• Title/Summary/Keyword: Marine structural element

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A Study for the Minimum Weight Design of a Coastal Fishing Boat (소형 연안 어선의 최소 중량 설계에 관한 연구)

  • Song, Ha-Cheol;Kim, Yong-Sub;Shim, Chun-Sik
    • Journal of Navigation and Port Research
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    • v.32 no.3
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    • pp.223-228
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    • 2008
  • As most of small fishing boats made of FRP have been constructed by experience in Korea, some structural safety problems have been occurred occasionally. To improve the structural strength and reduce the costs for construction and operation, optimum design for small fishing boat was carried out in this study. The weight of fishing boat and the main dimensions of structural members are chosen as objective function and design variables, respectively. By the combination of global and local search methods, a hybrid optimization algorithm was developed to escape the local minima and reduce CPU time in analysis procedure, and finite element analysis was performed to determine the constraint parameters at each iteration step in optimization loop. Optimization results were compared with the real existing fishing boat, and the effects of optimum design were examined from points of view; structural strength, material cost, etc.

Damage-Based Seismic Performance Evaluation of Reinforced Concrete Frames

  • Heo, YeongAe;Kunnath, Sashi K.
    • International Journal of Concrete Structures and Materials
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    • v.7 no.3
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    • pp.175-182
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    • 2013
  • A damage-based approach for the performance-based seismic assessment of reinforced concrete frame structures is proposed. A new methodology for structural damage assessment is developed that utilizes response information at the material level in each section fiber. The concept of the damage evolution is analyzed at the section level and the computed damage is calibrated with observed experimental data. The material level damage parameter is combined at the element, story and structural level through the use of weighting factors. The damage model is used to compare the performance of two typical 12-story frames that have been designed for different seismic requirements. A series of nonlinear time history analyses is carried out to extract demand measures which are then expressed as damage indices using the proposed model. A probabilistic approach is finally used to quantify the expected seismic performance of the building.

A Study on the Determination of Minimum Welding Condition Based on Structural Strength under Launching for Tandem Blocks (선체 블록 진수 시 필요한 최소 용접 구조 강도 평가에 관한 연구)

  • Myung-Su Yi;Joo-Shin Park
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.28 no.7
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    • pp.1267-1273
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    • 2022
  • Although the Korea shipbuilding industry has recently been receiving most of the orders for ships in the world, production processes are being disrupted due to a shortage of manpower at the production site. This is because the workers quit the shipyard as both work and wages were reduced due to the long slump in the shipbuilding industry. The main reason for the increase in orders was the large-scale orders for Qatar LNG carriers, and the situation in which the technical specifications required for ships are becoming more complex is also working to an advantage. Because the contract delivery time is of utmost importance for ships, the dock launch plan is the most important management item among the shipyard's major processes. The structure to be built in the dock may be a hull that has left the design work or a finished vessel, and in some cases, it is often at the level of some blocks of the hull. When launching, the hull is affected by the hogging or sagging moment due to the fluid force, and securing the safety of the structural strength of the block connection is of utmost importance. In a normal process, the connecting member launches after welding has been completed, but in actual shipbuilders, quick decision-making is needed on the conditions for securing structural safety to comply with the docking schedule. In this study, a detailed analysis method and applicability using a bending stress evaluation method and finite element analysis modelling were analyzed to rationally judge the above-mentioned problems from an engineering point of view. The main contents mentioned in the thesis can be used as good examples when conducting similar structural strength evaluations in the future.

A Study on the Shape Optimization and Structural Analysis of the Suction Chamber for an ECO Vacuum Filter System (ECO Vacuum Filter System 용 흡입 챔버의 구조해석 및 형상 최적화에 관한 연구)

  • Lee, Choon-Man;Ha, Jae-Hyeon;Woo, Wan-Sik;Kim, Eun-Jung
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.12
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    • pp.971-977
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    • 2016
  • Recently, the problem of the accumulation of fine sludge from the cutting oil generated during machining processes has become a major threat to the environment. The fine sludge has adverse affects on the human body and the environment, and significantly contributes to marine pollution. However, a microfiltration technique that can process the sludge still needs to be studied and developed on a global scale. Therefore, it is necessary to develop eco-friendly equipment such as an ECO vacuum filter system and eco-friendly technologies for processing cutting oil. In this study, a structural analysis was carried out using a finite element method (FEM). Improved models of the suction chamber for the ECO vacuum filter system were proposed based on the analysis of the displacement and stress of the system. The model with the best result was then optimized using the commercial software, ANSYS. It was confirmed that, in the optimized model, displacement and stress were reduced in comparison with the initial model. Finally, the structural stability of the optimized model was verified through analysis.

A Study on the Structural Stability and Effectiveness of Rope Cutter for Ship's Propeller (선박추진기용 로프절단장치의 구조 안정성 및 효용성에 관한 연구)

  • Kim, Jun-Soo;Seul, Youngyoon;Lee, Du-Yong;Park, Kitae;Kim, Tae Hun;Choi, Jae-Hyuk;Lee, Won-Ju
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.4
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    • pp.550-556
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    • 2021
  • The scissor-type rope cutter is the most widely used amongst all kinds of commercially available rope cutters in Korea. In this study, we performed finite element analysis on the scissor-type rope cutter. We determined the structure of the cutter that would ensure its stable operation in various situations involving rope entanglement, and verified its effectiveness by testing it in the lab and in an actual ship. These investigations revealed that when the propeller shaft was not rotated by rope entanglement, the constant torque generated by the engine resulted in the torsion of the rope cutter and maximum deformation in the lower blade, which was not restricted by finite element analysis. With increasing blade thickness, the maximum values of deformation and equivalent stress decreased, resulting in a rise in the safety factor. At the constant blade thickness, the effect of the torque variations on the maximum equivalent stress and the maximum deformation is independent of the position of the external force of the rope cutter and decreases in direct proportion. The results of this study confirmed that the rope-cutter structure determined by analysis could lead to a hassle-free removal of ropes and fishing nets under all conditions and environments.

Development of Foundation Structure for 8MW Offshore Wind Turbine on Soft Clay Layer (점토층 지반에 설치 가능한 8MW급 해상풍력발전기 하부구조물 개발)

  • Seo, Kwang-Cheol;Choi, Ju-Seok;Park, Joo-Shin
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.2
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    • pp.394-401
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    • 2021
  • The construction of new renewable energy facilities is steadily increasing every year. In particular, the offshore wind farm market, which has abundant development scalability and a high production coefficient, is growing rapidly. The southwest sea has the highest possible offshore wind power potential, and related projects are to be promoted. This study presents a basic design procedure by the EUROCODE and considers structural safety in the development of an effective of shore wind foundation in the clay layer. In a previous study, the wind power generator of 5MW class was the main target, but the 8MW of wind turbine generator, which meets the technical trend of the wind turbine market in the Southwest sea, was selected as the standard model. Furthermore, a foundation that fulfills the geological conditions of the Southwest sea was developed. The structural safety of this foundation was verified using finite element method. Moreover, structural safety was secured by proper reinforcement from the initial design. Based on the results of this study, structural safety check for various types of foundations is possible in the future. Additionally, specialized structural design and evaluation guidance were also established.

Parallelized Topology Design Optimization of the Frame of Human Powered Vessel (인력선 프레임의 병렬화 위상 최적설계)

  • Kim, Hyun-Suk;Lee, Ki-Myung;Kim, Min-Geun;Cho, Seon-Ho
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.1
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    • pp.58-66
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    • 2010
  • Topology design optimization is a method to determine the optimal distribution of material that yields the minimal compliance of structures, satisfying the constraint of allowable material volume. The method is easy to implement and widely used so that it becomes a powerful design tool in various disciplines. In this paper, a large-scale topology design optimization method is developed using the efficient adjoint sensitivity and optimality criteria methods. Parallel computing technique is required for the efficient topology optimization as well as the precise analysis of large-scale problems. Parallelized finite element analysis consists of the domain decomposition and the boundary communication. The preconditioned conjugate gradient method is employed for the analysis of decomposed sub-domains. The developed parallel computing method in topology optimization is utilized to determine the optimal structural layout of human powered vessel.

Estimation of Buckling and Ultimate Strength of a Perforated Plate under Thrust (면내압축하중을 받는 유공판의 좌굴 및 최종강도 평가에 관한 연구)

  • Ko, Jae-Yong;Park, Joo-Shin;Joo, Jong-Gil
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.10 no.2 s.21
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    • pp.41-47
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    • 2004
  • Plate has cutout inner bottom and girder and Door etc. in hull construction absence is used much, and this is strength in case must be situated, but establish in region that high stress interacts sometimes fatally in region that there is no big problem usually by purpose of weight reduction, a person and freight movement, piping etc.. Because cutout‘s existence is positioning in this place, and, elastic bucking strength by load causes large effect in ultimate strength. Therefore, perforated plate elastic bucking strength and ultimate strength is one of important design criteria to decide structural elements size at early structure design step of a ship. Therefore, we need reasonable & reliable design formula for elastic bucking strength of the perforated plate. The author computed numerically ultimate strength change about several aspect ratios, cutout dimension, and plate thickness by using ANSYS Finite element analysis code based on finite element method in this paper.

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Effect of stress-strain curve changing with equal channel angular pressing on ultimate strength of ship hull stiffened panels

  • Sekban, Dursun Murat;Olmez, Hasan
    • Structural Engineering and Mechanics
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    • v.78 no.4
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    • pp.473-484
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    • 2021
  • Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

Plasticity and Fracture Behaviors of Marine Structural Steel, Part IV: Experimental Study on Mechanical Properties at Elevated Temperatures (조선 해양 구조물용 강재의 소성 및 파단 특성 IV: 고온 기계적 물성치에 관한 실험적 연구)

  • Choung, Joon-Mo;Im, Sung-Woo;Park, Ro-Sik
    • Journal of Ocean Engineering and Technology
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    • v.25 no.3
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    • pp.66-72
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    • 2011
  • This is the fourth of a series of companion papers dealing with the mechanical property reductions of various marine structural steels. Even though a reduction of the elastic modulus according to temperature increases has not been obtained from experiments, high temperature experiments from room temperature to $900^{\circ}C$ revealed that initial the yield strength and tensile strength are both seriously degraded. The mechanical properties obtained from high temperature experiments are compared with those from EC3 (Eurocode 3). It is found that the high temperature test results generally comply with the prediction values by EC3. Based on the prediction of EC3, time domain nonlinear finite element analyses were carried out for a blast wall installed on a real FPSO. After applying the reduced mechanical properties, corresponding to $600^{\circ}C$ to the FE model of the blast wall, more than three times the deflections were observed and it was observed that most structural parts experience plastic deformations exceeding the reduced yield strength at the high temperature. It is noted that a protection facility such as PFP (passive fire protection) should be required for structures likely to be directly exposed to fire and explosion accident.