Seismic Performance of a Model Reinforced Concrete Bridge Pier Before and After Retrofit
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A series of experimental and analytical studies was performed on a 1/3 scale model pier before and after retrofit. The scale model represented a typical eastern U.S. non-seismically designed concrete bridge pier. The pre-retrofitted model pier was tested under quasi-static inelastic loading and was governed by flexure at moderate drift levels, but ultimately limited by the cap beam-column joint shear capacity and a subsequent loss of bond strength in improperly anchored column longitudinal reinforcement. A seismic retrofit philosophy - "capacity analysis and redesign" was introduced and implemented to retrofit the damaged model pier resulting in a seismically strengthened and stiffened structure. The experimental behavior of the retrofitted model pier demonstrated that the failure due to joint shear and bond/anchorage could be avoided. However, the reduced clear column height due to retrofitting the pier cap beam and foundation beam led to an increase in mechanism strength which subsequently resulted in a premature semi-ductile column shear failure. Comparison with the experimental and analytical study on the companion prototype pier subassemblage before and after retrofit showed the failure mode to be similar to that of the scaled model. The model pier before and after retrofit was evaluated by the two existing methods advocated by the FHWA Retrofitting Manual for Highway Bridges - that is the Capacity/Demand method and the Equivalent Lateral Strength method.