Behavior of R/C Bridge Bent with Grade Beam Retrofit under Simulated Earthquake Loads

Results from an in-situ lateral load test of a reinforced concrete bridge bent, whose design was inadequate under current seismic codes are presented. Details of a reinforced concrete grade-beam seismic retrofit design are provided. A nonlinear analysis model including soil-structure interaction predicted the experimental results with reasonable accuracy. Structural displacement ductility and that resulting from bent cap and foundation flexibility were compared to theoretical relations. Limiting strains and stresses for reinforcement in columns, bent-cap column joints, lap splices, and pile-cap column joints were measured and compared to the literature. Comparison of the experimental column plastic hinge length to predictive relationships shows that the latter slightly underestimate the measured plastic hinge length. Damage indices based on energy were used to evaluate the performance. Comparison with a test of a bridge bent without a grade beam retrofit shows that the foundation seismic retrofit was successful in enhancing the performance of the system.