• Steel and Composite Structures
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• v.28 no.4
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• pp.461-470
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• 2018

In this study, the effect of polyurethane foam filler, in addition to surface layer thickness and core material thickness, on vibration characteristics of sandwich structures was investigated. The manufacturing process was carried out according to the Taguchi method. The natural frequencies and damping ratios of the produced samples were determined experimentally for fixed-free boundary conditions. In addition, solid models were developed for test samples and their finite element analyses were performed with $ANSYS^{(R)}$ to obtain their natural frequencies and mode shapes. An acceptably good agreement was found with the comparison of experimental results with the numerically obtained ones. The most effective parameters on the vibration characteristics of the sandwich structure were determined by the Taguchi method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.151-158
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• 1999

The single layer latticed domes have various behaviors with each geometrical shape and scale, and they are affected by vertical component as well as horizontal component of the dynamic load. And they represent very different earthquake responses under each ground acceleration compared with another structural systems. Generally, all of the members of latticed domes undergo three dimensional deflections if they are subjected to arbitrary one dimensional horizontal load under earthquake motions. And their response characteristics are very different to their shapes, rise/span ratios, and damping mechanisms. In this study the .earthquake response behavior is verified according to the factor of each shape, rise/span ratio, ana damping ratio of latticed domes, which undergo horizontal and vertical earthquake motions by numerical approaches.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.52-59
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• 2004

In this paper, the efficacy of the MR damper-based control systems for vibration suppression of stay cables has been experimentally investigated. The performance of the several control strategies for the semiactive control system, such as the clipped-optimal control, the Lyapunov stability theory-based control, the maximum energy dissipation and the modulated homogeneous friction, has been compared with that of the passive-type control systems employing MR dampers. To do this, the full-scale stay cable, which is the same as used for the in-service cable-stayed bridge in Korea, is considered. The acceleration and the displacement of the stay cable as well as the damping force of the MR damper are measured. The velocity of the cable at the damper location, which is needed for some control algorithms, is obtained by differentiating the measured displacement. The damping ratios of the cable system employing the MR damper, which can be estimated by the Hilbert transform-based method, shows effectiveness of each control strategy considered.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1377-1383
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• 2005

Mechanical properties of Municipal Solid Wastes(MSW) and their influencing parameters were studied by using a series of triaxial compression tests and resonant column tests. The shear strength of MSW can be modeled by a bilinear failure criterion. As the unit weight increasing, cohesion and internal friction were increased linearly on semi-log scale. As the proportion of waste to soil increases, maximum shear moduli tend to decrease whereas minimum damping ratios increase. Shear moduli and damping of degradable waste are higher than those of non-degradable MSW.

• Wind and Structures
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• v.12 no.3
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• pp.259-279
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• 2009

The paper is concerned with the numerical study of the cross-wind response of the 295 m-tall six-flue industrial chimney, located in the power station of Belchatow, Poland. The response of the chimney due to turbulent wind flow is caused by the lateral turbulence component and vortex excitation with taking into account motion-induced wind forces. The cross-wind response has been estimated by means of the random vibration approach. Three power spectral density functions suggested by Kaimal, Tieleman and Solari for the evaluation of the lateral turbulence component response are taken into account. The vortex excitation response has been calculated by means of the Vickery and Basu's model including some complements. Motion-induced wind forces acting on a vibrating chimney have been modeled as a nonlinear aerodynamic damping force. The influence of three components mentioned above on the total cross-wind response of the chimney has been investigated. Moreover, the influence of damping ratios, evaluated by Multi-mode Random Decrement Technique, and number of mode shapes of the chimney have been examined. Computer programmes have been developed to obtain responses of the chimney. The numerical results and their comparison are presented.

• Steel and Composite Structures
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• v.16 no.1
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• pp.1-21
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• 2014

Knee Braced Frame (KBF) is a special form of ductile eccentrically braced frame having a diagonal brace connected to a knee element, as a hysteretic damper, instead of beam-column joint. This paper first presents an experimental investigation on cyclic performance of two knee braced single span one-story frame specimens. The general test arrangement, specimen details, and most relevant results (failure modes and hysteretic curves) are explained. Some indexes to assess the seismic performance of KBFs, including ductility; response reduction factor and energy dissipation capabilities are also subsequently discussed. Experimental results indicate that the maximum equivalent damping ratios achieved by test frames are 21.8 and 23% for the specimens, prior to failure. Finally, a simplified analytical model is derived to predict the bilinear behavior of the KBFs. Acceptable conformity between analytical and experimental results proves the accuracy of the proposed model.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.91-97
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• 1995

Cyclic tests were performed with dowel joints which are being widely used for furniture manufacturing in Korea. In this study, effects of various factors-such as species of joint members, diameter and length of dowels, and space between dowels-on stiffness, strength and damping ratio of joints were evaluated and concluded as follows: 1. Under cyclic loads, failure of dowel joints were caused by bending failure of dowels. 2. Dowel joints were evaluated to be stiff but general load carrying capacities were relatively low. 3. Joint moduli and damping ratios of dowel joints decreased as diameter and length of dowels, and space between dowels increased. 4. In dowel joints, properties of dowel itself have greater effects on stiffness and strength of joints than properties of joint members.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.176-184
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• 1999

Dynamic characteristics of pantograph-catenary system that supplies electrical power to high-speed trains are investigated. A simple catenary is composed of the contact and messenger wires connected by hamgers possessing bi-directional stiffness properties. The influences of parameters that determine the contact properties of pantograph-catenary system are investigated through numerical simulations. For the catenary, a finite difference model composed of 10 spans is constructed. The contact and messenger wires are modeled as strings with respective tension and damping ratio values. The pantograph is modeled as a linear 3-degree-of-freedom system. It is found that the tension, number of hangers and damping ratios as well as the speed of the train significantly influence the contact forces and contact separation rate

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.489-496
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• 1998

The single layer latticed domes have various behaviors with each geometrical shape and scale, and they are affected by vertical component as well as horizontal component of the dynamic load. And they represent ye different earthquake responses under each ground acceleration compared with another structural systems. Generally, all of the members of latticed domes undergo three dimensional deflections if they are subjected to arbitrary one dimensional horizontal load under earthquake motions. And their response characteristics are very different to their shapes, rise/span ratios, and damping mechanisms. In this study, the earthquake response behavior is verified according to the factor of each shape, rise/span ratio, and damping ratio of latticed domes, which undergo horizontal and vertical earthquake motions by numerical approaches.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.39-42
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• 2007

It is necessary to estimate the dynamic characteristics of stay cables ie., the natural frequencies and the damping ratios of the stay cables to design cable damper for appropriate mitigation of cable vibrations and/or to estimate the tension of cables in service. In this study, a cable exciting robot for evaluating dynamic characteristics of stay cables has been developed, and the feasibility of the developed system has been demonstrated through a field test on the stay cable installed at the test yard of Highway and Transportation Technology Institute (HTTI). The dynamic characteristics of the stay cable were estimated based on acceleration data as well as displacement measured by digital image processing technique.