New torsional irregularity index for structures with non - parallel systems irregularity using response spectrum analysis

This paper investigates the seismic response of ۶ steel moment- resisting steel frames with non-parallelsystem irregularity. The maximum inter-story drift ratios and peak global roof drift were adopted as thecritical response parameters. Equivalent static method (ESM) and response spectrum analysis (RSA) wereused to evaluate the seismic response of the frames. A new definition for torsional irregularity coefficientbased on the response spectrum analysis (RSA) is proposed. It is shown that it is essential to undertakedynamic analysis for design of structures with irregularity in plan and to capture the higher mode effectsin non - parallel systems irregularity.