Project Abstract
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To investigate how reliably physics-based simulations capture ground motion features that significantly affect structural response, we examined the nonlinear dynamic response of a 20-story moment frame building under simulated and recorded motions at different shaking intensities up to the onset of collapse. Initially, we compared the building response under sets of recorded and simulation ground motions, where the motions in each set are selected to have comparable spectral shape and significant duration. Recorded ground motions were selected and scaled from the PEER NGA database. Simulated motions were selected and scaled from the GP, SDSU and EXSIM datasets of the SCEC Broadband-Platform validation study. A fourth set of simulated ground motions was selected without scaling from the SCEC CyberShake database. Overall, the structural demand parameters were similar from the recorded and simulated ground motions, indicating that when ground motions have comparable elastic spectra and durations, the differences in response are statistically insignificant. The analyses do, however, highlight potential problems with using simulated motions to assess structures whose fundamental period is close to the splicing period (T~ 2 sec) used in hybrid broadband simulations. In the second part of the study, we examined the use of the SCEC CyberShake hazard characterization and ground motions as a replacement alternative to conventional seismic hazard and ground motion selection and scaling. This CyberShake comparison is ongoing, but results to date indicate that the structural response data are comparable when the underlying hazard curve is similar for the CyberShake and conventional approaches. Conversely, the results demonstrate the potential benefits of using simulated Cybershake motions in situations where the physics-based simulations capture unique geologic features that are not represented well by conventional seismic hazard analysis based on empirical Ground Motion Prediction Equations. |
