Unintended Consequences of Modeling Damping in Structures
Publication: Journal of Structural Engineering
Volume 134, Issue 4
Abstract
This paper investigates the consequence of using Rayleigh proportional damping in the analysis of inelastic structural systems. The discussion is presented theoretically, as well as by example through the analysis of a simple five-story structure. It is shown that when the stiffness portion of the system damping matrix is based on the original system stiffness, artificial damping is generated when the structure yields. When the damping matrix is based on the tangent stiffness but the Rayleigh proportionality constants are based on the initial stiffness, a significant but reduced amplification of damping occurs. When the damping is based on the tangent stiffness and on updated frequencies based on this stiffness, virtually no artificial damping occurs. The paper also investigates the influence on effective damping when localized yielding occurs in areas of concentrated inelasticity. In such cases, it is possible to develop artificial viscous damping forces that are extremely high, but that are not easy to detect. Such artificial damping forces may lead to completely invalid analysis. The paper ends with recommendations for performing analysis where the artificial damping is eliminated, or at least controlled.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 134 • Issue 4 • April 2008
Pages: 581 - 592
Copyright
© 2008 ASCE.
History
Received: Jun 19, 2006
Accepted: Jul 26, 2007
Published online: Apr 1, 2008
Published in print: Apr 2008
Notes
Note. Associate Editor: M. Asghar Bhatti
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