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Viscoelastic (VE) dampers are sensitive to temperature, excitation frequency, and strain level. As they dissipate the kinetic energy from earthquake or wind-induced structural vibrations, their temperature increases from the heat generated, consequently softening their VE materials and lowering their dynamic mechanical properties. Temperature increase can be significant for long-duration loading, but can be limited by heat conduction and convection which depend on damper configuration. The writers analytically explored such effect on the six different dampers by using their previously proposed three-dimensional finite-element analysis method. Results provided better understanding of how heat is generated within the VE material, conducted and stored in different damper parts, and dispersed to the surrounding air. These results also led to characterization of both local (e.g., temperatures, properties, and strain energy density) and global (e.g., hysteresis loops, and stiffness) behavior of VE dampers, and provided a framework for a new simplified one-dimensional (1D) modeling approach for time-history analysis. This new proposed 1Dmethod greatly improves the computation time of the previously proposed long-duration method coupling fractional time-derivatives VE constitutive rule with 1D heat transfer analysis. Unlike the previous method, it idealizes uniform shear strain and VE material property distributions for computational efficiency, but still simulating non-uniform temperature distribution along the thickness direction of the VE material. Despite the approximations, it accurately predicts VE damper global responses.

In this paper, we study applicability of the proposed modeling method for bending-shear model to various frame types. The Height of target building models are 80m to 400m, as well as three different structural frames such as moment resisting frame, center core frame and outrigger frame combined with center core. This modeling method is based on dynamic characteristics regardless resistance forces of complicated member. Therefore, we confirmed that the proposed method can be applied and obtained high modeling accuracy for various frame type building models.

In this study, we proposed a new modeling method for bending-shear model. The proposed modeling method is based on eigenvalue analysis and pure bending moment load analysis of the building model. The calculation procedure of bending stiffness is very simple because all displacements obtained from pure bending moment analysis is bending components. Moreover, we set a constraint condition that the first mode components completely match in the calculation procedure of shear stiffness. This modeling method used the dynamic characteristic of the building model, and we can obtain high modeling accuracy.

It has been predicted recently that the Nankai Trough Earthquake will cause extreme ground motion. The earthquake brings possibility of great damaging the existing super tall buildings in the metropolitan cities of Japan. As a mitigating strategy, seismic retrofitting using damper is commonly used to improve the structural performance of the existing super tall buildings against the earthquake. Frequently, installation of dampers is restricted by the existing building configuration, and an effective design method for this matter has not been studied extensively. Furthermore, when using oil dampers for retrofitting, there may be the cases that sufficient damping effect cannot be obtained in terms of displacement control. The authors address the above-mentioned issues by proposing a design method to determine optimal damper arrangement and investigating the application of displacement controller (gap brace) which exhibits rigidity after a certain displacement. A member-to-member model of an existing super tall building was used in this study. Finally, a design method was proposed using the combination of oil dampers and gap braces.

In order to study effectiveness of dampers in the super-tall buildings subjected to long-period and long-duration earthquake, four types of full-scale dampers typically used in Japan are exam-ined by the long-duration harmonic loading tests. The test specimens are the so-called oil damper, viscous damper, viscoelastic damper, and steel damper, respectively. Different behavior and vari-ations in their dynamic properties are observed, and they are summarized by referring to distinct materials and mechanisms of the dampers. The viscous and viscoelastic dampers show relatively large variations in the dynamic properties, and simplified evaluation rules to predict the peak cy-clic force variations for the dampers are proposed.

Viscoelastic (VE) dampers are known to be effective in mitigating structural vibrations of long-period tall buildings. Their dynamic mechanical properties (i.e., damping and stiffness) are highly dependent to the loading frequency and temperature. The co-authors had previously proposed a simplified performance evaluation method for full-scale brace-type VE dampers. However, the VE dampers they evaluated had almost the same ambient temperatures. For this, the authors of this current study conducted low ambient temperature tests and used the results to extend the original performance evaluation method mentioned above to cater wider range of initial temperatures.

Studies showed that properly employed viscoelastic (VE) dampers can mitigate wind-induced vibrations of tall buildings. These devices work by absorbing kinetic energy and converting it to small amount of heat. Since VE dampers are temperature- and frequency-sensitive, increase of temperature results to decrease of VE damping properties. In their past studies on simple lap-type two layered VE dampers under long-duration loading, the authors experimentally and analytically showed the effects of heat generation and heat transfer. Heat was effectively dispersed to the surrounding air bringing the simple VE damper to thermal equilibrium. Nowadays, VE dampers are made of several thin layers of VE materials, and due to high computational cost in carrying-out finite element analysis, few analytical studies are done for full-scale multi-layered VE dampers. This paper addresses this matter by implementing the previously proposed three-dimensional model of the co-authors into a multi-layered VE damper under long-duration sinusoidal loading, and results are verified with experiment. It shows that the 3D-FEM technique can be used to predict the temperature-dependency of a multi-layered VE damper.