ABSTRACT
In order to investigate the fatigue crack propagation properties of rib-to-deck weld joint toe and root details for orthotropic steel decks, the suspension bridge with the 1688 m main span of the Nizhou bridge in Nansha bridge project was selected as the engineering background and the digital fatigue tests of these details were carried out based on extended Finite Element Method (XFEM) and numerical fracture mechanic theory, which could reflect the actual stress characteristic. The welding residual stress field simulation was carried out for the orthotropic steel deck manufacturing process. The residual stress result shows that there is a large residual tensile stress in the welding area of the rib-to-deck toe and root details, and the peak value of the Von-Mises stress at the rib-to-deck joint is close to the yield stress of Q345 steel. A muti-scale whole bridge finite element model was established considering construction condition for the orthotropic steel deck construction process. The fatigue crack propagation could be simulated by XFEM coupling with welding residual stress field, live load and dead load stress field. The results of fatigue crack propagation behavior display that the fatigue crack at the weld root is led by mode I, which could keep in the plane during the crack propagation. And the fatigue crack at the weld toe is mix mode I-II-III crack led by mode I, which cannot keep in the plane during the crack propagation, but slightly deflection.
