A study on the effects of torsional component of ground motions on seismic response of low‐ and mid‐rise buildings

Abstract

SummaryThe torsional component of ground motion is a potential factor to excite the torsional response of buildings during earthquake, which is not explicitly considered in seismic design codes. Building codes have proposed accidental eccentricity to consider the effect of torsional component and other unpredicted factors, which may contribute to torsion in buildings. This study investigated the effects of torsional component on the buildings' responses and the adequacy of the accidental eccentricity. For this purpose, the torsional component of some selected ground motions was generated using single‐station procedure. Subsequently, 5, 10, and 15‐story buildings with different ratios of rotational to translational frequencies were analyzed; first, by translational components only, and second, by simultaneous application of translational and torsional components. Also, the role of mass eccentricity in the effects of torsional component was studied. Furthermore, all models were reanalyzed by applying the 5% accidental eccentricity, and the effects of torsional component and accidental eccentricity were compared accordingly. Results indicated that torsional component has significant impact on the buildings' responses and can increase the displacement and drift ratio up to 36% and 41%, respectively. However, the 5% accidental eccentricity is not sufficient to take account the torsional component effects, and leads to unreliable responses.