Impact-induced torsional failure mechanism and simplified analysis model for double-column bridges subjected to vessel oblique collisions

Abstract

Current bridge design specifications and codes worldwide typically assume vessel impact forces act at the center of bridge piers, failing to account for the torsional effects on double-column piers resulting from potential oblique vessel collisions at the pile cap end. To address this limitation, a torsion test on a RC column was conducted to investigate the progression of torsional damage and determine the torque-deformation relationship. The experimental results were subsequently used to validate the numerical modeling techniques for simulating torsional failure in RC columns. Furthermore, based on the case of an actual bridge torsional failure caused by an oblique vessel collision, a high-fidelity finite element (FE) model of vessel-bridge oblique collision was developed to reveal failure process and mechanism of the bridge, which remain unrecorded and poorly understood. The damage patterns and residual displacements predicted by numerical simulation were compared with field observations from the accident, and the potential conditions leading to such failures were further investigated. Additionally, a simplified coupled analysis model for oblique vessel collisions with bridges was established using a two-degree-of-freedom system, with methods for determining equivalent masses and spring parameters in the normal and transverse directions derived analytically. The results indicate that the damage pattern predicted by the high-fidelity FE simulation of the double-column pier align closely with field observations, providing reliable insights into the detailed failure mechanisms of actual accidents. Moreover, the responses predicted by the simplified model show excellent agreement with those from the full barge impact model, demonstrating its effectiveness for simulating vessel-bridge oblique collisions.