• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.95-105
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• 1997

Structures subjected to strong seismic excitation may undergo inelastic deformation cycles. The resulting cumulative fatigue damage process reduces the ability of structures and components to withstand seismic loads. Yet, the present earthquake resistance design methods focus mainly on the maximum displacement ductility, ignoring the effect of the cyclic responses. The damage parameters closely related to the cumulative damage need to be properly reflected on the aseismic design methods. In this study, two cumulative damage assessment methods derived from the plastic fatigue theory are investigated. The one is based on the hysteretic ductility amplitude, and the other is based on the dissipated hysteretic energy. Both methods can consider the maximum ductility and the cyclic behavior of structural response. The validity of two damage methods has been examined for single degree of freedom structures with various natural frequencies against two different earthquake excitations.

• Tribology and Lubricants
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• v.21 no.1
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• pp.16-20
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• 2005

Friction and wear characteristics between two steel surfaces under fretting condition are investigated experimentally. The fretting damage caused by low-amplitude oscillatory sliding can be classified into three regimes of gross-slip, mixed-slip and partial-slip due to stick-slip phenomenon. One of the most important characteristics of fretting wear is the transition from gross-slip to mixed-slip. This study was focused on getting the degree of stick-slip out of the friction transition under fretting condition. Fretting wear is divided into three conditions of gross-slip/mixed-slip/partial-slip. The criteria for the division are friction and displacement amplitude, wear scar morphology and dissipated energy. In this test, friction force and displacement were measured for detecting the transition from mixed-slip to gross-slip and qualitatively predicting the degree of the wear.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.37-43
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• 1993

The simplest vibrtion absorber is the impact damper which consists of a small mass allowed to impact between two gaps sp that energy is dissipated by conversion into noise and heat. Impact damping is a passive vibration control technique to attenuate the vibrations of lightly damped. It has been investigated to reduce the excessive vibrations of turbin blades, radar antennas, machine tools and tall light poles. In this paper, the efficiency of impact vibration absorber was investigated. A steady state vibration of two equispaced impacts per cycle was assumed. The analysis based on the assumption has been considered and the theory is examined experimentally.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.3
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• pp.164-169
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• 2002

This paper mainly discusses the hard breakdown of 2.2-nm-thick $SiO_2$ films. It is shown that the hard breakdown event of a 2.2-nm-thick $SiO_2$ film greatly depends on the applied electric field. It is strongly suggested that the local weak spots created by applying a low initial stress to a 2.2-nm-thick $SiO_2$film resist the onset of hard breakdown. In other words, it is anticipated that the stored electrostatic energy is fast dissipated by trap-assisted tunneling in 2.2-nm-thick $SiO_2$ film. Consequently, it is strongly suggested that 2.2-nm-thick $SiO_2$ films are intrinsically quite robust.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.565-570
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• 2000

The objective of this paper is to analyse the high-strength concrete columns subjected to reversed cyclic and axial loads by using nonlinear analysis model and compare the experimental results with analysis. The analytical parameters are the compressive strength of concrete, spacing of lateral reinforcement and lateral reinforcement ratio. In this study, the proposed analytical model takes ito account the influence of confined concrete, tension stiffening and strain hardening of steel. The high-strength concrete columns are used to model fiber section element. The analysis results are shown comparatively good prediction on envelope curve, accumulative dissipated energy, deformability and so on.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.1-6
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• 2004

It is important to estimate the total AC loss which is the total energy, or power, dissipated in the superconductor in the simultaneous application of AC transport current and an AC external magnetic field. Experimental and numerical works on AC loss estimation of high $T_c$ superconductors in the author's group are reviewed. The method and the set-up for total AC loss measurements are described. The experimental results for a twisted Bi-2223 multifilamentary tape and a Y-123 mm conductor are given. A general theory for numerical electromagnetic field analysis of superconductor by the finite element method is explained. The numerical results for twisted Bi-2223 multifilamentary tapes and a rectangular superconductor simulating coated conductors are presented.

• Earthquakes and Structures
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• v.13 no.3
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• pp.299-307
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• 2017

High Damping Rubber bearings (HDR bearings) have been used in the seismic design of bridge structures widely in China. In earthquakes, structural natural periods will be extended, seismic energy will be dissipated by this kind of bearing. Previously, cyclic loading method was used mainly for test studies on mechanical properties of HDR bearings, which cannot simulate real seismic responses. In this paper, Real-Time Substructure (RTS) test study on mechanical properties of HDR bearings was conducted and it was found that the loading rate effect was not negligible. Then the influence of peak acceleration of ground motion was studied. At last test results were compared with a numerical simulation in the OpenSees software framework with the Kikuchi model. It is found that the Kikuchi model can simulate real mechanical properties of HDR bearings in earthquakes accurately.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.695-698
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• 2008

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and $SF_6$-PTFE mixture vapor affect the performance of an self-blast circuit breaker. After a number of tests, nozzle in circuit breaker is disassembled, a section of ablated nozzle is investigated precisely. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker is solved. Before applying a section model, developed program is verified with experimental data. Performance of ablated nozzle shape is compared with original model through analysis program.

• Earthquakes and Structures
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• v.1 no.3
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• pp.253-267
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• 2010

A novel simple approach is presented for the seismic analysis of continuous buried pipelines subject to fault ruptures. The method is based on the minimization of the total dissipated energy during faulting, taking into account the basic factors that affect the problem, namely: a) the pipe yielding under axial and bending load, through the formation of plastic hinges and axial slip; b) the longitudinal friction across the pipe-soil interface; c) the lateral resistance of soil. The advantages and drawbacks of the proposed method are highlighted through a comparison with previous approaches, as well as with finite element calculations accounting for the 3D kinematics of the pipe-soil-fault systems under large deformations. Parametric analyses are also provided to assess the relative influence of the various parameters affecting the problem.

• Earthquakes and Structures
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• v.1 no.3
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• pp.307-326
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• 2010

This paper is concerned with the optimal seismic design of added viscous dampers in yielding plane frames. The total added damping is minimized for allowable values of local performance indices under the excitation of an ensemble of ground motions in both regular and irregular structures. The local performance indices are taken as the maximal inter-story drift of each story and/or the normalized hysteretic energy dissipated at each of the plastic hinges. Gradients of the constraints with respect to the design variables (damping coefficients) are derived, via optimal control theory, to enable an efficient first order optimization scheme to be used for the solution of the problem. An example of a ten story three bay frame is presented. This example reveals the following 'fully stressed characteristics' of the optimal solution: damping is assigned only to stories for which the local performance index has reached the allowable value. This may enable the application of efficient and practical analysis/redesign type methods for the optimal design of viscous dampers in yielding plane frames.