• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1279-1288
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• 2023

Recently, domestic leisure boats have been actively researching eco-friendly product development to enter the global market. Since the hulls of existing leisure boats are mainly made of fiber reinforced plastic (FRP) or aluminum, design techniques for securing structural safety by applying related materials have been mainly studied. In this study, an initial structural design safety assessment of a trimaran pontoon leisure boat with a modular hull structure and eco-friendly high-density polyethylene (HDPE) material was conducted, and sensitivity evaluation and optimization analysis for lightweight design were performed. The initial structural design safety assessment was carried out by creating a finite element analysis model and applying the loading conditions specified in the ship classification regulation to check whether the specified allowable stresses are satisfied. For the sensitivity evaluation, the influence of stress and weight of each hull structural member was evaluated using the orthogonal array design of experiments method, and an approximate model based on the response surface method was generated using the results of the design of experiments. The optimization analysis set the thickness of the hull structural members as the design variable and considered the optimal design formulation to minimize the weight while satisfying the allowable stress. The algorithm of the optimization analysis applied the Gradient-population Based Optimizer (GBO) to improve the accuracy of the optimal solution convergence while reducing the numerical cost. Through this study, the optimal design of a newly developed eco-friendly trimaran pontoon leisure boat with a weight reduction of 10% was presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.340-350
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• 2006

This paper is concerned with a practical guide for the ultimate longitudinal strength assessments of ships' hull structure. Rigorous non-linear structural analysis for three tanker models has been carried out to examine the ultimate strength behavior. Formula of estimating the ultimate longitudinal strength has been proposed which is modified with the results of non-linear finite element analysis of hull girders. Computational reliability and accuracy of the large-scale non-linear finite element analysis and the proposed simplified formula are verified through comparing their results with that of 1/3 scale frigate model test and DNVs program. Additionally, the ultimate longitudinal strength for ten tanker models is compared with those by the method specified in the 2nd Draft of common structural rule for tankers, which is being developed by IACS.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1041-1063
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• 2014

Some results on the hydroelasticity of ultra large container ships related to the beam structural model and restoring stiffness achieved within EU FP7 Project TULCS are summarized. An advanced thin-walled girder theory based on the modified Timoshenko beam theory for flexural vibrations with analogical extension to the torsional problem, is used for formulation of the beam finite element for analysis of coupled horizontal and torsional ship hull vibrations. Special attention is paid to the contribution of transverse bulkheads to the open hull stiffness, as well as to the reduced stiffness of the relatively short engine room structure. In addition two definitions of the restoring stiffness are considered: consistent one, which includes hydrostatic and gravity properties, and unified one with geometric stiffness as structural contribution via calm water stress field. Both formulations are worked out by employing the finite element concept. Complete hydroelastic response of a ULCS is performed by coupling 1D structural model and 3D hydrodynamic model as well as for 3D structural and 3D hydrodynamic model. Also, fatigue of structural elements exposed to high stress concentration is considered.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.3
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• pp.187-199
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• 2019

In the case of gas carriers and oil tankers, pipes are installed on the upper deck as a moving passage to load LPG, LNG, crude oil, etc. Pipes used for loading or unloading liquid cargo in cargo holds are connected to the hull through support structures. However, many cases of hull damage have been reported where the various equipment and support structures are installed on the upper deck. It is assumed that not only the structural discontinuity where the hull and the pipe support structure meet, but also action due to the pipe loads and the hull girder bending moment are simultaneously affected. This paper deals with the design and strength evaluation of the support structure of pipes and cables installed on the upper deck of commercial ships and offshore structures. For these supporting structures, design conditions and working loads were defined. The design procedure was established through the structure analysis on the method of determining the member dimensions. A series of finite element analysis was performed on the factors to be considered in the design and the effects were discussed. The accuracy and design periods of the strength evaluation was improved and reduced by application of the automation program in the finite element analysis. It is also expected that the design reliability of the shipyard is improved.

• Journal of Ocean Engineering and Technology
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• v.31 no.5
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• pp.357-363
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• 2017

The sloshing pressure acting on a membrane-type LNG CCS is a typical irregular impact load, and the structural response of a tank system induced by sloshing also shows very complex behavior, including fluid structure interaction. Therefore, it is not easy to accurately estimate the sloshing impact pressures and resulting structural response. Moreover, a huge time consuming process to deal with the enormous pressure data obtained during a model tank test and the following structural analysis would be inevitable. To reduce the computation time for structural analysis, in this study, a rational structural modeling strategy was considered, and a simplified scheme to analyze the dynamic structural responses of an LNG CCS was introduced, which was based on the concept of the linear combination of the triangular response functions obtained by a transient response analysis of structures under unit triangular impact pressure. A structural analysis of a real Mark III membrane type insulation system under the sloshing impact pressure time histories obtained by model tests was performed using the various proposed structural models and simplified analysis scheme. The results were investigated in detail, including the elastic support effects of the hull structure.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.5
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• pp.378-386
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• 2017

In this paper, a method is presented for the optimal design of submarine pressure hull structures by taking advantage of genetic algorithm techniques. The objective functions and design constraints in the process of structural optimization are based on the ultimate limit states of hull structures. One of the benefits associated with the utilization of genetic algorithm is that the optimization process can be completed within short generations of design variables for the pressure hull structure model. Applied examples confirm that the proposed method is useful for the optimal design of submarine pressure hull structures. Details of the design procedure with applied examples are documented. The conclusions and insights obtained from the study are summarized.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1408-1415
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• 2005

Active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuator is performed. Finite element modeling is used to obtain governing equations of motion and boundary effects of end-capped smart hull structure. Equivalent interdigitated electrode model is developed to obtain piezoelectric couplings of MFC actuator. Modal analysis is conducted to investigate the dynamic characteristics of the hull structure, and compared to the results of experimental investigation. MFC actuators are attached where the maximum control performance can be obtained. Active controller based on Linear Quadratic Gaussian (LQG) theory is designed to suppress vibration of smart hull structure. It is observed that closed loop damping can be improved with suitable weighting factors in the developed LQG controller and structural vibration is controlled effectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.217-222
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• 2005

Active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuator is performed. Finite element modeling is used to obtain governing equations of motion and boundary effects of end-capped smart hull structure. Equivalent interdigitated electrode model is developed to obtain piezoelectric couplings of MFC actuator. Modal analysis is conducted to investigate the dynamic characteristics of the hull structure, and compared to the results of experimental investigation. MFC actuators are attached where the maximum control performance can be obtained. Active controller based on Linear Quadratic Gaussian (LQG) theory is designed to suppress vibration of smart hull structure. It is observed that closed loop damping can be improved with suitable weighting factors in the developed LQG controller and structural vibration is controlled effectively.

• Journal of Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.82-87
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• 2006

An approach to model a high-speed monohull vessel is introduced. The high-speed monohull form belonging to the category of multihull is drawing new attention, due to the rapidly growing trend of fast passenger ships and military purpose. Multihull forms are much thinner in their overall shape, compared to those of the conventional commercial vessels. Moreover, the parent hull forms are not readily obtainable when a new design is intended, which makes it hard to perform various technical calculations in terms of hull optimization, hydrodynamic computation, structural design, and so forth. In this paper, a parametric technique is used to design a high-speed hull form. To model a hull form, NURBS (Non Uniform Rational B-Spline) representation is used. The goal of research is to provide a fast and convenient tool to design an initial hull form with fewer parameters available in the early design stage. The technique employed in this paper will be applied to the design of multihull forms, such as catamaran, trimaran, and semi-swath.