Project Abstract
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We evaluated CyberShake (ver 15.12) simulated ground motions using probabilistic seismic demand analysis of Ordinary Standard Bridges (OSBs). For five Southern California sites, catalogs of simulated ground motions representing a time-span of 200,000 years with diverse sites and local seismicity conditions were obtained from Cybershake (ver 15.12). Approximately 20,000 ground motions from events with Mw > 6.0 were collected for each site. These waveforms were applied to four OSB structures to calculate the bridge column drift ratio (CDR). A set of hazard-targetted scaled recorded ground motions are attained to conduct Incremental Dynamic Analysis (IDA) for all combinations of site and OSBs to obtain CDRs. The obtained IM-EDP relations were integrated with the ground motion Intensity Measure (IM) hazard curves to compute EDP hazard curves. The effect of uncertainty in the ground motion incidence angle with respect to bridge structures is incorporated by applying the ground motions at 10o increments and obtaining the median CDR termed as Rot50CDR. The estimated Rot50CDR at various return periods is used to build the empirical EDP hazard curves and compared against the EDP hazard curves obtained from NLTHA using the Cybershake’s simulated ground motions. The EDP hazard curves from the two methods are compared and sources of difference between the results are identified. The results show that CyberShake (ver. 15.12) simulation can be used for the seismic performance assessment of OSBs with short periods. Long-period OSBs tend to have larger EDPs once subjected to CyberShake (ver. 15.12) simulations as compared to the EDPs obtained using recorded ground motions. |
