Conference Paper Dynamic Analysis Model of Viscoelastic Dampers Considering Temperature-Rise and Heat Convection under Long Duration Loading

笠井, 和彦  ,  KASAI, KAZUHIKO  ,  佐藤, 大樹  ,  Sato, Daiki  ,  OSABEL, DAVE M  ,  Osabel, Dave M

Description
Viscoelastic dampers dissipate energy through shear deformation of the viscoelastic materials; generating heat within the material causing it to soften. Therefore, under long duration excitation such as long period and duration earthquake, as well as wind loading, heat conduction and convection can occur and control the rise of temperature. The writers previously proposed two analytical methods simulating these effects and frequency sensitivities. First method combines three-dimensional heat transfer analysis and static analysis using common finite element model of the damper to estimate its dynamic properties referring to inclination and fatness of the hysteresis loop. The properties are estimated for every cycle considering transient state, or only a cycle which represents steady state cycle. The second method combines one-dimensional heat transfer analysis and viscoelastic constitutive rule using fractional time-derivatives of stress and strain, and it calculates step-by-step the force-deformation time histories of the damper. The present paper applies the above two methods to investigate the dampers of different proportions causing changes in heat generation, conduction, and convection. The paper also proposes a modified algorithm for calculating fractional time-derivatives of stress and strain, i.e., an approximate method using uniform shear strain distribution at every step. The analytically obtained deformed shape of the viscoelastic material is almost a straight-line, suggesting to idealize a uniform shear strain distribution. This modified algorithm is sufficiently accurate and hold advantage over the original algorithm in calculation time. The analysis models in this study accurately predict the real behavior of a viscoelastic damper when subjected to long duration loadings.

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