Cross-frame diaphragms for steel girder bridges using the AASHTO LRFD bridge design specifications

Intermediate cross-frame diaphragms of composite steel girder bridges can serve distinct functions. They can stabilize the compression flanges, transfer wind loads, and distribute live loads. Alternative components or measures can, and do, carry the wind loads into the bearings and distribute the live load to the girders. Thus, the functions most significant to cross-frame diaphragms are the stabilization of the compression flanges of the steel girders. The AASHTO LRFD Bridge Design Specifications (AASHTO 1994) specify provisions to determine the need and spacing of intermediate cross-frame diaphragms for these essential functions. These provisions and the rationale for eliminating or minimizing the use of cross-frame diaphragms are discussed herein.