Evaluation method for practical application of viscoelastic damper using equivalent sinusoidal waveforms of long-duration random excitations in along- and across-wind directions
Viscoelastic (VE) damper is a well-known passive control device in mitigating structural vibrations of high-rise buildings induced by long-period earthquakes and long-duration strong wind. Since its dynamic properties are dependent on several factors such as loading frequency and temperature, the increase of its temperature from dissipating kinetic energy significantly affects its behavior, particularly for long-duration loading. Analysis models incorporating such effect had been proposed by focusing on heat generation and transfer. Some of them are nonlinear hysteresis models based on VE constitutive rule using fractional time derivatives of shear stress and strain, while some employ three-dimensional finite element method. Despite being experimentally verified to be accurate, these models were not extensively implemented for arbitrary loading. Moreover,their accuracy are inherently limited to the appropriate estimation of convective heat transfer parameters. However, in practice, a certain degree of deviation due to some uncertainties can be tolerable. Pursuant to these situations, this paper proposes an evaluation methodology for practical wind application of VE dampers by employing some models previously proposed by the writers. To incorporate frequency-dependency, a total of eight (8) long-duration random waveforms of VE damper deformations in the along- and across-wind directions are used in this study. Their equivalent-sinusoidal waveforms are obtained, and used primarily to rationally estimate the single value of heat transfer parameter applicable to the considered range of loading conditions. Time–history analysis results for the random waveforms show that local responses (e.g., damper temperature) are sensitive to the estimated heat transfer parameter. However, pertaining to structural design practice, the predicted global responses (e.g., damper stiffness) have less sensitivity to estimated heat transfer parameter and are in good agreement with the test.
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