• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1211-1220
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• 2004

The confined concrete subjected multi-axial stresses have been known as the strength of concrete increases significantly. Many researchers have studied in confining effects of concrete, and now are studying in many fields. However, there are few passive confinements by steel tube. Although Mander et al. studied the concrete confined by transverse reinforcements, the confinement by steel tube differs from confining of reinforcements. To investigate the influence of concrete strength increased by confining conditions in steel, 51 specimens confined by different shapes and thicknesses of steel tube were tested and compared.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.317-322
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• 1995

This study is to examine the usefulness in using precast girder-infilled steel tube column in reinforced concrete structures through the analysis of the test results, in order to develope the new composite structural system using precast girder-Infilled steel tube column, The variables of specimen are strength of concrete, the numble of hoops, the form of beam-column The variables of specimen are strength of concrete, the number of hoops, the form of beam-column joints. By raising strength of concrete and incresing number of hoops in beam-column joint, it becomes clear to take similar structure capacity to monolithic structures.

• 한국구조물진단유지관리공학회 논문집
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• 제27권2호
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• pp.25-32
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• 2023

이 연구에서는 기존 프리캐스트 콘크리트 (Precast concrete, PC) 더블월 시스템의 복잡한 제작 공정을 간소화하면서 콘크리트 패널 형성 시 발생할 수 있는 레이턴스 등의 결함을 제거하고자 고안된 새로운 PC 더블월 공법을 소개하고 이때, PC 패널이 운반 또는 현장 콘크리트 타설 시 손상되지 않고 간격을 유지하는 역할을 하는 각형 강관에 대한 인장저항 성능을 규명하기 위한 실험적 연구를 수행하였다. 각형 강관의 단부 상세를 변수로 인장실험을 계획하였으며 개구부 형성에 따른 강판의 처리방법, 매립 콘크리트의 존치 유무, 추가적인 장부작용 확보를 위한 철근용접 등을 변수로 설정하여 효과적인 강관 단부 상세를 도출하고자 하였다. 결과적으로, 강관 단부의 측면을 절개한 강판을 강관 단부 방향 안쪽으로 절곡한 강관 실험체 (ST_CP)를 제외하고 기준실험체 (ST)에 비하여 20~30% 가량 증가한 최대 인장강도를 나타내었다. 기준실험체 내부에 콘크리트를 채운 실험체 (ST_CON)가 PC 더블월 제작 시 구성되는 각형 강관 연결부와 유사한 상세를 가지며 추가적인 시공과정과 비용이 요구되지 않으므로 가장 적합한 연결상세인 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제56권1호
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• pp.67-83
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• 2015

The load transfer mechanism and load-bearing capacity of cast steel joints for H-shaped beam to square tube column connection are studied based on the deformation compatibility theory. Then the monotonic tensile experiments are conducted for 12 specimens about the cast steel joints for H-shaped beam to square tube column connection. The findings are that the tensile bearing capacity of the cast steel joints for beam-column connection depends on the ring of cast steel stiffener. The tensile fracture happens at the ring of the cast steel stiffener when the joint fails. The thickness of square tube column has little influence on the bearing capacity of the joint. The square tube column buckles while the joint without concrete filled, but the strength failure happens for the joint with concrete filled column. And the length of welding connection between square tube column and cast steel stiffener has little influence on the load-bearing capacity of the cast steel joint. Finally it is shown that the load-bearing capacity of the joints for H-shaped beam to concrete filled square tube column connection is larger than that of the joints for H-shaped beam to square tube column connection by 10% to 15%.

• Steel and Composite Structures
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• 제14권2호
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• pp.191-204
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• 2013

A hybrid double skin concrete filled (HDSCF) circular steel tube column is proposed in this study. The yield strength of the outer steel tube is larger than 690MPa and the inner tube has less strength. In order to achieve efficiency with the high strength outer tube, a feasibility study on reducing the thickness of the tube below the specified design codes for CFTs was conducted based on an experimental approach. The experiment also took variables such as thickness of the inner tube, hollow ratio, and strength of concrete into consideration to investigate the behavior of the HDSCF column. In order to estimate the applicability of design equations for CFTs to the HDSCF column, test results from CFT and HDSCF columns with design codes were compared. It was found that the axial compressive performance of the proposed HDSCF column is equivalent to that of the conventional CFT member irrespective of design variables. Furthermore, the design equation for a circular CFT given by EC4 is applicable to estimate the ultimate strength of the HDSCF circular steel tube column.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.712-717
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• 2005

When the weight if a concrete member makes problems, or when the cost of the concrete is relatively high, it may be economical to use a hollow concrete member. But a hollow R.C column may have poor ductility because of the brittle failure at the inner face of the hollow R.C column. This brittle failure results from the absence of the confinement at the inner face of the hollow R.C column. To avoid this brittle failure an internally confined hollow R.C column by a steel tube was developed before. In this study, a hollow R.C column is internally confined by a corrugated steel tube instead of a general flat steel tube. And a column ductility is performed. Test results show that the energy ductility ratio of a internally confined hollow R.C column by a by a corrugated steel tube corresponds to $80\%$ of the energy ductility ratio of a general solid R.C column.

• Steel and Composite Structures
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• 제10권4호
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• pp.317-329
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• 2010

According to the results of 9 circular concrete filled steel tube (CFT) push-out tests, a new theoretical model for average bond stress versus free end slip curve is proposed. The relationship between verage bond stress and free end slip is obtained considering some varying influential parameters such as slenderness ratio and diameter-to-thickness ratio. Based on measured steel tube strain and relative slip at different longitudinal positions, the distribution of bond stress and relative slip along the length of steel tube is obtained. An equation for predicting the varying bond-slip relationship along longitudinal length and a position function reflecting the variation are proposed. The presented method can be used in the application of finite element method to analyze the behavior of CFT structures.

• Steel and Composite Structures
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• 제17권5호
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• pp.735-751
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• 2014

Concrete-filled steel tube (CFT) composite columns, either circular (CCFT) or rectangular (RCFT), have many economical and aesthetic advantages but the behavior of their connections are complicated. This study aims to investigate, through an experimental program, the performance and behavior of different connections configurations between circular concrete filled steel tube columns (CCFT) and gusset plates subjected to shear and axial compression loadings. The study included seventeen connection subassemblies consisting of a fixed length steel tube and gusset plate connected to the tube end with different details tested under half cyclic loading. A notable effect was observed on the behavior of the connections due to its detailing changes with respect to capacity, failure mode, ductility, and stress distribution.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.541-562
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• 2006

This paper compares the performance of axially loaded concrete filled steel tube (CFST) columns cast using a conventionally vibrated normal concrete (NC) and a novel self-consolidating concrete (SCC) made with a new viscosity modifying admixture (VMA). A total of sixteen columns with a standard compressive strength of about 50 MPa for both SCC and NC were tested by applying concentric axial load through the concrete core. Columns were fabricated without and with longitudinal and hoop reinforcement (Series I and Series II, respectively) in addition to the tube confinement. The slenderness of the columns expressed as height to diameter ratio (H/D) ranged between 4.8 and 9.5 for Series CI and between 3.1 and 6.5 for Series CII. The strength and ductility of SCC columns were found comparable to those of their NC counterparts as the maximum strength enhancement in NC columns ranged between 1.1% and 7.5% only. No significant difference in strain development was found due to the presence of SCC or NC or due to the presence of longitudinal and hoop reinforcement. Biaxial stress development in the steel tube as per von Mises yield criterion showed similar characteristics for both SCC and NC columns. The confined strength ($f^{\prime}_{cc}$) of SCC was found to be lower than that of NC and $f^{\prime}_{cc}$ also decreased with the increase of slenderness of the columns. Analytical models for the prediction of confined concrete strength and axial strength of CFST columns were developed and their performance was validated through test results. The proposed models were found to predict the axial strength of CFST columns better than existing models and Code based design procedures.

• 한국강구조학회 논문집
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• 제9권1호통권30호
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• pp.121-128
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• 1997

It has been reported by the existing papers that the ultimate load capacity and energy absorption capacity of the CFST column are considerably higher than those resulting from a simple addition of the capacities of the concrete and the steel tube. It is normally believed that the confined effect for the infilled concrete due to the hoop tension of steel at the parameter of cross sections can remarkably improve the ductility and energy absorption capacities of the CFST columns. This paper provides the results of a study on the load-carrying capacities and energy absorption capacities of the CFST columns, a numerical analysis method, i. e. N-M interaction curves and Moment curvature relationships. The numerical approaches are verified by comparing with the existing test results and the circular and square steel tube sections are selected to clarify the amount of confinement effects to improve the ultimate deformable capacity(a ultimate strain value) of the infilled concrete. Then, an adequate value of the ultimate strain of the infilled concrete and an equation of the ultimate capacity of the CFST column are suggested.