Introducing a New Spectral Intensity Measure Parameter to Estimate the Seismic Demand of Steel Moment-Resisting Frames Using Bayesian Statistics

In this article, it is intended to find a proper spectral Intensity Measure parameter (IM), using Bayesian statistics, to estimate the seismic demand of steel moment-resisting frames in such a way that applying this IM to both parts of seismic demand estimation, i.e. the probabilistic seismic demand model and collapse fragility curve, leads to a precise estimation for all frames with different heights. After results show that finding such IM parameter is impossible among spectral accelerations individually, due to effects of different modes and nonlinear behavior of structures, the area under the spectral acceleration is introduced as a new IM. Considering the results of incremental dynamic analysis of frames subjected to 80 selected ground motion records, on the condition of selecting a suitable interval of periods, this new IM can reduce the dispersion of results. This interval can be defined as [αTm-βT1], in which T1 and Tm are the first period and the period with 95% mass participation and α and β are two modification coefficients.