The effect of eccentricity and asymmetry in the plan on the performance level in existing steel buildings with a medium bending frame.

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Title:	The effect of eccentricity and asymmetry in the plan on the performance level in existing steel buildings with a medium bending frame.
Authors:	NEZAMISAVOJBALAGHI, Kaveh^1,2 Kaveh.Nezamisavojbolaghi@iau.ac.ir
Source:	Sigma: Journal of Engineering & Natural Sciences / Mühendislik ve Fen Bilimleri Dergisi. Feb2026, Vol. 44 Issue 1, p83-92. 10p.
Subjects:	Torsion, Ductility, Symmetry, Seismic response, Steel buildings, Structural design, Displacement (Mechanics)
Abstract:	The evaluation of the torsional effects of earthquakes on the performance of steel buildings with medium-ductility moment frames, which are widely used in seismic regions, is critical because of their high flexibility and significant energy absorption capacity. Amplification of the seismic response of buildings owing to torsion and the precise and influential factors in its creation and amplification during an earthquake is essential. Design and seismic strengthening regulations should pay more attention to geometric asymmetry as a significant factor in amplifying building response. This study investigated the combined effect of geometric asymmetry in one direction with the effect of eccentricity in three states—accidental torsion, significant torsion, and severe torsion—as influencing factors on performance levels and vital parameters such as ductility changes. The selected models with five and nine stories have symmetric and asymmetric plans, at least in one direction, designed according to the Standard 2800 fourth edition and the National Steel Buildings Iran Regulations fifth edition. Then, by creating significant and severe torsional irregularities in the models of existing buildings using the guidelines for seismic rehabilitation of existing structures with nonlinear static analysis (pushover), the performance levels of the buildings were evaluated. The results indicate that the asymmetry in the plan in one direction compared to the symmetric plan reduces the performance level of 5-story models by more than 9-story models. In addition, changes in Ductility and seismic response due to torsion in 5-story buildings are more significant; therefore, asymmetry in one direction with severe torsion causes a 43% reduction in Ductility. These findings underscore the need for further research to fully understand the implications of asymmetry and torsion in seismic design and to incorporate these findings into future seismic codes and design practices. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

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Abstract:	The evaluation of the torsional effects of earthquakes on the performance of steel buildings with medium-ductility moment frames, which are widely used in seismic regions, is critical because of their high flexibility and significant energy absorption capacity. Amplification of the seismic response of buildings owing to torsion and the precise and influential factors in its creation and amplification during an earthquake is essential. Design and seismic strengthening regulations should pay more attention to geometric asymmetry as a significant factor in amplifying building response. This study investigated the combined effect of geometric asymmetry in one direction with the effect of eccentricity in three states—accidental torsion, significant torsion, and severe torsion—as influencing factors on performance levels and vital parameters such as ductility changes. The selected models with five and nine stories have symmetric and asymmetric plans, at least in one direction, designed according to the Standard 2800 fourth edition and the National Steel Buildings Iran Regulations fifth edition. Then, by creating significant and severe torsional irregularities in the models of existing buildings using the guidelines for seismic rehabilitation of existing structures with nonlinear static analysis (pushover), the performance levels of the buildings were evaluated. The results indicate that the asymmetry in the plan in one direction compared to the symmetric plan reduces the performance level of 5-story models by more than 9-story models. In addition, changes in Ductility and seismic response due to torsion in 5-story buildings are more significant; therefore, asymmetry in one direction with severe torsion causes a 43% reduction in Ductility. These findings underscore the need for further research to fully understand the implications of asymmetry and torsion in seismic design and to incorporate these findings into future seismic codes and design practices. [ABSTRACT FROM AUTHOR]
ISSN:	13047191
DOI:	10.14744/sigma.2026.1969