The focus of this research is on conducting a performance-based earthquake engineering assessment of self-centering bridge columns for structural concrete bridges. Standard highway bridges in highly seismic regions are typically designed for columns to undergo large inelastic deformations during severe earthquakes, which can result in residual displacements. These residual displacements are a measure of post-earthquake functionality in bridges, and can determine whether a bridge remains usable following an earthquake. To mitigate the effects of residual displacements, a number of self-centering systems for bridge columns using unbonded post-tensioned (UBPT) reinforcing steel are proposed and investigated. The research reported herein had three objectives: (1) to assess and develop simulation methods and models that can accurately capture key performance attributes of reinforced concrete and unbonded
post-tensioned concrete bridge piers, to facilitate their comparison; (2) to provide a systematic assessment of various self-centering bridge column systems in terms of engineering performance, as well as expected repair costs and downtime, including a quantitative comparison to current code-conforming reinforced concrete bridge designs using the perf ormance-based earthquake engineering methodology developed by the Pacific Earthquake Engineering Research Center; and (3) to evaluate the performance-based earthquake engineering methodology itself. The unbonded post-tensioned systems were found to perform comparably to the conventional reinforced concrete system in terms of peak drifts. Reductions to column damage in the case of some of the systems were found not to justify th eir higher initial costs. However, the unbonded post-tensioned columns sustained considerably lower residual drifts than the reinforced concrete columns, leading to significant reductions in expected bridge downtime following large earthquakes. These significant reductions in downtime make the unbonded post-tensioned systems desirable for important bridges that must remain operational following an earthquake.
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