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Lead consultant for 450 metre span cable-stayed bridge on Chao Phya River linking Bangkok with Thonburi on expressway system. At the time of its construction this was the longest spanning cable-stayed bridge in the world. Peter Fraenkel & Partners, leading an international consortium of consulting engineers, were appointed by the Expressway and Rapid Transit Authority of Thailand to undertake a feasibility study and the detailed design of a 3.5 km section of the proposed Bangkok expressway, which included a crossing of the Chao Phya River.
During Phase I of the project, alternative crossing arrangements were investigated: immersed tube, bored tunnel, cable stayed bridge and suspension bridge. For a bridge, navigation requirements were such that there could be no piers within the main waterway and the clearance should be a minimum of 41m above highest water level. This would result in a high level bridge with 1000m long approach viaducts on either side of the river. A tunnel would be at least 800m long with 500m long approach ramps on either bank. A comprehensive study was undertaken of alternative structural forms for both the bridge and tunnel options and their approaches, which involved extensive ground investigations. The final recommendation was that the high level cable-stayed bridge would be the most suitable and economically advantageous solution. The consortium then undertook detailed design and construction supervision of the bridge. The main 450m span over the river was supported by a single central plane of cables and at the time it was the largest structure of its type in the world. The project also included approximately 2km of prestressed concrete approach viaducts, together with interchanges with the existing road system and toll collection facilities. Special provisions were made at the bearings of the approach viaducts, to cater for long term settlement resulting from water extraction by deep well pumping in the soft Bangkok clay.
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