Practical Development and Application of Fragility Functions

Abstract

A second-generation performance-based earthquake engineering (PBEE-2) procedure has been developed by the Pacific Earthquake Engineering Research (PEER) Center and others that estimates the probabilistic future seismic performance of buildings and bridges in terms of system-level decision variables such as repair cost, casualties, and loss of use (dollars, deaths and downtime). The Applied Technology Council has undertaken to transfer the methodology to professional practice [ATC 2005]. The methodology involves four stages: hazard analysis, structural analysis, damage analysis, and loss analysis. This paper addresses the damage analysis, whose inputs are demand parameters calculated in a suite of multiple-degree-of-freedom nonlinear dynamic analyses, and whose output is the damage state of each damageable structural and nonstructural component in the facility. The analysis uses fragility functions, which in this context give the probability that a component, element or system will be damaged to a given or more severe damage state as a function of a single predictive demand parameter such as story drift or floor acceleration. One such fragility function is required for each component type and damage state. Many building-component fragility functions have been created in the past, but no comprehensive set of procedures exists on how to create them. This paper summarizes such a standard developed for ATC-58. See Porter et al. [2006] for more detail, examples, commentary, and alternative approaches.