• Computers and Concrete
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• 제29권 5호
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• Computers and Concrete
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• 제13권2호
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• pp.291-308
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• 2014

A nonlinear, three-dimensional finite element analysis was conducted on six intermediate L-shaped spandrel beams using the "ANSYS Civil FEM" program. The beams were constructed and tested in the laboratory under eccentric concentrated load at mid-span to obtain a combined loading case: torsion, bending, and shear. The reinforcement case parameters were as follows: without reinforcement, with longitudinal reinforcement only, and reinforced with steel bars and stirrups. All beams were tested under two different combined loading conditions: T/V = 545 mm (high eccentricity) and T/V = 145 mm (low eccentricity). The failure of the plain beams was brittle, and the addition of longitudinal steel bars increased beam strength, particularly under low eccentricity. Transverse reinforcement significantly affected the strength at high eccentricities, that is, at high torque. A program can predict accurately the behavior of these beams under different reinforcement cases, as well as under different ratios of combined loadings. The ANSYS model accurately predicted the loads and deflections for various types of reinforcements in spandrel beams, and captured the critical crack regions of these beams.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.583-591
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• 2005

The ship plating is generally subjected to combined in-plane load and lateral pressure loads. In-plane loads include axial load and edge shear, which are mainly induced by overall hull girder bending and torsion of the vessel. Lateral pressure is due to water pressure and cargo. These load components are not always applied simultaneously, but more than one can normally exist and interact. Hence, for more rational and safe design of ship structures, it is of crucial importance to bitter understand the interaction relationship of the buckling and ultimate strength for ship plating under combined loads. Actual ship plates are subjected to relatively small water pressure except for the impact load due to slamming and panting etc. The present paper describes an accurate and fast procedure for analyzing the elastic-plastic large deflection behavior up to the ultimate limit state of ship plates under combined loads. In this paper, the ultimate strength characteristics of plates under axial compressive loads and lateral pressure loads are investigated through ANSYS elastic-plastic large deflection finite element analysis with varying lateral pressure load level.

• Composites Research
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• 제21권1호
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• pp.40-45
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• 2008

자동차용 유압브레이크 고무호스 어셈블리 제품은 자동차에 장착되어 실제로 사용 중에 가압, 굽힘, 비틀림, 열하중 등의 복합적인 스트레스를 받는다. 고무호스의 재질은 EPDM(ethylene-propylene diene monomer)고무와 PVA(polyvinyl acetate)섬유 보강층 그리고 중간고무로 NR(natural rubber)고무가 사용되고 있다. 고무호스 어셈블리 제품의 내구성과 파괴 메커니즘을 조사하기 위해 굽힘과 비틀림의 반복하중 사이클 수가 10만, 20만, 30만, 40만, 최종파열 사이클 수까지 되도록 시험하였다. 유압브레이크 고무호스의 초기크랙 발생을 알아보기 위해 제품 시험편을 다이아몬드 휠커터를 이용하여 수직 절단하여 폴리싱한 후 광학현미경과 주사형 전자현미경(SEM)으로 단면을 관찰하였다. 40만 사이클의 피로하중을 받은 시험편을 보면 외면고무와 PVA섬유 사이의 계면을 따라 길이 1mm의 층간분리가 일어났으며, 이러한 손상은 외면고무의 표피층으로 균열을 진전시켜 고무호스를 최종적으로 찢어지게 하는 것이다.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1461-1469
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• 2011

본 논문은 3 차원 유한요소해석 기법을 이용하여 토오크 시험을 위한 표준시험시편의 각도 및 동심 오열이 시편의 응력과 변형률 변화에 미치는 영향을 분석하였다. 해석 결과의 정량적 비교를 위해 각, 동심 및 복합 축 오열에 대한 평균 굽힘 변형률을 적용하였으며, 시편 형상에 따른 축 오열 영향을 확인하기 위해 환봉형 시편과 튜브형 시편에 대해 각각 유한요소해석을 실시하였다. 해석결과로부터 얻어진 변형률과 응력의 변화로 축 오열의 종류와 방향을 예측하는 일반적인 기준을 제시하였으며, 초기 항복조건을 적용하여 축 오열이 토오크 시편의 초기 항복 모멘트에 미치는 영향을 분석하였다.

• Structural Engineering and Mechanics
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• 제85권1호
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• pp.81-88
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• 2023

This paper begins by analyzing cable vibrations due to external excitations and their effects on the overall dynamic behavior of cable-stayed bridges. It is concluded that if the natural frequency of a cable approaches any natural frequency of the bridge, the cable loses its rigidity and functionality. The results of this analysis explain the phenomenon that occurred on the Dubrovnik Bridge in Croatia during a storm and measures for its retrofit. A field test was conducted before the bridge was opened to traffic. It was concluded: "The Bridge excited unpleasant transverse superstructure vibration with the frequency of approximately 0.470 Hz. Hence, it seems possible that a pair of stays vibrating in phase may excite deck vibrations". Soon after this Bridge opened, a storm dumped heavy damp snow in the area, causing the six longest cable stay pairs of the main span to undergo large-amplitude vibrations, and the superstructure underwent considerable displacements in combined torsion-sway and bending modes. This necessitated rehabilitation measures for the Bridge including devices to suppress the large-amplitude vibrations of cables. The rehabilitation and monitoring of the Bridge are also presented here.

• Steel and Composite Structures
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• 제9권4호
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• pp.367-380
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• 2009

This study focuses on the experimental evaluation of the flexural-torsional performance of high strength thin-walled composite members. A series of tests on composite members with various sectional aspect ratios subjected to eccentric cyclic loads were conducted. Test results show that the composite member's torsional strength could be approximated using a series of linear segments and evaluated using the superposition of the component steel and reinforced concrete responses. It is also validated from the tests that the strength deterioration of members subjected to combined loads is closely related to the aspect ratios of the sections. An interaction expression between the bending and torsion for high strength thin-walled composite members is proposed for engineering practice references.

• 한국농공학회지
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• 제44권3호
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• pp.73-84
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• 2002

Nominal shear strength of concrete beam is the combined strength of concrete shear strength and steel shear strength in current design code. But Torsional moment strength of concrete is neglected in calculation of the nominal torsional moment strength of reinforced concrete beam in current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But the tensile stresses of concrete after cracking are neglected in bending and torsion in design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded to the nominal torsional moment strength of reinforced concrete beam. To verify the validity of the proposed model, the nominal torsional moment strengths according to CEB, two ACI codes(89, 99) and proposed model are compared to experimental torsional strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• Steel and Composite Structures
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• 제35권5호
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• pp.641-657
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• 2020

A unique lightweight string truss deployable bridge assembled by thin-walled fiber reinforced polymer (FRP) and metal profiles was designed for emergency applications. As a new structure, investigations into the static structural performance under the serviceability limit state are desired for examining the structural integrity of the developed bridge when subjected to unsymmetrical loadings characterized by combined torsion and bending. In this study, a full-scale experimental inspection was conducted on a fabricated bridge, and the combined flexural-torsional behavior was examined in terms of displacement and strains. The experimental structure showed favorable strength and rigidity performances to function as deployable bridge under unsymmetrical loading conditions and should be designed in accordance with the stiffness criterion, the same as that under symmetrical loads. In addition, a finite element model (FEM) with a simple modeling process, which considered the multi segments of the FRP members and realistic nodal stiffness of the complex unique hybrid nodal joints, was constructed and compared against experiments, demonstrating good agreement. A FEM-based numerical analysis was thereafter performed to explore the effect of the change in elastic modulus of different FRP elements on the static deformation of the bridge. The results confirmed that the change in elastic modulus of different types of FRP element members caused remarkable differences on the bending and torsional stiffness of the hybrid bridge. The global stiffness of such a unique bridge can be significantly enhanced by redesigning the critical lower string pull bars using designable FRP profiles with high elastic modulus.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2005년도 춘계학술발표회
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• pp.147-154
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• 2005

선체를 구성하는 판부재는 일반적으로 면내하중과 횡하중의 조합하중이 작용하게 된다 면내하중으로서는 주로 전체적인 선체거더의 휨과 비틀림에 의한 압축하중 및 전단하중이 있다. 횡하중은 수압과 화물압력에 의해서 작용하게 된다. 이러한 하중의 요소들은 항상 동시에 작용하는 것이 아니지만 한 개 이상의 하중이 존재하고 상호작용하게 된다. 그러므로, 좀더 합리적이고 안정적인 선박구조의 설계를 위해서는 이러한 조합하중이 선체판에 작용할 경우에 발생하게 되는 좌굴 및 최종강도거동의 상호관계를 좀더 자세히 분석할 필요가 있다. 실제로 선체판은 슬래밍과 팬팅과 같은 충격하중을 제외하고는 상대적으로 적은 수압이 작용하게 된다. 본 연구논문에서는 조합하중을 받는 선체판부재의 거동에 있어서 최종한계상태설계법에 기반을 둔 탄소성대변형 유한요소해석을 수행하였다. 본 연구에서는 압축하중과 횡하중이 판부재에 작용하였을 경우 횡하중의 크기에 따른 영향을 탄소성대변형 유한요소해석(ANSYS)을 수행하여 분석하였다.