• 복합신소재구조학회 논문집
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• 제2권1호
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• pp.23-29
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• 2011

본 연구에서는 CFRP쉬트로 보강된 원형 CFT기둥의 압축거동을 관찰하고 설계식을 제안하였다. 원형 CFT기둥의 CFRP쉬트의 보강효과를 관찰하기 위해 10개의 실험체를 제작하여 중심축하중 실험을 수행하였다. 실험변수로는 CFRP쉬트 보강겹수와 직경-두께비(D/t)이다. 실험결과 원형CFT기둥에 CFRP쉬트 보강을 통해 압축내력을 증가시킨 것으로 나타났다. 끝으로 ACI 440code를 응용하여 CFRP 보강된 원형 CFT기둥의 압축내력을 예측하기 위한 설계식을 제안한다. 제안식을 분석한 결과 실험결과와 비교적 일치한 것으로 나타났다.

• Steel and Composite Structures
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• 제9권4호
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• pp.325-348
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• 2009

This paper is concerned with steel-concrete composite plate girders curved in plan. At the design stage these girders are assumed sometimes to act independent of the deck slabs resting on them in order to simplify the analysis. The advantage of composite action between the steel girders and concrete deck is not utilized. Finite element modeling of such composite action in plate girders is considered in this paper. Details of the finite element modeling and the non-linear analysis of the girders are presented along with the results obtained. Tension field action in the web panels similar to those observed in the straight plate girders is also noticed in these girders. Finite element and experimental results in respect of curved steel plate girders and straight composite plate girders tested by other researchers are presented first to assess the accuracy of the modeling. Effects of parameters such as curvature, steel flange width and web panel width that affect the behavior of composite girders are then considered in the analyses. An approximate method to predict the ultimate strength of horizontally curved composite plate girders is also presented.

• Steel and Composite Structures
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• 제43권6호
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• pp.689-706
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• 2022

Thin-walled square concrete-filled double steel tubular (CFDST) columns composed of the inner circular tube filled with concrete can be used to carry the large axial loads or strengthen existing CFST columns in composite constructions. This paper reports an experimental program carried out on short square CFDST columns loaded concentrically. The influences of important column parameters on the post-buckling performance of such columns are investigated. Test results exhibit that the inner circular tube significantly improves the ultimate loads and the ductility of such columns compared to conventional concrete-filled steel tubular (CFST) and double-skin CFST (DCFST) columns with an inner void. A mathematical model developed is used to simulate the ultimate strengths and load-strain curves of such columns loaded axially. Furthermore, the ultimate strengths of such columns are predicted using existing codified design models for conventional CFST columns as well as the formulas proposed by previous researchers and compared against a large database comprising 500 CFDST columns. Lastly, an accurate artificial neural network model is developed for the practical applications of such columns under axial loading.

• 콘크리트학회논문집
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• 제12권2호
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• pp.21-30
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• 2000

In the Ultimate Strength Design, the design strength of a member is determined by multiplying the strength reduction factor to the nominal strength. This concept may be a reasonable approach, however it can not consider failure modes appropriately. Moreover, column design strength diagram show an abrupt change at a low level of axial load, which does not seem to be reasonable. This research compares the design strength determined by the strength resistance factors. As the material resistance factors for flexure and compression, 0.65 and 0.90 are proposed for concrete and steel, respectively. The design strength calculation process by applying material resistance factors addresses failure modes more effectively than by applying member strength reduction factor, and provides more resnable design strength for reinforced concrete flexural and compression members.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.277-287
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• 1996

Based on the developments of the reliability-based steel structural analysis and design as well as the extending knowledgy on the probabilitic characteristics of loading and resistance the probability based design criteria have been successful Iy developed for many students. The existing design codes, which are genarally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of loads and resistance and the basic reliability concepts. It is recognized to develope the design criteria by ETCM(Expected Total cost Minimization). In this study, therefore, the proper probability based design criteria (Optimum load and resistance factor design formats ) has been developed based on the safety levels observed from calibration Iii th existing standards, which applies to the ultimate limit states of steel structural members.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.275-282
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• 2001

In this paper, nonlinear analyses of RC (Reinforced Concrete) columns are conducted, and an improved criterion to estimate the design load carrying capacity of slender RC columns is proposed. To simulate the material nonlinearty including the cracking of concrete, the layer model is adopted, and the initial stress matrix is considered for the simulation of P- effect. After correlation studies with previous numerical results to verify the efficiency of the developed numerical model, many parameter studies are followed, and a regression formula which can give more exact resisting capacity of slender RC columns is introduced on the basis of the obtained numerical results.

• Steel and Composite Structures
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• 제35권1호
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• pp.93-109
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• 2020

Developed from conventional concrete filled steel tubular (CFST) members, concrete-encased CFST has attracted growing attention in building and bridge practices. In actual construction, the inner CFST is erected prior to the casting of the outer reinforced concrete part to support the construction preload, after which the whole composite member is under sustained service load. The complex loading sequence leads to highly nonlinear material interaction and consequently complicated structural performance. This paper studies the full-range behaviour of concrete-encased CFST columns with initial preload on inner CFST followed by sustained service load over the whole composite section. Validated against the reported data obtained from specifically designed tests, a finite element analysis model is developed to investigate the detailed structural behaviour in terms of ultimate strength, load distribution, material interaction and strain development. Parametric analysis is then carried out to evaluate the impact of significant factors on the structural behaviour of the composite columns. Finally, a simplified design method for estimating the sectional capacity of concrete-encased CFST is proposed, with the combined influences of construction preload and sustained service load being taken into account. The feasibility of the developed method is validated against both the test data and the simulation results.

• 콘크리트학회논문집
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• 제23권6호
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• pp.731-740
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• 2011

KCI 2007, ACI 318-08에 제시된 모멘트재분배 방법은 등분포 중력하중을 받는 연속 휨재에 대하여 검증된 방법이다. 횡하중에 의한 모멘트재분배 및 비탄성 거동은 중력하중과 전혀 다른 메커니즘을 발생된다. 이 연구에서는 기초역학에 근거하여 중력하중과 횡하중을 받는 철근콘크리트 모멘트골조의 보에 발생되는 모멘트재분배와 소성변형의 관계를 정량화하고, 이로부터 보의 소성변형능력에 근거한 모멘트재분배 설계법을 제안하였다. 제안된 모멘트재분배비는 KCI 2007, ACI 318-08 등 기존 설계기준과 마찬가지로 극한한계상태의 단면해석으로 결정되는 철근의 인장변형률로 정의된다. 또한 모멘트재분배비는 경간, 철근비, 단면강성, 변형경화 거동에 의하여 영향을 받는다. 제안된 방법을 사용하여 탄성해석으로 구한 설계모멘트를 재분배시키는 설계 가이드라인 및 예제를 제시하였다.

• 한국지반환경공학회 논문집
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• 제5권4호
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• pp.33-45
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• 2004

본 연구에서는 조립토 다짐말뚝에 대해 보다 체계적인 실내모형실험을 수행하여, 조립토 다짐말뚝과 인접지반의 하중분담 특성, 말뚝의 길이변화에 따른 지지력 특성, 재하면적의 크기 및 말뚝의 설치간격(인접지반의 치환율) 등이 지지력에 미치는 영향, 또한 군말뚝의 경우 위치별 말뚝의 지지력 특성 등, 궁극적으로 조립토 다짐말뚝의 합리적 설계를 위한 극한지지력 평가시 고려되어야 할 여러 조건하에서의 실험결과에 대한 분석이 수행되었다. 분석결과, 지배적인 파괴형태는 원추형에 가까운 팽창파괴임을 재차 확인하였으며, 재하면적이 커짐에 따라 극한지지력이 증가하는 현상도 확인하였다. 또한 말뚝의 설치간격이 줄어들수록 극한지지력은 증가하며, 설치위치에 따라 극한지지력이 변화하고, 말뚝의 길이가 극한지지력에 미치는 영향은 미소한 것으로 나타났다.

• 한국공간구조학회논문집
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• 제8권5호
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• pp.59-65
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• 2008

최근, 교량교각과 같은 기둥구조물의 사용성능을 향상시킴과 동시에 복잡한 도심지 내 효율적 공간활용을 위해 콘크리트 충전강관(CFT: concrete-filled steel tube)의 적용이 점차 증가하고 있다. 이러한 기둥구조물의 정확한 설계를 위해서는 재료 및 기하학적 특성에 따른 콘크리트 충전강관 기둥의 거동에 관한 실험적 연구가 요구된다. 이에 본 연구에서는 압축강도실험을 통하여 외경-두께비 (D/t) 및 강재-콘크리트 단면적비 (As/Ac)에 따른 콘크리트 충전강관 기둥의 극한강도 분포특성에 대해 명확히 파악하였다. 또한 콘크리트 배합강도에 따른 콘크리트 충전강관 기둥의 극한강도 분포특성을 실험을 통하여 명확히 파악하였다. 실험결과의 고찰을 통하여 압축하중을 받는 콘크리트 충전강관 기둥의 극한강도는 콘크리트 강도보다 강과의 단면특성에 주로 의존함을 알 수 있었다.