Peak floor acceleration demands in torsionally irregular buildings

Abstract

AbstractAccurate estimation of the peak floor acceleration (PFA) plays a crucial role in ensuring the seismic safety of a building, its contents, and attachments. This study investigates amplification in PFA due to building torsion. Torsionally irregular reinforced‐concrete moment‐resisting frame buildings are analyzed under bidirectional earthquake excitations for five levels of ductility demands. A total of 5600 nonlinear dynamic analyses are conducted on the considered buildings while subjected to the far‐field ground motions suite. It is shown that the existing code provisions significantly underpredict the PFA demands at the flexible edge of elastic and moderately inelastic torsionally irregular buildings. The torsional amplification factors for PFA demands depend on the building's torsional and strength characteristics. Further, these torsional amplification factors are correlated well with the building's elastic floor displacement‐based torsional irregularity indices. Practice‐oriented equations are proposed to predict the torsional amplification factors for PFA demands in torsionally irregular buildings. The proposed equations can be easily used after estimating the elastic floor displacement‐based torsional irregularity indices using the modal superposition method. When applied with the latest ASCE 7 provisions, the proposed equations provide reasonably accurate estimates of the PFA demands in torsionally irregular buildings.