Bridges

Steel trough girders are an efficient form of structure for long-span curved bridges. Analysis and design of these structures need to incorporate the proposed construction sequence to ensure that the girders have sufficient capacity not only for the completed structure but also for the potentially numerous states of the structure during construction. There is a range of approaches to the construction staging of steel trough girder bridges that can require different construction methodologies, such as the use of drop-in spans, temporary supports and span-by-span techniques. Each of these will result in varying temporary structure configurations during construction that need to be considered in the analysis and design of the girders. Site constraints will usually govern the adopted construction methodology, along with available lifting plant. The authors have both contributed to the detailed design phase and construction phase services for the East Zone of the West Gate Tunnel Project in Melbourne. This project included several steel trough girder bridges with spans up to 100m on curved alignments: and with heavily constrained site conditions. Based on this recent project experience, this paper will present critical aspects of the analysis and design of steel trough girder bridges for longer span curved bridges. These critical aspects include temporary torsional stiffness; external bracing arrangements; temporary supports; splicing platforms; stage deflection analysis; precamber; and analysis modelling techniques using modern structural analysis software.