Investigation on Seismic Performance and Retrofit of Reinforced Concrete C-bent Columns

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C-bent columns are vulnerable under extreme ground motions due to eccentric axial force and bending moment. Once ground excitation becomes extensive, compression failure of column at the plastic hinge is initiated at the compression side resulting in a significant residual drift in this direction. In this study, peculiar seismic response of C-bent columns was clarified based on hybrid loading tests and analysis on reinforced concrete columns. Based on results of loading experiment, a nonlinear hysteretic model was developed to take account of combined bending and torsion under a constant axial force. Two seismic retrofit measures were proposed and developed. Through loading xperiment, effectiveness of those methods for mitigating residual drift in the compression side was verified. Application of finite element method to C-bent columns showed that finite element method predicts peculiar nonlinear hysteretic behavior of C-bent columns with reasonable accuracy. Strong nonlinear seismic response of bridges supported by C-bent columns was analyzed using a nonlinear hysteretic model for combined torsion and flexure which was developed in this study.