Stress and Fracture Analysis for Welded Plate Girders in Bridge Structures
Welded plate girders are a common feature in bridge construction. Most plate girders are fabricated using fusion welding processes, since welding produces high strength joints at relatively low cost. Unfortunately, a number of brittle fracture structural failures have been known to occur in close proximity to certain types of welded joints in bridge structures. These failures are usually attributed to a high degree of constraint introduced by welding attachments to the girder web and the high residual stresses in the neighborhood of the weld. To accurately analyze the failure behavior in these welded structures, it is necessary to determine the welding residual stresses, and combine these stresses with the stress state obtained from external loads. The main impact of the residual stresses, is on the level of triaxiality in the detail and hence the location of crack initiation. Once a crack has initiated, a serious cleavage fracture may occur because of the inability of the material to plastically yield under conditions of high multiaxial constraint. Crack arrest may not occur until the crack has grown a great distance. Further subcritical crack growth is primarily governed by the alternating external loads acting on the structure, with the residual stresses playing only a secondary role. This study demonstrates the application of a finite element methodology that combines three separate finite element procedures to determine the fracture behavior. First, a nonlinear transient welding simulation is performed to obtain the welding residual stresses. Second, the local stresses caused by external loading are calculated. Finally, in the last step, the stresses are superposed and used as input for the fracture analysis. In the fracture analysis, the direction of crack propagation and stress intensity factors, as a function of crack length, are calculated according to mixed mode linear elastic fracture mechanics. The paper presents results from example FEA computations and compares predicted crack trajectories with observations from actual welded plate girder failures.
Welding FEA Constraint Triaxiality Crack propagation Stress intensity factor Fracture mechanics Residual stress
Cumali Semetay Hussam Mahmoud Herman F. Nied
Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015, USA, 1(6 Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urban Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015, USA, 1(6
国际会议
南京
英文
158-162
2007-10-16（万方平台首次上网日期，不代表论文的发表时间）