• Steel and Composite Structures
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• 제38권3호
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• pp.305-317
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• 2021

The mechanical behavior of the outer square inner circular concrete-filled dual steel tubular (SCCFT) stub columns under axial compression is investigated by means of experimental research, numerical analysis and theoretical investigation. Parameters such as diameter ratio, concrete strength and steel ratio were discussed to identify their influence on the mechanical properties of SCCFT short columns on the basis of the experimental investigation of seven SCCFT short columns. By establishing a finite element model, nonlinear analysis was performed to discuss the longitudinal and transverse stress of the dual steel tubes. The longitudinal stress characteristics of the core and sandwich concrete were also analyzed. Furthermore, the failure sequence was illustrated and the reasonable cross-section composition of SCCFT stub column was proposed. A formula to predict the axial load capacity of SCCFT stub column was advanced and verified by the results from experiment and the finite element.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.207-217
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• 2018

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and overloading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

• Steel and Composite Structures
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• 제5권6호
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• pp.459-484
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• 2005

In recent years, the use of steel tube confined concrete (STCC) columns has been the interests of many structural engineers. The present study is an attempt to study the monotonic and cyclic behaviours of STCC columns. For the monotonic behaviours, a series of tests on STCC stub columns (twenty one), and beam-columns (twenty) were carried out. The main parameters varied in the tests are: (1) column section types, circular and square; (2) tube diameter (or width) to thickness ratio, from 40 to 162, and (3) load eccentricity ratio (e/r), from 0 to 0.5. For the cyclic behaviours, the test parameters included the sectional types and the axial load level (n). Twelve STCC column specimens, including 6 specimens with circular sections and 6 specimens with square sections were tested under constant axial load and cyclically increasing flexural loading. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes. It was found that STCC columns exhibit very high levels of energy dissipation and ductility, particularly when subjected to high axial loads. Generally, the energy dissipation ability of the columns with circular sections was much higher than those of the specimens with square sections. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes such as AIJ-1997, AISCLRFD- 1994, BS5400-1979 and EC4-1994.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.96-97
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• 2014

Green Frame is a column-beam structure built by steel frame joints embedded in the columns and beams. Here, the steel frame embedded in the columns and beams is not a standardized product, instead it needs to be order-produced. The quantity for each steel frame size should be calculated to estimate the quantity of steel frames to be manufactured. However, it is highly time-consuming and requires a lot of effort in calculating the quantity of steel frames, for there are a wide range of steel frame types that are embedded in the columns and beams. To solve this problem, the study proposes an algorithm for calculation of the amount of steel frames with ease and promptness. When a program is developed using the algorithm proposed in the study in connection to the information on precast concrete members prepared in the design phase, it is anticipated that the manpower required as well as the manufacturing time will be decreased.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.345-360
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• 2022

In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.

• Steel and Composite Structures
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• 제1권1호
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• pp.51-74
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• 2001

A series of tests on concrete-filled SHS (Square Hollow Section) stub columns (twenty), columns (eight) and beam-columns (twenty one) were carried out. The main parameters varied in the tests are (1) Confinement factor (${\xi}$) from 1.08 to 5.64, (2) concrete compression strength from 10.7MPa to 36.6MPa, (3) tube width to thickness ratio from 20.5 to 36.5. (4) load eccentricity (e) from 15 mm to 80 mm and (5) column slenderness (${\lambda}$) from 45 to 75. A mechanics model is developed in this paper for concrete-filled SHS stub columns, columns and beam-columns. A unified theory is described where a confinement factor (${\xi}$) is introduced to describe the composite action between the steel tube and filled concrete. The predicted load versus axial strain relationship is in good agreement with stub column test results. Simplified models are derived for section capacities and modulus in different stages of the composite sections. The predicted beam-column strength is compared with that of 331 beam-column tests with a wide range of parameters. A good agreement is obtained. The predicted load versus midspan deflection relationship for beam-columns is in good agreement with test results. A simplified model is developed for calculating the member capacity of concrete-filled SHS columns. Comparisons are made with predicted columns strengths using the existing codes such as LRFD (AISC 1994), AIJ (1997), and EC4 (1996). Simplified interaction curves are derived for concrete-filled beam-columns.

• 한국공간구조학회논문집
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• 제7권3호
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• pp.79-86
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• 2007

최근, 건설되어지는 강구조물들의 장경간화 및 고층화로 인하여 고강도강재의 적용이 점차 요구되고 있다. 고강도강재는 적용구조물들을 공간 및 두께들 감소시킴으로써 외관성 및 경제성을 증가시킬 수 있는 장점이 있다. 이러한 고강도 강재의 적용을 위해서는 좌굴에 대한 기준이 필요하나 현재 국내의 경우 이러한 좌굴에 관한 연구가 미흡하다. 이에 본 연구에서는 3차원 탄소성 유한변위 프로그램을 이용하여 고강도 박스단면 트러스 부재의 좌굴거동에 대한 해석적 연구를 수행하였다. 고강도강재를 적용한 박스단면 트러스부재의 허용 압축응력에 대한 기준을 제안하였으며 그 적용성을 확인하였다. 그리고 고강도 트러스 부재의 설계에도 적용할 수 있음을 명확히 하였다.

• 한국공간구조학회논문집
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• 제7권6호
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• pp.69-74
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• 2007

교량의 교각과 같은 원형기둥구조물의 성능과 강도을 향상시키기 위해 최근 콘크리트 충전강관(CFT: concrete-filled steel tube)의 적용이 점차 증가하고 있다. 이러한 콘크리트 충전강관 구조물의 정확한 소성설계를 위해서는 사용된 재료인 강재 및 콘크리트의 대변형 거동을 구현할 수 있는 소성모델이 필요하다. 본 연구에서는 사용강재의 실험을 통하여 제안된 소성모델을 적용한 탄소성 대변형 해석을 개발하였으며 콘크리트 충전강관 기둥 해석과 실험 결과에 비교하여 그 정도 및 타당성을 검증하였다. 그리고 개발된 프로그램을 이용하여 콘크리트 충전강관 기둥의 초기처짐이 극한장도에 미치는 영향 및 상관관계를 명확히 파악하였다.

• Steel and Composite Structures
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• 제22권6호
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• pp.1487-1505
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• 2016

This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.

• 한국강구조학회 논문집
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• 제17권5호통권78호
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• pp.605-615
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• 2005

수평하중을 받는 콘크리트충전 각형강관 기둥의 축력과 변형능력의 관계를 조사하기 위하여 실험 및 해석적 연구를 수행하였다. 36개 기둥으로 구성된 실험 시리즈는 일정 축하중과 수평하중 하에서 반복실험을 실시하였다. 반복 수평하중을 받는 기둥이 저항할 수 있는 축하중을 보증내력 한계축력이라고 규정하였으며, 해석 모델은 수평하중을 받는 캔틸레버 기둥을 모델화하였다. 반복 횡하중을 받는 기둥의 축하중을 누적보증내력 한계축력이라고 정의하였다. 본 연구의 목적은 주어진 동일부재각에 부합하는 축력과 수평하중을 받는 콘크리트 충전강관 기둥의 보증내력 한계축력을 연구하기 위한 것이며, 두 번째는 콘크리트 충전강관 기둥의 누적보증내력 한계축력과 보증내력 한계축력의 비교가 본 연구의 목적이다.