segment: Standard segment:
INSA-segmart
heavy end diaphgram required to stiffen the box section and for anchorage of p.t. cables required to deviate tendons thin webs (35cm)
19.02.2002
Prof. Dr.-Ing. G. Rombach Technical University of Hamburg-Harburg
Segmental Bridges
Page: 3 INSA Rennes, Feb. 2002
172.5 50
1022.5
No. 3 No. 1,2 No. 4 No. 5 No. 6
1020
1360
1022.5
No. 8 No. 7
4525cm (12 segments à 340cm + 2 segments à 172.5cm )
top view
No.3 No. 4 No. 5 No. 2 No. 1 No. 6
No. 7
No. 8
symmetry line
Figure 3 Tendon layout
INSA-segmart
19.02.2002
Prof. Dr.-Ing. G. Rombach Technical University of Hamburg-Harburg
Segmental Bridges
Page: 4 INSA Rennes, Feb. 2002
D3 : 1090 - 1560cm D2 : 700-1190cm
Pier Segment
Nr. 1
Nr. 2 Nr. 3
240
Nr. 4 Nr. 5
30 80 130 180
Nr. 6
Deviator Segment Nr. 1 Nr. 5 Nr. 4 Nr. 6
Standard Segment
20 40
20
Detail B
35
Detail A
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