• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.511-516
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• 2008

Recently, many researchers are studying a high-strength concrete, composite materials and composite structures to build structures more economic and stable all over the world. For instance, there is CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure to maximize the efficiency of structure and economic. In this study, linear-elastic behavior analysis of CFTA gider filled with high-strength concrete was performed by using ABAQUS 6.5-1 and also the result was analyzed.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.320-325
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• 2001

In this study, CT specimen were prepared from Pressure Vessel Steel which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ and in the range of stress ratio of 0.05 and 0.3 by means of opening mode displacement. At the constant street ratio, the threshold stress intensity factor range ΔK$_{th}$ in the early stage of fatigue crack growth(Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth(Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm do/dN -ΔK in RegionII, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate do/dN is rapid in proportion to descending temperature in Region IIand the cryogenic-brittleness greatly affect a material with decreasing temperature.e.greatly affect a material with decreasing temperature.

• Steel and Composite Structures
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• 제37권5호
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• pp.503-516
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• 2020

A novel spiral confined angle-steel reinforced concrete (SCARC) column was developed in this study. A total of 16 specimens were prepared and tested (eight of them were tested under axial loading, the other eight were tested under eccentric loading). The failure processes and load-displacement relationships of specimens under axial and eccentric loads were examined, respectively. The load-carrying capacity and ductility were evaluated by parametric analysis. A calculation approach was developed to predict the axial and eccentric load-carrying capacity of these novel columns. Results showed that the spiral reinforcement provided enough confinement in SCARC columns under axial and low eccentric loads, but was not effective in that under high eccentric loads. The axial load-carrying capacity and ductility of SCARC columns were improved significantly due to the satisfactory confinement from spirals. The outer reinforcement and other construction measures were necessary for SCARC columns to prevent premature spalling of the concrete cover. The proposed calculation approach provided a reliable prediction of the load-carrying capacity of SCARC columns.

• Journal of Welding and Joining
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• 제20권4호
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• pp.510-516
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• 2002

Recently the laser welding technology has been applied increasingly for the automotive bodies. But the lap joint laser welding for 3 dimensional automotive body is new while the butt joint laser welding is well known as the tailored blank technology. In this study, the process window was found for the full penetration welding of the lap joint of the 1mm-thick high strength steel sheets. The limit curves and characteristic curves were suggested to define the boundaries and the contour lines in a space of the welding speed and the gap size. The characteristics of the weld sectional geometry were used to determine the limit curves. They are bead width, penetration depth and sectional area. After the observed data was analysed carefully, it was noticed that there was a transition point at which the sectional shape was changed and the bead area jumped as the welding speed was increased. Also a new concept of 'input energy Per volume' was suggested to distinguish the difference at the transition Point. The difference of sectional areas at the transition point can be related to the dynamic keyhole phenomena.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.516-521
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• 2000

Most of studies, using ESPI method, have handled tension, thermal and vibration analysis, and is limited to isotropic materials. However, tension and vibration simultaneously are loaded in real structure. Also, almost study using ESPI method is locally limited to the analysis on the isotropic materials and a few studies on the anisotropic materials have reported. Existing methods, such as the accelerometer method and FEA method, to analyze vibration have some disadvantages. Using the accelerometer method that is generally used to analyze vibration phenomena, it is impossible to analyze vibration on the oscillating body and one can observe no vibration mode shape during experiment. In case of the FEA method, it is difficult to define boundary conditions correctly if the shape of a body tested is complex, and one can just obtain vibration mode shapes on the peak amplitude in each modes. In this study, plane plate of stainless steel(STS304), isotropic material, that is used as structural steel is analyzed about vibration characteristics under tension. Also, in the study of stainless steel, the characteristics of composite material(AS4/PEEK) used as high strength structural material in aircraft is evaluated about vibration under tension, and studies the effect of tension on vibration.

• Steel and Composite Structures
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• 제17권4호
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• pp.497-516
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• 2014

The ultimate carrying capacity of axially loaded welded square box section members made of medium and high strength steels (nominal yield stresses varying from 345 MPa to 460 MPa), with large width-to-thickness ratios ranging from 35 to 70, is analyzed by finite element method (FEM). At the same time, the numerical results are compared with the predicted results using Direct Strength Method (DSM), modified DSM and Effective Yield Strength Method (EYSM). It shows that curve a, rather than curve b recommended in Code for design of steel structures GB50017-2003, should be used to check the local-overall interaction buckling strength of welded square section columns fabricated from medium and high strength steels when using DSM, modified DSM and EYSM. Despite all this, EYSM is conservative. Compared to EYSM and modified DSM, DSM provides a better prediction of the ultimate capacities of welded square box compression members with large width-thickness ratios over a wide range of width-thickness ratios, slenderness ratios and steel grades. However, for high strength steels (nominal yield strength greater than 460 MPa), the numerical and existent experimental results indicate that DSM overestimates the load-carrying capacities of the columns with width-thickness ratio smaller than 45 and slenderness ratio less than 80. Further, for the purpose of making it suitable for a wider scope, DSM has been modified (called proposed modified DSM). The proposed modified DSM is in excellent agreement with the numerical and existing experimental results.

• 터널과지하공간
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• 제10권4호
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• pp.516-525
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• 2000

최근, 도시 재개발과 산업설비 개·보수에 따른 노후화된 콘크리트 및 철근구조물에 대하여 환경 공해가 발생하지 않는 해체 기술 개발에 대한 요구가 급증하고 있다. 본 연구는 철근 구조물의 폭발절단 해체를 위한 성형폭약을 개발하기 위하여 폭발절단 효과에 영향을 주는 요소인 대상 구조물의 재질 및 형상, 두께와 강도 특성, 성형폭약의 형상, 폭약의 종류, 장약량, liner의 종류, stand-off distance, 성형폭약의 폭 및 너비, 기폭방법에 따른 영향과 폭발 절단시 발생되는 폭풍압에 의한 진동 및 소음의 영향 등을 검토함으로 폭발절단 최적조건을 선정하였다. 따라서, 본 연구를 통해 얻어진 폭발절단기술은 강교, 공장, 폐선박 등의 해체에도 적용될 것이다.

• 한국전산구조공학회논문집
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• 제23권5호
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• pp.509-516
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• 2010

본 연구에서는 가새와 강골조를 이용하여 철근콘크리트 모멘트 골조의 내진성능을 보강하는 방법에 대하여 연구하였다. 해석모델은 중력하중에 대해서만 설계된 3층 3경간의 RC 모멘트 골조 건물이다. 먼저 유한요소해석을 이용하여 RC구조물과 가새 접합부의 응력/변형 분포 상태를 파악하고, 접합부의 응력 집중현상을 방지하기 위하여 철골 모멘트골조를 추가하여 보강설계를 수행하였다. 내진보강을 위한 가새는 일반 철골 가새와 비좌굴 가새의 두가지 종류의 가새를 적용하고, 보강 전후 구조물의 강도 및 연성도를 비선형 정적 및 동적해석을 통해 비교하였다. 해석결과에 따르면 추가되는 철골 모멘트골조와 가새를 동시에 사용할 경우 구조물의 강도 및 연성능력의 증가에 큰 효과가 있는 것으로 나타났다. 추가되는 철골 모멘트골조는 단면이 크지 않을 경우 강도의 증가에 큰 영향을 미치지 않는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.513-516
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• 2008

본 연구는 부식생성물의 공극충전에 의한, 부식 반응량 및 이산화탄소의 확산속도 변화를 고려한 철분혼입 콘크리트의 염화물이온침투 예측모델에 관한 연구이다. 본 모델은 염화물이온 침투영역에서 염화물이온과 철이온의 반응 및 염화물이온의 확산에 기초한다. 또한 본 모델은 콘크리트 조직이 부식 생성물로 인해 치밀해져, 콘크리트의 염화물이온 침투저항성이 억제되는 것에 대해서도 해석이 가능하다. 모델에 의한 예측치와 철분을 혼입한 콘크리트에 있어서의 실측값은 잘 일치하였고, 재령이 경과함에 따라 철분무혼입 콘크리트에 비해 염화물이온 침투속도가 상당히 늦어지는 것으로 나타났다. 결론적으로 본 모델은 대기중에 노출된 콘크리트의 물시멘트비 및 철분 혼입 유무와 혼입율에 따른 염화물이온 침투 예측이 가능하였다.

• Journal of Welding and Joining
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• 제35권1호
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• pp.26-33
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• 2017

This study aims to investigate the suitability of requirement for post-weld heat treatment(PWHT) temperature when different P-No. materials are welded, which is defined by ASME Sec. III Code. For SA-516 Gr. 60 and SA-106 Gr. B carbon steels that are typical P-No. 1 material, simulated heat treatment were conducted for 8 h at $610^{\circ}C$, $650^{\circ}C$, $690^{\circ}C$, and $730^{\circ}C$, last two temperature falls in the temperature of PWHT for P-No. 5A low-alloy steels. Tensile and Charpy impact tests were performed for the heat-treated specimens, and then microstructure was analyzed by optical microscopy and scanning electron microscopy with energy-dispersive spectrometry. The Charpy impact properties deteriorated significantly mainly due to a large amount of cementite precipitation when the temperature of simulated heat treatment was $730^{\circ}C$. Therefore, when dissimilar metal welding is carried out for P-No. 1 carbon steel and different P-No. low alloy steel, the PWHT temperature should be carefully selected to avoid significant deterioration of impact properties for P-No. 1 carbon steel.