Bridges

The Rail Integration and Systems (RIS) Alliance (comprising the Cross River Rail Delivery Authority, Queensland Rail, CPB contractors, UGL, Aecom and Jacobs) is part of Brisbaneís wider Cross River Rail (CRR) project to provide the rail systems required to integrate CRR into the Queensland rail network. A key focus area for the Alliance is the upgrade of the Exhibition Station in central Brisbane. Exhibition Station is being redeveloped to become a major dual level rail station, with a new elevated platform supported by twin adjacent rail viaducts to be constructed over the existing tracks. The site is highly constrained with road bridge crossings of the existing tracks immediately to the north and south, both with substandard vertical clearances. A through-girder solution was developed as it provides a minimal structural depth beneath the rails, and a minimal substructure footprint due to an increased span-to-depth ratio.

The through-girder bridge developed consists of two U-shaped superstructure forms; a 3-span continuous concrete unit that is longitudinally post-tensioned, and a two-span steel trough-girder with composite cross girders. The 10m wide concrete girder spans have an overall structural depth of 2m and is continuous over a three-span length. The concrete solution did not have capacity for the final two spans as a separate continuous girder without an undesirable increase in overall structural depth. A steel trough-girder solution was developed that matched the structural depth and assisted the construction program by removing stressing operations from the critical path. This paper covers both the superstructure and substructure design, outlining the constraints of incorporating the bridge structures within the brownfield station redevelopment, and the solutions developed in collaboration with the Constructor. Steel reinforcement congestion of the post tensioned structures was a particular concern which led to the development of a fully detailed 3D Revit model identify clashes and as an aid in the reinforcement placement strategy.