• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.139-146
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• 2004

In this paper, the seismic analysis and the modeling techniques have been introduced for seismic performances assessment, when seismic isolation bearings are applied to a real bridge. Nonlinear time-history analysis is carried out using finite element analysis program. El Centro earthquake(1940, N00W) used as earthquake ground excitations. The seismic response of seismically isolated bridge is compared with that of a bridge using conventional Pot Bearings, after obtaining the displacements of the deck, the deformations of the piers, shear forces and moments of the bottoms of the piers. The analytical analysis results show that seismic isolation bearing, especially seismic isolation bearings with sliding mechanism, could reduce earthquake forces.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1805-1813
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• 2010

This paper presented regarding an parametric study to investigate seismic capacity evaluation of semi-rigid steel frame infilled with composit panel. In order to propose the optimum retrofit of the steel frame, we analysed the various pattern of retrofitted steel frame subjected to weak/medium earthquake. Steel frame with composit panel was analysed by Time history analyses analysis. The model were analysed using the suites of ground motion developed by NEHRP project on steel moment resisting frame. These earthquakes consist of 20 horizontal ground acceleration record each, i.e., a 10%, 50% probability of accidence in a 50 year period. We considered the semi-rigid connection which are commonly used in field, and modeled the nonlinear connection element (GAP) between panel and frame. It was shown that how is the steel frame with composit panel effected. We also examined the response of retrofitted frame.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.509-516
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• 2014

Accuracy of seismic response evaluated by a capacity spectrum method (CSM) is generally known to be less than that by Incremental dynamic analysis (IDA). In this paper, a procedure for IDA based seismic fragility curves for steel moment resisting frames was suggested. This study compares seismic fragility curves using the suggested method (IDA method) with those using a CSM and intends to verify the validity of the IDA method. The shapes of both seismic fragility curves are similar in slight and moderate damage states. However, in the case of extensive and complete damage states, the fragility curves obtained from the IDA method presents a more steep slope due to less variation (or uncertainties). This is due to the fact that the IDA method can properly capture the structural response beyond yielding rather than the CSM.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.707-714
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• 2011

The inter-story drift ratio is used to evaluate the damage of buildings by the earthquake. This is known that as the inter-story drift ratio decreases, the seismic damage decreases. Although to reduce the inter-story drift ratio is the important issue in the seismic design, no practical inter-story drift design method has bean developed. This study presents an optimal inter-story drift design method to improve the seismic performance of the steel moment frames using the resizing algorithm. The objective function of the proposed method is to minimize the differences of the inter-story drift ratios so that the inter-story drift ratios of the building could be distributed evenly and be reduced. Because this method redesigns the sectional properties of structural members base on the displacement participation factor calculated by the unit-load method, this can improve the seismic performance of the structure without the iterative structural analysis. The efficiency of this algorithm was demonstrated by the application to steel moment frames.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.233-242
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• 2008

This study presents a non-prismatic beam element for modeling the elastic and inelastic behavior of steel beams, which have the post-Northridge(cover plate) connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatric members with increased beam section (IBS) connection is in the closed-form. The plasticity model is of a discrete type and is composed of a series of nonlinear hinges connected by rigid links. The hardening rules can model the inelastic behavior for monotonic and random cyclic loading, and the effects of local buckling. Moreover the determination of yield surfaces, stiffness parameters, and hardening (or softening) rule parameters for IBS beam element were described. Analytical results of the IBS beam element show good correlation with test data and FEM results.

• The Journal of the Petrological Society of Korea
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• v.25 no.3
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• pp.253-260
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• 2016

A moment magnitude 3.1 earthquake occurred in the Seoul metropolitan region (SMR), Korea, on 9 February 2010. The unexpected shaking attracted much attention and raised concerns about the seismic hazards and risks in the SMR, which was regarded as an area safe from any earthquake hazard. The SMR has a population of 25 million and is one of the largest metropolitan areas in the world. A shakemap for a scenario earthquake with magnitude 6.5 and focal depth 12 km implies that the SMR will be exposed to serious risk because of its large population and the high vulnerability of its buildings. Although the instrumentally recorded earthquakes discussed in this article cannot be classified as major events, they should not be discounted as insignificant. Considering the low seismicity, micro-earthquakes below the magnitude of a conventional seismic network can achieve would be used to estimate background information in the evaluation of earthquake hazards and risks.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.235-242
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• 2010

Two moderate earthquakes with local magnitude 4.9 and 5.0 at the Yellow Sea area occurred successively around Hong island on March 22, 2003 and Baengnyeong island on March 30, 2003, respectively, close to the Korean Peninsula. Focal mechanisms by the waveform inversion analysis are strike slip faulting with a thrust component for the March 22 event, and normal faulting for the March 30 event. The direction of P-axes of two events were ENE-WSW which were similar to previous studies on that of P-axes in and around the Korean Peninsula. Moment magnitudes determined by the waveform inversion analysis were 4.7 and 4.5, respectively, whereas those determined by spectral analysis were 4.8 and 4.6, respectively. As regards the March 22 event, regional stress by combined tectonic forces from compressions of plates colliding to the Eurasian plate, rather than mere local stress, was indicated. However, it was estimated that the March 30 event took place when the weak zone generated from the existing collision zone was reactivated when subjected to local stress in the tensile direction. This seismological observation indirectly supports the idea that the collision zone may extend to the Korean Peninsula.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.155-162
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• 2006

This study presents the seismic risk assesment for an extradosed bridge with seismic isolators of lead rubber bearings(LRB). First, the seismic vulnerability of a structure and then the seismic hazard of the site are evaluated using earthquake data set and seismic hazard map in Korea, and then the seismic risk of the structure is assessed. The nonlinear seismic analyses are carried out to consider plastic hinges of bridge columns and nonlinear characteristics of soil foundation. The ductility demand is adopted to describe the nonlinear behavior of a column, and the moment-curvature curve of a column is assumed to be bilinear hysterestic. The fragility curves are represented as a log-normal distribution function for column damage, movement of superstructure, and cable yielding. And seismic hazard is estimated using the available seismic hazard maps. The results show that the effectiveness of the seismic isolators for the columns is more noticeable than those for cables and girders, in seismic isolated extradosed bridges under earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.4 s.50
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• pp.67-76
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• 2006

In this paper the moment transfer efficiency of a web and the strain concentration at the RHS (Rectangular Hollow Section) column-to-steel beam connections was evaluated. Initially, non-linear finite element analysis of five bare steel beam models was conducted. The models were designed to have different detail at their beam-to-column connection, so that the flexural moment capacity was different respectively. Analysis results showed that the moment transfer efficiency of the analytical model with RHS-column was poor when comparing to model with WF(Wide Flnage)-column due to out-of-plane deformation of the RHS-column flange. The presence of scallop and thin plate of RHS column was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of the steel beam-to-column connections. Analytical results were compared with the previous experimental results. The analytical and the previous experimental results showed that the strain concentration was inversely proportional to the moment transfer efficiency of a beam web and the deformation capacity of connection was poor as their moment transfer efficiency degrades. Further finite element analyses of composite beam with a floor slab revealed that the neutral axis moved toward the top flange and the moment transfer efficiency of a beam web decreased, which led to premature failure of the connection.

• Computational Structural Engineering
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• v.11 no.1
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• pp.46-57
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• 1998

노스리지 지진하의 모멘트 저항 강 뼈대 구조물에 대한 사례연구결과를 요약하면 다음과 같다. 1) 탄성과 비탄성 동적해석 방법의 신뢰도가 구조물의 동적거동의 모형화에 크게 영향을 받는다는 것을 알 수 있었고 구조물의 동적거동의 모형화를 위한 보다 개선된 지침과 기준의 필요성이 부각되었다. 2) 비탄성 횡방향 정적해석은 6층높이의 건물까지는 비탄성동적해석과 유사한 결과를 보였으나 10층 이상의 건물에서는 고차 모드 효과를 고려하지 못하여 상당히 상이한 결과를 나타냈다. 3) 응답스펙트럼 해석은 노스리지 지진하에서 탄성 시간이력 해석에 비하여 100%까지 상이한 결과를 보였다. 특정지진에 대한 구조물거동의 상세조사시 응답 스펙트럼 해석 대신 시간이력해석을 수행하는 것이 바람직하다. 4) 탄성 부재력의 저항능력 비와 소성 회전각 등의 거동지수 등은 현존하는 건물의 연결부 손상을 검사하기 위한 지침을 마련하는데 도움을 줄 수 있지만 특정 연결부를 검사에서 배제시키는 유일한 근거로 사용되어서는 안될 것으로 판단된다.