The disaggregation of output from Probabilistic Seismic Hazard Analysis (PSHA) has become a frequently used tool in recent years. The output from this procedure allows one to understand the condi- tional probability distribution of the earthquake scenarios that contribute to seismic hazard at a specified ground motion level. In this paper, the concept of disaggregation is extended to Probabilistic Seismic Demand Analysis (PSDA)—a performance-based engineering procedure that combines ground motion hazard infor- mation with probabilistic structural response. Disaggregation of this analysis provides the distribution of ground motion intensities contributing to exceedance of a given structural response level. This information provides additional insight to the engineer, and is also useful for verifying that a sufficient range of ground motion levels has been considered the assessment of a structure. PSDA disaggregation is combined with a PSHA disaggregation to determine the distribution of Magnitude-Distance pairs (i.e., scenarios) that contrib- ute to the exceedance of a given structural response level. A procedure is also presented for disaggregation with a vector-valued measure of ground motion intensity. The disaggregation methodology is outlined and an example analysis is performed to demonstrate the information provided.

Many approximate methods for Nonlinear Dynamic time history Analysis (NDA) have been recently proposed to estimate inelastic responses in multi-degree-of- freedom (MDOF) structures. This paper will focus on two methods: (i) the modified modal pushover analysis (MMPA, Chopra et al. (2004)), and (ii) the method proposed by Mori (Mori et al. 2004), which incorporates inelastic shape functions into the approximation. The objective is to extend these two approximate methods to develop a structural demand hazard curve via a Probabilistic Seismic Demand Analysis. Unlike assessing the performance of structures for a given ground motion hazard level, the structural demand hazard curve provides multi-objective structural performance information, which has been integrated from all possible ground motion hazard levels. This paper will describe a methodology to approximate incremental dynamic analysis results from nonlinear static analyses, and then further to integrate such results with an inelastic spectral displacement ( ) ground motion hazard curve ( di S Sdi λ ) (Tothong and Cornell 2005a). These inelastic spectral ordinates provide an improvement over conventional elastic ones. The resulting demand hazard curves are then compared with one obtained from rigorous NDA. This comparison identifies apparent strengths and weaknesses of using these methods as estimates of NDA results.