Seismic collapse performance of special moment steel frames with torsional irregularities

Many building structures exhibit torsional irregularity, which is a type of horizontal irregularity. It is difficult to estimate the inelastic response of torsionally irregular structures subjected to earthquake ground motions using numerical analyses because torsionally irregular structures experience both lateral displacement and floor rotation. This study evaluates the collapse performance of multi-story model structures with various degrees of torsional irregularity via nonlinear response history analyses. This study also proposes a procedure for computing design story drift demands, which allows torsionally irregular structures to have uniform collapse risk irrespective of the degree of torsional irregularity.