Finite Element Analysis of Reinforced Concrete Bridge Piers Under Sequential Vehicle Impact and Seismic Loads: Case Study

Piers play a crucial role in transferring loads in bridge structures. Preserving these structures against hazardous loading is therefore important for ensuring their resilience. Current studies do not fully explain reinforced concrete (RC) piers’ dynamic behavior and failure modes under sequential vehicle impact and seismic loading. Bridge systems face increased risks from multiple extreme events, as vehicle collisions can compromise pier integrity, reducing seismic resilience. This research aims to address this gap by analyzing combined effects of these hazards. A case study is carried out that creates a three-dimensional finite element (FE) model of a cast-in-place (CIP) half-scale pier in LS-DYNA, based on typical prototype highway bridges in Utah, U.S. The FE models are validated against experimental results, showing good agreement. To assess the residual seismic capacity of RC piers after an impact event, the model underwent a sequential loading protocol: an initial impact load to simulate accident damage, followed by quasi-static cyclic loading to simulate seismic activity. During cyclic loading, post-impact piers displayed distinct damage patterns compared with undamaged piers, with shear cracks and concrete spalling causing early failure. CIP piers can withstand vehicle impacts from up to 0.9 ton (0.82 metric ton) vehicles at 22 mph (35.4 km/h), to meet Caltrans Seismic Design Criteria (SDC) requirements. However, higher impact conditions compromise structural integrity. An impact from a 0.9 ton (0.82 metric ton) vehicle at 31 mph (49.9 km/h) results in a reduced ductility response from 8.2 to 1.7, and an impact from a 2 ton (1.81 metric ton) vehicle at 22 mph (35.4 km/h) results in a reduced ductility response of 2.8. In both cases, the calculated ductility fails the SDC requirement and American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications for Load and Resistance Factor Design (LRFD) Seismic Bridge Design.