Assessment of Structure-Specific Intensity Measures for the Probabilistic Seismic Demand Analysis of Steel Moment Frames

Given the inherent uncertainty in seismic response, seismic performance assessment of structures should be conducted within a probabilistic framework. One of the most efficient probabilistic approaches is the IM-based probabilistic seismic demand analysis (PSDA). In this method, an intermediate parameter, which is known as the intensity measure (IM), is used to decouple the seismological and structural uncertainties. Two intensity measures of IMoc and (S-a)(rms) were introduced for near-fault pulse-like records in previous research. These IMs are defined based on the optimal combination of spectral displacements and root-mean-square of spectral accelerations at effective periods, respectively. In this research, to consider the efficiency of these IMs under a set of 90 records that contains both near-fault and ordinary ground motion records, we conducted the PSDA for five moment-resisting frames with the number of stories ranges from 3 to 15. Results show that IMoc and the advanced intensity measure of IM1I&2E exhibit the highest correlation with the expected damage for the most frames, especially moderate and relatively long-period ones. IM1I&2E is defined based on the inelastic spectral displacement with the higher-mode modification. In addition, comparison of the drift hazard curve of different frames shows that by increasing the structural height, the amount of drift hazard will decrease. However, comparing to other cases, the reduction rate of drift hazard along with increasing the number of stories from three to six is significant.