New definition for torsional irregularity based on floors rotations of reinforced concrete buildings

Abstract

Earthquake investigations confirm that un-symmetric buildings suffer more damage than their symmetric counterparts. Torsional vibrations due to irregularity are one of the main factors which cause damage to buildings. Seismic codes include provisions to consider the torsional vibrations in the design of structures. However, the design of the stiff side elements may be unconservative. In this study, a total of 15 Dual system buildings were analyzed using nonlinear dynamic analysis to propose a new definition for torsional irregularity considering the effects of plan asymmetry on the earthquake response of mid-rise dual system buildings. Based on the analysis results, two new equations were derived using nonlinear regression analysis to check the torsional irregularity and the torsional amplification. Afterward, the proposed torsional irregularity provisions were compared with the torsional irregularity provisions of Europe code (EC-8), Japanese code & ASCE 7-16 code, and the results indicate that the torsional irregularity provisions of all the codes are unconservative. The current investigation proposes new equations to be used in the existing codes for torsional irregularity design considerations to improve the accuracy of the current codes' torsional irregularity provisions.