Torsional Responses under Bidirectional Seismic Excitations: Effect of Instantaneous Load Eccentricities
Publication: Journal of Structural Engineering
Volume 139, Issue 1
Abstract
Torsional response for one-way or two-way asymmetric linear/nonlinear structural systems under uni- and bidirectional seismic excitations increases the maximum displacement demand on structural systems. In this study, we consider instantaneous load eccentricities caused by the motion of the center of mass. The eccentricities, which are time dependent, exist even for linear elastic two-way symmetric structures under seismic excitations, as the relative displacement between the center of mass and center of stiffness may not necessarily be negligible. The quantification of this second-order effect on structural response is not available in the literature. Equations are developed and some numerical results are obtained by incorporating this second-order effect for linear elastic structures under bidirectional excitations to quantify the importance of this phenomenon. The results obtained by considering more than 100 ground motion records suggest that, on average, an underestimation of seismic displacement demand can occur if this second-order effect is ignored, especially for two-way symmetrical systems. The degree of underestimation depends on the dynamic characteristics of the system and the record.
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Acknowledgments
The financial support received from the Natural Science and Engineering Research Council of Canada is gratefully acknowledged. The assistance provided by C. S. Lee for the numerical analyses is gratefully appreciated and acknowledged.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 139 • Issue 1 • January 2013
Pages: 133 - 143
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Sep 30, 2010
Accepted: Mar 7, 2012
Published online: Mar 10, 2012
Published in print: Jan 1, 2013
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