Performance assessment of multi-column RC bridge bents seismically retrofitted with buckling-restrained braces

Abstract

The lateral performance of substandard reinforced concrete (RC) bridge bents seismically retrofitted using buckling-restrained braces is assessed using experimentally obtained data and non-linear numerical models. First, expected performance of RC bridge components and a description of substandard highway bridges typically found in the Northwest of the United States is presented. Then, the paper focuses on three major aspects. (1) The comparison of strains recorded from large-scale cyclic experiments to target performance levels found in current seismic retrofit specifications. Strains in concrete and steel are compared to strain limits for operational and life safety performance levels. (2) The development of representative non-linear numerical models based on sub-assemblage tests of buckling restrained braces and tests of retrofitted bents. Numerical models for the RC bridge bents and for the buckling-restrained braces are presented and validated to the experimental results both in terms of the overall behavior as well as the component strain levels. (3) The seismic performance assessment of the validated models using non-linear time history analyses and ground motions from crustal as well as subduction sources. The results from these analyses demonstrate the effectiveness of reducing RC component strains and drift demands on RC Bridge bents retrofitted with buckling-restrained braces to values that allow the bent to not only achieve life-safety performance level, but also operational performance level when the retrofit is explicitly designed using a fuse concept.