• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.1
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• pp.101-108
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• 2012

Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and bending moments of the deck and pylon. Comparison study of an improved initial force method and TCUD method for determination of initial cable forces in cable-stayed bridges is presented in this paper. For this purpose, an elastic catenary cable element and a nonlinear frame element are firstly described. And concepts and algorithm of two analysis methods are then presented. Finally to demonstrate the validity and the accuracy of two methods, numerical examples for initial state problems of cable-stayed bridges are given and compared based on these methods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.937-957
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• 2017

Urban roads are not only congested with vehicles and pedestrians, but also have many pipelines buried to provide convenience for inhabitants. In addition, urban inhabitants live comfortably in buildings adjacent to the road for residence, business, commerce, rest and so on. Therefore, despite the high cost of land, urban underground buildings with high land use efficiency are constantly being built. Recently, the construction of underground buildings has caused social problems such as the collapse of surrounding roads and adjacent buildings. Institutional improvement is being actively carried out to improve this. In this study, a new type of MSRC diaphragm wall was developed and a study on the construction method of underground building was carried out. It is intended to secure the underground excavation safety of underground buildings in urban areas and effectively prevent land subsidence complaints. Also, a reasonable design method of MSRC diaphragm walls using the ultimate strength design method is presented through the flexural performance Experiment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.205-213
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• 2003

The primary purpose of this study is to investigate punching shear capacity of flat plate slab using high strength concrete in column. It may be much contributed to economy efficiency and structural advantages that High Strength Concrete(HSC) used for vertical member and Normal Strength Concrete(NSC) for horizontal member. Therefore, six plate flat slab specimens with HSC column and NSC slab had been made and tested with real scale. The major variables were compressive strength of concrete(fck=285, $460kgf/cm^2$), extended length of HSC from column face and amount of shear reinforcements. As the result of this test, the maximum load and punching shear capacity of specimens is affected by extended length and shear reinforcements.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.545-552
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• 2020

This study evaluated the support performance of fiber-net integrated shotcrete in tunnel support system developed for the purpose of improving constructability and stability while fully performing its mechanical performance as a tunnel support materials by four-point bending test, two-dimensional numerical analysis, and cross-sectional analysis. As a result of evaluating the flexural performance through a four-point bending test, in the case of fiber-net reinforced shotcrete, the tensile performance of fiber-net resulted in a continuous increase in load after crack occurrence, unlike steel fiber reinforced shotcrete. Also, the results of the tunnel cross-sectional structure analysis for ground conditions and the cross-sectional analysis of fiber-net and steel fiber reinforced shotcrete showed that sufficient support performance can be exhibited even if the thickness of fiber-net reinforced shotcrete was reduced compared to the previous one. Additionally, through these results, the support pattern of fiber-net integrated shotcrete in tunnel support system, which can be applied efficiently to the construction sections requiring higher stability among the rock mass class III, was proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.169-178
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• 2009

Ring-type steel fibers (RSFs) of the closed circular shape, have different resistance mechanisms other than straight steel fibers. RSFs also maintain the same value of the orientation factor for the plane enclosed by the fiber ring perimeter. In this research, comparative studies were performed for the panels reinforced with RSFs and with straight steel fibers of $15kg/m^3$ and $30kg/m^3$, respectively. Resisting mechanisms of RSFs were identified and higher toughness indices were experimentally observed for the concrete panels reinforced with RSFs than with straight steel fibers. Orientation factor for the RSF was suggested. It was found that RSFs were more effective in increasing toughness for the panel specimens with relatively thinner thickness than beam specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.171-180
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• 2008

The aim of this paper is to clarify the structural performance of RC beams strengthened with Carbon Fibre Reinforced Polymer(CFRP) plates using channel-type anchorage system. Twelve RC beams were specifically designed without and with a channel-type anchorage system, which was carefully detailed to enhance the benefits of the strengthening plates. All the twelve beams were identical in terms of their geometry but varied in their internal reinforcement, concrete strength. All the beams were tested under four point bending and extensively instrumented to monitor strains, cracking, load capacity and failure modes. The structural response of all the twelve beams is then critically analyzed in terms of deformability, strength and failure processes. It is shown that with a channel-type anchorage system, a brittle debonding failure of a strengthened beam can be transformed to an almost ductile failure with well-defined enhancement of structural performance in terms of both deformation and strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.79-86
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• 2008

Four RC shear wall specimens with a/d of 2.2 are designed. And a flexural retrofitting is performed for one specimen by both enlarging wall section and adding additional vertical reinforcements. Also the effectivity of jaketting wall sides is evaluated for the two methods using only steel plate or welded wire mesh with enlargement of section. Cyclic loads are applied to the retrofitted specimens according to the loading history proposed by ACI under constant axial force. Test result showed that the strength and ductility of specimen were improved where the section was enlarged after the installation of additional vertical reinforcements. Confining the ends of wall by U shape W.W.F. with enlargement of section showed most excellent structural capacity regarding to the strength and ductility. Retrofitting by using steel plate was much effective not only to protect the abrupt decrease of strength after yield but also to improve the deformation capacity.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.243-254
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• 1997

최근들어 구조물의 노후화와 차량하중 등의 증가로 구조물의 손상이 커지고 있으며 보강의 필요성이 절실히 대두되고 있다. 강판보강공법은 강성의 확실한 증가와 내구성 등으로 인하여 그 동안 폭넓게 사용되어 오고 있으나 효율적 보강을 위한 공법과 이론이 아직까지도 정립되지 않은 상태이다. 따라서 본 연구의 목적은 그 동안의 실험결과를 중심으로 보강도니 철근콘크리트보의 파괴기구와 박리거동을 분석하고 이로부터 합리적인 박리하중 산정이론을 제한하는데 그 목적을 두고 있다. 보강된 강판의 길이와 두께 등의 영향을 고찰하고,기존의 이론을 분석하여 기존이론의 불합리한 점을 밝혔으며, 이들을 보완한 수정이론을 제시하엿다. Roberts의 이론은 강판의 두께가 증가함에 따라 오히려 박리하중이 약간 증가하고 있어 실제적인 실험거동과 차이가 나고 있다. 본 연구의 제안식은 실제 거동을 합리적으로 표현하고 있으며, 앞으로 보강설계에 유용한 자료가 될 것으로 기대되고 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.243-247
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• 2008

An analytical approach to calculate time-dependent stresses and strains in initially cracked reinforced concrete section with biaxial bending was proposed. The method utilized the aging coefficient approach of Bazant and the linear creep theory. The position of neutral axis and strain and stress distributions of cracked section after creep and shrinkage were determined from the requirements of strain compatibility and equilibrium of a section. With this proposed algorithm, examples were given for rectangular section and a comparative analysis for stress and strain was also made.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.216-222
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• 2002

With deterioration of the nation's infrastructure comes the growing, need for effective means of rehabilitating structures. Possibly one for the most challenging tasks is to upgrade the overall capacity of concrete structure. Therefore, considerable efforts are still being made to develop new construction materials. Rehabilitation of damaged RC structures occasionally requires the removal and replacement of concrete in the tension zone of the structural members. Typical situation where the tension zone repair is necessary is when the concrete in the tension zone in beams or slabs has spalled off as a result of corrosion in the bottom reinforcing bars or due to extensive fire. The rehabilitation of such conditions normally involves the removal of the concrete beyond the reinforcement bars, cleaning or replacing the tensile bars and reinstatement of concrete to cover the steel bars the original shape and size. This study focused on the flexural behavior of reinforced concrete beams strengthened by steel strand and carbon fiber sheet in the tension zone. The properties of beams are 15$\times$25 cm rectangular and over a 200cm span. Test parameters in this experimental study were strengthening methods, jacking volume, the number of sheet. We investigated the flexural behavior of simply supported RC beams which are strengthened with the carbon fiber sheet, monotonic loads. Attention is concentrated upon overall bending capacity, deflection, ductility index, failure mode and crack development of repaired and rehabilitated beams.