• 한국전산구조공학회논문집
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• 제24권3호
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• pp.237-248
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• 2011

강섬유 보강 콘크리트의 인장연화특성은 구조적 거동에 매우 중요한 역할을 하며, 강섬유 보강 초고성능 콘크리트의 우수한 구조성능을 파악하기 위해서는 인장연화거동의 정밀모델링 및 이를 반영한 수치해석 기법이 필요하다. 따라서, 이 논문에서는 강섬유로 보강된 콘크리트의 부재의 인장연화거동 특성을 고려한 휨 거동을 예측하기 위한 수치해석 기법을 제시하였다. 강섬유 보강 콘크리트의 하중-균열개구변위 실험결과를 반영하여 가상균열모델에 근거한 균열방정식과 역해석 기법에 의해 인장연화모델링을 수행하였다. 또한, 인장연화거동을 반영한 재료모델링을 수행하였다. 제시기법에 의한 초고성능 콘크리트 보의 모멘트-곡률 수치해석 결과를 실험결과와 비교 분석하였으며, 수치해석 결과와 실험결과는 비교적 잘 일치하고 있다. 제안기법에 의해 강섬유 보강 초고강도 콘크리트 보의 휨강도를 정확하게 예측할 수 있다고 판단된다.

• 열처리공학회지
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• 제28권2호
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• pp.68-74
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• 2015

The low cycle fatigue (LCF) and creep-fatigue (hold time tension fatigue, HTTF) tests were performed on the modified 25Cr-13Ni cast stainless steel, which was selected as a candidate material for exhaust manifold in automotive engine. The exhaust manifold is subjected to an environment in which heating and cooling cycle occur due to the running pattern of automotive engine. Several types of fatigue behaviour such as thermal fatigue, thermal mechanical fatigue and creep-fatigue are belong to the main failure mechanisms. High temperature tensile test was firstly carried out to compare the sample with the traditional cast steel for the component. The low cycle fatigue and HTTF tests were carried out under the strain controlled condition with the total strain amplitude from ${\pm}0.6%$ to ${\pm}0.7%$ at $800^{\circ}C$. The hysteresis loops of HTTF tests showed significant stress relaxation during tension hold time. With the increase of tension hold time, the fatigue life was remarkably deceased which caused from the formation of intercrystalline crack by the creep failure mechanism.

• 한국공간구조학회논문집
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• 제14권2호
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• pp.69-78
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• 2014

The purpose of this study is to increase applicability of high strength steel, HSA800 to the structure. Selected study of structure is to consider high strength steel, and following parts, 1) Tensile member with no consider of buckling, 2) Truss existing both tension and compression members with small slenderness ratio. This studied structure is included tension column hang on to the upper bridge truss. The structure element quantity with apply HSA800 instead of SM570 is reduced about 38.9% of tension column and 29.7% of bridge truss. In addition, the number of element's division is reduced about two sections due to reduction of self weight that the crane is able to lift up. This improves to reduce erection sequence and construction period which can save about a month. All connections are reviewed as welding and bolt. Also, the cost of welding is reduced about 41.3% due to apply HSA800. In conclusion, applying HSA800 to the hanging structure aggressively can secure economic and constructability.

• Tribology and Lubricants
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• 제24권6호
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• pp.338-342
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• 2008

Tensile test results using three kinds of steel structure specimens are measured and compared. Slip coefficient between shot blasted steel plates was greater than 0.6. For the case of the plates coated with Super zinc, it revealed that the coefficients were greater than 0.5. On the other hand, Super epoxy coating decreased its slip coefficient less than 0.25. Steel plates coated with Super zinc are proved to be practically applicable to the steel structures with anti-corrosion characteristics and clean surfaces.

• Computers and Concrete
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• 제18권1호
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• pp.139-154
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• 2016

Since the concrete strength around the reinforcement rebar affects the tension stiffening, the tension stiffening effect of ultra high performance concrete on the concrete members reinforced by steel rebar is examined by testing the specimens with circular cross section with the length 850 mm reinforced by a steel rebar at the center of a specimen's cross section in this research. Conducting a tensile test on the specimens, the cracking behavior is evaluated and a curve with an exponential descending branch is obtained to explain the post-cracking zone. In addition, this paper proposes an equation for this branch and parameters of equation is obtained based on the ratio of cover thickness to rebar diameter (c/d) and reinforcement percentage (${\rho}$).

• 한국강구조학회 논문집
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• 제24권5호
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• pp.491-501
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• 2012

현재 강재교각 기초부의 설계에 적용되어지고 있는 형식은 기초 콘크리트 내부에 앵커프레임을 설치하여 교각부와 연결하는 형태로 설계 및 시공을 하고 있다. 이는 복잡한 설계와 시공으로 인하여 기초부의 크기가 커지고, 과대 설계되는 경향이 있다. 본 연구에서는 고성능강을 이용한 교각 기초부의 연결상세와 관련하여 새로운 형상을 제안하기 위하여 기존 설계기준에 의한 시험체와 고장력 앵커를 사용한 새로운 연결형상 시험체 등 총 3개의 시험체를 제작하여 실내 시험을 실시하였다. 이를 통하여 각 시험체의 성능을 비교 분석하여 연결형식에 따른 구조물의 거동특성을 분석하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.74-79
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• 2004

The shape of cold rolled steel sheets is the degree of flatness, and the flatter, the better. Because undesirable strip shapes of cold rolled steel sheets can affect not only visible problem but also automatic working process in customer's lines, the requirement of the customers is more and more stringent. So we usually used the tension leveler to make high quality of strip flatness. For the improvement of the quality of strip flatness, this report developed three-dimensional FEM (Finite Element Method) simulation model, and analysis about the strain and stress distribution of strip in the tension leveling process.

• 소성∙가공
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• 제26권6호
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• pp.333-340
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• 2017

The cyclic hardening behavior of transformation-induced plasticity (TRIP) steels shows tension-compression asymmetry known to be attributed to transformation of retained austenite into martensite during deformation. In this work, YoshidaUemori hardening model was used to represent the asymmetric hardening behavior of TRIP1180 steel. Yoshida-Uemori hardening model parameters were obtained from three sets of data: tension-compression, compression-tension, and a combination of the two. Material models were validated for U-bending and springback.

• Computers and Concrete
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• 제8권4호
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• pp.445-463
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• 2011

In the design of reinforced concrete (RC) beams, apart from providing adequate strength, it is also necessary to provide a minimum deformability even for beams not located in seismic regions. In most RC design codes, this is achieved by restricting the maximum tension steel ratio or neutral axis depth. However, this empirical deemed-to-satisfy method, which was developed based on beams made of normal-strength concrete (NSC) and normal-strength steel (NSS), would not provide a consistent deformability to beams made of high-strength concrete (HSC) and/or high-strength steel (HSS). More critically, HSC beams would have much lower deformability than that provided previously to NSC beams. To ensure that a consistent deformability is provided to all RC beams, it is proposed herein to set an absolute minimum rotation capacity to all RC beams in the design. Based on this requirement, the respective maximum limits of tension steel ratio and neutral axis depth for different concrete and steel yield strengths are derived based on a formula developed by the authors. Finally for incorporation into design codes, simplified guidelines for designing RC beams having the proposed minimum deformability are developed.

• 한국강구조학회 논문집
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• 제26권3호
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• pp.205-217
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• 2014

본 연구에서는 인장 플랜지에 HSB 고성능 강재를 적용한 강합성 복합단면 I-거더의 정모멘트에 대한 휨저항강도 및 연성 요구조건을 검토하였다. AASHTO LRFD 설계기준에서 강합성 거더의 정모멘트에 대한 공칭 휨저항강도 및 연성 요구조건은 소성모멘트와 소성 중립축을 이용하여 규정하고 있으며, 이때 소성모멘트와 소성중립축은 일반 강재에 대하여 유도된 값이다, 하지만 응력-변형률 거동에서 일반강재와 다르게 HSB 고성능 강재의 소성영역은 명확히 정의될 수 없다. 따라서 고성능 강재의 이상화된 응력-변형률 곡선을 통해 고성능 강재의 소성영역을 가정하여 소성모멘트를 정의하였으며, 다양한 치수를 갖는 임의의 단면에 대하여 수행된 수치 해석의 결과를 통해 인장 플랜지에 HSB 고성능 강재를 적용한 강합성 복합단면 I-거더의 연성 요구조건 및 공칭 휨저항강도 산정식을 제안하였다.