Probabilistic Assessment of the Benefits of Retrofitting Nonductile Concrete Buildings in Terms of Regional Losses

Grey, Samantha Michelle

Graduate Thesis Or Dissertation

Probabilistic Assessment of the Benefits of Retrofitting Nonductile Concrete Buildings in Terms of Regional Losses Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/5x21tf79c

Abstract

Los Angeles, California, is a densely populated city located in an area of high seismic hazard. The region’s aging building stock has contributed to concerns about the seismic resilience of the community. Recent research has highlighted the vulnerability of nonductile concrete buildings and their associated risk to safety and post-disaster recovery. Currently, there are approximately 1500 nonductile concrete buildings in the city of Los Angeles, motivating discussions for retrofit policies to mitigate the risk stemming from these buildings. While the understanding of individual building retrofit is important for the building owner, investor, and/or tenants, the evaluation of structural retrofit on an entire community can help influence policy decisions. This thesis combines advances in probabilistic regional seismic risk assessments with new assessments of retrofit performance of nonductile concrete buildings designed according to ASCE 41 to assess the benefits of retrofit policies in Los Angeles, considering a representation of the existing pre-1980 concrete buildings. Using the Seismic Performance Prediction Program (SP3) and the FEMA P-58 methodology, seismic losses for each building are presented in terms of economic losses, repair times, and fatalities. Sixty-seven different regional retrofit strategies are subsequently evaluated in terms of their ability to satisfy retrofit objectives addressing reduction in displacement of residents, in loss of occupiable building space, in earthquake-induced fatalities, and in earthquake-induced repair costs. The results show that retrofitting a minimum of 60% of the buildings to the Immediate Occupancy performance level fulfills a number of possible regional retrofit strategies and objectives for the City of Los Angeles. Design retrofits to Collapse Prevention and Life Safety performance levels require retrofitting a larger number of buildings to achieve the same improvements in regional performance, and in some cases cannot achieve the overall goals.

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