FEMA P695 methodology for safety margin evaluation of steel moment resisting frames subjected to near‑field and far‑field records

摘要

This study presents the impact of near-field and far-field earthquakes on the seismic design of Intermediate MomentResisting Frame (IMRF) and Special Moment Resisting Frame (SMRF) structures through FEMA (Federal Emergency ManagementAgency) P695 methodology to highlight the importance of probabilistic collapse as well as seismic performancefactors of these structures. The purpose of this study is to investigate the collapse performance of steel intermediate andspecial moment resisting frame systems as the most common structural systems in urban areas in order to assess theseismic performance factors used for the design using nonlinear static and dynamic analysis methods. In this regard, asthe representatives of low-rise to high-rise buildings, archetypes with 5-, 10- and 15- story of intermediate and specialmoment resisting frames are designed and then the nonlinear models are developed in OpenSees software. Nonlinearstatic analyses are performed to assess the overstrength and ductility of these systems. The effects of near-field andfar-field ground motions on these frames are investigated through incremental dynamic analysis. These analyses areperformed with 22 far-field and 20 near-field ground motion records using FEMA P695 methodology. The results showthat near-field earthquakes have serious impacts on the collapse probability of structures. The superiority of specialmoment resisting frame over intermediate moment resisting frame is quantified in terms of safety margin and mediancollapse capacity under both near-field and far-field earthquakes. Finally, the results indicate that the response modificationfactors introduced in seismic design code are acceptable for intermediate moment resisting frame and specialmoment resisting frame under far-field ground motions. However, in the near-field sites while SMRF system meets therequirements of FEMA P695 methodology, the IMRF system does not satisfy these criteria.