• Journal of Industrial Technology
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• v.25 no.A
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• pp.23-30
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• 2005

The capacity spectrum method(CSM) can be used for the evaluation of inelastic maximum response of structures and has been recently used in the seismic design using the incorporation of pushover analysis and response spectrum method. To efficiently evaluate seismic performance of multi-degree-of freedom(MDOF) bridge structures, it is important that the equivalent response of MDOF bridge structures should be calculated. To calculate the equivalent response of MDOF system, equivalent responses are obtained by using Song method, Fajfar method and Calvi method. Also, those responses are applied to CSM method and seismic performance of bridge according to the ESDOF method are compared and evaluated straightforwardly.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.77-84
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• 2006

Unlike homogeneous material structure, the behavior of masonry structure is not perfectly elastic even in the range of small deformations because it is a non-homogeneous and anisotropic composite structural material, consisting of masonry units, mortar, and grout. This paper proposes a simplified way of investigating the evolution of the deformation and damage of the structure subjected to a series of successive ground motions with varying shaking. Especially, the most simple but useful algorithm of Fast Fourier Transformation (FFT) has been adopted to investigate the evolution of the deformation and damage of the structure tested on the shaking table. Moreover, the development of a hi-linear curve for an equivalent SDOF system which is obtained by exploiting the frequency and stiffness relationship was discussed. Finally, some important findings related to inelastic properties of the URM are summarized.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.45-52
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• 2006

In this paper, we analyze on the effect of LCR filter to mitigate transient overvoltage on the high voltage induction motor fed by H-bridge cascaded 7-level inverter. The switching surge voltage that it was occurred in inverter appears transient overvoltage at the motor input terminal. the transient overvoltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. The effect of transient overvoltage appears more serious in high voltage induction motor than low voltage induction motor. We selected LCR filter for reduction of the transient overvoltage. Consequently, we demonstrated that the LCR filter connected to the invertor output terminals greatly reduces the transient voltage stress and ringing. The results of simulation show the suppression of transient overvoltage at the motor end of a long cable. using EMTP

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.435-443
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• 2010

This study presents key parameters for the structure installed with MR controller in reducing its responses. MR controller is regarded as Bingham model of which control forces are frictional and viscous ones. The parameters are identified as friction force ratios, $R_f$ and $R_h$ which are, respectively, ratio of MR controller friction force to static restoring force for free vibration and ratio of the friction force to amplitude of harmonic force. Structure-MR controller system shows nonlinear response behavior due to friction force. Energy balance strategy is adopted to transform the behavior to linear one with equivalent damping ratio. Finally, proposed equivalent linear process is compared to the nonlinear one, which turns out to give acceptably good results.

• Journal of the Korea Convergence Society
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• v.10 no.11
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• pp.303-308
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• 2019

This study suggests a method for deriving earthquake response based on log-normal distribution in order to obtain realistic and reliable probability and statistical seismic response of structures. The development of three earthquake suites were presented, with a brief description of 2%, 10%, and 50% in 50 years probability of exceedance according the USGS Los Angeles probabilistic seismic hazard maps. In order to analyze the basic dynamic behavior, a Single-Degree-of-Freedom (SDOF) structure was selected and the seismic response spectrum representing the response of each natural period was plotted. Overall, the mean response values presented through the log-normal distribution is lower than the standard normal distribution. Thus, it is considered that the former method can be provided as the effective cost on performance-based seismic design more than the latter one.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.187-192
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• 2018

This thesis is about the study of inverter terminal boxes in a explosion proof type exhaust fan that can control wind volume and operating time. In Korea, there is no ventilator to adjust the amount of wind and operating time when working in poor conditions. The purpose of the project is to create a explosion terminal box that can control the operating time and wind speed of a suitable explosion ventilator in hazardous environments. The two explosion-proof switches allow the operation time to be driven 1 hour, 3 hours and continuous time, and the speed of the induction motor rotation was set in 3 stages at 2000 rpm, 2600 rpm and 3000 rpm to control the volume. The tested motor used a half-horsepower barrier three-phase induction motor and a full-bridge inverter to set the desired flow rate and operating time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.371-380
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• 2023

To calculate seismic fragility, it is important to select input earthquake ground motions that can properly express the characteristics of the target site. This study analyzed the seismic fragility of a single-degree-of-freedom (SDOF) model based on input earthquake ground motions in strong and low-to-moderate seismic regions. As a first step, a total of four sets of input earthquake ground motions were selected,: two sets measured near or far from overseas strong earthquake records and two sets exhibiting the characteristics of low-to-moderate earthquake regions in South Korea. A nonlinear SDOF model for three natural periods was applied to the target structure, and incremental dynamic analysis was used for fragility analysis. In addition, four damage states were defined, and seismic fragility results for each natural period of the nonlinear SDOF model for the four aforementioned input earthquake ground motion sets were obtained for each damage state.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.327-330
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• 2001

본 논문에서는 고압 대전력 3상 유도전동기의 고정자 권선을 이용한 전압원 인버터의 병렬운전 방식을 제안한다. 현재 사용되고 있는 대부분의 4극 이상 대전력 유도전동기는 각 상의 권선이 외부에서 접근이 가능하도록 외부단자가 설치되어 있으며, 이들 외부단자를 이용하여 복수대의 전압원 인버터를 병렬운전하여 대전력 유도전동기를 구동할 수 있다. 이와 같이 고압 대전력 유도전동기를 복수 개의 전압원 인버터를 병렬 운전하여 구동할 경우, 특정 인버터의 고장발생 시 비록 구동 토크는 감소될지라도, 나머지 인버터로 시스템을 계속 구동할 수 있어 시스템의 고장대처능력을 향상시킬 수 있다. 또한 병렬 운전되고 있는 각 인버터의 스위칭 동작에 대해 서로 위상 차를 갖게 함으로서, 등가 스위칭 주파수를 증가시켜 출력 토크 리플 감소와 입력 전류 리플 감소, DC Link 커패시터의 크기 감소와 같은 좋은 특성을 얻을 수 있다. 또한 각 인버터로의 전력의 분산에 의해 시스템에서 발생하는 EMI 영향을 감소시킬 수 있다. 본 논문에서는 제안한 방식을 컴퓨터 시뮬레이션을 통해 특성을 증명하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.1
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• pp.9-16
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• 2020

The objective of this study is to propose closed-form solutions to the free vibration response of single-degree-of-freedom (SDOF) systems, as part of fundamental research on dynamic systems with Coulomb friction. The motion of a dynamic system with Coulomb friction is described by a nonlinear differential equation, and, due to the variation in the sign of friction force term with the direction of motion, it is difficult to obtain the closed-form solution. To solve this problem, the nonlinear differential equation is directly computed by numerical integration, or an approximated solution is indirectly obtained using a linear differential equation wherein the damping effect due to Coulomb friction is replaced by an equivalent viscous damping term. However, these conventional methods do not provide a closed-form solution from a mathematical point of view. In this regard, closed-form solutions to the free vibration response of SDOF systems with Coulomb friction are derived herein by considering that the sign of the friction force term is reversed in each half-cycle of motion and by expanding it to the entire time history using the power series function. In addition, for a given initial condition, both the number of free vibration half-cycles and the response at the instant when free vibration motion stops are predicted under the condition that the motion of free vibration is stopped when the amplitude of the friction force is higher than that of the restoring force due to stiffness.