Robustness design of multi-span through tied-arch bridge considering systemic hanger failure

To investigate the dynamic impact of systemic hanger failure on the multi-span through tied-arch bridge, firstly, three numerical calculation methods were employed to simulate the effects of hanger breakage: the LS-DYNA restart method, the element birth and death method, and the full-dynamic analysis method. The simulated effects were then compared with dynamic response data of the hanger breakage test to identify the optimal method for modeling systemic hanger failure. Secondly, to enhance the robustness and prevent progressive collapse in multi-span through tied-arch bridge structures, two structural systems were proposed: the simply-supported continuous structure and the rigid integral tied-arch structure. The failure simulation method was employed to compare the dynamic response of the remaining structure under systemic hanger failure before and after structural transformation. Additionally, the Simple-Johnson-Cook model was utilized to simulate the damage process of the bridge and determine the final damage mode of the structure. On this basis, the progressive collapse and damage mechanism of the structure under systemic hanger failure was further investigated. Research results show that the error between the simulation results and the test data of the LS-DYNA restart method is relatively small, enabling better simulation of conditions when the hanger experiences instantaneous damage. For the simply-supported continuous structure, in the event of systemic hanger failure, the final damage extent of the bridge system is the lowest, and the force transmission path is extended, effectively delaying the damage process of the structure, reducing the risk of progressive collapse accidents, and providing additional time for traffic evacuation. However, for the rigid integral tied-arch structure, due to the high initial stiffness, stress concentration may occur, leading to premature local failure of the bridge system. Consequently, the simply-supported continuous structure can be utilized in the design of newly constructed multi-span through tied-arch bridges or readily applied to enhance the robustness of existing bridges through the installation of replaceable joints on pier tops.