Modeling Dependence of Peak Floor Acceleration and Maximum Interstory Drift Ratios with Gaussian Copulas

This study introduces a multivariate demand model for Engineering Demand Parameters (EDPs) in Performance Based Seismic Design (PBSD), utilizing Gaussian copulas to characterize the dependence structure of the demand vector. The effectiveness of this approach is assessed by comparing EDPs generated using Gaussian copulas against those assumed under a joint lognormal distribution. This validation study is further carried forward to values of economic loss for the four special steel moment frames obtained via the three sets of EDPs. The Performance Assessment Calculation Tool (PACT) developed by the Federal Emergency Management Agency (FEMA) P-58 (2015) is used for loss estimation. Results indicate that using copulas to represent the dependence structure of EDPs better captures the characteristics of the population of EDPs rather than assuming a joint lognormal distribution. Distributions of economic loss generated using copulas match the loss generated from the true observations of EDPs better than loss generated assuming a joint lognormal distribution. The sample size of the selected and scaled ground motions required for the generation of realizations of building response via nonlinear dynamic analysis is also investigated, which proves to yield more accurate values of response but, at the expense of using a larger number of initial observations.