• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.30-30
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• 2011

국내의 내진설계 기준은 1988년에 처음 도입되었으며, 최근 점차 강화되고 있는 실정이다. 공동주택에 주로 적용되는 전단벽식 구조시스템에서 증가된 지진력에 저항하기 위해서는 벽량과 철근이 증가하게 되어 공사비가 상승하게 된다. 이러한 단점을 보완하기 위한 제진설계의 필요성이 대두되고 있는 실정인데, 기존의 제진장치는 주로 가새형 또는 벽체형을 대부분이라 평면계획에 제약이 있다. 따라서 전단벽식 구조의 공동주택의 제진설계 시에는 우리나라와 같은 중 약진 지역에 적합하고 저렴한 비용으로 충분한 내진성능과 평면의 가변성을 확보할 수 있는 댐퍼의 선택이 필요하다. 본 연구의 목적은 기존의 가새형 및 벽체형 제진장치의 국내 공동주택 적용시의 문제점인 평면의 가변성 확보에 유리하고, 수동형 제진장치의 장점을 추구할 수 있는 마찰댐퍼를 삽입한 커플링보 제진시스템의 내진성능을 조사하는 것이다. 내진성능을 평가하기 위해서 실대형 커플링보 실험체를 계획하고 제작하였다. 실험체는 2개로 구성되어 있으며, 하나는 기존의 철근배근 상세를 갖는 철근콘크리트 커플링보 실험체와 커플링보에 마찰댐퍼가 삽입된 실험체이다. 횡하중에 대한 성능을 평가하기 위해서 유사정적 반복가력실험을 실시하였다. 엑츄에이터로부터 실험체 상보의 가력지그를 통해 하중이 전달되도록 하였으며, 가력은 최초 0.25%의 층간변형각부터 변위제어를 통해 목표 층간변형각인 1.5% 이상까지 진행되도록 하였다. 실험결과, 두 실험체의 이력곡선과 에너지 흡수능력을 평가하였다. RC 실험체는 핀칭현상이 관찰되었고, 가력이 진행됨에 따라 커플링보와 벽체에서의 균열이 확산되어 종국적으로 취성적인 커플링보의 전단파괴가 발생하였다. 마찰댐퍼를 삽입한 실험체는 계획된 마찰거동이 잘 발휘되어 목표 층간변형각인 1.5%까지 이선형거동이 잘 나타났다. 최대 내력은 RC 실험체가 3배 이상 크지만, 누적층간변형각에 따른 에너지 흡수능력은 마찰댐퍼 실험체가 2배 이상 우수한 결과를 보였으며, 커플링보 및 벽체에서의 균열이 매우 저감되었다.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.511-520
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• 2009

In this study, the Ocean Tide Loading (OTL) constituents were detected by the Precise Point Positioning (PPP) technique using GPS. Then, the GPS estimates of OTL constituents were compared with the predictions of the ocean tide models. We picked three permanent GPS stations as test sites and they are ICNW, SEOS, and CJUN. To detect the OTL constituents using GPS, we created vertical coordinate time series at 10-minute intervals using the PPP approach implemented in the GIPSY software. Through the tidal harmonic analysis of this height time series, the four major constituents ($M_2$, $S_2$, $K_1$, $O_1$) were determined. The amplitude obtained from the GPS height time series of the OTL constituents showed best match with the model predictions at CJUN, while the phase showed closest match at ICNW. The amplitude accuracy of the $M_2$, which is the dominant factor out of the 11 major constituents, was 24.8% on average.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.75-92
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• 1999

In this paper, the seismic analysis model for seismically isolated KALIMER reactor structures is developed and the modal analysis and the seismic time history analysis are carried out for seismic isolation and non-isolation cases. To check the seismic stress limit according to the ASME Code, the equivalent seismic stress analyses are preformed using the 3-D finite element model. From the seismic stress analysis, the seismic margins are calculated for structural members. The limit of seismic load is defined to show that the maximum input acceleration ensures the structural safety for seismic load. In comparison of seismic responses between seismic isolation and non-isolation cases, the seismic isolation design gives significantly reduced acceleration responses and relative displacements between structures. The seismic margin of KALIMER reactor structure is high enough to produce the limit seismic load 0.8g.

• Computational Structural Engineering
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• v.9 no.1
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• pp.33-45
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• 1996

A general stiffener element which includes transverse shear deformation is formulated using the p-version finite element method. Hierarchic C/sup o/-shape functions, derived from Integrals of Legendre polynomials, are used to define the assembled stiffness matrix of the stiffener with respect to the local reference frame is transformed to the plate reference system by applying the appropriate transformation matrices in order to insure compatibility of displacements at the junction of the stiffener and plate. The transformation matrices which account for the orientation and the eccentricity effects of the stiffener with respect to the plate reference axes are used to find local behavior at the junction of the stiffener and the relative contributions of the plate and stiffener to the strength of the composite system. The results obtained by the p-version finite element method are comared with the results in literatures, especially those by the h-version finite element analysis program, MICROFEAP-II.

• Geotechnical Engineering
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• v.3 no.1
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• pp.39-52
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• 1987

Model pile tests are performed, first, to estimate donwndrag exerted on pile surfaces due to the settlement of surrounding soils, and, second, to evaluate the efficiency of the downdrag reduction methods such as the bitumen coating method and the method of the attachment of an enlarged base. Test results show that the downdrag forces may be expressed as 0.25(;effective overburden). Bitumen coating reduces the downdrag by more than 50 percent, and the enlarged base attachment method is also effective, whose effectiveness increases as the sixte of the base increases as expected. When the bitumen coating and enlarged base are both applied, the downdrag force is reduced as much as 90 percent. Finally, it is found that the quantity of the relative displacement between the pile and the surrounding soil downdrag is extremely small.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.57-70
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• 2012

For soft ground, a pile foundation is typically used as a substructure of transmission tower. However, differential settlement between the foundations can cause structural damage of transmission tower. The connected-pile foundation is a type of group foundation consisting of four foundations connected with beams, and it was suggested in USA and Japan. In this study, a series of 1/8 scale model pile tests were performed to investigate the effect of load direction and stiffness of connecting beam on the responses of connected-pile foundation. As a result, the load capacities of the connected-pile foundation were larger than those of the conventional group pile foundation. For example, under the given test conditions in this paper, the resistibility against differential settlement was improved significantly for connected-pile foundation and its efficiency was maximized when the stiffness of connecting beams is about 25% of the mat foundation.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.55-61
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• 2008

One of the most recent base-isolation systems to improve the earthquake resistance of structures is the Friction Pendulum System(FPS). Simple in design but with versatile properties, the FPS has been used in some of the world s largest seismically isolated buildings, bridges and chemical tanks. FPS using PTFE(Polytetrafl-uoroethylene) based material has been developed to provide a simple and effective way for structures to achieve earthquake resistance. PTFE materials are soft, and are apt to become deformed easily after a few working cycles. In this study, magnetic force is used rather than the usual PTFE materials to improve the material shortcomings. A MF-FPS(Magnetic force-Friction Pendulum System) is proposed, and us shown to effectively protect structures against earthquakes. To demonstrate the advantages of this new system, the MF-FPS is compared with FPS as an attempt to prove its performance. A six-degree-of-freedom model is considered as a numerical example. The ground acceleration data of El Centro, Mexico and Gebze earthquakes are used as seismic excitations. The results showed that MF-FPS improved performance compared with FPS.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.415-421
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• 2013

In order to extend the service life of a nuclear power plant(NPP) ensuring the structural safety, effective and efficient management of NPP considering structural deteriorations and various natural hazard risks has been treated as a significant tool(IAEA 1998). The systemic efforts is required to prevent the potential loss of NPPs resulting from the natural hazard including earthquakes, hurricane and flooding since the Fukushima accident. Earthquake risk of building structures can be mitigated through appropriate seismic isolation system installation. It has been known that a seismic isolation system can lead to reduction of the deleterious effect on ground motion induced by earthquakes, and structural safety can be improved. In this paper, the NPP life-cycle management is reviewed. Furthermore, effect of seismic isolation on the NPP life-cycle cost analysis with earthquake, and cost-benefit analysis in terms of life-cycle cost when applying the seismic isolation systems to NPP are introduced.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.285-294
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• 2005

The behaviors of the ground in crossed zone and the existing upper tunnel in shallow cover due to the excavation of new lower tunnel crossed to that was studied. Model test was performed in the large scale test pit, the size was '$4.0m(width){\times}3.8m(height){\times}4.1m(length)$'. Test ground was constructed uniformly by sand in middle density and test with the crossed angle of $56^{\circ}$ (obliquely) were performed. The numerical analysis was performed on equal condition with model test. Results of the study by model test and numerical analysis show that earth pressure and settlement of the ground in crossed zone were redistributed due to the longitudinal arching effect by the excavation of lower tunnel. Model test shows that upper tunnel blocks stress flow due to the longitudinal arching effect by excavation of lower tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.49-62
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• 2007

A new earth pressure equation acting on the vertical shafts in cohesionless soils has been proposed by modifying the equations proposed by others. In order to verify the modified equation, model tests which can control uniform wall displacement with depth to radial direction were conducted. Model tests were performed with three different wall friction angles and two different relative densities. The measured values were larger than estimated values when assuming $\lambda=1$ ; smaller than those when assuming $\lambda=1-sin\phi$. The parameter, $\lambda$ is the ratio of tangential stress to vertical stress and is the most critical value in proposed equation. A method which can estimate the earth pressure on vertical shafts in layered soils is also proposed by reasonably assuming the failure surface of layered soils and using the modified equation. In order to verify the proposed method, in-situ measurement data have been collected from the three in-situ vertical shafts installed in layered soils. Most of earth pressures converted from measured data match reasonably well with estimated values using proposed method.