The 50-year expectations of structural residual seismic capacity ratios based on uniform collapse probabilities

Abstract

To achieve a more reliable assessment on structural residual seismic capacity (RSC) in case of sequence-type earthquakes, the procedures for the estimate of the 50-year expectations of RSC ratios of buildings with different importance categories and different precautionary intensities are developed based on the context of the specified uniform collapse probabilities. In accordance with the Chinese design background, the uniform collapse probability corresponding to each case is specified conservatively by its lowest limit as the uncertainty coefficient increases from 0.275 to 0.95. By these specified uniform collapse probabilities, the rare-level and great-level intensities and corresponding peak ground accelerations for all precautionary regions are modified. Further, the combination of local and global structural resilience indexes obtained from RSC ratio curves results in the expectations of Y-year RSC ratios of various buildings. With the assumed linear relation between the expectations and the collapse probability density functions, the expectations of the RSC ratios for different life extensions to 50-year design service life are also provided by corresponding specified uniform collapse probabilities. The efficiency of two types of passive control devices, especially base isolators, for the improvement of structural RSC and resilience is demonstrated by a case study on an 8-story RC frame.