Fitting improved hazard models for SAC/FEMA-compatible seismic analysis

Abstract

An improved method of fitting second-order analytical functional forms of seismic hazard compatible with SAC/FEMA-style analysis is presented for use in performance-based earthquake engineering. A novel set of expressions based on fitting at three distinct return periods is proposed and a series of computational tools to automate this are provided. Analysts can simply provide the empirical output of seismic hazard analysis to obtain the best analytical fit. The method is based on a selection of three return periods that can be adjusted depending on the needs with the purpose of error reduction. The proposed model is compared to available fitting functions, such as the least-squares method or based on two return periods that have be typically used to date. Comparative analyses in terms of hazard fit and also the implications on risk estimates indicate error reductions across the entire hazard despite using three return periods for fitting the functional form. The proposed fitting method is envisaged to be used in line with closed-form expressions of SAC/FEMA methodology for a more practice-oriented implementation of seismic risk analysis in design and assessment.