ABSTRACT
The integral joint of steel truss girder is widely used in the construction of modern large-span suspension bridges due to its advantages of simple course of manufacture and installation. However, the complex cross-section geometry and the inevitable existence of welding residual stress during the welding process, which would cause fatigue problems under the long process of cyclic vehicle loading. A framework for fatigue assessment of integral joints of steel truss girder in large-span suspension bridge is thus presented in this study. The main features of the framework include multi-scale finite element bridge model, vehicle induced stress, the simulation of complex welding residual stress field, and the crack propagation simulation of fatigue-prone details of integral joints. Based on the Linear Elastic Fracture Mechanics (LEFM) and Extended Finite Element Method (XFEM), the digital fatigue test was carried out. According to the digital fatigue test results, the cracking growth mode of fatigue-sensitive details of integral joints in steel truss girder were determined, and the fatigue damage characteristics of fatigue-prone details were analyzed. The results indicate that the developed framework is applicable and the Mixed-mode crack propagation law was identified in fatigue-prone details, and the fatigue growth life will be overestimated irrespective of the welding residual stress.
