• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.167-174
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• 1997

Viscoelastic dampers have been successfully applied in building structures to reduce vibration by wind and earthquakes. It may be inefficient or be uneconomical that viscoelastic damper is installed at each story of building structures. Although the number of viscoelastic dampers is reduced, if viscoelastic dampers are installed at only suitable places in building structures, vibration would be controlled by efficiency. In this paper, responses of building structures according to the situation of viscoelastic dampers are compared. Then efficient and economical arrangements of viscoelastic dampers are proposed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.367-374
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• 1999

this paper focuses on the dynamic characteristics of full-scale viscoelastic dampers through the experimental study. Viscoelastic dampers which dissipate the response energy of a building under earthquake excitation make a role of increasing damping capacity of the building. Therefore it is important to recognize the damping behavior of viscoelastic dampers. Full-scale viscoelastic dampers are made of three types of rubbers for experimental test. The hysteretic behavior is obtained through the load-deformation experiment over the various loading frequencies and damper strains The experimental results show the good performance of viscoelastic dampers under earthquake excitations,

• Structural Engineering and Mechanics
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• v.3 no.6
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• pp.569-581
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• 1995

In this paper, the seismic behavior of a 10-story building equipped with viscoelastic dampers is analyzed. The effects of ambient temperature, the thickness, the total area, and the position of the viscoelastic dampers are studied. Results indicate that the energy-absorbing capacity of viscoelastic damper decreases with increasing the ambient temperature. The thickness and the total area of viscoelastic dampers also affect the seismic mitigation capacity. The thickness cannot be too small, which is not effective in vibration reduction, nor can it be too large, which not only increases the cost but also reduces the seismic resistance. The total area of viscoelastic dampers should be determined properly for optimum damper performance at the most economical design. The mounting position of viscoelastic dampers also influences the structure's seismic performance. Numerical results show that, if properly equipped, the VE dampers can reduce the structural response both floor displacement and story shear force and increase the overall level of damping in structures during earthquakes.

• Structural Engineering and Mechanics
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• v.11 no.1
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• pp.71-87
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• 2001

A frequency domain response analysis is presented for building frames passively controlled by viscoelastic dampers, under harmonic ground excitation. Three different models are used to represent the linear dynamic force-deformation characteristics of viscoelastic dampers namely, Kelvin model, Linear hysteretic model and Maxwell model. The frequency domain solution is obtained by (i) an iterative pseudo-force method, which uses undamped mode shapes and frequencies of the system, (ii) an approximate modal strain energy method, which uses an equivalent modal damping of the system in each mode of vibration, and (iii) an exact method which uses complex frequency response function of the system. The responses obtained by three different methods are compared for different combinations of viscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, the effect of the modelling of viscoelastic dampers on the response is investigated for a certain frequency range of interest. The results of the study are useful in appropriate modelling of viscoelastic dampers and in understanding the implication of using modal analysis procedure for building frames which are passively controlled by viscoelastic dampers against base excitation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.155-162
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• 2001

In this study a structure with viscoelastic and viscous dampers with identical damping coefficient subjected to stationary seismic and wind load were analyzed in time and frequency-domain to compare motion control capability of viscous and viscoelastic dampers. The dampers were placed based on story drift and acceleration obtained from RMS responses. According to the analysis results, the motion control capability of viscous dampers turned out to be superior to that of the viscoelastic dampers for the case of seismic load. On the contrary, in case of wind load, the viscoelastic dampers were more effective in the mitigation of dynamic responses. However, it was also found that the differences were in a narrow margin.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.197-203
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• 2001

This study presents the results of shaking table test of scaled model structures with added viscoelastic dampers, which are considered to be one of the most efficient means of upgrading existing structures against seismic loads. The experimental results were compared with those from analysis based on the linear modeling of viscoelastic dampers. The parameters obtained from free vibration test were utilized in the analysis. According to the results the added viscoelastic dampers turned out to be effective in reducing the responses of the model structures. It was also found that the analysis with linear modeling of viscoelastic dampers could simulate the test results accurately.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.171-177
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• 2002

The viscoelastic dampers are considered to be one of the most efficient means of upgrading existing structures against seismic loads. Generally in the dynamic analysis of a structure with added viscoelastic dampers the internal forces of the dampers are represented by constants that are linearly proportional to displacement and velocity. The purpose of this study is to verify the validity of the linear Kelvin model by comparing the results from the linear analysis with those obtained from the more rigorous nonlinear model such as fractional derivative model. According to the results the structural responses of 1-DOF structure obtained using the linear model are very close to those obtained from nonlinear model. However for multi-D0F structure the difference between the results from both models is enlarged as a results of the assumptions associated with the linear modeling of the viscoelastic dampers.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.249-257
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• 1998

Vibration-resistant rubbers, whose elastic and shear behaviors are similar to viscoelastic materials, are used to make bracing dampers to reduce the building vibration. Experimental study is carried out to find the vibration characteristics of the dampers installed in the building model. The natural frequencies and modal damping ratios are obtained from the free vibration test and Fourier analysis. Shaking table test is performed to find the response behavior of the building model under earthquake loading. The present experimental study shows that the bracing dampers have the behavior of viscoelastic dampers, which increase the modal damping ratios and viscoelastic characteristics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.196-203
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• 1998

Viscoelastic dampers have been successfully applied to building structures for reduction of vibration induced by wind or earthquakes. But accurate estimation of responses of building structures with viscoelastic dampers is very difficult, because the properties of viscoelastic damper is dependent on temperature and frequency of vibration. For efficient control of building vibration, required damping of viscoelastic damping device need be estimated and dynamic analysis method which can estimate the response of building structure with viscoelastic damper system is indispensable. In this paper, an efficient dynamic analysis method of a building structure with viscoelastic dampers is proposed. Efficiency and accuracy of the proposed method are verified comparing analytic results with shaking table test results using reduced building models.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.387-393
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• 2001

Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.