Reliability of a 4-Story Steel Moment-Resisting Frame against Collapse Due to Seismic Excitations

This paper illustrates a process for estimating the uncertainty in estimation of collapse capacity of buildings in seismic excitation using Monte Carlo simulation and FOSM method. The structure used in this study is a 4-story steel moment-resisting frame designed based on current seismic provisions whose collapse prediction has been validated through a collapse test of a 1:8 scale model structure at the University of Buffalo's NEES Equipment Site. It is shown that the uncertainty in estimation of collapse capacity due to uncertainty in estimation of deformation parameters of beams and columns that control component nonlinear behavior is moderately dependent on the correlation between these parameters. For the 4-story steel moment-resisting frame used in this study the uncertainty in estimation of collapse capacity due to component modeling uncertainties varies between 0.25 and 0.35 for correlation between these parameters ranging from 0.3 to 1.0. This is due to the fact that for the 4-story structure, the P-Δ effect is the major reason for collapse rather than building component deterioration. Results of this research show that the probability of collapse for the 4-story structure at the 2/50 hazard level can increase from 3% to 18% once a confidence of 90% is sought for the collapse probability.