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

Abstract

The 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.

The Torsional Response of Civil Engineering Structures during Earthquake from an Observational Point of View

“…Finally, according to Falamarz-Sheikhabadi and Ghafory-Ashtiany [ 10 ], β = 0.05 seems to be conservative with respect to the influence of rotational ground motion for asymmetric buildings; i.e., the inherent eccentricity due to the CM/CR shift is prevalent in the structural response. Recently, Rahat Dahmardeh et al [ 110 ] concluded that torsional component can increase the structural displacement and drift ratio up to 36% and 41%, respectively, and they confirmed that = 0.05 is not sufficient for accidental eccentricity and may lead to unreliable structural responses. In all cases, the increase in displacement due to accidental torsion is greater than that recommended in the design codes.…”

Numerical Modeling of Structural Irregularities on Unsymmetrical Buildings

“…Especially, torsional irregularity effects cannot be fixed after real earthquake loads, so the subject is still hot. There are new studies on torsional provisions [15][16][17][18]. Also, Structural Equation Modeling (SEM) can be applied after static and dynamic load calculations [19].…”