Empirical Damage Relationships and Benefit-Cost Analysis for Seismic Retrofit of URM Buildings

Abstract

Benefit-cost analyses for seismic retrofit of unreinforced masonry (URM) buildings in downtown Victoria, British Columbia, Canada were undertaken, considering the seismic hazard, building value, occupant/pedestrian exposure, a variety of strengthening measures, and local construction costs. The analyses are underpinned by building motion-damage relationships developed based on observed damage in past earthquakes in California and New Zealand. The considered upgrading measures ranged from parapet bracing to comprehensive seismic upgrades consistent with local practices. Parapet bracing and other partial retrofits were shown to have favorable benefit-cost ratios and thus be strong candidate measures for risk mitigation programs. Full upgrades were shown to have less favorable benefit-cost ratios. While applied to Victoria, the generality of the methodology and the use of observed damage data from California and New Zealand make the findings of this study particularly relevant for similar locations throughout the Pacific Northwest and abroad.