Failure Phenomena due to Seismic Pounding: Dominant Effects of Soil Interaction and Abutment Stiffness Softening on Impact Dynamics

Seismic pounding between bridge superstructures and abutments is a critical issue that often causes severe parapet crushing. This study investigates the collision dynamics and failure mechanisms using a large-scale, progressive 3D finite element analysis, systematically demonstrating how advanced modeling alters impact behavior. The analysis, driven by sinusoidal base excitation, simulates a three-span steel box-girder bridge colliding with reinforced concrete (RC) wing abutments. The stepwise analysis revealed a clear progression. A baseline rigid-wall model showed a brief collision duration (0.08 s). Incorporating backfill soil-structure interaction (Step 2) extended the duration (0.156 s). Critically, introducing material non-linearity of the RC abutment to simulate its failure (Step 3) further lengthened the duration (0.304 s) while drastically reducing the peak impact force by over 50% through energy dissipation. This progression demonstrates that modeling both soil and abutment non-linear failure is essential, as these factors, often omitted, fundamentally redefine the collision's duration and intensity. This finding redefines the actual load transferred to the superstructure. This paper concludes that accurately modeling the abutment's energy dissipation is a critical prerequisite for any subsequent assessment of superstructure damage, such as simulating the complex stress propagation and crushing failure within the RC deck slab itself.