Seismic performance of MR steel frames via Incremental Dynamic Analysis

The Incremental Dynamic Analysis (IDA) represents a promising design approach to assess the performance and post-earthquake load carrying capacity of steel frames. Generally, only the maximum transient inter-story drift is considered as damage intensity measure (DM), when IDA is carried out. In the Authors' opinion, to better appraise all the aspects characterizing the damage state of the structures, additional DMs should be considered, like residual inter-story drift, residual load carrying capacity and low-cycle fatigue (LCF) damage, whose quantitative evaluation is currently neglected in seismic design provisions. The presented paper deals with Moment-Resisting (MR) steel frames for which the structural performance is evaluated via IDA. In particular, four multi-story frames differing for the beam-to-columns connections have been considered. The aforementioned DMs have been evaluated at the specific seismic intensity correspondent to the design performance level of Immediate Occupancy, Life Safety and Pre-Collapse. Research outcomes underline how the additional information obtained from the proposed DMs provide a more accurate prediction of the damage state of MR frames, with respect to the one assessed only with the maximum transient inter-story drift, especially when damage and residual load carrying capacity have to be quantify.