Conditional Scenario Spectra (CSS) for Hazard-Consistent Analysis of Engineering Systems

Abstract

Objective assessment of the seismic response of engineering systems is achievable through estimating the rate of exceedance (risk) of the engineering-demand parameters (EDPs), which are usually obtained by performing dynamic analyses with incrementally scaled seed ground motions. However, assigning rates of occurrence to such EDPs is difficult because the input ground motions are inconsistent with those that go into the hazard estimation. The Conditional Scenario Spectra (CSS) are a set of realistic ground-motion spectra with assigned rates of occurrence that reproduce the hazard at a site over various hazard levels and over a period range. The CSS methodology is an improvement over the CS method in that it includes the additional step of adjusting the rates to ensure the consistency of the target hazard. In this article, a step-by-step procedure for estimating the CSS is presented. The analysis of a structural system illustrates the uses of the CSS set for assessing EDPs over a wide range of demand intensity so that the estimation of the risk of these EDPs can be accomplished with ease.