Fragility based Life Estimation Methodology for Critical Facilities

This paper presents a fragility based life cycle loss estimation methodology for (i) assessing the seismic performance of a system with structural and nonstructural components and (ii) estimating life cycle losses for that system. The loss estimation methodology consists of (i) seismic hazard analysis, (ii) fragility analysis, and (iii) life cycle cost estimation. Seismic fragility is the probability of system failure as a function of some seismic intensity parameters and failure is defined as the exceedance of some limit states by the corresponding structural/nonstructural response quantities. The limit states for fragility analysis are considered as random variables and a multidimensional threshold of limit states has been proposed to calculate fragility information of structural / non-structural systems that consider multiple variables [1]. A case study, the MCEER West Coast Demonstration Hospital located in the San Fernando Valley in Southern California, has been considered to demonstrate the developed methodology developed for fragility analysis. Fragility curves are obtained for structural systems for several uncertain limit states. The results show the importance of a correct evaluation of the limit states for comparing different rehabilitation techniques [4]. The loss estimation methodology, for assessing the seismic performance of a system and for estimating life cycle losses, is based on the fragility information of that system [3]. The seismic performance is measured by the losses related to the consequences of system damage and system recovery time. The input to the analysis consists of (i) structural/nonstructural systems properties, (ii) seismic hazard information at the site where the system is located, (iii) limit states definitions, (iv) rehabilitation strategies, and (v) a reference time. Estimates of losses can be derived using fragility information, financial models, and available resources. A structural/nonstructural system located in New York City is used to demonstrate the methodology. Fragilities surfaces [2] are obtained for structural/nonstructural components and systems for several limit states. Also, statistics are obtained for life time losses corresponding to different rehabilitation alternatives.