Probabilistic seismic demand model and optimal intensity measures for mid-rise steel modular building systems (MBS) under near-field ground motions

Establishing suitable probabilistic seismic demand models (PSDMs) is a key part of the probabilistic performance-based method. Intensity measures (IMs) are used as a connection between earthquake hazard and seismic response in performance-based earthquake engineering. This study identifies the optimal intensity measures (IMs) of probabilistic seismic demand models for steel Modular Building Systems (MBSs) subjected to near-field earthquake ground motions. It is achieved by performing a Cloud analysis utilizing two sets of near-field ground motions: 72 pulse-like and 120 non-pulse-like ground motions. The nonlinear time history analysis is carried out using a finite-element model of a 6-story mid-rise MBS. For this aim, a total of 36 scalar intensity measures were collected. Based on a large number of regression analyses between the IMs and Engineering Demand Parameters for the studied MBS, the selected IMs were evaluated on several criteria, including correlation, efficiency, practicality, sufficiency, and proficiency. Finally, in the framework of PSDMs, different fragility curves and seismic demand hazard curves were generated for the studied MBS.