Modeling Viscoelastic Damping in Civil Structures

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Modeling Viscoelastic Damping in CiAl StructuresCo-Pi's Daniel J. Inman and Eric M. AustinThe goal of this research is to examine the nature of viscoelastic damping mechanisms in structures and structural components at all levels from basic constitutive relations to final usage in finite element codes. Many finite element codes incorporate simple forms of damping matrices, but as the performance demands of civil structures increases, the importance of more accurate damping matrices increases dramatically.Viscoelastic damping mechanisms are difficult quantities to model, yet the damping these mechanisms produce determines the major features of the time response of a system due to wind, traffic, or earthquake loads, and thus it is often a key design issue. Finite element codes are the chief tools for predicting vibration response, yet the least developed part of finite element methodology is how damping is incorporated into dynamic finite element models. Most current commercial codes readily available to practicing engineers include damping only in an ad hoc, nonphysical way. Here it. is proposed to investigate three promising methodologies that will allow damping to be included in finite element codes that is both physically based yet computationally compatible with existing finite element practice.The primary goal of this research is to explore a new approach to incorporating the effects of viscoelasticity into standard finite element models for time-domain analyses. This observer-based approach is intended to be an alternative to the internal-variable methods that have appeared in recent years. The basic concept is that internal variables used to model time-domain viscoelastic behavior are similar to unmeasurable states, and this research is aimed at bringing decades of controls research to bear on this problem.I