• 한국구조물진단유지관리공학회 논문집
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• 제4권1호
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• pp.131-138
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• 2000

In this study, physical and engineering properties of ordinary portland cement and microcement were investigated to verify reinforcing effect of underpinning of open caisson foundation by using microcement grouting. Laboratory injection tests such as infiltration and injection in case of seepage for the stream bed soil at ${\bigcirc}{\bigcirc}$ Great Bridge in Seoul were carried out. Field injection tests to reinforce open caisson foundation at ${\bigcirc}{\bigcirc}$ Great Bridge were performed and the ability of application by microcement grouting was evaluated. From the test results, physical and engineering properties of microcement are better than those of ordinary portland cement. Also, the ability of infiltration and solidity in case of seepage is better than that of ordinary portland cement. Therefore, it is concluded that microcement is an excellent material to reinforce open caisson foundation of the existing bridge structure under the water and can be used as underpinning material of general foundations.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.659-662
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• 2009

In this paper described are the performance design guidelines of writing the items of foundation structures for designers. To accept the new performance code instead of existing design code in the construction market, performance design focuses on requirements to guidelines of foundation structure.

• Geomechanics and Engineering
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• 제24권1호
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• pp.29-42
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• 2021

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load-displacement behavior of piles, the pile-soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

• 한국지반공학회논문집
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• 제23권4호
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• pp.149-160
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• 2007

본 논문에서는 송전철탑 심형기초의 주면마찰력을 평가하고자 충북 음성지역의 편마암에 대해 총 6회(1/8규모 5회, 1/2규모 1회) 현장시험을 실시하였다. 시험결과 파괴형태는 기초체와 암반의 마찰파괴가 아닌 굴착으로 인한 손상된 주변암반 및 기존암반의 절리상태에 지배되는 것으로 나타났으며, 주면마찰력 평가결과 기존의 송전철탑 심형기초에 적용하고 있는 값보다 약 20$\sim$30% 증가되는 것을 확인할 수 있었다. 또한 기초타설시 사용되는 라이너플레이트의 영향을 살펴보고자 기존 철탑 기초에 대해 시추조사를 4회 실시하였다. 라이너플레이트 배면콘크리트의 압축강도는 타설시 설계강도의 63$\sim$72%였으며, 주면마찰력의 설계기준치를 만족하는 것으로 나타났다.

• Smart Structures and Systems
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• 제24권4호
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• pp.525-539
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• 2019

In this study, vibration characteristics of a gravity-based caisson-foundation breakwater system are investigated for ambient and geometric parameters such as various waves, sea levels, and foundation conditions. To achieve the objective, following approaches are implemented. Firstly, operational modal analysis methods are selected to identify vibration modes from output-only dynamic responses. Secondly, a finite element model of an existing caisson-foundation breakwater system is established by using a structural analysis program, ANSYS. Thirdly, forced vibration analyses are performed on the caisson-foundation system for two types of external forces such as controlled impacts and wave-induced dynamic pressures. For the ideal impact, the wave force is converted to a triangular impulse function. For the wave flow, the wave pressure acting on the system is obtained from wave field analysis. Fourthly, vibration modes of the caisson-foundation system are identified from the forced vibration responses by combined use of the operational modal analysis methods. Finally, vibration characteristics of the caisson-foundation system are investigated under various waves, sea levels, and foundations. Relative effects of foundation conditions on vibration characteristics are distinguished from that induced by waves and sea levels.

• 한국해양공학회지
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• 제38권2호
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• pp.74-85
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• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.982-987
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• 2002

Recently, as size of building structure becomes larger, mat area of building structure is supported on Inhomogeneous foundation. The equipment machineries in building are mostly on basement story. The slab of the lowest basement story with equipment machineries is considered as plate supported on foundation with concentrated masses. In this paper, vibration analysis of rectangular thin plate is done by use of rectangular finite element with 4 nodes. The solution of this paper are compared with existing solution and natural frequencies of thin plates, with concented mass, on inhomogeneous Pasternak foundation are calculated

• 한국지반공학회지:지반
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• 제9권2호
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• pp.55-64
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• 1993

연약지반상에 댐이나 제방과 같은 토질구조물을 성토할 경우에는 구조물 뿐만아니라 기초지반에도 상당히 큰 변형이 일어나게 된다. 그러므로 성토에 의하여 최종적으로 형성된 토공단면은 연약기초지반에 놓여있는 형태가 아니라 제체의 일부가 연약점토지반 내로 치환된 형태가 된다. 본 연구에서는 축조재의 Dumping에 의하여 발생하는 치환깊이와 축조후 토공단면의 변형형태를 추정하고자 하였으며 제시된 이론과 수치해석 결과를 검증하고자 모형실험을 수행하였다. 또한 보강재 부설에 따른 보강효과도 관찰하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권12호
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• pp.5969-5973
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• 2012

Introduction: Andhra Pradesh (AP) is one of the largest tobacco producing states in India. About 29% of adults in AP currently use tobacco in some form. Almost 24% of males and 4% of females are smokers. The prevalence of tobacco use in the state is higher than the national average of 15% for male and 2% for female smokers. However, few attempts have been made to understand the current situation of tobacco control resources, activities and strategies in the context of such a high tobacco prevalence state. The present study aimed to identify the gaps in existing tobacco control program and areas where tobacco control efforts can be integrated. Methods: Data were collected using both quantitative and qualitative methods. Semi-structured interviews were undertaken with a total of 95 key officials of state health departments, program managers, and project directors in six districts to understand ongoing tobacco control efforts. To facilitate the interviews, semi-structured guides were developed. Simple descriptive statistical analysis was conducted on the quantitative data using SPSS version 17. Results: The results of the situational analysis suggest that a sufficient health workforce and infrastructure with the potential to integrate tobacco control activities is available in the surveyed districts. However, lack of integration of the tobacco control program intothe tuberculosis control program and the National Rural Health Mission was observed. Information, education and communication activities were lacking at block level health facilities. Conclusions: Our findings indicate that lack of trained health professionals, paucity of dedicated funds, lack of information, education and communication materials and low priority given to tobacco control activities are some of the factors which impede integration of tobacco control into existing health and developmental programmes in the districts of Andhra Pradesh, India.

• 한국지반공학회논문집
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• 제35권3호
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• pp.17-24
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• 2019

본 연구는 지반 위 얕은 기초의 지지력에 대한 특성을 파악하기 위하여 지반 조건, 기초 크기, 기초 형상 등의 다양한 조건에 대하여 3차원 유한요소해석을 수행하여 기존의 지지력 이론과 비교 검토하였다. 유한요소해석 결과 극한지지력은 기초크기에 따라 지지력이 거듭제곱이나 로그 식으로 차츰 수렴하였고, 지반강도가 증가할수록 지지력 증가가 커지지 않는 직선적인 변화를 보였다. 기존 지지력 이론과 비교한 결과 순수모래는 지지력 비($q_{FEA}/q_{theory}$)가 Terzaghi식의 결과와 가장 유사하였다. 순수점토는 약 0.4~0.6, 일반토사는 0.3~1.3 정도로 산정되었고, 지반강도가 증가할수록 지지력 비가 감소하면서 1.0 이하로 나타났다. 기초 크기에 따른 지지력을 1.0m 기초의 지지력으로 정규화시킨 지지력 비($q_u/q_{u(1.0)}$)는 순수모래에서 ${\phi}=25^{\circ}$, $30^{\circ}$, $35^{\circ}$일 때 이론식의 35%, 15%, 5% 정도로 산정되었고, 순수점토는 크기 효과가 없었으며, 일반토사는 지반강도가 작은 경우에 순수모래의 이론식에 대해 약 10% 이하로 나타났다. 지반강도 증가에 따른 지지력 비는 내부마찰각의 영향이 큰 것으로 나타났다. 기초형상별 지지력 비에 따른 형상계수는 기초형상에 따라 다르게 나타났고, 원형기초는 1.5, 정사각형 기초는 1.3, 직사각형 기초와 연속 기초는 1.1~1.0의 형상계수를 나타내었다.