Fragility Relationships for Populations of Buildings 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 report, improved fragility relationships for populations of buildings are developed based on inelastic response analysis. Special focus is placed on the class of wood frame buildings which constitutes the majority of exposed stock in many regions of the USA. The capacity curves are retrieved from the available finite element based pushover analysis in the relevant literature. Extension to other building types is performed using the available capacity diagrams from the FEMA-developed loss assessment software HAZUS.

Demand is simulated by synthetically-generated ground motions representing a probable earthquake in the Central USA. Structural assessment is carried out using an advanced Capacity Spectrum Method (CSM) which is developed and presented in the report. Thus, all the required components of fragility analysis - namely capacity, demand, and structural response - are based on rigorous analysis. Using the building classification of the HAZUS loss assessment software, both HAZUS-compatible and conventional fragility relationships are derived for two different soil conditions. Comparisons with HAZUS fragility curves as well as with those from other studies are undertaken. The parameters of the improved fragility relationships are provided for reliable use in loss assessment software.

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