| Description |
This study quantifies the impact of different ground motion selection methods on the seismic performance evaluation of steel special moment frames. Two methods are investigated: A "traditional" approach, herein referred to as the PEER method, and a newer approach known as the conditional mean spectrum (CMS) method. The PEER method selects ground motions using the risk-based maximum considered earthquake (MCER) as the target spectrum, while the CMS method uses the conditional mean spectrum that anchor to the MCER at multiple conditioning periods. Three special moment frames of 4-, 8-, and 16-stories are designed in accordance with ASCE/SEI 7-10 to represent archetype steel frame buildings on the Western United States. The seismic performance of these frames are assessed with the nonlinear dynamic procedure prescribed in ASCE/SEI 41-13, using ground motions selected and scaled in accordance with both methods. The performance of the buildings is evaluated at the Collapse Prevention (CP) performance level for a far-field site located in Los Angeles, CA. The CMS method results in lower mean and median response in terms of demand-to-capacity ratios in the reduced beam sections and column hinges of the 4-, 8-, and 16-story buildings. Ground motions selected and scaled using CMS result in a smaller dispersion of the output parameters in most of the beam and column elements of the three frames with a higher chance of lower dispersion if the conditioning period that results in highest mean demand-to-capacity ratio is T1. The results of this study show that the ground motion selection process can cause significant differences in structural response that may lead to different retrofitting decisions. These results provide motivation for building standards, such as ASCE/SEI 41, to advocate implementing the CMS method as an alternative ground motions selection approach. |
