• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.291-301
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• 1998

This paper is a study on the structural behavior of CFCT(Concrete-Filled Circular Tubular) column to H-beam connections with longitudinal rib. The important parameters are being longitudinal rib or not. variable column thickness(5.8mm. 9.2mm. 12.0mm. 15.0mm) around the joint between CFCT and H-beam and the width of flange to diameter. Test results are summarized for the strength, initial stiffness, failure mode and energy absorption capacities of each specimen. These are compared with the theoretical results(Yield line theory, numerical analysis). Therefore, the purpose of this paper is to investigate the stiffness and the strength of connections to evaluate the structural behavior of the CFCT column to H-beam connections with longitudinal rib.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.299-305
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• 2013

This paper presents the experimental results of behacior of slender square hollow section columns strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. Three long specimens were fabricated and one stub column were fabricated. The main parameters were the number of CFRP layers. From the tests, it was observed that global buckling were occurred at the center of specimen for unretrofitting slender column. However, CFRP retrofitting could prevent the global buckling of slender column. Maximum increase of 22% was also achieved in axial-load capacity with three longitudinal layered CFRP applied on four sides of steel tubes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.295-301
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• 2009

In general the stability of soil nail-slope system, the shear resistance is neglected because the tensile resistance of nail acts mainly for slope stabilization. This is because that deformed steel is generally used for nail and it does ductile behavior. In other side when the steel pipe with high rigidity is used for nail, the shear resistance at failure surface work more than deformed steel. In order to analyze effects of shear resistance at the soil nail-slope system with high steel piped nail, a series of numerical analyses were performed. Also numerical analyses at 3 conditions - 5 nailed, 7 nailed, 9 nailed at the same slope were perfomed for investigating the trend of shear resistance effect. From these 3D numerical analyses, it was found that the maximum shear resistances at each nails were larger in case of steel piped nail and because of this, the factor of safety at the condition of the steel piped nail appears larger than that of deformed steel nail.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.259-266
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• 2009

The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the numerical models and the related input parameters were analyzed to simulate the axial load-movement relations, which were obtained from the compression loading tests for the cylindrical specimens of the steel pipe, the concrete, and the steel-concrete composite. As the results, the behavior of the steel pipe was simulated by the von-Mises model and that of the concrete by the strain-softening model, which decreases cohesion and dilation angles as the function of plastic strains. In addition, the reinforcing bars in the concrete were simulated by applying the yielding moment and decreasing the sectional area of the bars. The applied numerical models properly simulated the yielding behavior and the reinforcement effect of the steel-concrete composite piles. The parametric study for the real-size piles showed that the material strength of the steel-concrete composite pile increased about 10% for the axial loading and about 20~45% for the horizontal loading due to the reinforcement effect by the surrounding steel pipe pile.

• Geotechnical Engineering
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• v.12 no.4
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• pp.5-20
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• 1996

In this study it was analyzed by 2-D FEM and 3-D FEM to evaluate the ground reinforceing effect of steel pipe reinforced multi -step grouting (SPRG) technique and the behavior of ground in the vicinity using the nonlinear FEM program for the ground condition of alluvium located on the top of tunnel applied by SPRG technique. It was found that the nonlinear 3-D analysis performed better than 2-D analysis in evaluating the usefulness of the SPRG technique, and it was also found that the safety was relatively secured by the stiffness of steel pipe to distribute the concentrated stress in the tunnel faceing. It was reported that the change of settlement on the top of tunnel becomes about 40% of the total expected settlement before tunnel faceing reaches tunnel gauging point, and 60% of the total expected settlement while tunnel facing passes tunnel gauging point and takes a distance about tunnel diameter. With the aid of the SPRG technique the control range of displacement and stress of the ground in the vicinity could be reached up to tunnel top, namely depth ratio from 0.38 to 0.83 or 2D(D : tunnel diameter) before the tunnel facing, and about 20% of settlement control in this particular case was possible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2C
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• pp.81-90
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• 2009

In this study the behavior of a steel pipe structure used as an auxiliary method was evaluated by the convergence-confinement method and load-transfer approach, and the result was compared with that of numerical approach and in-situ measured data. As calculated partially increased displacement of the installed pipe to obtain the tunnel displacement. A numerical analysis simulate well the general behavior of measured displacement of tunnel crown. Through this study, it was found that the proposed procedure produces conservative result so that it can be applied in preliminary design of the auxiliary method of tunnel face.

• Proceedings of the KAIS Fall Conference
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• 2006.11a
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• pp.106-110
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• 2006

중공 R.C 기둥은 중실 R.C 기둥에 비해 자중의 감소나 재료의 절감의 장점을 가지고 있다. 하지만 중공 R.C 기둥은 안쪽면의 취성파괴로 인하여 낮은 연성 거동을 할 가능성이 있다. 이러한 문제점을 해결하기 위해 중공 부재 내의 콘크리트 3축 구속 상태로 존재하게 하는 강관으로 보강된 중공 R.C 기둥이 강영종, 한택희 (2005) 등에 의해 개발되었다. 본 연구는 강관으로 보강된 중공 R.C 기둥에 대하여 중공비를 0.5~0.85까지 변화 시켜 중공비에 따른 작용하중에 대한 안전율, 연성도, 재료비에 대한 거동 특성을 파악하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.625-639
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• 2018

This study is about the reinforcing type of reinforcement method which is reinforced in tunnel portal of tunnel with bad ground condition. Generally, it is known that the horizontal reinforcement method is more effective than the conventional reinforcement method. However, as a limitation of the tunnel construction technology, it is being constructed by the superposition reinforcement method. In recent years, high-strength large-diameter steel pipes and horizontally oriented longitudes (L = 30.0~50.0 m) construction technology have been developed. Therefore, it is required to study reinforcement method of tunnel portal reinforcement method. Therefore, 3-D numerical analysis (Midas GTS NX 3D) was performed by setting the reinforcement method (No reinforcement type, overlap reinforcement type and horizontal reinforcement type) and ground condition as parameters. As a result, it was considered that the reinforcement effect was the largest as the horizontal reinforcement type of the reinforcement method was the smallest in the displacement and the support material stress. Based on the results of the numerical analysis, horizontal steel pipe grouting was applied to the actual tunnel site. The displacement of the tunnel portal and the stress of the support material occurred within the allowable values and were considered to ensure sufficient stability.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.169-176
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• 2014

This paper presents the experimental results of behavior of square CFT columns with large the width-ro thickness ratio strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. The main parameters were b/t ratio and the number of CFRP layers and 6 specimens were fabricated. The values of b/t were ranged from 60 to 100. From the tests, Maximum increase of 16% was also achieved in axial-load capacity with three transverse layered CFRP applied on four sides of steel tubes. The load capacity decreased up to 41% comparing with nominal load capacity of unstrengthened CFT column. However, for CFRP strengthened CFT, the load capacity decreased up to 32%. Finally, from the load-strain relationships, the local buckling occurred before yield point of steel tubes. Also, from the load-strain relationships, it was observed that local buckling were delayed on CFT columns by CFRP sheets retrofitting.

• Railway Journal
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• v.14 no.1
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• pp.42-48
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• 2011