Bridge columns located in regions of high seismicity are generally designed with a large ductility capacity. Although this design strategy is both economical and prevents collapse, such columns develop high ductility demands when subjected to strong-ground motion, resulting in large permanent displacements. To minimize such residual displacements in reinforced concrete (RC) columns, a design is proposed whereby longitudinal post-tensioning strands replace some of usual longitudinal mild reinforcing bars. The seismic performance of such partially prestressed RC columns under near-field strong ground excitation is investigated through a series of earthquake simulation tests.
Based on the results from a series of quasi-static and dynamic analyses conducted prior to the tests, a partially prestressed RC column model was designed that varied the configuration of the tendon, the number of the tendons and longitudinal mild reinforcement, and the prestressing force.
The earthquake simulation tests demonstrated that (1) the proposed design reduced residual displacement significantly; (2) the proposed design did not result in an increase in the maximum response displacement, despite reduced energy dissipation; and (3) the proposed design did not affect the failure mode. To offset the advantage gained by replacing mild reinforcing bars with unbonded tendons to mitigate residual displacements post-event, the tests also revealed the vulnerability of the proposed design to aftershocks.
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