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

Abstract

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

Enhancement of the Fragility Capacity of RC Frames Using FRPs with Different Configurations at Joints

“…The collapse margin ratio (CMR) is a comprehensive tool that reflects the complete seismic capacity of buildings [ 15 ]. This parameter, based on the FEM P695 report [ 41 ], is defined as the ratio of the median intensity of a collapse level ground motion (complete damage state), to the spectral acceleration with the MCE and collapse level earthquake, .…”

“…Steel-brace retrofitting showed an increased improvement in seismic response to earthquakes. Heshmati et al [ 15 ] studied the effect of far-field and near-field earthquake records on the seismic design of IMRF and SMRF structures according to FEMA P695 methodology. They showed that the response modification factors introduced in seismic the design code for IMRF and SMRF under far-field records met the requirement criteria of FEMA P695.…”