The importance of accidental design eccentricity in seismic design of steel buildings with dual system under the effect of far- and near-fault ground motions

Document Type : Research Article

Authors

Sahand University of Technology

Abstract

Seismic responses of buildings are amplified due to torsion. To account for the effects that cause torsion and are not considered in the design process of buildings, the seismic codes introduce “accidental design eccentricity (ADE)”. In this study, the adequacy of the Iranian Standard No. 2800 provisions about the design eccentricity was investigated. To this end, the 5-story torsionally-stiff and torsionally-flexible buildings with dual lateral load resisting system were studied. The mass eccentricity in plan-asymmetric buildings was assumed to be equal to 0.10b and 0.20b where b is the plan dimension. Nonlinear time history analyses were performed using far-field (FF), non-pulse (NP) and pulse-like (FD) near-field records for the models in two cases. In the first case, the effect of the ADE on the seismic demands of symmetric and asymmetric-plan buildings was investigated. Finally, to consider what happens when an actual accidental mass eccentricity (AME) is introduced in an already designed building, the mass center of the buildings was shifted by ±0.05b (b is the dimension of the building perpendicular to the earthquake direction) simultaneously in both directions and the buildings (with and without ADE) were analyzed for the earthquake sets described above. For the buildings investigated in this research, the results indicate that the provision related to the accidental design eccentricity has little influence (less than 10%) on the inelastic seismic responses for torsionally-stiff buildings and can be ignored. Also, the accidental mass eccentricity has more influence (maximum 38%) on the inelastic seismic responses of torsionally-flexible buildings but the accidental design eccentricity has less influence on the reduction of seismic responses. Therefore, it seems that the accidental design eccentricity needs to be modified for torsionally-flexible buildings.

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References

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Amirkabir Journal of Civil Engineering
Volume 52, Issue 7
October 2020
Pages 1705-1728

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