• 대한건축학회논문집:구조계
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• 제35권7호
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• pp.139-146
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• 2019

This study examined the effect of various arrangement methods for forming peripheral closed hoops in the jacket section on the axial behavior of section enlargement strengthening columns. Four types of peripheral closed hoops arranged in the jacket section were prepared as follows: 1) Closed connection of prefabricated bar units (column P); 2) V-clip installation across the overlapped legs of channel-type bars (column V); 3) Use of glass fiber mesh for an alternative of steel bars (column F); and 4) combination of prefabricated bar units and glass fiber mesh (column PF). The V-clip is designed to form the closed hoops in the jacket section using the overlapped channel-type bars, preventing the opening of the channel bar legs. The glass fiber mesh is to examine the feasibility to apply for closed hoops in the jacket section as an alternative for steel bars, considering the easy construction. In the jacket section of all the strengthened columns, V-ties were arranged for supplementary ties, avoiding the interruption of the existing column. The axial stiffness and strength of the strengthened columns were insignificantly affected by the arrangement methods of closed hoops in the jacket section. The axial ductility ratio of the strengthened columns P, V, and PF was enhanced more than twice of that measured in the non-seismic existing column. However, the column F exhibited a lower ductility than the other strengthened columns because of the fracture of the mesh at the ultimate strength of the column. The V-clip approach was favorable to enhance the ductility of the strengthened column, preventing the opening of the legs of channel-type bars.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.53-66
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• 2022

The main objective of the present research was investigating the effects of a floating wave barrier installed in front of an offshore jacket structure on the wave height, base shear, and overturning moment. A jacket model with the height of 4.55 m was fabricated and tested in the 402 m-long wave flume of NIMALA marine laboratory. The jacket was tested at the water depth of 4 m subjected to the random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20 cm, 23 cm, and 28 cm. Two different cross sections with the same area were selected for the wave barrier: square and rhombus. Results showed that the average decrease in the jacket's base shear due to the presence of a floating wave barrier with square and rhombus cross section was 24.67% and 34.29%, respectively. The use of wave barriers with square and rhombus cross sections also resulted in 19.78% and 33.11% decrease in the jacket's overturning moment, respectively. Hence, it can be concluded that a floating wave barrier can significantly reduce the base shear and overturning moment in an offshore jacket structure; and a rhombus cross section is more effective than an equivalent square section.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.56-63
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• 2018

이 연구에서는 연성중심의 보강을 위하여 벽체의 양단부에서 경계요소를 형성하는 내진 보강공법이 적용된 벽체의 반복 휨 거동을 평가하였다. 벽체 경계요소에서 구속효과를 위한 횡보강은 프리스트레스트 와이어로프를 사용하였다. 주요 변수는 제시된 단면 확대공법의 보강 높이로 하였다. 최소 보강 높이는 보강 벽체와 기존 벽체의 모멘트 분포의 비교로부터 결정하였다. 실험결과, 제시된 보강방법은 벽체의 휨 강성 및 연성향상에 매우 효율적이었는데, 최대내력 시 강성과 최대내력의 80%지점에서 산정한 일손상지수는 무보강 벽체에 비해 각각 평균 46%와 210% 증가하였다. 보강높이가 벽체의 일손상지수 증가에 미치는 영향은 보강높이가 $2.0l_w$ 이상일 때 중요하지 않았다. 보강된 벽체의 휨 내력은 ACI 318-14에서 제안하는 등가응력블록을 통한 예측 값보다 22% 이상 높았다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.231-235
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• 1999

Cooling characteristics of cooling jacket for spindle system with built-in motor are studied. for the analysis, three dimensional model for the cooling jacket is built by using finite volume method. The three dimensional model includes the estimation on the amount of heat generation of bearing and built-in motor and the thermal characteristic values such as heat transfer coefficients on the boundary. The temperature distributions and the cooling characteristics are analyzed by using the commercial software FLUENT. Numerical results show that stream-wise cross section area and flow rate are important factors for cooling characteristics of cooling jacket. Cooling performance of cooling jacket is good in condition that stream-wise cross section's horizontal length is close to its vertical one and flow rate is high. This results show that heat transfer is dominated by velocity profile and heat transfer area.

• Steel and Composite Structures
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• 제19권5호
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• pp.1077-1094
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• 2015

This paper presents an experimental study on the effectiveness of simultaneous application of carbon fiber-reinforced polymer (CFRP) and steel jacket in strengthening slender reinforced concrete (RC) column. The columns were 200 mm square cross section with lengths ranging from 1600 to 3000 mm. Ten columns were tested under axial load. The effects of the strengthening technique, slenderness ratio, cross-section area of steel angle and CFRP layer number were examined in terms of axial load-axial strain curve, CFRP strain, steel strip strain and steel angle strain. The experiments indicate that strengthening RC columns with combined CFRP and steel jacket is effective in enhancing the load capacity, ductility and energy dissipation capacity of RC column. Based on the existing models for RC columns strengthened with CFRP and with steel jacket, a design formula considering a slenderness reduction factor is proposed to predict the load capacity of the RC columns strengthened with combined CFRP and steel jacket. The predictions agree well with the experimental results.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.691-696
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• 2000

Cooling characteristics of cooling jacket for spindle system with built-in motor are studied. Three dimensional model was selected for the analysis of the helical-type cooling jacket. This model includes the estimation on the amount of heat generation from bearing and built-in motor and the thermal characteristic values such as heat flux on the boundary. The temperature distributions are analyzed and the cooling by Nusselt number and total heat transfer coefficient. Numerical results show that stream-wise cross section area and flow rate are important factors for cooling characteristics of cooling jacket.

• 한국구조물진단유지관리공학회 논문집
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• 제22권6호
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• pp.81-88
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• 2018

이 연구에서는 실제 단면크기를 갖는 철근 콘크리트 기둥의 내진보강을 위한 단면확대 공법에서 효율적인 띠철근 배근 방법을 평가하였다. 비내진 상세를 갖는 기존 기둥의 단면크기는 $450{\times}450mm$이며, 단면확대 보강기둥의 단면크기는 $750{\times}750mm$이다. 확대 단면에서의 폐쇄형 외부 띠철근 배근을 위해 ㄷ-형 띠철근의 겹칩이음 및 철근 선조립 공법을 제시하였으며, 보조 띠철근으로서 크로스타이 앵커링 시공 및 V-타이를 고려하였다. 실험 결과, 무보강 기둥 및 ㄷ-형 외부 띠철근을 적용한 보강기둥의 압축내력은 ACI 318-14의 공칭내력과 비슷한 수준인 반면 철근 선조립 공법을 적용한 기둥의 압축내력은 ACI 318-14의 공칭내력 대비 1.25배 높았다. 특히 철근 선조립 공법을 적용한 보강 기둥의 압축 연성비는 크기효과에 의한 연성비 저하 가능성에도 불구하고 기존 기둥에 비해 139% 증가하였다. 즉, 제시된 철근 선조립 공법은 단면확대 보강기둥에서 주철근 조기 좌굴방지 및 콘크리트 구속에 효율적인 띠철근 상세로 평가될 수 있었다.

• Structural Engineering and Mechanics
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• 제84권4호
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• pp.517-530
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• 2022

In re-assessing the Jacket-type fixed steel structures, the current standards often allow the simplicity of corrosion sections using local buckling or equivalent section approach to applying empirical formulae of frame stress and resistance analyses. However, those approaches can lead to significant errors for non-uniform corroded frames in a specific area, including force distribution, stress, and allowable strength of the tubular section, compared to the actual cases. This paper investigates a suitable approach to determine the actual stress on non-uniform corroded tubular frames under compression through the non-linear ABAQUS model by considering the effect of large deformation on the frame axis and the frame section. There are 3 scenarios of interest. In the 1st and 2nd scenarios with simple corrosion cases, the stress ratios using the numerical model and theoretical formulae correspond to the calculation of allowable strength reduction ratios in standards. However, scenario 3, which describes non-uniform corroded sections based on survey data, provides considerable differences in results. Therefore, it proves the reliable and effective results when using this method to analyze the resistance of the actual corroded section in the Jacket platforms.

• 한국의류산업학회지
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• 제12권6호
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• pp.789-795
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• 2010

The purpose of this study was to examine the appropriate surplus of clothing for a jacket bodice pattern of middle-aged obese men by using the 3D virtual twin and virtual garment simulation system. The results were as follows ; 1. BMI rate of middle-aged males was 28.13 which was equivalent to mild obesity, whereas WHR(W/H ratio from waist to hips) rate was near 1.00 which was highly dangerous against their obesity. In case of middle-aged obese men, the WHR was significantly higher than the entire middle-aged men's average and the section shape in which their thickness was relatively more than width. 2. As a result of appearances evaluation through virtual garment simulation, the cut-off amount of the side seam and the center back was regulated accordingly. Hereby, the final tolerance range was set up at 21.15 cm at the hips, so that the appearances became better and the bilateral distribution of the cross section and space length was formed symmetrically. Especially in case of increasing the cross amount of hems to produce a natural silhouette of the waist-to-hips parts, the ease of buttocks was judged to be moderate, but it turned out that a wavy cross section was made and the silhouette was not good. Thus it was found to be not good that the ease of the hips became excessively increased in proportion as circumference of waist and belly were increased in obesity. The use of the virtual twin made it impossible to comprehend the appearances and ease correspondent to motions. In order to evaluate wearing fitness, therefore, the system should be improved so as to change arm positions and perform various motions.

• 한국해안해양공학회지
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• 제2권1호
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• pp.43-50
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• 1990

본 연구는 허용응력 설계법에 의한 파랑하중을 받는 스틸자켓의 부재단면 최적화를 다루고 있다. 건설경비의 최적화에 대한 목적함수로서 스틸자켓의 중량을 택하였으며 제약조건은 구조물의 변위와 응력이 허용치 내에 있도록 하였다. 비선형 최적화문제는 수정된 Newton-Raphson법을 이용한 SUMT 방법을 사용하여 해석하였다.