Fatigue of Curved Steel Bridge Elements: Fatigue Tests of Curved Box Girders

摘要

Eight types of welded details representing AASHTO Categories B, C, D, and E are selected for placement on three full-scale curved steel box girders. The fatigue behavior of the welded details is monitored while subjecting the box girders to approximately two million constant amplitude load cycles. Primary fatigue crack growth due to the longitudinal normal stress ranges caused by bending and warping torsion was observed. Secondary fatigue crack growth was also observed and was due to transverse forces in the diaphragms and the introduction of out-of-plane forces and displacements into the webs and flanges. The observation of primary fatigue crack growth at the welded details indicates that their fatigue behavior is adequately described by the present AASHTO Categories B, C, D, and E which are applicable to straight girders. The observed patterns of secondary fatigue crack growth are described in detail. Several modifications of the assemblies to improve their resistance to secondary fatigue crack growth were made and their effectiveness is described. The report closes with an itemized summary of significant conclusions and recommendations for further study.