• 한국지진공학회논문집
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• 제20권7_spc호
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• pp.453-460
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• 2016

The Gyeong-Ju earthquake in the magnitude of 5.8 on the Richter scaleoccurred in September 12, 2016. Because there are many nuclear power plants (NPP) near the epicenter of the Gyeong-Ju earthquake, the seismic stability of nuclear power plants is becoming a social problem. In order to evaluate the safety of seismically isolated NPP, the seismic response of a NPP subjected to the Gyeong-Ju earthquake was compared with those of 30 sets of artificial earthquakes corresponding to the nuclear standard design spectrum (NSDS). A 2-node model and a simple beam-stick model were used for the seismic analysis of seismically isolated NPP structures. Using 2-node model, the effect of internal temperature rise, decrease of shear stiffness, increase of lateral displacement and decrease of vertical stiffness according to nonlinear behavior of lead-rubber bearing (LRB) were evaluated. The displacement response, the acceleration response, and the shear force response of the seismically isolated nuclear containment structure were evaluated using the simple beam-stick model. It can be observed that the seismic responses of the isolated nuclear structure subjected to Gyeong-Ju earthquake is significantly less than those to the artificial earthquakes corresponding to NSDS.

• 한국산학기술학회논문지
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• 제14권1호
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• pp.445-453
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• 2013

본 논문은 등가정적하중법에 의해 설계된 경부고속철도 구간 중 PSC Box Girder 대표 교량들을 대상으로 등가정적법과 응답스팩트럼법을 이용하여 지진력이 산정되었고, 지진력의 차이가 확인된다. 해석법 비교를 위하여 상용유한요소 프로그램을 이용하여 5개 교량에 대한 3차원 유한유소 모델이 구성되었고, 각 해석법의 의한 지진력이 비교되었다. 고유주기가 저차에서 지배되는 경우, 지반조건과 고유주기의 따라 지진가속도가 산정되는 응답스팩트럼법과 등가정적하중법과의 차이가 커지는 것이 확인되었다. 이렇게 산정된 지진력에 차이에 따른 내진성능 평가 결과 설계 지진력 보다 큰 지진력의 적용으로 인한 것으로 내진 보강의 필요성을 의미한다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.67-74
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• 2001

This paper presents the Safe Shutdown Earthquake(SSE) input motion for the seismic design of the Advanced Power Reactor 1400(APR1400). The Design Ground Response Spectra(DGRS) far the SSE is based on the design spectrum specified in regulatory Guide(RG) 1.60 of U.S. Nuclear Regulatory Commission(US NRC), anchored to a Peak Ground Acceleration(PGA) of 0.3g and enriched in the high frequency range. This SSE seismic input motion is to be applied to the seismic analysis as the free-field seismic motion at the ground surface of both the rock and generic soil sites fur APRI1400. The enrichment for APR1400 seismic input motion is performed considering the current US NRC regulations, the seismic hazard studies performed by the Lawrence Livermore National Laboratory (LINL) and Electric Power Research Institute(EPRI) for the Central and Eastern United States nuclear power plant sites, and the seismic input motions used in the design certifications of the three existing U.S. advanced standard plants. It is represented by a set of DGRS and the accompanying Target Power Spectral Density(PSD) Function in both the horizontal and vertical directions.

• Earthquakes and Structures
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• 제13권2호
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• pp.119-130
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• 2017

This paper presents a numerical investigation on the seismic behavior of isolated bridges with supplemental viscous damping. Usually very large displacements make seismic isolation an unfeasible solution due to boundary conditions, especially in case of existing bridges or high risk seismic regions. First, a suggested optimal design procedure is introduced, then seismic performance of three real bridges with different isolation systems and damping levels is investigated. Each bridge is studied in four different configurations: simply supported (SSB), isolated with 10% damping (IB), isolated with 30% damping (LRB) and isolated with optimal supplemental damping ratio (IDB). Two of the case studies are investigated under spectrum compatible far-field ground motions, while the third one is subjected to near-fault strong motions. With respect to different design strategies proposed by other authors, results of the analysis demonstrated that an isolated bridge equipped with HDLRBs and a total equivalent damping ratio of 70% represents a very effective design solution. Thanks to confirmed effective performance in terms of base shear mitigation and displacement reduction under both far field and near fault ground motions, as well as for both simply supported and continuous bridges, the suggested control system provides robustness and reliability in terms of seismic performance also resulting cost effective.

• 한국전산구조공학회논문집
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• 제20권4호
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• pp.463-468
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• 2007

최근 일본에서 발생한 지진으로 이동통신용 전자장비들이 많이 파손되었으나. 국내에서 제작되어 일본에 설치된 모제품은 강진에서도 대부분 구조적 손상이 없었다. 본 논문에서는 이동통신 네트워크 장비의 정/동적 특성을 평가하기 위하여 제품의 유한요소 모델을 생성하여 정적 및 동적 구조해석을 수행하였다. 또한 Zone 3 GR-63-CORE 동적 실험을 수행하여 제품의 안정성을 검증하였고, 유한요소 구조해석 결과와 비교하여 실험과 해석 결과가 유사함이 입증되었다. 구조해석 결과인 동적 응답특성은 실험보다 다소 크게 나왔으며, 부재의 특성파악을 위해 구조물의 치수를 설계변수로 하여 진동특성에 대한 민감도 해석으로 고유진동수에 민감한 부재를 판별하였고, 치수변경으로 경량화 설계치를 산출하였다. 경량화된 디자인의 동적 응답변위가 원래 디자인보다 작게 나와 최적화 결과가 유용할 것으로 보인다.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.99-111
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• 2019

To investigate the seismic performance of long-span partially earth-anchored cable-stayed bridge, a super long-span partially earth-anchored cable-stayed bridge scheme with main span of 1400m is taken as example, structural response of the bridge under E1 seismic action is investigated numerically by the multimode seismic response spectrum and time-history analysis, seismic behavior and also the effect of structural geometric nonlinearity on the seismic responses of super long-span partially earth-anchored cable-stayed bridges are revealed. The seismic responses are also compared to those of a fully self-anchored cable-stayed bridge with the same main span. The effects of structural parameters including the earth-anchored girder length, the girder width, the girder depth, the tower height to span ratio, the inclination of earth-anchored cables, the installation of auxiliary piers in the side spans and the connection between tower and girder on the seismic responses of partially ground-anchored cable-stayed bridges are investigated, and their reasonable values are also discussed in combination with static performance and structural stability. The results show that the horizontal seismic excitation produces significant seismic responses of the girder and tower, the seismic responses of the towers are greater than those of the girder, and thus the tower becomes the key structural member of seismic design, and more attentions should be paid to seismic design of these sections including the tower bottom, the tower and girder at the junction of tower and girder, the girder at the auxiliary piers in side spans; structural geometric nonlinearity has significant influence on the seismic responses of the bridge, and thus the nonlinear time history analysis is proposed to predict the seismic responses of super long-span partially earth-anchored cable-stayed bridges; as compared to the fully self-anchored cable-stayed bridge with the same main span, several stay cables in the side spans are changed to be earth-anchored, structural stiffness and natural frequency are both increased, the seismic responses of the towers and the longitudinal displacement of the girder are significantly reduced, structural seismic performance is improved, and therefore the partially earth-anchored cable-stayed bridge provides an ideal structural solution for super long-span cable-stayed bridges with kilometer-scale main span; under the case that the ratio of earth-anchored girder length to span is about 0.3, the wider and higher girder is employed, the tower height-to-span ratio is about 0.2, the larger inclination is set for the earth-anchored cables, 1 to 2 auxiliary piers are installed in each of the side spans and the fully floating system is employed, better overall structural performance is achieved for long-span partially earth-anchored cable-stayed bridges.

• Earthquakes and Structures
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• 제11권5호
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• pp.741-777
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• 2016

A simplified approach of assessing torsionally balanced (TB) and torsionally unbalanced (TU) low-medium rise buildings of up to 30 m in height is presented in this paper for regions of low-to-moderate seismicity. The Generalised Force Method of Analysis for TB buildings which is illustrated in the early part of the paper involves calculation of the deflection profile of the building in a 2D analysis in order that a capacity diagram can be constructed to intercept with the acceleration-displacement response spectrum diagram representing seismic actions. This approach of calculation on the planar model of a building which involves applying lateral forces to the building (waiving away the need of a dynamic analysis and yet obtaining similar results) has been adapted for determining the deflection behaviour of a TU building in the later part of the paper. Another key original contribution to knowledge is taking into account the strong dependence of the torsional response behaviour of the building on the periodic properties of the applied excitations in relation to the natural periods of vibration of the building. Many of the trends presented are not reflected in provisions of major codes of practices for the seismic design of buildings. The deflection behaviour of the building in response to displacement controlled (DC) excitations is in stark contrast to behaviour in acceleration controlled (AC), or velocity controlled (VC), conditions, and is much easier to generalise. Although DC conditions are rare with buildings not exceeding 30 m in height displacement estimates based on such conditions can be taken as upper bound estimates in order that a conservative prediction of the displacement profile at the edge of a TU building can be obtained conveniently by the use of a constant amplification factor to scale results from planar analysis.

• 대한기계학회논문집A
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• 제35권3호
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• pp.289-297
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• 2011

명시적 유한요소법은 비선형성이 많은 대형 문제를 푸는 데는 꼭 필요하지만 종종 그 결과의 해석에 있어서는 어려움이 수반된다. 특별한 경우, 가속도의 과도응답은 극심한 불연속, 과도한 노이즈 또는 앨리어싱이 발생하여 평가가 불가능할 때도 있다. 본 논문에서는 유한요소법의 명시적분에 의한 과도응답 및 응답스펙트럼의 새로운 후처리기법을 제안한다. 해석기에 의한 가속도 거동의 수치적인 에러를 제거하고 물리적인 가속도를 추출하기 위하여 가우스커널을 이용하는 평활화법을 제안하였다. 이 평활화는 신호처리 필터링 기법과 같이 복잡한 주파수에 대한 고려가 없이도 속도에 대한 결과와 응답스펙트럼을 참조함으로써 행해진다. 특히 가우스커널 평활화는 가속도의 피크 값을 잘 나타내면서도 평활도가 우수하였다. 제안된 평활화법에 의하여 부드러운 가속도는 물론 이를 이용하여 설계에서 필요한 층 응답스펙트럼을 구할 수 있다.

• 대한조선학회논문집
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• 제43권3호
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• pp.351-361
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• 2006

The fatigue strength analysis of VLFS is carried out by using a 3-dimensional plate finite element model with a zooming technology which performs the modeling of wide portions of the structure by a coarse mesh but the concerned parts by a very fine mesh of t by t level. And a stepwise substructure modeling technique for global loading conditions is applied which uses the motion response of the global structure from 2-D plate hydroelastic analysis as the enforcing nodal displacements of the concern 3-D structural zooming model. Seven incident wave angles and whole ranges of frequency domains of wave spectrum are considered. In order to consider the effect of breakwater, the modified JONSWAP wave spectrum is used. Applying the wave data of installation region, the longterm spectrum analysis is done based on stochastic process and the fatigue life of the structure is estimated. Finally some design considerations from the view point of fatigue strength analysis of VLFS are discussed.

• 한국전자통신학회논문지
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• 제9권5호
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• pp.555-560
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• 2014

본 논문에서 850nm~1000nm 파장대역에서 레이저를 검출하기 위한 고감도 실리콘 포토다이오드를 제조하고 전기적 및 광학적 특성을 분석하였다. 소자의 크기는 $5000{\mu}m{\times}2000{\mu}m$이며 두께는 $280{\mu}m$로 제조하여 TO-5 형태로 패키징 하였다. 전기적 특성으로 암전류는 5V 역 전압 일 때 0.1nA의 값을 나타내었으며 정전용량은 0V일 때 1kHz 주파수 대역에서 32.5pF와 200kHz 주파수 대역에서 32.4pF로 적은 정전용량의 값을 나타내었다. 또한 출력신호의 상승시간은 10V의 전압일 때 20.92ns로 고속 응답특성을 확인하였다. 광학적 특성으로는 890nm에서 최대 0.57A/W의 분광감응도를 나타내었고 1000nm에서는 0.37A/W로 감소한 분광감응도를 나타내고 있지만 870nm~920nm 파장대역에서는 비교적 우수한 분광감응도를 나타내었다.