Fragility relationships for populations of woodframe structures based on inelastic response

In the absence of comprehensive and statistically viable observational damage data, there is a pressing need for simulation-based fragility relationships for populations of structures so as to improve the reliability of earthquake loss assessment studies. In this article, improved fragility relationships for woodframe structures are developed based on inelastic response. Capacity curves are obtained from detailed finite element models, demand is simulated by synthetically generated earthquake ground motions representing a probable earthquake in the Central USA, and structural assessment is carried out using an advanced capacity spectrum method (CSM) presented elsewhere. Thus, all the required components of fragility analysis-namely, capacity, demand, and structural response-are founded on simulated ( analytical) behavior. Building classification of the HAZUS loss assessment software is adopted and both HAZUS-compatible and conventional fragility relationships are derived for two different soil conditions. Comparisons with HAZUS fragility curves are given. The parameters of the improved fragility relationships are provided for reliable use in loss assessment software.