• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.99-105
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• 2000

For multi-body dynamic problems. especially coalescent eigenvalue problems with multiobjective optimization, the design sensitivity analysis is too much complicated mathematically and numerically. Therefore, this article proposes a new technique for structural dynamic modification using a mode modification and homologous structures design method with Genetic Algorithm(GA). In this work, the homologous structure of the resiliently mounted multi-body for marine diesel generator systems is studied and the problem is treated as a combinational optimization problem using the GA. In GA formulation, fitness is defined based on penalty function approach. That include homology, allowable stress and minimum weight of common plate.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.739-753
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• 2014

There have been many packages that can be employed to analyze plane frames. However, because most structural analysis packages suffer from closeness of system, it is very difficult to integrate it with an optimization package. To overcome the difficulty, we proposed a possible alternative, DAMDO, which integrate Design, Analysis, Modeling, Definition, and Optimization phases into an integrative environment. The DAMDO methodology employs neural networks to integrate structural analysis package and optimization package so as not to need directly to integrate these two packages. The key problem of the DAMDO approach is how to generate a set of reasonable random designs in the first phase. According to the characteristics of optimized plane frames, we proposed the ratio variable approach to generate them. The empirical results show that the ratio variable approach can greatly improve the accuracy of the neural networks, and the plane frame optimization problems can be solved by the DAMDO methodology.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.571-575
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• 2008

An engine cradle is a quite important structural assembly for supporting the engine, suspension and steering parts of vehicle and absorbing the vibrations during the drive and the shock in the car crash. Recently, the engine cradle having structural stiffness enough to support the surrounding parts and absorbing the shock of collision has been widely used. The hydroforming technology may cause many advantages to automotive applications in terms of better structural integrity of parts, reduction of production cost, weight reduction, material saving, reduction in the number of joining processes and improvement of reliability. We focus on increasing the durability and the dynamic performance of engine cradle. For realizing this objective, several optimization design techniques such as shape, size, and topology optimization are performed. This optimization scheme based on the sensitivity can provide distinguished performance improvement in using hydroforming.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.203-210
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• 2002

The great advantages on the Genetic Algorithms(GAs) are ease of implementation, and robustness in solving a wide variety of problems, several GAs based optimization models for solving complex structural problems were proposed. However, there are two major disadvantages in GAs. The first disadvantage, implementation of GAs-based optimization is computationally too expensive for practical use in the field of structural optimization, particularly for large-scale problems. The second problem is too difficult to find proper parameter for particular problem. Therefore, in this paper, a Distributed Hybrid Genetic Algorithms(DHGAs) is developed for structural optimization on a cluster of personal computers. The algorithm is applied to the minimum weight design of steel structures.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.45-50
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• 2021

In the recent fourth industrial revolution, the demand for additive processes has emerged rapidly in many mechanical industries, including the aircraft and automobile industries. Additive processes, in contrast to subtractive processes, can be used to produce complex-shaped products, such as three-dimensional cooling systems and aircraft parts that are difficult to produce using conventional production technologies. However, the limitations of additive processes include nonuniform surface quality, which necessitates the use of post-processing techniques such as subtractive methods and grinding. This has led to the need for hybrid machines that combine additive and subtractive processes. A hybrid machine uses additional additive and subtractive modules, so product deformation, for instance, deflection, is likely to occur. Therefore, structural analysis and design optimization of hybrid machines are essential because these defects cause multiple problems, such as reduced workpiece precision during processing. In this study, structural analysis was conducted before the development of an additive/subtractive hybrid processing machine. In addition, structural optimization was performed to improve the stability of the hybrid machine.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1119-1139
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• 2014

A damage-based seismic design procedure for steel frame structures is formulated as an optimization problem, in which minimization of the initial construction cost is treated as the objective of the problem. The performance constraint of the design procedure is to achieve "repairable" damage state for earthquake demands that are less severe than the design ground motions. The Park-Ang damage index is selected as the seismic damage measure for the quantification of structural damage. The charged system search (CSS) algorithm is employed as the optimization algorithm to search the optimum solutions. To improve the time efficiency of the solution algorithm, two simplifying strategies are adopted: first, SDOF idealization of multi-story building structures capable of estimating the actual seismic response in a very short time; second, fitness approximation decreasing the number of fitness function evaluations. The results from a numerical application of the proposed framework for designing a twelve-story 3D steel frame structure demonstrate its efficiency in solving the present optimization problem.

• Composites Research
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• v.35 no.1
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• pp.31-37
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• 2022

In this study, an optimal structural design framework has been developed for the structural design of composite helicopter blades. The optimal design framework is constructed using PSGA (Particle Swarm assisted Genetic Algorithm), which combines the genetic algorithm and particle swarm optimizer. The optimization process consists of a finite element (FE) modeling over the blade section, two-dimensional (2D) cross-sectional FE analysis, and 1D rotating blade analysis. In the design process, the geometric curves and surfaces are formed using the B-spline scheme while discretizing the sections via a FE mesh generation program Gmsh. The blade cross-sections are created in accordance with the design variables when performing the blade structural analysis. The proposed optimization design framework is applied to a modernization of the HART II (Higher-harmonic Aeroacoustics Rotor Test II) blades. It is demonstrated that an improved blade design is reached through the current optimization framework with the satisfaction of all design requirements set for the study.

• Smart Structures and Systems
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• v.16 no.1
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• pp.1-26
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• 2015

Minimizing construction cost and reducing seismic damage are two conflicting objectives in the design of any new structure. In the present work, we try to develop a framework in order to solve the optimum performance-based design problem considering the construction cost and the seismic damage of steel moment-frame structures. The Park-Ang damage index is selected as the seismic damage measure because it is one of the most realistic measures of structural damage. The non-dominated sorting genetic algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. To improve the time efficiency of the proposed framework, three simplifying strategies are adopted: first, simplified nonlinear modeling investigating minimum level of structural modeling sophistication; second, fitness approximation decreasing the number of fitness function evaluations; third, wavelet decomposition of earthquake record decreasing the number of acceleration points involved in time-history loading. The constraints of the optimization problem are considered in accordance with Federal Emergency Management Agency's (FEMA) recommended seismic design specifications. The results from numerical application of the proposed framework demonstrate the efficiency of the framework in solving the present multi-objective optimization problem.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.125-132
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• 2008

Structural optimization is widely adopted in the design of structures with the development of computer aided design and computer technique recently. By applying the structural optimization in the last decades, designers have gained the design scheme of structures more feasibly and easily. In this paper, an optimal design of one 30-story high rise steel structure is performed considering material non-linearity. Based on finite element analysis and adaptive simulated annealing algorithm, the optimal weight of structure is derived under constraints of allowable yield stress, shear stress and serviceability.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.3
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• pp.194-202
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• 2016

This study aims to review a topology optimization based on finite element analysis (FEA) for conceptual design of platform in the 10MW class floating type wave-wind hybrid power generation system (WHPGS). Two topology optimization theories, density method (DM) and homogenization design method (HDM) were used to check which one is more effective for a simplified structural design problem prior to the topology optimization of platform of WHPGS. From the results of the simplified design problem, the HDM was applied to the topology optimization of platform of WHPGS. For the conceptual platform design of WHPGS, FEA model was created and then the structural analysis was performed considering offshore environmental loads at installation site. Hydrodynamics analysis was carried out to calculate pressure on platform and tension forces in mooring lines induced from the offshore environmental loads such as design wave and current. Loading conditions for the structural analysis included the analysis results from the hydrodynamic analysis and the weights of WHPGS. Boundary condition was realized using inertia relief method. The topology optimization of WHPGS platform was performed using the HDM, and then the conceptual arrangement of main structural members was suggested. From the results, it was confirmed that the topology optimization might be a useful tool to design the conceptual arrangement of main structural members for a newly developed offshore structure such as the floating type WHPGS.