• Structural Engineering and Mechanics
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• 제84권2호
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• pp.155-165
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• 2022

The use of electricity and communication between electronic devices is increasing daily, which makes the stability of electrical power supply vital. Since the 1990s, large earthquakes have occurred frequently causing considerable direct damage to electrical power facilities as well as secondary damage, such as difficulty in restoring functions due to the interruption of electric power supply. Therefore, it is very important to establish measures to protect electrical power facilities, such as transformers and switchboards, from earthquakes. In this study, a 154 kV transformer whose service life had expired was installed on the base fabricated by simulating the field conditions and conducting the shaking table tests. The dynamic characteristics and seismic behavior of the 154 kV transformer were analyzed through the resonance frequency search test and seismic simulation test that considers the front, rear, left, and right directions. Since the purpose of this study is to analyze the acceleration amplification in the bushing due to the acceleration amplification, the experimental results were analyzed focusing on the acceleration response and the converted acceleration amplification ratio rather than the failure due to the displacement response of the transformer. The seismic force amplification at the transformer bushing was evaluated by simulating the characteristics of electrical power facilities in South Korea, and compared with the IEC TS 61463 acceleration amplification factor. Finally, the amplification factor at zero period acceleration (ZPA) modified for each return period was summarized. The results of this study can be used as data to define the amplification factor at ZPA of the transformer bushing, simulating the characteristics of electrical power facilities in Korea.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.41-48
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• 1999

Small earthquake records with magnitude 2.7-4.8 recorded in Kyungsang Basin during 1995-1997 were analysed. Total of 87 records consisted of 16 events instrumented at 11 stations,. Mean dominant period at each station mean zero period acceleration of each component and the acceleration response spectra were analysed. Spectral value increases as magnitude increases and the predominant frequency band expands to low frequency zone as magnitude increases.

• Earthquakes and Structures
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• 제23권2호
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• pp.115-128
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• 2022

One common method to select input ground motions to predict dynamic behavior of structures subjected to seismic excitation requires spectral acceleration (S_a) match target mean response spectrum. However, dispersion of ground motions, which explicitly affects the structural response, is rarely discussed in this method. Generally, selecting ground motions matching target mean and variance has been utilized as an appropriate method to predict reliable seismic response. The goal of this paper is to investigate the impact of target spectra variance of ground motions on structural seismic response. Two sets of ground motions with different target variances (zero variance and minimum variance larger than inherent variance of the target spectrum) are selected as input to two different structures. Structural responses at different heights are compared, in terms of peak, mean and dispersion. Results show that increase of target spectra variance tends to increase peak floor acceleration, peak deformation and dispersions of response of interest remarkably. To short-period structures, dispersion increase ratios of seismic response are close to that of S_a of input ground motions at the first period. To long-period structures, dispersions of floor acceleration and floor response spectra increase more significantly at the bottom, while dispersion increase ratios of IDR and deformation are close to that of S_a of input ground motions at the first period. This study could further provide useful information on selecting appropriate ground motion to predict seismic behavior of different types of structures.

• Structural Engineering and Mechanics
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• 제67권6호
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• pp.603-616
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• 2018

In this study, the acceleration vector in each time step is assumed to be a mth order time polynomial. By using the initial conditions, satisfying the equation of motion at both ends of the time step and minimizing the square of the residual vector, the m+3 unknown coefficients are determined. The order of accuracy for this approach is m+1, and it has a very low dispersion error. Moreover, the period error of the new technique is almost zero, and it is considerably smaller than the members of the Newmark method. The proposed scheme has an appropriate domain of stability, which is greater than that of the central difference and linear acceleration techniques. The numerical tests highlight the improved performance of the new algorithm over the fourth-order Runge-Kutta, central difference, linear and average acceleration methods.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.58-65
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• 2005

A method measuring angular speed and estimating angular acceleration of an automotive wind shield wiper pivot with limited resources has been proposed. Limited resources refer to the fact that processes cannot be operated in real-time with a regular notebook running a Microsoft Windows. Also, they refer to the fact that data acquisition cards have only two general purpose counters as many generic cards do. An optical incremental encoder has been employed for measuring angular motion. To measure the angular speed of the pivot, periods for the encoder's output pulses have been measured as the speed is related to the reciprocal of the period. Since only information acquired from one counter channel is the magnitude of the angular speed, sign correction is necessary. Also the information for the exact time when a pivot passes left and right dead points is also missing and the situation is inherent to the hardware setup. To find out the zero-crossing time of the angular speed, a linear interpolation technique has been employed. Lastly, to overcome the imperfection of the mechanical encoders, the angular speed has been curve fitted to a spline. Angular acceleration can be obtained by a differentiation of the angular speed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1992년도 봄 학술발표회 논문집
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• pp.19-25
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• 1992

The modal combination methods are studied for estimating the maximum structural responses in the seismic analysis by the response spectrum method. The most important problem in the modal combination is how to account for the correlation between the modal responses and to combine the high frequency modes (of which frequencies are greater than that at which the spectral acceleration approximately returns to the ZPA(zero period acceleration)). In this study, therefore, the widely known methods are investigated and compared among the numerous ones proposed up to now including those recommended in Regulatory Guide 1.92. The applicability of each method is investigated through example analyses also.

• 한국지구과학회지
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• 제28권2호
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• pp.179-186
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• 2007

응답스펙트럼은 내진설계에 있어서 중요한 기초자료의 하나이다. 응답스펙트럼을 얻기 위하여, 한반도에서 발생하는 지진들의 지진원 특성에 근거하여 다수의 강진동을 Boore(2005)에 의해 개발된 컴퓨터 프로그램 SMSIM을 사용하여 모사하였다. 여러 연구결과들에 대한 충분한 검토를 통하여, 모사에 필요한 입력자료들을 선정하였다. 모사된 강진동으로부터 얻은 응답스펙트럼은 가속도 1.0 g에 대하여 정규화하여 미국 원자력위원회(1973)의 표준응답스펙트럼과 비교하였다. 이 연구에서 얻어진 응답스펙트럼의 스펙트럼 진폭은 대략 10 Hz 이상의 고주파 대역에서 표준 응답스펙트럼 값에 비하여 큰 것으로 나타났다. 또한 응력강하량의 변화에 따른 응답스펙트럼의 변화를 평가하였다. 그 결과 큰 응력강하량에 대한 응답스펙트럼의 스펙트럼 진폭은 저주파 범위내에서 큰 값을 나타냄을 제시하였다.

• 대한기계학회논문집A
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• 제20권1호
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• pp.127-134
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• 1996

In general, seismic isolators which are made of laminated rubber and shim plate have characteristics of complex hysteretic behavior. When shear deformation of the seismic isolator is small, the isolator hassimple hysteretic almost bi-linear behabior. But on large shear deformation hardening effects may occur. This paper proposes a moldeling method of the seimic isolator with modified hysteretic bi-linear model which can consider the hardening effects. From the results of the seismic analyses of the isolated system it is shown that the responses are singificantly reduced compared with those of the non-isolated system. The modified hysteretic bi-linear model of the isolator gives larger ZPA(zero period acceleration) than those of the simple hysteretic bi-linear model and the equivalunt spring-damper model.

• 전산구조공학
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• 제3권1호
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• pp.71-81
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• 1990

Base isolation system은 구조물의 기초하부에 설치되며 지진에 의한 구조물의 피해를 감소시켜 준다. 지금까지 많은 공학들에 의해 여러가지 base isolation system이 개발되었으나 실용화된 것은 1970년대에 laminated rubber bearing(LR type)이 개발되고서부터 였다. 최근에는 laminated rubber bearing밑에 미끄럼판을 둔 새로운 base isolation system(SR type)이 개발되었다. 본 연구에서는 isolation system과 구조물의 여러가지 성질에 따른 isolation효과에 대한 연구를 수행하였다. 이 연구의 결과, isolaion system은 지진하중이 작용할 때 건물에 발생하는 피해를 상당히 감소시킴을 알 수 있으며, isolaion system의 주기가 길어짐에 따라 isolation효과는 증가함을 알 수 있다. 그리고 건물의 높이가 증가함에 따라 isolation효과는 줄어든다는 것을 알 수 있다. SR type isolation system이 있는 건물에 지진하중이 작용할 때, 건물내부에서 발생하는 가속도와 층간변위, 그리고 전체변위는 LR type의 경우보다 작으므로 보다 효율적이라는 것을 알 수 있다.