Effect of the Los Angeles Soft-Story Ordinance on the post-earthquake housing recovery of impacted residential communities

Post-earthquake recovery models can be used to quantify the resilience-related benefits of policies intended to mitigate building seismic risk. An assessment of the effect of the Los Angeles Soft-Story Ordinance on the post-earthquake housing recovery of residential communities is presented. An inventory of approximately 8000 buildings located in five Los Angeles neighborhoods is considered. The neighborhoods vary based on the percentage of soft-story buildings, population density and the fraction of renter- and owner-occupied residences. Archetype buildings that are representative of the target inventory are developed based on a building-by-building survey performed using Google Street View. Variations in the number of stories and presence and layout of the soft first story are considered in the development of the archetypes. Analytical building-level damage fragility curves are developed using the results from nonlinear analyses of structural models representing each archetype. A scenario-based damage assessment is performed using shaking intensities generated from the Southern California ShakeOut scenario, and a discrete-time state-based stochastic process model is used to represent post-earthquake recovery. The quantified effect of the Ordinance retrofit varied based on the considered recovery metric. For instance, the initial loss of occupancy for the entire inventory is reduced by 25%. However, if the time to restore 90% occupancy is used as the recovery performance metric, the Ordinance retrofit leads to a 64% reduction.