• 한국강구조학회 논문집
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• 제13권3호
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• pp.279-287
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• 2001

본 논문은 중심축하중을 받는 콘크리트충전 각형강관 단주의 거동에 관한 연구이다. 총 11개의 실험체가 실험되었고, 실험의 변수는 강관의 폭/두께비와 강재의 항복 응력도에 대한 콘크리트의 압축강도비(응력도비)이다. 폭/두께비의 범위는 20.22에서 91.75이고 응력도비는 0.068에서 0.0955이다. 본 실험의 변수범위를 초과하는 기존의 실험결과를 수집하고 변수의 범위를 확장하여, 각각의 변수가 미치는 영향을 고찰하였다. 또한, Hajjar가 제안한 다항식의 모델을 수정하여 콘크리트충전 각형강관 단주의 내력식을 제안하였고.

• 한국강구조학회 논문집
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• 제15권1호
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• pp.51-57
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• 2003

현행 강구조 설계기준은 일반 구조용 강재의 이론과 실험에 의한 결과에 근거를 한다. 그러나 오스테나이트계 스테인리스 강재는 일반 구조용 강재와 달리 연속항복 현상이 일어난다. 설계기준강도를 결정짓는 옾셋강도는 현행 설계기준의 판폭두께비 제한값에 영향을 미친다. 단주압축 실험결과 0.2% 옾셋강도를 설계기준강도로 하면 허용응력도 설계법과 한계상태 설계법에서 정하고 있는 판폭두께비의 규정을 모두 만족하였다. 또한 일반 구조용 강재와 달리 판폭두께비를 만족시키지 못하는 경우에도 최대내력에 도달하기 전에 국부좌굴이 발생하지만 급격한 내력저하는 일어나지 않았다.

• Steel and Composite Structures
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• 제12권1호
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• pp.73-92
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• 2012

The effect of element interaction and material nonlinearity on the ultimate capacity of stainless steel plated cross-sections is investigated in this paper. The focus of the research lies in cross-sections failing by local buckling; member instabilities, distortional buckling and interactions thereof with local buckling are not considered. The cross-sections investigated include rectangular hollow sections (RHS), I sections and parallel flange channels (PFC). Based on previous finite element investigations of structural stainless steel stub columns, parametric studies were conducted and the ultimate capacity of the aforementioned cross-sections with a range of element slendernesses and aspect ratios has been obtained. Various design methods, including the effective width approach, the direct strength method (DSM), the continuous strength method (CSM) and a design method based on regression analysis, which accounts for element interaction, were assessed on the basis of the numerical results, and the relative merits and weaknesses of each design approach have been highlighted. Element interaction has been shown to be significant for slender cross-sections, whilst the behaviour of stocky cross-sections is more strongly influenced by the material strain-hardening characteristics. A modification to the continuous strength method has been proposed to allow for the effect of element interaction, which leads to more reliable ultimate capacity predictions. Comparisons with available test data have also been made to demonstrate the enhanced accuracy of the proposed method and its suitability for the treatment of local buckling in stainless steel cross-sections.

• Steel and Composite Structures
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• 제20권3호
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• pp.501-512
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• 2016

High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

• 국제초고층학회논문집
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• 제7권4호
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• pp.327-342
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• 2018

Geopolymer concrete (GPC), which is recognised as an environmentally friendly alternative to ordinary Portland cement (OPC) concrete, has been reported to possess high fire resistance. However, very limited research has been conducted to investigate the behaviour of geopolymer concrete-filled steel tubular (GCFST) columns at either ambient or elevated temperatures. This paper presents the compressive test results of a total of 15 circular concrete-filled steel tubular (CFST) stub columns, including 5 specimens tested at room temperature, 5 specimens tested at elevated temperatures and the remaining 5 specimens tested for residual strength after exposure to elevated temperatures. The main variables in the test program include: (a) concrete type; (b) concrete strength; and (c) curing condition of geopolymer concrete. The test results demonstrate that GCFST columns have similar ambient temperature behaviour compared with the conventional CFST counterparts. However, GCFST columns exhibit better fire resistance than the conventional CFST columns. Meanwhile, it is found that the GCFST column made with heat cured GPC has lower strength loss than other columns after exposure to elevated temperatures. The research results highlight the possibility of using geopolymer concrete to improve the fire resistance of CFST columns.

• Structural Engineering and Mechanics
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• 제88권1호
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• pp.95-107
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• 2023

In this study, circular thin-walled reinforced high strength concrete-filled steel tube (RHSCFST) stub columns with various tube thicknesses (i.e., 1.8, 2.5 and 3.0mm) and reinforcement ratios (i.e., 0, 1.6%, 2.4% and 3.2%) were fabricated to explore the influence of these factors on the axial compressive behavior of RHSCFST. The obtained test results show that the failure mode of RHSCFST transforms from outward buckling and tearing failure to drum failure with the increasing tube thickness. With the tube thickness and reinforcement ratio increased, the ultimate load-carrying capacity, compressive stiffness and ductility of columns increased, while the lateral strain in the stirrup decreased. Comparisons were also made between test results and the existing codes such as AIJ (2008), BS5400 (2005), ACI (2019) and EC4 (2010). It has been found that the existing codes provide conservative predictions for the ultimate load-carrying capacity of RHSCFST. Therefore, an accurate model for the prediction of the ultimate load-carrying capacity of circular thin-walled RHSCFST considering the steel reinforcement is developed, based on the obtained experimental results. It has been found that the model proposed in this study provides more accurate predictions of the ultimate load-carrying capacity than that from existing design codes.

• 한국강구조학회 논문집
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• 제26권5호
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• pp.473-483
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• 2014

건축구조기준에 따라 HSA800 강재의 합성기둥 적용시에는 실험 또는 해석적 방법을 통하여 적용의 타당성을 검증해야 한다. 이에 본 연구에서는 합성기둥으로 주로 사용되는 H형강 매입형, 각형강관 및 원형강관 충전형 합성기둥 단면을 대상으로 HSA800 강재를 적용한 단주압축실험을 실시하고, 이를 통하여 축방향 내력 및 건축구조기준의 합성기둥 설계압축강도 설계식 적용의 타당성을 평가하였다. 실험결과 매입형 합성기둥의 경우 HSA800 강재의 설계기준항복강도를 저감없이 사용하기 위해서는 건축구조기준의 설계압축강도 산정식의 조정이 필요한 것으로 나타났으며, 이를 위해 띠철근 간격 조정 및 콘크리트의 유효단면적 사용을 제안하였다. 충전형 합성기둥의 경우에는 각형, 원형충전강관 기둥 모두 별도의 강도 저감이나 설계압축강도 산정식의 조정 없이 사용이 가능할 것으로 판단된다.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.545-552
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• 2009

이 연구에서는 y형강판과 L형강으로 기둥의 외부를 구성하고 내부에 콘크리트를 타설하여 완성하는 yLRC (Reinforced Concrete with y-shape steel sheets and L-shape steel angles) 합성기둥에 대한 기초적인 실험을 수행하였다. yLRC 합성기둥은 철골과 콘크리트의 합성작용으로 단면성능이 우수하고, 거푸집 공사와 배근 공사를 생략할 수 있으므로 공기단축과 시공성 향상에도 상당한 효과를 나타낼 것으로 예상된다. L형강의 폭-두께비가 압축강도에 미치는 영향을 분석하기 위해서 L형강의 폭-두께비를 실험변수로 하는 6개의 실험체 (축소실험체 3개 및 실대실험체 3개)를 제작하고, 이 실험체에 대하여 중심축하중 실험을 수행하였다. 실험결과를 바탕으로 yLRC 합성기둥의 압축거동 및 압축강도에 대한 역학적인 특성을 분석하였다.

• 콘크리트학회지
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• 제7권5호
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• pp.133-144
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• 1995

본 연구는 콘크리트 충전강관을 고층 건물의 구조부재로 이용하기 위한 연구의 일환으로서 강관의 폭두께비, 세장비와 충전콘크리트의 강도를 주요 변수로 하여 강관이 콘크리트를 단순 구속하는 경우의 재하조건으로서 일련의 실험을 콘크리트 충전강관 기둥의 역학적인 거동 특성을 고찰하였다. 얻어진 결론을 요약하면 다음과 같다. (1)구속 콘크리트의 파괴양상은 단주의 경우 시험체 단부에서의 압괴에 의한 $45^{\circ}$정도의 사인장 파괴가 이루어졌으며 장주의 경우 횡방향 휨 파괴 양상을 나타내었다. (2)원형강관으로서 콘크리트를 구속함으로서 변형능력의 향상과 동시에 콘크리트의 연성 효과를 증대시킬 수 있었다. (3)강관의 세장비, 폭두께비, 콘크리트의 강도를 고려하여 콘크리트의 구속계수를 이용하여 강관에 의해 구속된 내부 콘크리트와 충전 강관 기둥의 최대내력 산정식을 제안하였다.

• Steel and Composite Structures
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• 제42권4호
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• pp.513-538
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• 2022

This paper reports on experiments addressing the buckling and collapse behavior of an innovative built-up cold-formed steel (CFS) columns. The built-up column consists of four individual CFS lipped channels, two of them placed back-to-back at the web using two self-drilling screw fasteners at specified spacing along the column length, while the other two channels were connected flange-to-flange using one self-drilling screw fastener at specified spacing along the column length. In total, 12 experimental tests are reported, covering a wide range of column lengths from stub to slender columns. The initial geometric imperfections and material properties were determined for all test specimens. The effect of screw spacing, load-versus axial shortening behaviour and buckling modes for different lengths and screw spacing were investigated. Nonlinear finite element (FE) models were also developed, which included material nonlinearities and initial geometric imperfections. The FE models were validated against the experimental results, both in terms of axial capacity and failure modes of built-up CFS columns. Furthermore, using the validated FE models, a parametric study was conducted which comprises 324 models to investigate the effect of screw fastener spacing, thicknesses and wide range of lengths on axial capacity of back-to-back and flange-to-flange built-up CFS channel sections. Using both the experimental and FE results, it is shown that design in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZS) standards is slightly conservative by 6% on average, while determining the axial capacity of back-to-back and flange-to-flange built-up CFS channel sections.