Seismic Hazard Analysis of Nonlinear Structures. I: Methodology

Abstract

Conventional seismic hazard analysis methodology is generalized to estimate directly the annual seismic risk of exceeding a specified level of postelastic damage in real structures. The procedure makes use of empirical statistics of the nonlinear‐response‐based factor FDM that is a measure of the damage potential of ground motions to multi‐degree‐of‐freedom structures. Using a two‐dimensional model of a jacket‐type offshore platform and a large sample of observed time histories, it is confirmed that (as for single DOF systems): (1) There is no significant dependence of the average of FDM on magnitude and distance; and (2) its coefficient of variation is relatively small. These two facts make the method practical. They were confirmed for both local (member‐level) damage measures and global collapse, for variations in structure and foundation modeling, and for various durations. A companion paper presents applications to two large three‐dimensional, multi‐degree‐of‐freedom, nonlinear models of actual structures.