Evaluating Self-Centering Behavior of Unbonded Prestressed Bridge Columns Using a New Performance Index Based on Quasi-Static Analysis

In order to fulfill post-earthquake operational requirements, in recent years, there has been an increasing interest in developing self-centering structural systems, where self-centering elements are used with combinations of energy dissipation elements in parallel. It was demonstrated experimentally and numerically that such systems exhibit robust flag-shape hysteretic behavior under seismic load. A new performance index for evaluating self-centering behavior of the bridge column is developed in this paper based on the flag-shape hysteresis and the index can be obtained conveniently. Parametric analysis was carried out to investigate the effects of different parameters on the seismic response of a SDOF system. The results show that the residual displacement decreases as the new performance index increases and the residual displacement is negligible when the performance index [Formula: see text] exceeds unity (1.0). Furthermore, parametric analysis was conducted to investigate the effects of design parameters on the self-centering behavior of an unbonded pre-stresed reinforced concrete column (UBPS column). The design parameters include the prestressing force, the bonded longitudinal reinforcement ratio and the area of unbonded strands. Results show that either increasing the prestressing force or decreasing the amount of longitudinal reinforcement can result in smaller residual displacement and a higher value of the new index.