• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.100-112
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• 2002

Naval vessels are not regulated by the class rules, but by the special regulations. This study introduces the concept and characteristics of the regulations of U.S. Navy which has been the most reliable standards in design of naval vessels in Korea, and intends to help designers to comprehend the effect of each regulation on design results. Also, an optimum structural design method combined with the structural analysis theory is proposed for naval vessels following the regulations of U.S. Navy and is applied to the design of a naval vessel. After application of the optimum design method, its validity is shown and an optimum design of midship section is obtained. In addition, the optimum spaces or longitudinals and transverse web frames are found and the effect of main design variables can be investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1163-1164
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• 2013

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.48-58
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• 2002

There is a purpose of this study for the proposal of the optimum technique utilized for the vibration design initial step. The stiffened plate structure for the ship hull is made for analysis model. To begin with, dynamic characteristics of stiffened plate structure is analysed using FEM. Main vibrational mode of the structure is decided in the analytical result of FEM. The simplified equation on the natural frequency of the main vibrational mode is induced. Next, sensitivity analysis is carried out using the simplified equation, and rate of change of dynamic characteristics is calculated. Then, amount of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of panel, cross section moment of stiffener and girder become a design variable. The validity of the optimization method using simplified equation is examined. It is shown that the result effective in the optimum modification for natural frequency of the stiffened plate structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.397-401
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• 2008

Knowledge of dynamic characteristics of structural elements often can make difference between success and failure in the design of structure due to resonance effect. In this paper an analytical model of a cantilever beam having midpoint load is considered for structural optimization. This involves creating the geometry which allows parametric study of all design variables. For that purpose optimization of cantilever beam is elaborated in order to find the optimum geometry which minimizes its volume eventually for minimum weight using ANSYS. But such geometry could be obtained by different combinations of width and height, so that it may have the same cross sectional area yet different dynamic behavior. So for optimum safe design, besides minimum volume it should have minimum vibration as well. In order to predict vibration different dynamic analyses are performed simultaneously to solve the eigenvalues problem assuming no damping initially through MATLAB simulations using state space form for modal analysis, which identifies the resonant frequencies and mode shapes belonging to the lowest three modes of vibration. And next by introducing damping effects tip displacement, bending stress and the vertical reaction force at the fixed end is evaluated under some dynamic load of varying frequency, and finally it is discussed how resonance can be avoided for particular design. Investigation of results clearly shows that only structural analysis is not enough to predict the optimum values of dimension for safe design. Potentially this technique will meet maintenance and cost goals of many organizations particularly for the application where dynamic loading is invertible and helps a lot ensuring that the proposed design will be safe for both static and dynamic conditions.

• Structural Monitoring and Maintenance
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• v.1 no.4
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• pp.427-449
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• 2014

A hybrid optimization method for the identification of state-space models is presented in this study. Hybridization is succeeded by combining the advantages of deterministic and stochastic algorithms in a superior scheme that promises faster convergence rate and reliability in the search for the global optimum. The proposed hybrid algorithm is developed by replacing the original stochastic mutation operator of Evolution Strategies (ES) by the Levenberg-Marquardt (LM) quasi-Newton algorithm. This substitution results in a scheme where the entire population cloud is involved in the search for the global optimum, while single individuals are involved in the local search, undertaken by the LM method. The novel hybrid identification framework is assessed through the Monte Carlo analysis of a simulated system and an experimental case study on a shear frame structure. Comparisons to subspace identification, as well as to conventional, self-adaptive ES provide significant indication of superior performance.

• Structural Engineering and Mechanics
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• v.6 no.1
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• pp.31-40
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• 1998

The research and applications of numerical methods of design optimization on structural dynamic behaviors are presented in this paper. The emphasis is focused on the dynamic design optimization of aerospace structures, particularly those composed of composite laminate and sandwich plates. The methods of design modeling, sensitivity analysis on structural dynamic responses, and the optimization solution approaches are presented. The numerical examples of sensitivity analysis and dynamic structural design optimization are given to demonstrate the effectiveness of the numerical methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.21-34
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• 2008

An improved optimum design method for reinforced concrete frames using integrated genetic algorithm(GA) with direct search method is presented. First, various sets of initially assumed sections are generated using GA, and then, for each resultant design member force condition optimum solutions are selected by regression analysis and direct search within pre-determined design section database. In advance, global optimum solutions are selected from accumulated results through several generations. Proposed algorithm makes up for the weak point in standard genetic algorithm(GA), that is, low efficiency in convergence causing the deterioration of quality of final solutions and shows fast convergence together with improved results. Moreover, for the purpose of elevating economic efficiency, optimum design based on the nonlinear structural analysis is performed and therefore makes all members resist against given loading condition with the nearest resisting capacity. The investigation for the effectiveness of the introduced design procedure is conducted through correlation study for example structures.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.474-479
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• 1998

In this paper, the structural behavior of R.C. multi-layered floor structure including foam concrete layer is numerically analyzed. For the analysis, 3D interface element has been implemented to finite element analysis program to consider the interfacial behavior of multi-layered floor structure which consists of rubber layer, foam concrete layer and mortar layer on RC slab. Based on analysis results on multi-layered structure, its structural behavior is analyzed according to geometrical and material properties of foam concrete. Optimum material property of each layer of the floor structure is proposed to get optimum multi-layered concrete structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.51-58
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• 1989

Through a series of analyses of specific structures it is shown that incremental collapse may be the critical design criterion and that shakedown analysis can be used as a design tool. Using shakedown analysis technique, a nonlinear structural optimization program has been developed. This incorporates : (ⅰ) design constraints on elastic stresses and deflections ; (ⅱ) constraints for the prevention of incremental collapse and soft story failure ; and (ⅲ) the constraint on the fundamental period of structure. A five-step design procedure is proposed by using this program to obtain the optimum design that satisfies all the requirements of comprehensive earthquake-resistant design.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.86-93
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• 2010

The tilting index table has attached to CNC machining center with 3axes, it can be improvement of its performance and its machining efficiency. The tilting index table is a key unit in order to manufacture some non-rotational and 3-dimensional parts, using the conventional machining center. In this study, structural analysis is carried out by FEM simulation using the commercial software ANSYS Workbench 11 to develop tilting index table using direct drive motor. The shape of the tilting index table obtained from the optimization was analyzed and compared with the initial model. Also, the initial model was modified based on the optimization model and the result was verified to have the acceptable improvement.