• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.5
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• pp.23-29
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• 2008

This study investigates the dynamic instability of strength-limited bilinear single degree of freedom (SDF) systems under seismic excitation. The strength-limited bilinear hysteretic model best replicates the hysteretic behavior of the steel moment resisting frames. To estimate the dynamic instability of SDF systems, the collapse strength ratio is used, which is the yield-strength reduction factor when collapse occurs. Statistical studies are carried out to estimate median collapse strength ratios and those dispersions of strength-limited bilinear SDF systems with given natural periods, hardening stiffness ratios, post-capping stiffness ratios, ductility and damping ratios ranging from 2 to 20% subjected to 240 earthquake ground motions recorded on stiff soil sites. Equations to calculate median and standard deviation of collapse strength ratios in strength-limited bilinear SDF systems are obtained through nonlinear regression analysis. By using the proposed equations, this study estimated the probabilistic distribution of collapse strength ratios, and compared this with the exact values from which the accuracy of the proposed equations was verified.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.83-92
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• 2002

지반조건은 구조물의 지진거동에 매우 큰 영향을 미치고 성능에 기준한 내진설계에 중요한 요소이다. 이 논문에서는 지진에 의한 지반의 비선형성을 포함한 지반의 비선형성이 구조물의 탄성지진거동에 미치는 영향을 지반 구조물 일괄해석 유한요소법과 지반의 비선형성을 구현하기 위해 Ramberg-Osgood 토질모델에 대한 근사 선형 반복해석 법으로 연구하였다. 연구는 말뚝기초의 유무를 고려한 주기가 변하는 선형 단자유도계에 지표에서 기록된 1940년 El Centro 지진을 적용하여 수행하였다. 연구결과에 의하면 연약지반의 비선형 특성 영향이 구조물의 탄성 지진거동에 매우 중요하고, 성능에 기준한 지반의 비선형성을 고려한 구조물의 내진설계가 필요하다는 것을 잘 보여주고 있다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.23-31
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• 2001

지반 위에 세워진 구조물의 지진응답해석시 지반-구조물 상호작용 영향은 지반으 선형특성을 고려하여 간주되었는데 최근 연구결과에 의하면 구조물 지진해석에서 연약지반의 비선형 특성이 중요한 요소로서 인식되었다. 하지만 지반-구조물계의 복잡한 비선형 특성 때문에 내진설계 기준에서 비선형 지반특성을 고려하기에는 아직도 어려움이 많다. 이 논문에서는 UBC 지반종류 $S_{D}$ 지반 위에 놓인 중규모의 얕은 온통기초와 묻힌 온통기초위에 세워진 건물에 대한 단자유도계 선형 지진해석을 연약지반의 비선형성을 고려하여 최대가속도가 0.17g 과 0.36g 인 Taft E-W 및 El Centro N-S 지진기록을 사용하여 수행하였다. 비선형 지진해석을 결과를 선형해석 결과와 비교하였을 때, 비선형 응답스펙트럼의 최대가속도가 지반의 비선형성 때문에 상당히 줄어드는 것으로 나타나 지반의 비선형성을 고려한 더효율적인 내진설계의 가능성을 보여준다.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.185-192
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• 2004

We calculate moment magnitudes of earthquakes occurred in the southern part of the Korean Peninsula from January, 2001 to February, 2004 and compare them with local magnitudes published by KMA(Korea Meteorological Administration) and KIGAM(Korea Institute of Geoscience and Mineral Resources). From this study, we find that local magnitudes of KIGAM have higher correlation with moment magnitudes than local magnitudes of KMA have. We induce a proper conversion formula by analyzing relation between published local magnitudes and calculated moment magnitudes. The induced formula can be used to unify kinds of magnitudes in earthquake catalogues and unified earthquake catalogues can be applied as necessary factors for analyzing earthquake characteristics, seismic hazards or attenuation formulas in the southern part of the Korean Peninsula.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.111-112
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• 2010

This study proposes a new methodology of earthquake damage evaluation for R/C Buildings combined with shear and flexural failure systems, based on non-linear required strength spectrum. Part I shows a concept of methodology of earthquake damage evaluation, which is estimated on the basis of system ductility, non-linear required strength spectrum and remaining seismic capacity ratio.

• 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.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.71-80
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• 2003

Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.101-111
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• 2006

This paper proposes a method for modeling new fault ground motion due to moderate size earthquakes in Stable Continental Regions (SCRs) for the first time. The near fault ground motion is characterized by a single long period velocity pulse of large amplitude. In order to model the velocity pulse, its period and peak amplitude need be determined in terms of earthquake magnitude and distance from the causative fault. Because there have been observed very few new fault ground motions, it is difficult to derive the model directly from the recorded data in SCRs. Instead an indirect approach is adopted in this work. The two parameters, the period and peak amplitude of the velocity pulse, are known to be functions of the rise time and the slip velocity. For Western United States (WUS) that belongs active tectonic regions, there art empirical formulas for these functions. The relations of rise time and slip velocity on the magnitude in SCRs are derived by comparing related data between Western United States and Central-Eastern United States that belongs to SCRs. From these relations, the functions of these pulse parameters for NFGM in SCRs can be expressed in terms of earthquake magnitude and distance. A time history of near fault ground motion of moderate magnitude earthquake in stable continental regions is synthesized by superposing the velocity pulse on the for field ground motion that is generated by stochastic method. As an demonstrative application, the response of a single degree of freedom elasto-plastic system is studied.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.13-24
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• 2000

최근 국내에서 많이 건설되어지고 있는 주상복합 건축물은 하부의 골조형식과 상부의 벽식 구조가 결합된 구조형식을 가지고 있다 따라서 지진 발생시 동일한 형식을 가진 건축물과는 상이하고 복잡한 반응을 보이게 된다 이러한 건축물의 등가정적 해석시 국내 규준에서는 기타구조물로 분류하여 3.5 의 반응수정계수를 적용하고 있다 그러나 이 계수는 검증되어지지 않는 상태로 사용되어지고 있으므로 상당한 위험성을 내포하고 있다 본 연구에서는 단순화한 주상복합 건물의 해석 및 실제의 건물에 대한 3차원 비선형 해석을 통하여 반응수정계수를 유도하였다 유도된 반응수정계수는 ATC 기준과 우리나라 기준의 차이를 고려한 보정을 수행하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.11-22
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• 1998

An axisymmetric shell element which includes the effects of the meridional and circumferential cable prestresses is developed. It is coded for personal computer by the maximum use of axisymmetic properties and the dynamic analysis is performed under the seismic exitations. A ring element is used to fully utilize the characteristics of the axisymmetric shell. The eigenvalue solutions using 20 elements under the initial prestresses are in good agreement with the exact solutions. The results of the seismic analysis show that the radial deflection under the meridional prestress is a little larger than that under the circumferential prestress. The finite element model developed in this study can be very useful to the design applications.