• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.4
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• pp.1-12
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• 2011

Seismic fragility analysis has been developed to evaluate the seismic performance of existing nuclear power plants, but now its applicability has been extended to buildings and bridges. In general, the seismic fragility curves are evaluated from the nonlinear time-history analysis (THA) using many earthquake ground motions. Seismic fragility analysis using the nonlinear THA requires a time consuming process of structural modeling and analysis. To overcome this shortcoming of the nonlinear THA, simplified methods such as the displacement coefficient method (DCM) and the capacity spectrum method (CSM) are used for the seismic fragility analysis. In order to evaluate the accuracy of the seismic fragility curve calculated by the DCM and the CSM, the seismic fragility curves of a reinforced concrete shear wall structure calculated by the DCM and CSM are compared with those calculated by the nonlinear THA. In order to construct a numerical fragility curve, 190 artificially generated ground motions corresponding to the design spectrum and the methodology proposed by Shinozuka et al. are used.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.83-93
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• 2004

In this study. the Modified Response Displacement Method(MRDM) for seismic design of underground box-type structures is proposed. Firstly, to investigate the applicability of the conventional RDM, various parametric studies are performed according to buried depth and soil conditions. Results from the conventional RDM are compared with those of time history analysis in terms of the maximum bending moment and relative displacement. The comparison shows that the velocity response spectrum and the determination method of foundation modulus which significantly influence the accuracy of RDM should be modified. Thus, the modified velocity response spectrum and the new determination method of foundation modulus are proposed under consideration of domestic conditions. In order to demonstrate the accuracy and validity of the proposed MRDM numerical analyses are performed according to different parameters such as depth of base rock, height and width of box, buried depth and soil condition. the comparison with the results of the time history analysis verifies the feasibility of the proposed MRDM for the seismic analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.145-154
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• 1998

The motion-limiting devices can be used for reducing the maximum and residual displacements of the multi-span continuous bridges with inelastic elements such as isolation bearings and plastic hinges formed in piers. For the design of motion-limiting device, the nonlinear time history analysis is required. But the time history analysis is time consuming and very complex. This study suggests the simple design procedure of the motion-limiting devices using the equivalent elastic analysis method and the acceleration-displacement spectrum concept. The suggested design procedure can be used very effectively for determining the location and gap size of the motion-limiting devices.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.109-119
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• 2004

A design procedure for velocity-dependent supplemental dampers, such as viscous or viscoelastic dampers, required to meet the desired performance objectives was developed using displacement spectra. The amount of supplemental damping required to satisfy given performance limit state was obtained first from the nonlinear static procedure using displacement spectra, then dampers were appropriately distributed throughout the stories to realize the required damping. The proposed method was applied to multi-story steel frames, and the structures were analyzed by time history analysis to validate the accuracy of the design procedure. According to the analysis results the maximum displacements of the model structures retrofitted by the supplemental dampers turned out to be restrained well within the given target values.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.103-111
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• 2001

본 연구에서는 능력스펙트럼법을 이용하여 성능목표를 만족하기 위하여 필요한 점성 감쇠기？ 양을 간단하고 직접적인 방법으로 산정하는 방법에 관하여 연구하였다. 먼저 능력스펙트럼법을 이용하여 구조물의 비탄성 응답을 구하고 구조물의응답과 목표변위의 차이를 이용하여 필요한 유효감쇠비를 구하였다. 그리고 이러한 유효감쇠비를 이용하여 필요한 점성감쇠기의 양을 선정하였다. 본 연구에서 제안한 방법의 타당성을 검증하기 위해 10층의 철골조 건물에 세 가지 유형의 층지진하중을 가하고 제안된 절차에 따라 필요한 감쇠기의 양을 구하였다. 해석결과에 따르면 제안된 방법에 의하여 설계된 점성 감쇠기를 해석 모델에 설치하고 시간이력 해석을 수행한 결과 최대응답은 목표변위와 잘 일치함을 발견하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.1
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• pp.45-52
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• 2001

에너지 소산장치가 설치된 건무의 비선형 시간이력해석은 복잡하고 많은 시간이 소모된다. 본 연구에서는 비선형 정적해석법인 능력 스펙트럼을 이용하여 구조물의 주어긴 거동 한계를 만족할 수 있는 감쇠기의 양을 산정하는 방법에 관하여 연구하였다. 먼저 능력스펙트럼법을 이용하여 건물의 비선형 정적응답을 구하고 건물의 응답과 목표변위의 차이를 이용하여 유효감쇠비를 구하고 이러한 유효 감쇠비를 이용하여 필용한 점성 감쇠기의 양을 구하였다. 본 연구에서는 단자 유도계에서 건물의 주기, 요구되는 탄성강도에 대한 항복강도의 비, 항복 후 강성비 등을 변수로 하여 연구를 수행하였다. 제안된 방법에 따라 설계된 점성 감쇠기를 설치한 예제 구조물의 시간이력 해석에 의한 최대 응답은 설계의 초기단계에서 사용한 목표변위와 잘 일치하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.25-37
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• 2008

The capacity spectrum method (CSM) is a simple and graphical seismic analysis procedure. Originally, it has been developed for buildings, but now its applicability has been extended to bridge structures. It is based on the capacity curve estimated by pushover analysis and demand spectrum reduced from linear elastic design spectrum by using effective damping or strength reduction factor. In this paper, the inelastic demand spectrum as the reduced demand spectrum is calculated from the linear elastic design spectrum by using the several formulas for the strength reduction factor. The effects of the strength reduction factor for the capacity spectrum analysis are evaluated for 3 types of symmetric and asymmetric bridge structures. To investigate an accuracy of the CSM which several formulas for strength reduction factor were applied, the maximum displacements estimated by the CSM are compared with the results obtained by nonlinear time history analysis for 8 artificially generated earthquakes. The maximum displacements estimated by the CSM using the SJ formula among the several strength reduction factors provide the most accurate agreement with those calculated by the inelastic time history analysis.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.137-148
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• 2008

In this study, 28 earthquake records with magnitudes from 5.3 to 7.9 are selected for dynamic analysis in order to assess applicability of the earthquakes for domestic seismic design. The assessment is performed using the seismic spectrum analysis of energy and acceleration. Based on results of the analysis, four acceleration time histories, which satisfy the Korean design standard response spectrum, are proposed. From the dynamic analysis using earthquake magnitudes from 6.4 to 7.9, it is found that horizontal displacements corresponding to earthquake magnitudes greater than 7 are two times larger than those with magnitude 6.5. Therefore, it can be stated that use of strong earthquakes, such as Miyagiken-ken-oki earthquake (Ofunato, $M_{JMA}=7.4$) and Tokachi-oki earthquake (Hachinohe, $M_{JMA}=7.9$), for the seismic design in Korea is not applicable, and may prove to be excessively conservative due to overestimated seismic force. From the dynamic analyses using the proposed acceleration time histories, effects of caisson quay wall dimension and the subsoil condition are investigated as well. The simplified design charts to evaluate horizontal displacements of caisson quay wall are also proposed based on earthquake magnitude 6.5 that is appropriate in Korea.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.1-7
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• 2002

A procedure for determination of performance point was developed based on the concept of the direct displacement-based design method. Using the proposed procedure, parametric study has been performed for various natural periods of the structure, yield strength, and the stiffness after the first yield. The proposed method was also applied to a 10-story steel frame, and the results were compared to those from the capacity spectrum method and the time history analysis. It was found from the comparison that there were good agreement between the results.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.1-12
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• 2000

단층에 근접한 지진동에 대하여 성능이 저하되는 단자유도계의 변위응답에 대하여 연구하였다 5% 의 감쇠비를 갖는 세단계의 성능저하시스템을 5개의 단층에 근접한 지진동에 대하여 해석하였다 해석결과로부터 성능저하시스템의 비탄성 변위응답은 비저하시스템에 비하여 큰 값을 나타냄을 알 수 있었다 또한 성능저하 특성이 증가할수록 변위응답은 커지는 경향이 있다 이러한 변위증폭은 구조물의 고유주기 강도와 성능저하특성에 영향을 받으며 짧은 주기영역에서는 큰 값을 나타내며 긴 주기영역에서는 변위증폭이 거의 발생하지 않는다 단층에 근접한 각각의 지진동에 대한 변위증폭의 최대값은 1초 보다 작은 주기영역에서 비저하시스템의 4배 정도이다 변위증폭계수의 평균값은 짧은 주기영역에서는 2의 값을 가지면 구조물의 고유주기가 길어질수록 1에 수렴해 감을 알 수 있었다.