Fatigue performance of KT type joints welds in all-welded composite truss bridges

In order to study the fatigue performance of the critical weld details of the KT type joints in fully welded composite truss bridges, the fatigue-sensitive truss members of the KT type joints were subjected to in-depth research and discussion. Firstly, the fatigue resistance of key weld details under simulated working conditions was verified by designing foot-size specimens and fatigue loading of welds. Moreover, the stress concentration factor for three types of fully welded T-shaped specimens were determined based on the strain results. The results showed that except for the specimens with obvious welding defects, no obvious fatigue crack growth was found after 6 million or even more fatigue loadings. Secondly, using crack initiation life calculation theory, based on the notch strain method and crack propagation method, the specific crack initiation life of the prepared specimens was calculated using verified finite element model test data. The simulation calculation results were consistent with the actual phenomenon, and no fatigue cracks appeared after 6 million load cycles, which proved the effectiveness of the analysis method. This study provides effective theoretical support for understanding the fatigue performance of key weld details in the nodes of all-welded composite truss bridges.