Empirical hurricane fragility assessment of elevated and slab-on-grade residential houses

Abstract

The widespread hurricane-induced damage to residential houses in the United States leads to severe social and economic impacts. Recent community-wide efforts by researchers within the natural hazards community to collect and curate post-hazard damage data have advanced the potential to assess structural vulnerability during extreme wind events. These efforts have led to data re-use and further analysis for detailed evaluation, allowing for the comparison of the performance of elevated versus slab-on-grade single-family residential houses during hurricanes. The empirically derived fragility functions from these damage assessment data offer a unique opportunity to evaluate the vulnerability of constructed buildings. This paper presents the development of empirical fragility functions for elevated and slab-on-grade residential houses, along with their building envelope components, when subjected to hurricane winds. It assesses the post-hurricane occupiability and the annual probability of failure for both elevated and slab-on-grade houses. Utilizing post-hurricane building performance data collected from 618 elevated and 1188 slab-on-grade single-family residential houses impacted by Hurricanes Irma and Harvey in 2017, we analyzed the relationship of damage to the estimated peak 3-sec gust wind speed at each house. The analysis yields the assignment of each house to one of five damage state categories, from which we developed the fragility functions of buildings and building components in accordance with FEMA's HAZUS Hurricane model. Results showed that the developed empirical fragility functions for building envelope components of elevated houses have a higher probability of failure compared to those installed on slab-on-grade houses. Additionally, the likelihood of elevated houses being unoccupiable after a hurricane is significantly higher than that of slab-on-grade houses in both Florida and Texas. For residential buildings constructed in the state of Florida, this study finds that elevated houses have a 39 %–74 % higher annual probability of failure due to hurricane wind compared to slab-on-grade houses for the different considered damage states.