Chapter 4: The Construction Process of Segmental Bridges
126.96.36.199 The West Gate Bridge
A much more severe failure of a bridge under construction occurred in 1970 in Australia, when a 112-m long steel box girder span of the West Gate Bridge, crossing the Lower Yarra River in the Melbourne area collapsed during construction (Royal Commission 1971). The description of the circumstances that led to the total failure and loss of 35 lives reads like a thriller, i.e. like a compilation of how not to perform a bridge project. Again, the construction influences were underestimated.
In this case, the whole project throughout the time before the collapse had been plagued with errors and omissions in overall structural design, in detailing, and in preparation and checking of field operations, as the Royal Commission (1971) concludes from its investigation. According to their report, already the design lacked proper consideration of the unusual erection method that had been proposed. Safety margins for the box girder that was divided into longitudinal halves were insufficient even despite strengthening that was added after failure of the Milford Haven Bridge in Wales some months earlier. Even earlier, in 1969 the Forth Danube Bridge in Vienna had suffered major buckling in the lower parts of its steel box girder (Royal Commission 1971).
Lack of open communication between project participants, especially between the engineering consultants and the contractor’s personnel, as well as other managerial disputes and strikes of union workers further contributed to the unhealthy atmosphere under which the novel structure was to be constructed.
Direct cause of the collapse was removal of bolts that connected the box girder halves in an attempt to straighten out buckling that had occurred. Matching the seams between the two halves of the steel box girder in the lifted position had already earlier proved to be very difficult, despite efforts of jacking them together and using heavy kentledges to match the camber lines of the spans. The asymmetric trapezoidal halves tended to bow out of shape when being jacked up at both ends. In its conclusion, the Royal Commission (1971, p97) once again stressed the need for continuous reviews, checks, and improvement particularly in bridge engineering:
“Engineers engaged on the design of major bridges cannot stand still. It is part of their duty, not only to their clients but to the community as a whole, to advance, to