• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.101-109
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• 2019

The bucket platform is a new structure suitable for construction of offshore bridge foundations and providing the temporary support for equipments and labour. The platform can be subjected to moment loading due to the eccentric loading or the horizontal load by wave and wind. Therefore, a three dimensional finite element analysis was performed to evaluate the moment bearing capacity of the bucket platform, varying soil density, the diameter and embedment depth of the bucket. The numerical modeling was verified and compared with the moment-rotation curve from a field loading test. The uniform sandy ground was assumed and the moment load was applied at the top plate of the platform, increasing bucket rotation. The moment-rotation relations were analyzed to determine the moment capacity, which was influenced by the embedment depth and diameter of the bucket. Finally, a preliminary design equation was suggested to estimate the moment bearing capacity.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.56-64
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• 2020

A wind tunnel test of 29.7% scaled model of NASA Common Research Model was performed in small low speed wind tunnel. The wind tunnel model was fabricated in Aluminium in consultation with NASA Langley Research Center and AIAA Drag Prediction Workshop committee members. The static aerodynamic forces and moments were measured at a relatively low Reynolds number of 0.3 × 10⁶ due to tunnel capability limitations. Pitching moment of three types of model support(Fin sting, Blade sting and Belly sting) were compared. The pitching moment for corrected Belly sting and Fin sting were similar. The result of pitching moment for Blade sting was very small.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.1048-1051
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• 2011

이 논문은 뇌졸중 환자를 대상으로 하여 불안정한 지지면에서의 균형 훈련이 안정 지지면에서의 균형 훈련과 비교하였을 때 균형 능력 향상에 어떠한 영향을 주는지 알아보고자 한다. 연구 대상자는 뇌졸중 환자 30명으로 안정지지면 운동군과 불안정 지지면 운동군으로 분류하여 주 3회 6주동안 실시하였다. 균형능력의 측정은 Good balance system를 사용하였다. 안정지지면 운동군에서는 속도모멘트만 감소하였고, 불안정 지지면 운동군에서는 내외측, 전후방, 속도모멘트에서 감소하여서, 안정 지지면 운동군보다 불안정 지지면 운동군에서의 운동이 균형 훈련이 좋은 것으로 나타났다. 눈을 감고 있을때는 눈을 뜨고 있을 때보다 안정 지지면과 불안정 지지면에서의 균형정도는 감소하는 것으로 나타났다. 따라서, 안정지지면에서의 균형훈련보다 불안정 지지면에서의 훈련이 더 효과가 있는 것으로 나타났다.

• Journal of Korean Society of Steel Construction
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• v.23 no.5
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• pp.547-555
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• 2011

An unstiffened top and seat angle connection is a type of partially restrained connection that is suitable for low- and medium-rise steel buildings. The plastic moment resisting capacity of such connection is needed in practical design, in addition to the accurate prediction of the initial rotational stiffness. Therefore, most of the studies conducted for the mentioned connections were performed to predict the initial stiffness and the plastic moment resisting capacity with varying geometric properties. The main parameters of such experimental tests were the thickness and high-strength bolt gauge distance of AISC LRFD-type A top and seat angle connections. Based on the test results, the analytical model was also proposed in this study. The applicability of the proposed model was verified by comparing the test results from this study with those of other studies.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.47-59
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• 2016

Rocking behavior of shallow foundation reduces the superstructure load during earthquake. However, because of deficiency of understanding of rocking mechanism and soil permanent deformation, it has not been applied to real construction. In this study, slow cyclic tests were conducted for embedded shallow foundations with various slenderness ratio via centrifuge tests. From the variation of earth pressure 'soil rounding surface' phenomenon which makes maximum overturning moment equal to ultimate moment capacity was observed. Rocking and sliding behavior mechanism was evaluated. Also, nonlinear behavior and energy dissipation increase as rotation angle increases. And ultimate moment capacity of embedded foundation is larger than that of surface foundation. Finally, adequate ultimate moment capacity can be suggested for seismic design through this study.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.3
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• pp.76-88
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• 2024

A significant cause of fall or overturning accidents in the construction industry, including landscaping construction and management, is work at heights using portable ladders. Portable ladders are classified as A-type or triangular support ladders depending on the number of supporting leg and support conditions. The tripod mobile ladder, which supports itself with only three supporting legs, is unstable and more prone to overturning compared to the A type ladders. Therefore, using the specifications of the tripod mobile ladder and the stability regulations of EN131-Part 7, overturning and resistance moment calculation formulas were derived for all directions in which overturning could occur. The moments calculated using these equations, and the overturning stability in each direction were evaluated. According to the calculation results, although there are differences depending on the direction, most are unstable for overturning at 8 or more steps. Based on these results, this study proposed measures to increase the moment of resistance by changing the weight, depth, and width, and using outriggers to ensure stability against the overturning of ladder. However, when changing the specifications of these measures, the size increases are excessive and the applicability is insufficient. On the other hand, outriggers are an applicable measure as they can ensure stability against overturning with only a minimum expansion length.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.105-111
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• 2012

Bucket foundations, which are used in the foundations of offshore wind turbines, should be able to withstand large amounts of horizontal and moment loads. Tripod bucket foundation, which combines three single buckets, has been used to increase horizontal and moment capacities. This study performed numerical analysis using ABAQUS (2010), to analyze the group effect and the bearing capacity of a tripod bucket in clay. Parametric studies were performed varying the bucket spacing ratio S/D (S=spacing between the centers of the bucket and the tower; D=diameter of the bucket) and depth ratio L/D (L=embedded length of skirt). The applied constitutive models were a linear elastic perfectly plastic model with Tresca yield criteria for normally consolidated clay and an elastic model for buckets. Loading in the vertical, horizontal, and moment directions was simulated with an increase in each movement at a reference point. The bearing behavior and the capacities of a single and a tripod bucket were compared. Capacity evaluation method of the tripod bucket was suggested using the capacity of a single bucket.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.17-24
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• 1992

It would be much effective that single column type pier is used in concrete slab bridges rather than ${\Pi}$ or gravity type pire is used. To determine the longitudinal benging moment in concrete slab bridges supported by single column type piers, the concept of effective width is applied. By elastic plate theory cooperated with finite element method, the distribution of the longitudinal moment of the slab supported by single column type piers is studied. The main variables are span, width. thickness of the slab, and column section size. The analytical results obtained are summarized and analysed to evaluate the maximum longitudinal negative moment, then a simplified method for calculating the longitudinal moment is proposed.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.155-155
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• 2011

일반적으로 I형 보에 횡하중이 작용하는 경우, 횡 변위와 함께 회전을 동반하는 횡-비틀림 좌굴(Lateral-Torsional Buckling)이 발생하게 된다. 이러한 I형 보의 탄성 및 비탄성 횡-비틀림 좌굴에 대한 해석적 이론적 연구는 이미 많은 연구자들에 의해 수행되었다(Timoshenko 등, 1961; Galambos, 1963; Lindner, 1974; Trahair, 1993). I형 보의 비지지 길이 내 하중이 작용할 때 모멘트 구배계수(Cb)는 하중이 부재 단면에 작용하는 위치에 따라 달라지게 되는데 이를 하중고 효과(Load Height Effects)라고 한다. 탄성 영역 내 비지지길이가 존재하는 I형 보의 하중고 효과를 고려한 모멘트 구배계수 제안식은 Nethercot & Rockey(1971)에 의해 연구된 바 있다. 또한 Helwig 등(1997)은 Nethercot & Rockey(1971)의 제안식을 간략화 하여 탄성 영역 내 비지지길이가 존재하는 I형 보의 하중고 효과를 고려한 모멘트 구배계수식을 제안하였다. 그러나 현재까지 진행 된 하중고 효과에 대한 연구는 탄성 영역 내 비지지 길이가 존재하는 I형 보에 대한 제안식이며 현재까지 비탄성 영역 내 비지지 길이를 갖는 I형 보의 하중고 효과에 대한 연구는 진행된 바 없다. 본 연구는 비탄성 영역 내 비지지 길이가 존재하는 I형 보의 하중고 효과를 고려한 비탄성 횡-비틀림 좌굴강도에 대한 연구를 수행하였다. 하중조건으로는 집중하중 과 등분포 하중을 적용시켰으며, 비선형 횡-비틀림 좌굴 해석을 위해 잔류응력 및 초기변형을 고려하였다. Pi와 Trahair(1995)이 고려한 단순직선분포를 잔류응력으로 가정하였으며, 국내 I형강 표준 치수 허용치(현대제철, 2006)에 근거하여 부재 길이의 0.1%를 초기 최대 횡 변위로 적용하여 초기제작오차로 고려하였다. 유한요소해석결과를 바탕으로 Nethercot & Rockey(1971)와 Helwig 등(1997)의 연구내용을 바탕으로 범용구조해석 프로그램(ABAQUS, 2007)을 이용하여 비탄성 영역 내 존재하는 I형보의 횡-비틀림 좌굴강도를 산정하였다. 유한요소해석결과를 바탕으로 Nethercot & Rockey(1971)및 Helwig 등(1997)의 모멘트구배계수 제안식과 비교 분석 하였고 회기분석프로그램 MINITAB(2006)을 이용하여 비탄성 영역 내 비지지길이가 존재하는 I형보의 하중고 효과를 고려한 모멘트구배계수식을 개발 제안하였다. 본 연구에서 개발된 제안식은 경제적이고 합리적인 휨부재 강도평가에 적극 활용될 수 있으며, 비탄성 영역내 I형보의 횡-비틀림 좌굴강도 및 휨강도 연구에 널리 활용될 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.165-172
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• 2002

Generally, the steel rigid frame has been analyzed using finite element analysis tools. While many efforts have been poured into the understanding and accurate prediction for the nonlinear behavior of the columns and beam-columns connections, the base of the columns are modeled as simply hinged or fixed. However, the base of the steel columns practically is neither fixed not hinged. It behaves as semi-rigid. In this paper, the supports of the columns we modeled as semi-rigid and the importance of such approach in moment-resisting columns is evaluated. Two typical buildings designed by the US specification are modeled and analyzed by the finite element based on stiffness method and flexibility method. The column bases of three-story buildings are modeled as rotational springs with a varying degree of stiffness and strength that simulates the semi-rigidity of the base. Depending on the degree of stiffness and strength, the semi-rigidity varies from the hinged to the fixed. Buildings with semi-rigid column bases behaves similarly to the building with fixed bases. It has been numerically observed through the pushover and nonlinear time history analyses that the decrease of the stiffness of the column base induces the rotational demand on the int air beams. an increase of rotation demands on the first store connections and lead to a soft-story mechanists Due often to the construction and environmental effects, undesired reduction of column base stiffness may cause an increase of rotation demands on the first store connections and lead to a soft-story mechanism.