NUMERICAL FRACTURE SIMULATION OF DISTORTION-INDUCED FATIGUE CRACKS IN STEEL BRIDGES
Chun-Sheng Wang 1*, Yu-Zhu Wang 1, Jin-Qiang Feng 1 and Nai-Xuan Ma 1
1 Engineering Research Center for Large Highway Structure Safety of Ministry of Education, School of Highway, Chang’an University, Xi’an, China
Distortion-induced fatigue cracks are commonly observed in steel bridges under the action of the long-term traffic load and the environment, endangering the service safety of the bridges. In order to investigate the propagation behavior of distortion-induced fatigue cracks at web gaps in steel bridges, finite element models based on eXtended Finite Element Method (XFEM) were built to simulate the entire welding process of the vertical stiffener web gaps. The results of the welding process show that significant transverse welding residual tensile stress exists at the stiffener-to-web weld toes, and the peak value is close to the yield strength. Numerical fracture mechanical analysis results indicate that the initial crack angle has great influence on the crack propagation mode. Typical fatigue cracks at the vertical stiffener web gap are Mode I leading mixed mode cracks of Modes I, II and III. Dynamic crack propagation considering welding residual stress has faster propagation rate and is consistent with full-scale fatigue test results. The influence of welding residual stress cannot be neglected for analysis and assessment of distortion-induced fatigue cracks in steel bridges.
Steel bridge; Crack propagation; Numerical fracture mechanics; Distortion-induced fatigue; Extended finite element method