Torsional Properties of Composite Girders

The design and analysis of curved highway bridges requires the evaluation of the torsional properties of the bridge girder members. The application of "thin walled theory" can be applied to this problem with certain modifications. These modifications require consideration of the material property variations and the composite action of the deck slab and girders. Inclusion of these modifications into the general theory has resulted in a series of equations, which were then used to evaluate the torsional properties of typical composite highway girders. The relationship between the warping torsional property and the bending property of the various girders was then determined, yielding a series of approximate equations. These equations will be presented herein and will permit the designer to obtain preliminary maximum normal stresses. Approximate equations for evaluation of the torsional properties will also be given herein. The experimental testing of a series of composite girders has indicated that the application of thin walled theory is justified.