• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.750-758
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• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 25 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. And the result indicated that the modulus of subgrade reaction or $N_c$ value (5.3) apparently overestimated the bearing capacity of very soft ground such as dredged ground. Moreover, as a result of model test by partially constraining the preload of 23.0kgf using geotextile, the effect of bearing capacity($q_1$) appeared to be the largest till the loading stress was $0.4tf/m^2$ due to cohesion, while it reached 75% of the maximum bearing force after $0.4tf/m^2$ due to increase in the effect of bearing capacity($q_2$) caused by the tensile force of the reinforcement. Such results tended to have appeared constantly or very similarly with each other, irrespective of the type of reinforcement (geogrid, steel bar) and constraint conditions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.553-558
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• 2001

Recent destructive seismic events demonstrated the importance of mitigating human casualties and serious property damages in design and construction of structures. The Korean Bridge Design Specifications (1992) adopted seismic design requirements based on the AASHTO specification, and minor modification was made in 2000. The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable. The longitudinal reinforcement details affect seismic performance such as flexural failure and shear failure. This research aims to develop longitudinal steel connection details with confinement steel by experimental study for seismic performance of reinforced concrete bridge columns. Quasi-static test under three different axial load levels was conducted for 12 spiral column specimens. All the column specimens had the same aspect ratio of 3.5. The column specimens were transversely reinforced with spiral and with five different longitudinal steel connection. The final objective of this study is to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and improve construction quality.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.345-352
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• 2001

Recent destructive seismic events demonstrated the importance of mitigating human casualties and serious property damages in design and construction of structures. The Korean Bridge Design Specifications (1992) adopted seismic design requirements based on the AASHTO specification, and minor modification was made in 2000. The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable. The longitudinal reinforcement details affect seisimc performance such as flexural failure and shear failure. This research aims to develop longitudinal steel connection details with confinement steel by experimental study for seismic performance of reinforced concrete bridge columns. Quasi-static test under three different axial load levels was conducted for 12 spiral column specimens. All the column specimens had the same aspect ratio of 3.5. The column specimens were transversely reinforced with spiral and with five different longitudinal steel connection. The final objective of this study is to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and improve construction quality.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.135-140
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• 2002

Bridge columns in strong earthquake area are to be designed and constructed so that enough ductility should be guaranteed. Therefore, large amount of transverse reinforcement is required to confine core concrete of the bridge column by design specifications. In moderate seismicity regions, however, adopting the full ductility design concept sometimes results in construction problems due to reinforcement congestion. For the moderate seismicity regions, a design based on required ductility and required transverse reinforcement might be a reasonable approach. Ductility demand design or performance-based design might be an appropriate approach especially for regions of moderate seismic risk. The procedure and application of this design approach are presented in this paper.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.697-704
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• 2019

The public has grown more anxious towards domestic earthquakes that have been taking place since 2000, and regulations on seismic design has been strengthened. Out of 4,605 Air Force installations that require the application of seismic design, 2,982 remain unapplied. By taking budget issues and the time spent to implement seismic retrofit into account, this paper aims to list up seismic reinforcement priorities for airmen dormitories where they can potentially be most vulnerable to earthquakes. The priorities are extracted based on Data Envelope Analysis(DEA). To apply DEA, two sets of variables are set: seismic reinforcement costs as input variable: age of building, number of residents, and seismic load as output variables. At the end, suggestions are made for developing seismic reinforcement plans that can be applied to all Air Force installations.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.475-483
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• 2008

It is necessary to develop a national design method for surface reinforcement of very soft ground because most current design works rely on crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a sents of numerical analysis. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised the numerical analysis in order to compare the result of numerical analysis with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to find the appropriate material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to show the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation.

• 콘크리트학회논문집
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• 제11권3호
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• pp.141-152
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• 1999

Precast prestressed double-tee slab may be designed by the PCI Design Handbook. It is based on the bridge construction and is required for reorganization for the use of buildings in the domestic construction environments. Much enhanced sections are developed from the reforming process on the determined design factors in the previous experimental works on double tees. Pre-determined shape, reinforcement detail, and 5000 psi concrete strength can not be expected as the best solution for the domestic construction requirements because large amount of use on that systems are anticipated. Flexural tests are performed on four full-scale 12.5m proto-type models, "least depth double tee", which are resulted from the optimization process. Domestic superimposed live load regulation, domestic material properties which is available to product, building design requirements and economy in construction are considered as the main factors to establish. the first two sections are double tee section for 1.2 ton/$\m^2$ market live load with straight and one-point depressed strands and the second two are for 0.6 ton/$\m^2$ parking live load with those strand types. All of the specimens tested fully comply with the flexural strength requirements as specified by ACI 318-95. However, the research has shown that following improved considerations are needed for better result in practice. The locations and method of connection for the lowest bottom mild bar, connection method between precast and cast-in-place concrete, and dap-end reinforcement are need to be improved.

• 한국방재안전학회논문집
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• 제13권1호
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• pp.13-23
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• 2020

국내 도시철도는 2005년 내진설계가 본격적으로 도입되었으며, 내진성능평가 및 보강방법에 대한 많은 연구가 이루어졌다. 2009년 3월 공포된 지진재해대책법 시행령(현 지진화산재해 대책법 시행령)에 따라 2010년4월~2013년10월까지 일부 지자체에서 도시철도 지하화 구간의 내진성능 상세 평가 및 보강방안을 수립하였다. 그 후, 2018년 말까지 공용기간이 오래된 구간에 대하여 기존 도시철도의 내진성능 평가를 수행하였으며, 기 연구된 방법을 적용하여 다양한 공법으로 보강공사를 시행하고 있다. 그러나 다양한 보강재료과 이를 사용한 공법이 연구되었지만, 현재 도시철도 보강공사에 적용되고 있는 공법에 대한 분류 실태연구는 미비하다. 본 연구의 목적은 현재 도시철도 내진성능보강 공사에 적용중인 사례를 분석하여, 공법별 특징 및 적용 사유와 문제점을 제시하는데 있다.

• 콘크리트학회논문집
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• 제28권1호
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• pp.33-40
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• 2016

현재, 국내외 전단 설계기준에서 RC 및 PSC 부재의 전단보강철근의 최대항복강도를 제한하고 있다. 이는 고강도 전단보강철근을 사용한 RC 부재의 전단거동평가에 대한 선행 연구들에 근거한 것이다. 이에 비해 고강도 전단보강철근을 사용한 PSC 부재의 전단거동평가에 대한 연구는 미흡하며, PSC 부재는 긴장력에 의한 축압축력에 의해 RC 와는 다른 전단거동을 나타내므로 국내 기준에 대한 검증이 필요하다. 또한 이러한 제한으로 인해 고강도 철근을 PSC 부재에 적용할 경우 강도의 추가적인 상승분을 내력에 포함시킬 수 없어 고강도 재료의 사용을 저해시키는 요인으로 작용한다. 본 연구에서는 총 8개의 고강도 재료를 사용한 포스트텐션 PSC 보 전단실험을 실시하여 KCI-12 기준 및 ACI 318-14 기준의 항복강도 및 사인장균열의 폭을 검토하였다. ACI 318-14에서 요구하는 전단보강철근의 항복강도 제한값(420 MPa) 이상인 모든 PSC 실험체의 전단보강철근이 항복한 이후에 최대 내력에 도달하였으며, 실험 전단내력 또한 KCI-12 기준식의 전단강도 이상인 것으로 나타났다. 사용성 측면에서도 고강도 전단보강철근을 사용한 모든 실험체가 ACI 224위원회의 허용 균열폭(0.41 mm)을 초과하지 않았다. 본 연구의 실험결과에 근거하여 KCI-12 기준에서 제한하는 전단보강철근의 항복강도는 PSC 부재에 대해서 전단내력 및 균열의 사용성 측면을 모두 만족하는 것으로 판단되며 ACI 318-14의 전단보강철근 제한 기준은 다소 안전측에 속하는 것으로 사료된다.

• Computers and Concrete
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• 제11권6호
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• pp.571-585
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• 2013

Asymmetrical reinforcement for circular sections in wall piles is an efficient construction component with reduced embodied energy. It has been proven that asymmetrical reinforced wall piles may save more than 50% of the reinforcement than the traditional symmetrically reinforced circular sections. The use of this new type of structural member increases the number of variables in the design problem, which makes its use by engineers more complicated. In order to facilitate the use of the asymmetrically reinforced piles, this paper presents a criterion for the design of this type of structural member. The chosen criterion has been analyzed with the help of flexural capacity-cost curves. The new criterion is similar to the design procedure traditionally used for RC beams.