Lifetime seismic performance assessment on post-tensioned self-centering concrete frames considering long-term prestress loss

Prestressing force acts as the main provider of the moment resistance and self-centering capacity of posttensioned self-centering (PTSC) concrete frames. As the constantly compressed members are subjected to longterm deformations induced by the shrinkage and creep of concrete, the prestress loss would inevitably arise in PTSC frames. This study presents a comprehensive approach to assess the long-term seismic performance of PTSC concrete frames, in which the prestress loss is estimated and considered as the major degradation effect. Timedependent fragility functions are derived for each floor to detect the variations in the story performance and damage distribution of the structure. The proposed approach is applied to two PTSC concrete frames with and without appendant energy dissipators, respectively. Results indicate that the prestress loss imposes greater impact on the higher floors, and would change the position of the most vulnerable story. Moreover, the frame without energy dissipators suffers larger performance degradation as compared to the damped building.