THE EFFECT OF STRUCTURAL SYSTEM ON SELECTION OF INPUT GROUND MOTIONS FOR PERFORMANCE BASED SEISMIC DESIGN

One of the primary needs in seismic performance-based assessment of structures is nonlinear response history analysis. A wide variety of techniques has been developed to select input ground motions for this analysis. In one of the recent developed approaches (Conditional Spectrum method) the ground motion data set is selected using a target mean spectrum and target standard deviation. After acquiring proper ground motions, to assess structural performance, a seismic demand hazard curve (SDHC) is developed using nonlinear response history analysis.Here, it will be shown that the structural system and its nonlinear behaviour has significant influence on suitability of selected ground motion bin. To investigate this effect, the selected ground motions are compared for two 8-story steel frames with different seismic resisting systems; Special Moment Resisting Frame (SMRF) and Special Concentric Braced Frame (SCBF). In present study, to improve the accuracy of process, the generalized intensity drift spectrum (GIDS) equation is used as EDP prediction equation in order to calculation of a benchmark SDHC.According to the results, the difference of the SDHCs calculated using selected ground motions for two seismic resisting systems is negligible at seismic levels lower than DBE. However at higher intensity levels (e.g. MCE, and higher levels), they are deviated from benchmark SDHC (i.e. GIDS hazard curve). For proper estimate at this levels when the structural system has severe nonlinear behaviours (here SMRF system) a variety of IMs in addition to spectral acceleration (e.g., duration, CAV, AI, etc.) should be considered in the selection process, which means more complicated selection methods need to be applied.

Keywords:

Ground Motion Selection , Probabilistic Seismic Demand Analysis , Seismic Demand Hazard Curve , Conditional Spectrum , Generalized Inters Tory Drift Spectrum