Date of Award


Document Type


Degree Name

Doctor of Philosophy in Civil Engineering (PhD)

College, School or Department Name

Department of Civil and Environmental Engineering


Yue Li


Performance-based engineering (PBE) provides a probabilistic tool for assessing the seismic risk and performance of buildings. Only the mainshock hazard has been included in the current PBE framework, although the concern on aftershock hazard has been increased recently. This study develops methodologies to incorporate aftershock hazard into a PBE framework, and assesses the seismic risk and performance of non-ductile reinforced concrete (RC) frame buildings under mainshock and aftershock hazards. A seismic retrofit strategy for these buildings, base isolation, is also evaluated using the developed methodologies.

A methodology for synthesizing aftershock ground motions is proposed and validated to resolve the challenge imposed by limited aftershock records. Seismic risks for two nonductile RC frame buildings representing low-rise and mid-rise buildings are examined. Results show that aftershocks can increase structural responses and seismic risk. Based on the state-of-the-art mainshock-based performance assessment methodologies, a new assessment methodology is developed with incorporation of aftershock hazard. The interactive effects between a variety of post-quake decisions and aftershocks are also considered. The proposed methodology is utilized to estimate the direct loss, downtime, and fatalities for two RC frame buildings under MS-AS sequences. Results suggest that aftershocks can cause significant additional seismic loss. The characteristics of MS-AS sequences that may be the cause of the aftershock-induced additional consequence in terms of loss, downtime, and fatalities are discussed and identified through a statistical analysis. The important sources of uncertainty of post-quake decisions are also investigated though a sensitivity study.

A comparative study is also performed for a RC frame building before and after being retrofitted with base isolation to determine the risk mitigation due to base isolation. The seismic risk is found to be effectively reduced by base isolation. The effect of various sources of uncertainties in the base isolation system are investigated through a sensitive study using mainshock-aftershock (MS-AS) ground motions at a variety of intensity levels. The most important uncertainty sources are identified. Life-cycle cost-benefit analysis is also performed for the two RC frame buildings to evaluate the economical effectiveness of adopting base isolation as a seismic retrofit strategy with consideration of mainshock and aftershocks. It is revealed that the benefit from base isolation can outweigh the additional cost for buildings in regions with high seismicity, and that the benefit is more significant when aftershocks are considered. The influence of aftershocks and base isolation on the structural robustness is investigated. Limitations and future works are also presented.