• 콘크리트학회지
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• 제7권3호
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• pp.187-198
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• 1995

본 연구는 RC 박스거더교 상부구조의 체계신뢰성 해석과 체계신뢰성에 기초한 내하력 평가를 위하여 실용적이고 실제적인 신뢰성 모델 및 방법을 제안하였다. 시스템으로서 교량의 보유내하력을 정확히 예측한다는 것은, 특히 교량이 높은 여용성을 갖고 있고 열화손상이 심각한 경우에는 더욱 어려운 문제이다. 본 연구는 교량의 체계신뢰성에 상응하는 교량시스템강도로서 정의도리 수 잇는 등가의 시스템가동의 항으로 교량의 보유내하력을 평가하는 새로운 접근방법을 제안하였다. 즉, 이 방법은 체계신뢰성지수의 FOSM(Fdirst Order Second Moment)형태에서 유도된 등가시스템저항강도로서 보다 실제적이고 합리적인 극산시스템저항강도 평가방법이다. 본 연구에서 제안된 RC박스거더교를 위한 강도한계상태모형은 휨 및 전단강도에 기초하였다. 그리고 박스거더 상부구조의 체계신뢰성 문제는 주요 파괴 메카니즘이나 각거더의 한계파괴상태에 기초한 FMA(Failure Mode Approach) 로부터 획득한 직-병렬 혼합모델로서 정식화하였다. 제안된 모형의 신뢰성해석에는 AFOSM(Advanced First Order Second Moment) 과 IST(Importance Sampling Technique) 시뮬레이션 알고리즘을 사용하였다.

• 콘크리트학회논문집
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• 제28권4호
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• pp.463-471
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• 2016

이 연구에서는 롯드 앵커에 강재 링을 추가한 고전단 링앵커의 전단실험을 바탕으로 강도평가 모델을 개발하였다. 고전단 링앵커의 전단강도는 콘크리트 압축강도의 3/4 제곱에 비례하여, 강-콘크리트 합성구조에 사용되는 전단연결재와 유사한 강도 특성을 발현하였다. 콘크리트 압축강도, 측면연단거리, 롯드 묻힘깊이를 고려한 단일 고전단 링앵커 전단강도 평가 모델을 개발하였다. 22개 실험결과와 비교한 결과 [실험값]/[예측값]의 평균이 1.01 변동계수 7.57%로 나타났다. 한면에 4개씩 총 8개의 고전단 링앵커에 대한 Push 실험을 수행하고, 개발된 전단강도 모델과 비교하였다. 다수의 고전단 링앵커 Push 실험 결과, 단일 고전단 링앵커와 유사하게 측면 연단거리 100 mm에서는 쪼갬파괴가 발생되고, 측면 연단거리 150 mm에서는 쪼갬파괴와 지압파괴가 혼합되어 발생하였다. 쪼갬 파괴가 발생된 경우, 가력방향으로 고전단 링앵커 간격이 측면 연단거리의 4배인 400 mm이면 파괴면이 독립적으로 발생되어, 앵커 사이 간섭이 발생되지 않았다. 지압 파괴가 발생된 경우, 지압파괴의 영향 길이가 150 mm 미만으로 가력방향으로 고전단 링앵커의 간격이 200 mm를 확보하면 앵커 사이 상호 간섭이 발생되지 않았다. 다수 고전단 링앵커 Push실험에 의한 전단강도는 이 연구에서 개발된 예측강도의 평균 98%가 발현되었다. 개발된 전단강도 모델이 다수의 고전 단 링앵커의 전단강도 예측에도 활용될 수 있을 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제45권3호
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• pp.323-336
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• 2013

With the ongoing development in the computer science areas of artificial intelligence and computational intelligence, researchers are able to apply them successfully in the construction industry. Given the complexities indeep beam behaviour and the difficulties in accurate evaluation of its deflection, the current study has employed the Adaptive Network-based Fuzzy Inference System (ANFIS) as one of the modelling tools to predict deflection for high strength self compacting concrete (HSSCC) deep beams. In this study, about 3668measured data on eight HSSCC deep beams are considered. Effective input data and the corresponding deflection as output data were recorded at all loading stages up to failure load for all tested deep beams. The results of ANFIS modelling and the classical linear regression were compared and concluded that the ANFIS results are highly accurate, precise and satisfactory.

• Earthquakes and Structures
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• 제9권1호
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• pp.1-27
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• 2015

In this paper Fragility Curves (FCs) relevant to existing RC framed building types representative of the Italian building population designed only to vertical load and regular in-plan have been derived from an extensive campaign of non-linear dynamic analyses. In the generation of the FCs, damage states according to the EMS98 scale have been considered while the intensity measure has been defined by adopting an integral parameter, such as the Housner intensity. FCs have been generated by varying different parameters, including building age, number of storeys, presence and position of infill panels, plan dimensions, external beams stiffness and concrete strength. In order to verify the effectiveness of the damage prediction, comparisons were made between the results obtained from the proposed FCs with those deriving from both prominent fragility studies available in the technical literature and damage distributions observed in past earthquakes. Results show that damage grades obtained by adopting the proposed FCs are generally lower than those provided by the other approaches considered. A comparison with real damage data, shows that the proposed FCs generally estimate more severe damage distributions than those observed in past earthquakes, although they give lower differences with respect to the other approaches.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.501-504
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• 2004

This paper proposes degree of hydration based shrinkage prediction model of 40MPa HPC. This model shows degree of hydration which is defined as the ratio between the hydrated cement mass and the initial mass of cement is very closely related to shrinkage deformation. In this study, degree of hydration was determined by CEMHYD-3D program of NIST. Verification of the predicted degree of hydration is performed by comparison between test results of compressive strength and estimated one by CEMHYD-3D. Proposed model is determined by statistical nonlinear analysis using the program Origin of Origin Lab. Co. To get coefficients of the model, drying shrinkage tests of four specimen series were followed with basic material tests. Testes were performed in constant temperature /humidity chamber, with difference moisture curing ages to know initial curing time effect. Verification with another specimen, collected construction field of FCM bridge, was given in the same condition as pre-tested specimens. Finally, all test results were compared to propose degree of hydration based model and other code models; AASHTO, ACI, CEB-FIP, JSCE, etc.

• Earthquakes and Structures
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• 제8권1호
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• pp.185-204
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• 2015

This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.

• Steel and Composite Structures
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• 제32권1호
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• pp.141-156
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• 2019

This paper presents the flexural behaviour of stainless steel beam-to-tubular column joints with extended endplates subjected to static loading. Moment-rotation relationships were investigated numerically by using Abaqus software with geometric and material nonlinearity considered. The prediction of damages among components was achieved through ductile damage models, and the influence of initial geometric imperfections and residual stresses was evaluated in large fabricated stainless steel joints involving hollow columns and concrete-filled columns. Parametric analysis was subsequently conducted to assess critical factors that could affect the flexural performance significantly in terms of the initial stiffness and moment resistance. A comparison between codes of practice and numerical results was thereafter made, and design recommendations were proposed for further applications. Results suggest that the finite element model can predict the structural behaviour reasonably well with the component damage consistent with test outcomes. Initial geometric imperfections and residual stresses are shown to have little effect on the moment-rotation responses. A series of parameters that can influence the joint behaviour remarkably include the strain-hardening exponents, stainless steel strength, diameter of bolts, thickness of endplates, position of bolts, section of beams and columns. AS/NZS 2327 is more reliable to predict the joint performance regarding the initial stiffness and moment capacity compared to EN 1993-1-8.

• 한국구조물진단유지관리공학회 논문집
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• 제16권4호
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• pp.1-8
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• 2012

본 연구에서는 실물모형 화재시험 후 쉴드터널 라이닝의 손상평가를 수행하였다. 먼저 고온에 노출된 쉴드터널 라이닝의 코어 채취를 통해 잔존압축강도를 측정하고, X선 회절분석 및 열중량 분석으로 수열온도를 예측하였다. 코어 채취에 의해 측정된 잔존 압축강도를 통해 고온에 의한 부재의 강도저하를 평가할 수 있었다. 또한 정확한 수열온도 예측이 이루어진다면 기존의 연구결과를 통해 부재의 잔존압축강도를 추정할 수 있다. X선 회절분석 및 열중량 분석은 약 $450^{\circ}C$의 온도를 기준으로 수열온도 예측이 가능하지만 정량적인 수열온도의 판단에는 한계가 있었다. $400{\sim}600^{\circ}C$의 수열온도범위에서는 기기분석에 의한 평가와 더불어 해석적 기법이 병행된다면 보다 정확한 수열온도 예측이 가능할 것이다.

• Steel and Composite Structures
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• 제46권1호
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• pp.75-92
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• 2023

The novel composite cold-formed steel (CFS)/engineered cementitious composites (ECC) beams have been recently presented. The new composite section exhibited superior structural performance as a flexural member, benefiting from the lightweight thin-walled CFS sections with improved buckling and torsional properties due to the restraints provided by thinlayered ECC. This paper investigated the shear performance of the new composite CFS/ECC section. Twenty-eight simply supported beams, with a shear span-to-depth ratio of 1.0, were assembled back-to-back and tested under a 3-point loading scheme. Bare CFS, composite CFS/ECC utilising ECC with Polyethylene fibres (PE-ECC), composite CFS/MOR, and CFS/HSC utilising high-strength mortar (MOR) and high-strength concrete (HSC) as replacements for PE-ECC were compared. Different failure modes were observed in tests: shear buckling modes in bare CFS sections, contact shear buckling modes in composite CFS/MOR and CFS/HSC sections, and shear yielding or block shear rupture in composite CFS/ECC sections. As a result, composite CFS/ECC sections showed up to 96.0% improvement in shear capacities over bare CFS, 28.0% improvement over composite CFS/MOR and 13.0% over composite CFS/HSC sections, although MOR and HSC were with higher compressive strength than PE-ECC. Finally, shear strength prediction formulae are proposed for the new composite sections after considering the contributions from the CFS and ECC components.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.677-680
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• 2008

최근 초고강도와 고유동성을 가진 고성능 콘크리트에 대한 연구가 활발히 진행되고 있으며, 사용 실적도 점차 증가하는 추세에 있다. 그러나 고성능 콘크리트의 경우에는 수화열 이외에 자기수축으로 인해 균열이 발생하는 경우가 있어 고성능 콘크리트의 균열제어 및 설계에서 자기수축 변형을 반드시 고려해야 한다. 이에 따라, 본 연구에서는 셀룰로스 칩 화이바 및 팽창재를 혼입한 고성능 콘크리트의 자기수축 특성에 대한 실험 연구를 통해 자기수축 예측모델을 제안하고자 한다. 주요 실험변수는 팽창재 및 셀룰로스 칩 혼입률로 설정하였으며 물-시멘트 비는 13%로 고정하였다. 콘크리트의 유동성, 압축강도 및 자기수축 실험을 수행하였으며 팽창재 및 셀룰로스 칩 화이바의 혼입량이 클수록 고성능콘크리트의 자기수축 길이변화율이 감소하는 경향을 보였다.