• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.89-96
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• 2016

Compressive axial behavior of the variable cross-section soft ground reinforced foundation is investigated from the field load test results at ${\bigcirc}{\bigcirc}$ construction site in Incheon city. Variable cross-section soft ground reinforced foundation is a type of partial-displacement pile formed by mixing bidding material with in situ soils to obtain a rigid and strong variable cross-section column in a relatively soft ground. The foundations are usually constructed as a group; however in this study, only single foundation was installed and tested under compressive axial load on foundation head. For the comparison of the variable cross-section soft ground reinforced foundation axial behavior, behavior of typical Pretensioned spun high strength concrete (PHC) pile constructed on a relatively soft ground near the surface was analyzed. It was concluded that variable cross-section soft ground reinforced foundation efficiently resists against axial load with sufficient stiffness and strength within a considerable range of axial load magnitude.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.9-20
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• 2002

The purpose of this research is to develop computational procedures for studying nonlinear soil-structure interaction Problems. In orders to study soil-structure interaction behavior, the finite element analysis for the strip footing subjected to both vortical and lateral loads, and foundation layer reinforced with sheet pile are considered, interface elements are used between the footing and the soil to model the interaction behavior The main analyzed results are as follows; 1. For the prediction of settlement and lateral displacement, the result due to interface element was evaluated larger then without interface element. 2. For the determination of ultimate bearing capacity, the value using interface element appeared smaller by 12%, which was safe. 3. The horizontal and vertical displacement of strip footing affected by the presence of interface element.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.3-9
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• 2007

With a growing concern about the state of infrastructure worldwide, the demand for the development of reliable nondestructive testing techniques (NDT) is ever increasing. Among possible NDT techniques, microwave method is proven to be effective in fast and non-contact inspection of concrete structures and inclusions inside concrete. It is also found that the microwave method has a potential in detecting the delamination between fiber reinforced polymers (FRP) plate and concrete. On the other hand, ultrasonic method can be another way to find the delamination. In this paper, the research work needed for the development of a reliable microwave method and ultrasonic method is studied in the measurements of concrete specimens reinforced with FRP. Concrete specimens are made with FRP and artificial delamination inside. A microwave measurement system with hom antennas with high center frequency and broad frequency bandwidth are used to image inside concrete specimens for the detection of debonding between concrete and FRP. Also, ultrasonic method is used for the same condition. Both results are compared with each other.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.51-57
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• 2011

Irregular distributions of limestone cavity in Gang-Won province area may cause unexpected accidents from reduced serviceability or failure of structure. It is requested that an appropriate ground reinforcement method should be used to improve bearing capacity of structure, and the method should also be satisfied with environmental requirements. Among several methods used for foundation constructions in cavity area, Rod Jet Pile(RJP) method has been widely used. While the RJP method was used to improve bearing capacity for the railway bridge foundations, water pollutions of drinking water as well as fishery located adjacent to this project area were occurred. The main reason of the water pollution was cement runoff used in cement mortar during injecting material in RJP method. Laboratory tests were performed to prevent water pollution. The compaction mortar method using low movable material was selected for this project. The quality of water at a fishery adjacent to the site and the compressive strength of cores taken from the construction site were measured. Test results show that the water pollutions was minimized, and the average compressive strength of foundation material was over 5 MPa. As a result of this study, compaction mortar method can be used to ensure the bearing capacity of foundation and to prevent environment pollutions.

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.139-149
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• 1998

동적하중하에서 강섬유보강 콘크리트(SFRC)는 유연도 및 균열억제에서 우수한 재료로서 최근에 각종 구조물에 널리 사용되었으며, 특히 내진설계를 위한 강섬유보강 콘크리트 의 재료적 감쇠에 관한 규명이 절실히 요구되고 있다. 본 연구는 강섬유보강 콘크리트(SFRC)보의 재료적 감쇠효과증진을 실험적 및 수치해석적 방법으로 규명하는 데에 목적이 있으며, 일반적으로 강섬유 보강콘크리트(SFRC)보의 감쇠거동은 인장철근비, 강섬유의 혼입량과 형태, 콘크리트의 강도 그리고 응력의 크기에 좌우된다. 강섬유보강 콘크리트보의 감쇠비는 보의 균열상태 변화에따른 동적실험결과로부터 얻을 수 있으며, 일반적으로 강섬유보강 콘크리트는 증가된 에너지감쇠능력으로 인장철근이 소성전 상태에서 철근 콘크리트보의 경우보다 향상된 감쇠거동을 갖고 있는 것으로 판명되었다. 이들 결과의수치해석적인 입증을 위하여 curvature(곡률)와 감쇠값사이의 관계를 기초로 유한요소프로그램 (TICAL)을 개발하였으며, 결론적으로 0.44%인장철근비을 갖고 있는 강섬유보강 콘크리트의 감쇠비는 하중상태에 따라 철근 콘크리트보의 경우보다 약 5%에서 35%정도 향상된 감쇠비를 갖고 있는 것으로 조사되었다.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.255-265
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• 2007

As the mechanism and effect range of subsidence are altered according to the various conditions (the ground condition, the earth pressure, the geometric condition of underground cavity and the structure load), the analysis and prediction of subsidence in abandoned mining area are very difficult. Also, as the geological characteristics and the mining methods are differed in each mines, the application of the pre-existing reinforcements without improvement has a lot of difficulties and limits. In this study, the various underground investigation such as long-depth core drilling, seismic tomography and BIPS (borehole image processing system) were performed, the distribution of underground cavity and coal seam and rock relaxation condition were analyzed. And we predicted the type of subsidence and estimated the subsidence by theories of mining subsidence. With these results, we analyzed the mechanism of subsidence occurrence in the research object area. Finally, we improved existing methods which were applied to the abandoned mining area and also we established the rational reinforcement for the ground and structure foundation against each subsidence cause.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.191-200
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• 2006

The micropile, which is a kind of the in-situ manufactured pile with small diameter of 100~300mm, is constructed by installing a steel bar or pipe and injecting grout into a borehole. The application fields of micropile are being gradually expanded in a limited space of down-town area, because the micropile has various advantages with low vibration and noise in method and compact size in machine, etc. Mostly, the micropile has been applied to secure the safety of structures, depending on the increment of bearing capacity and the restraint of displacement. The micropile is expected to be used in various fields due to its effectiveness and potentiality in the future. The model test, focused on the interaction between micropile and soil in this study, was carried out. The micropile is installed under footing(concept of "structure supporting"). With the test results and soil deformation analysis, the reinforcement effect(relating to bearing capacity and settlement) was analysed in a qualitative and quantitative manner, respectively. Consequently, it is hoped to demonstrate the improvement of an efficiency and application in the design and construction of micropile.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.85-96
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• 2003

The Geocell system is the advanced system of Geo-grids, and is one of geosynthetics used for earth reinforcement of weak soil. It is the way to increase earth strength and bearing capacity by using three dimension type of geo-composite. This paper analyzed the bearing capacity mechanism of Geocell system for earth reinforcement. Plate loading tests under the model laboratory condition were performed, and the increase of bearing capacity and the decrease of settlement with shallow foundation were evaluated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.293-300
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• 2015

In this study, a series of forced vibration testing and ambient vibration measurement were performed at a lowrise masonry-infilled reinforced concrete frame structure before and after seismic retrofit and its dynamic properties were extracted using system identification techniques. Also, analytical models which show similar dynamic properties to the measures ones were constructed. The system identification results showed that damping ratios in x direction along which the dampers were installed has been increased. From the comparison between the analytical models, the effective stiffness of post-installed member and post-reinforced members(shear walls and damper frames) were only 50% of gross sectional stiffness of the members, which indicates that the these members were not fully integrated with the existing structure or members. In addition, support condition of post-installed footing has to be pinned in y direction to match the dynamic properties, which is seemingly caused by the change of fixity of the soil due to the installation of new footing.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.985-992
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• 2009

대형 구조물의 기초 시공 시 구조물의 하부지반이 불균질하거나 경사진 지반 또는 일반토사와 암반이 혼재된 지지력이 급격히 변화하는 구간에서 시공되는 경우가 많으며 이와 같은 경우에는 경제적인 최적의 방안으로 직접기초와 말뚝기초를 혼용하여 사용하는 방안이 필요하다. 그러나 일반적으로 기초의 안정성 확보를 위해 보수적으로 말뚝기초를 적용하는 경우가 대부분이며 소규모의 아파트 기초현장에서는 부분적으로 이질기초가 적용되나 이에 대한 보강이나 안정성 검토는 형식적으로 이루어지는 경우가 대부분이다. 본 연구에서는 직접기초와 파일기초가 적용되는 이질기초에 대한 수치해석을 통하여 이질기초 적용 시 기초 및 하부지반에 대한 거동을 평가하여, 이질기초에 대한 적용가능성 여부 및 기초하부에서의 개략적인 거동에 대하여 고찰하고자 한다.