• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.78-86
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• 2005

In this study, cantilever cylindrical shells with edge-stiffeners are analyzed. A versatile 4-node flat shell element which is useful for the analysis of shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. Three models by load conditions are considered. Model A, B and C are loaded by point load at the free edge, line load and external pressure respectively. A various parameter examples are presented to obtain proper stiffened length and stiffened thickness of edge-stiffeners. It is shown that the thickness of shell can be reduced more than 50% for Model A, about $20{\sim}30%$ for Model B by appropriate edge-stiffeners.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1089-1092
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• 2001

In order to measure the vibration of a ribbed clindrical shell, the principle of reciprocity has been implemented. An accelerometer was fixed at the position defined as the excitation point. An impact hammer was used to tap at the response array points (64 points) located along the circumference of the shell. The frequency response function was reciprocally measured at each point in turn. The response data was processed to obtain the frequency/wavenumber spectrum. From the spectrum the characteristics of wave propagation on the ribbed cylindrical shell have been observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.581-586
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• 2018

Cast iron manhole lids cause environmental pollution during the manufacturing process, and the work environment is very poor. In addition, if the height of the manhole cover does not match the height of the road surface, it causes considerable inconvenience and safety problems. This study proposes a height - adjustable steel manhole cover that can replace cast iron manhole covers and easily match the road surface with the upper surface of the manhole cover. Structural analysis was performed to grasp the design variable of the structure of the manhole cover, satisfying the required quality performance. To fabricate a manhole cover that satisfies the required load capacity, the optimal design for the U-shaped reinforcement structure was made. The cylindrical shape of the height adjustment part and the low frame were formed by bending the steel sheet into a circular shape and then welding. Reinforcing bars were also made by bending a steel plate. The height adjustment groove was machined by a CNC milling machine. Four prototypes were fabricated and a load bearing test was carried out, and new manhole cover was made reflecting results of the test. In the load bearing test, there was no breakage of the welded part, and deformation occurred mainly at the contact area between the groove and gusset plate. Deformation of 1 to 2.7mm occurred due to a load of 450kN. On the other hand, after removing the load, there was almost no residual deformation, and the load bearing evaluation was judged to be satisfactory because the manhole cover could be disassembled and reassembled.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.477-485
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• 2012

Geometric configurations such as hull shape, wall thickness, stiffener layout, and type of construction materials are the key factors influencing the structural performance of pressure hulls. Traditional theoretical approach provides quick and acceptable solutions for the design of pressure hulls within specific geometric configuration and material. In this paper, alternative approaches that can be used to obtain optimal geometric shape, wall thickness, construction material configuration and stiffener layout of a pressure hull are presented. CAE(Computer Aided Engineering) based design optimization tools are utilized in order to obtain the required structural responses and optimal design parameters. Optimal elliptical meridional profile is determined for a cylindrical pressure hull design using metamodel-based optimization technique implemented in a fully-integrated parametric modeler-CAE platform in ANSYS. While the optimal composite laminate layup and the design of ring stiffener for a thin-walled pressure hull are obtained using gradient-based optimization method in OptiStruct. It is noted that the proposed alternative approaches are potentially effective for pressure hull design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.106-111
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• 2017

In this study, the stiffness of an LMU (Leg Mating Unit), which is a device required for installing the top side part of an offshore structure, was examined through structural analysis. This unit is mounted on the supporting point of the structure and is used to absorb the shock at installation. It is a cylindrical structure with an empty center. To support the vertical load, elastomeric bearings (EBs) and iron plates are laminated in layers. The stiffness of the EBs is basically influenced by the size of the bearings, but it varies with the number of laminated sheets inside the same sized structure. The relationship between the stiffener and the compressive stiffness is investigated, and its design is suggested. The stiffness of the EBs is analyzed by calculating the reaction force, while controlling the displacement. First, the relationship between the size of the reinforcing plate and the compressive stiffness is considered. Next, the relationship between the number of stacked reinforcing plates and the compression stiffness is considered. Different loads are required for each installed point. The goal is to design the compression stiffness in such a way that the same deformation occurs at each point in the analysis. In this study, ANSYS is used to perform the FE analysis.

• Composites Research
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• v.14 no.3
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• pp.42-50
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• 2001

Modeling of damage initiation in singly oriented ply (SOP) Fiber Metal Laminate (FML) under concentrated loading conditions was studied. The finite element method (FEM) base on the first order shear deformation theory is used for th\ulcorner modeling of damage initiation in SOP FML. The failure indices (FI) of the fiber prepreg and the metal laminate were calculated by using the Tasi-Hill failure criterion and the Miser yield criterion, respectively. To verify the present method, the failure analysis was conducted under uniaxial loading and cylindrical bending, then the analysis under concentrated load was conducted. The results show that the analysis is reasonable. An indentation test was conducted to compare a damage initiation load with a calculated FI. The test was conducted under two side clamped conditions to study the fiber orientation effect. Indentation curve was fitted using the Hertz equation and a damage initiation load is defined that the point which deviate the fitted curve from the real indentation curve. The damage initiation loads were obtained under various fiber orientations and compared with calculated FIs. The experiment was well matched with calculated FI. This results shows that the present method is suitable for the damage initiation modeling of SOP FML.

• Geophysics and Geophysical Exploration
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• v.12 no.2
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• pp.215-220
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• 2009

Cement based mortars are widely used to improve the soft ground of a dam site, highway construction, and karst voids. The mechanical properties of the mortar are well documented in literature, however very limited work is done on their physical properties such as electrical resistivity which is considered as one of the most important physical property known while improving the soft grounds. In this paper, electrical resistivity of the Portland cement mortars is examined by employing the Wenner technique. Cylindrical specimens with various water/cement ratios (w/c) ranges from 0.35, 0.45, 0.50 and 0.65 were cast and tested. The test results showed that the electrical resistivity of the mortar increases with increasing curing time and decreases with increasing water content and w/c. A reasonable, good relation was found between electrical resistivity and compressive strength of mortar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.865-873
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• 2013

This paper proposes a theoretical solution of elastic critical buckling load of infinitely long pipelines with non-uniform thickness under external pressure. The non-uniform cross section of pipelines can be considered as corroded or stiffened pipelines so that this paper can be a fundamental research of pipelines that are essential technology for offshore industries. The theoretical solution of pipelines with non-uniform thickness is derived with an assumption that a cylindrical shell under external pressure can be considered as a simple ring. The eigenfunctions are derived to obtain the critical buckling load. The reduced thickness and the reduced range are considered as variables in parametric analysis. The finite element analysis is performed to verify the theoretical solutions and the results of the analytic method and the finite element method are in good agreement.

• Bulletin of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.3-7
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• 2010

국내 조선소와 학교, 연구소에서 1990년대 중반 이전의 빙해선박에 대한 연구는 거의 이루어지지 않았다고 해도 과언이 아니다. 하지만 2000년대 초반부터 러시아가 St. Petersburg항을 통해 본격적으로 원유를 수출하기 시작하면서 내빙선 시장이 호황을 맞이하게 되었고 빙해선박 특히 내빙선박에 대한 관심이 집중되었다. 당시에 한국의 조선소들은 FMA rule 상의 엔진 출력이 과도한 것을 인지하고, 적정한 엔진 사양을 파악하기 위한 공격적인 연구개발로 ICE Class 1A, 1B, 1C의 선박을 상당히 많이 수주하여 선주에게 인도하였다. 또한 Ice belt의 구조적인 보강을 하기위한 설계와 연구가 활발히 진행되었다. 내빙선에 이어 쇄빙선의 연구에 관심을 집중시킨 선박은 최근 실해역에서 활동 중인 연구 조사선 "아라온"호 이다. 아라온호는 설계와 건조가 국내 조선소에서 이루어졌으며, 학계와 조선소 및 연구소에 쇄빙선에 대한 관심을 불러 일으켰다. 이와 비슷한 시기에 삼성 중공업에서 세계 최대 쇄빙선인 70K shuttle tanker를 수주 및 인도하면서 대형 쇄빙선 시장이 개척되어 국내외 조선소의 큰 관심을 불러일으키고 있다. 쇄빙 기술이 응용된 선박으로 Drill ship과 LNG FPSO등이 수주되어 현재 설계를 진행 중이다. 가장 최근에 현대중공업에서 수주한 원통형 FPSO의 경우 북해 지역에 투입을 목적으로 언론에 발표된 것과는 달리 발주처와 유럽의 관련 연구기관에서는 러시아 유전지역 투입을 염두에 두고 쇄빙관련 연구를 진행한 것으로 파악되고 있다. 본 기고에서는 이러한 빙해선박의 개발 및 건조 사례 현황을 기술하고, 향후 수주가능성이 있는 쇄빙선 분야와 조선소의 대응 전략 등에 대해서 정리해 보고자 한다.

• Composites Research
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• v.20 no.4
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• pp.31-41
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• 2007

Dome shape design methods of Filament Winding (FW) composite pressure vessel, which can suggest various dome contour according to the external loading conditions, were investigated analytically and numerically. The performance indices(PV/W) of the pressure vessels with same cylinder radius and boss opening but different dome shape were evaluated by finite element analysis under the internal pressure loading condition. The analysis results showed that as the dome shape becomes flat, the performance index decreases significantly due to the reduced burst pressure. Especially, for the case of the high value of the parameter ro, the ratio between the radii of the cylinder part and the boss opening, the flat dome is disadvantageous in the aspect of the weight reduction, and additional reinforcing dome design technique should be required to increase the burst pressure. For example, above ro=0.54 condition, the dome shape change according to the loading condition could cause the low burst pressure and increase of composite weight in dome region and is not recommendable except for the special case that maximum inner volume or sufficient space between skirt and dome is the primary design objective. However, at ro=0.35, the dome shape change brings not so significant differences in the performance of FW vessel.