2011

Lateral Torsional Buckling of Plate Girders with Flexible Restraints
The lateral -torsional stability of girders in composite steel-concrete bridge construction is a often a critical check before the concrete hardens and can provide support against lateral torsional buckling of the girders. Currently, both lateral and torsional bracing are used to ensure the girders’ stability, with plan bracing to provide lateral stability to the compression flange and discrete torsional restraints, or cross-frames, to provide torsional stability. Plan bracing, however, has been problematic for contractors as, depending on the location of the plan bracing, they may interfere with concrete reinforcement or they may present a long-term maintenance liability.

This project will investigate the behaviour and strength of plate girders with only discrete torsional bracing. The issues that this study is expected to address include 1) the effective unbraced length for the lateral torsional buckling check of the girder; 2) the stiffness and strength requirement for the torsional restraints; and 3) the effect of the concrete formwork in providing the lateral restraint. Large-scale experimental tests and finite element analysis will be conducted to evaluate the aforementioned. Appropriate recommendations, suitable for practical implementation, will be made to address the lateral torsional buckling stability of plate girders with flexible restraints.