Recommended Guidelines for Redundancy Design and Rating of Two-Girder Steel Bridges

摘要

The report presents the results of an investigation into the after-fracture redundancy of simple span and continuous, composite, and noncomposite steel two-girder highway bridges. A near full depth fracture is assumed to occur at any position along the length of one of the two girders. The fracture is assumed to penetrate the tension flange and full depth of the web, but not the compression flange. An analytical model is developed consisting of the fractured and unfractured girders together with a redundant bracing system consisting of top and bottom laterals and diaphragms. It is shown that the fractured structure carries dead and live toads as a 'pseudo space truss'. It is shown that the after-fracture behavior of the structure is primarily dependent on the strength and stiffness of the redundant bracing system and its connections to the girder flanges. It is shown that a properly designed and configured bracing system provides effective and efficient redundancy to a two-girder highway bridge.