• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2072-2078
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• 2003

In this paper, the boundary element analysis of viscoelastic strain energy release rate G(t) for the cracked linear viscoelastic solids has been attempted. This study proposes the G(t) equation and the calculating method of G(t) by time-domain boundary element analysis for the viscoelastic solids. The G(t) is defined as the derivative of the viscoelastic potential energy II(t) with respect to crack length a. Two example problems are presented to show the applicability of the proposed method to the analysis of the cracked linear viscoelastic solids. Numerical results of example problems show the accuracy and effectiveness of the proposed method.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.458-467
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• 2012

In this study, the linear viscoelastic response of a rectangular laminated plate is investigated. The viscoelastic properties, expressed by two basic spring-dashpot models, that is Kelvin and Maxwell models, is assumed in the range to investigate the influence of viscoelastic coefficients to mechanical behavior. In the present study, viscoelastic responses are performed for two popular equivalent single-layered theories, such as the first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT). Compliance and relaxation modulus of time-dependent viscoelastic behavior are approximately determined by Prony series. The constitutive equation for linear viscoelastic material as the Boltzmann superposition integral equation is simplified by the convolution theorem of Laplace transformation to avoid direct time integration as well as to improve both accuracy and computational efficiency. The viscoelastic responses of composite laminates in the real time domain are obtained by applying the inverse Laplace transformation. The numerical results of viscoelastic phenomena such as creep, cyclic creep and recovery creep are presented.

• Structural Monitoring and Maintenance
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• v.3 no.2
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• pp.175-194
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• 2016

Based on the change of traditional viscoelastic damper structure, a brand-new damper is designed to control simultaneously the translational vibration and the rotational vibration for platforms. Experimental study has been carried out on the mechanical properties of viscoelastic material and on its multi-dimensional seismic response control effect of viscoelastic damper. Three types of viscoelastic dampers with different shapes of viscoelastic material are designed to test the influence of excited frequency, strain amplitude and ambient temperature on the mechanical property parameters such as circular dissipation per unit, equivalent stiffness, loss factor and storage shear modulus. Then, shaking table tests are done on a group of single-storey platform systems containing one symmetric platform and three asymmetric platforms with different eccentric forms. Experimental results show that the simulation precision of the restoring force model is rather good for the shear deformation of viscoelastic damper and is also satisfied for the torsion deformation and combined deformations of viscoelastic damper. The shaking table tests have verified that the new-type viscoelastic damper is capable of mitigating the multi-dimensional seismic response of offshore platform.

• 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.

• Computers and Concrete
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• v.32 no.4
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• pp.383-392
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• 2023

The mechanical properties of Recycled Aggregate Concrete (RAC) with 100 percent Recycled Coarse Aggregate (RCA) under loading rates were investigated in depth. The theoretical model was validated utilizing the RAC elastic modulus obtained from cylindrical specimens subjected to various strain rates. Viscoelastic theories have traditionally been used to describe creep and relaxation of viscoelastic materials at low strain rates. In this study, viscoelastic theories were extended to the time domain of high strain rates. The theory proposed was known as reversed viscoelastic theory. Normalized Dirichlet-Prony theory was used as an illustration, and its parameters were determined. Comparing the predicted results to the experimental data revealed a high level of concordance. This methodology demonstrated its ability to characterize the strain rate effect for viscoelastic materials, as well as its applicability for determining not only the elastic modulus for viscoelastic materials, but also their shear and bulk moduli.

• Steel and Composite Structures
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• v.47 no.6
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• pp.743-757
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• 2023

In this paper, the dynamic response of a simply-supported composite sandwich plate with a viscoelastic core based on the Golla-Hughes-McTavish (GHM) viscoelastic model is investigated analytically. The formulation is developed using the three-layered sandwich panel theory. Hamilton's principle has been employed to derive the equations of motion. Since classical models, like kelvin-voigt and Maxwell models, cannot express a comprehensive description of the dynamic behavior of viscoelastic material, the GHM method is used to model the viscoelastic core of the plate in this research. The main advantage of the GHM model in comparison with classical models is the consideration of the frequency-dependent characteristic of viscoelastic material. Identification of the material parameters of GHM mini-oscillator terms is an essential procedure in applying the GHM model. In this study, the focus of viscoelastic modeling is on the development of GHM parameters identification. For this purpose, a new method is proposed to find these constants which express frequency-dependent behavior characterization of viscoelastic material. Natural frequencies and loss factors of the sandwich panel based on ESL and three-layered theories in different geometrics are described at 30℃ and 90℃; also, the comparisons show that obtained natural frequencies are grossly overestimated by ESL theory. The argumentations of differences in natural frequencies are also illustrated in detail. The obtained results show that the GHM model presents a more accurate description of the plate's dynamic response by considering the frequency dependency behavior of the viscoelastic core.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.3
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• pp.19-26
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• 2011

In order to estimate the viscous effects of clay over a wide range of strain levels, we confirmed the performance of a viscoelastic-viscoplastic constitutive model by simulating cyclic undrained triaxial tests to determine the cyclic strength and deformation characteristics of natural marine clay. The viscoelastic-viscoplastic constitutive model was then incorporated into an effective stress-based seismic response analysis to estimate the effects of an intermediate clay layer on the behavior of sand layers. Seismic response was simulated by the cyclic viscoelastic-viscoplastic constitutive model created with data recorded at Rokko Island, Kobe, Japan. The results show that a cyclic viscoelastic-viscoplastic constitutive model can provide a good description of dynamic behavior including viscoelastic effects, within a small strain range.

• Interaction and multiscale mechanics
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• v.6 no.1
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• pp.31-50
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• 2013

A five parameter viscoelastic model is developed to study harmonic waves propagating in the non-homogeneous viscoelastic filaments of varying density. The constitutive relation for five parameter model is first developed and then it is applied for harmonic waves in the specimen. In this study, it is assumed that density, rigidity and viscosity of the specimen i.e., rod are space dependent. The specimen is non-homogeneous, initially unstressed and at rest. The method of non-linear partial differential equation has been used for finding the dispersion equation of harmonic waves in the rods. A simple method is presented for reflections at the free end of the finite non-homogeneous viscoelastic rods. The harmonic wave propagation in viscoelastic rod is also presented numerically with MATLAB.