• Composites Research
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• v.25 no.6
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• pp.230-235
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• 2012

This paper presents the vibration characteristics and the optimization using the orthogonal array about applied composite optical structure of an aircraft. To acquire the vibration characteristics for stable line of sight, modal analysis are performed by using multi-body program ADAMS. And to optimize optical structure, for design variables were selected, larger-the-better characteristics were considered using results of S/N ratio and orthogonal array $L_9(3^4)$. When bearing constraints are selected, radial, axial and moment stiffness value are used to analysis for optimization until now. But B.S.R which is non-dimensional parameter is proposed, structures including bearings can be used for optimization. And then having a result of lager-the-better, the optimized values of each design variable were successfully suggested.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.2
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• pp.25-30
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• 2013

In this study a hybrid safety barrier system consisting of steel rail and carbon fiber reinforced polymer (CFRP) post is considered. W hile CFRP post is selected for impact energy reflection due to its high strength, steel rail is selected for impact energy absorption due to its high ductility. A numerical model considering the elastoplastic behavior of steel is formulated to simulate the dynamic responses of the hybrid system subject to an impact load. A hybrid roadside guard rail system of steel rail and CFRP post is proposed and analyzed with a case study. The numerical model for the hybrid roadside guard rail system is used to find optimized design of the proposed hybrid system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.198-201
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• 2002

It has been well-blown that sandwich structures are efficient to resist bending loads by increasing the moment of inertia of the panel. However, the accurate theoretical prediction of failure load and its optimization of sandwich beams for strength under concentrated loads were so complicated. Moreover, the appropriate selection of the variables, such as face thickness, core density and core thickness of the sandwich beam with many theories has continuously researched to satisfy for the given strength to weight structural requirement. There will be interesting to investigate the effect of those variables with its optimization for the load resistance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.197-205
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• 1992

For the optimal design of composite breakwaters, a computer program PROCOBRA is developed using the combined ALM-BFGS algorithm. A model formulation for the section design optimization problem of composite breakwaters is proposed where a concept of subsectional weighting factors is introduced in the objective function. Usability of the program is verified through a numerical example. From the study, it is found that the ALM-BFGS method is reliable and can be effectively applied for the design optimization of coastal structures. Compared with conventional design process, it is proved that the economical design of composite breakwaters is possible.

• Steel and Composite Structures
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• v.14 no.4
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• pp.397-408
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• 2013

This paper deals with multiobjective optimization of symmetrically laminated composite truncated circular conical shells subjected to external uniform pressure load and thermal load. The design objective is the maximization of the weighted sum of the critical buckling load and fundamental frequency. The design variable is the fibre orientations in the layers. The performance index is formulated as the weighted sum of individual objectives in order to obtain optimal solutions of the design problem. The first-order shear deformation theory (FSDT) is used in the mathematical formulation of laminated truncated conical shells. Finally, the effect of different weighting factors, length-to-radius ratio, semi-cone angle and boundary conditions on the optimal design is investigated and the results are compared.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.309-316
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• 1999

Laminated composite plates are very useful in various fields of engineering where high strength-to-weight and stiffness-to-weight ratios are required. Design optimization of composite structures has gained importance in recent years as the engineering applications of fiber reinforced materials have increased and weight savings has become an essential design objective. However, due to the anisotropic material properties of laminated composite structure it is very difficult to analyze and design. In this study, numerical optimization technique together with the finite element method is used to find the optimum design of FRP. Various combination of fiber orientation for the laminate layers are investigated and several local optimum solutions are found.

• Steel and Composite Structures
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• v.25 no.1
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• pp.105-116
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• 2017

This paper presents the dynamic stability study of laminated composite plates with different force combinations and aspect ratios. Optimum non-diverging stacking is obtained for certain loading combination and aspect ratio. In addition, the stability force is maximized for a definite operating frequency. A dynamic version of the principle of virtual work for laminated composites is used to obtain force-frequency relation. Since dynamic stiffness governs the divergence or flutter, an efficient optimization method is necessary for the response functional and the relevant constraints. In this way, a model based on the ant colony optimization (ACO) algorithm is proposed to search for the proper stacking. The ACO algorithm is used since it treats with large number of dynamic stability parameters. Governing equations are formulated using classic laminate theory (CLT) and von-Karman plate technique. Load-frequency relations are explicitly obtained for fundamental and secondary flutter modes of simply supported composite plate with arbitrary aspect ratio, stacking and boundary load, which are used in optimization process. Obtained results are compared with the finite element method results for validity and accuracy convince. Results revealed that the optimum stacking with stable dynamic response and maximum critical load is in angle-ply mode with almost near-unidirectional fiber orientations for fundamental flutter mode. In addition, short plates behave better than long plates in combined axial-shear load case regarding stable oscillation. The interaction of uniaxial and shear forces intensifies the instability in long plates than short ones which needs low-angle layup orientations to provide required dynamic stiffness. However, a combination of angle-ply and cross-ply stacking with a near-square aspect ratio is appropriate for the composite plate regarding secondary flutter mode.

• Steel and Composite Structures
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• v.21 no.3
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• pp.501-515
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• 2016

Seismic analysis for steel frame structure with brace configuration using topology optimization based on truss-like material model is studied. The initial design domain for topology optimization is determined according to original steel frame structure and filled with truss-like members. Hence the initial truss-like continuum is established. The densities and orientation of truss-like members at any point are taken as design variables in finite element analysis. The topology optimization problem of least-weight truss-like continuum with stress constraints is solved. The orientations and densities of members in truss-like continuum are optimized and updated by fully-stressed criterion in every iteration. The optimized truss-like continuum is founded after finite element analysis is finished. The optimal bracing system is established based on optimized truss-like continuum without numerical instability. Seismic performance for steel frame structures is derived using dynamic time-history analysis. A numerical example shows the advantage for frame structures with brace configuration using topology optimization in seismic performance.

• Steel and Composite Structures
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• v.47 no.6
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• pp.759-779
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• 2023

The paper proposes two hybrid metaheuristic optimization and artificial neural network (ANN) methods for the close prediction of the ultimate axial compressive capacity of concentrically loaded concrete filled double skin steel tube (CFDST) columns. Two metaheuristic optimization, namely genetic algorithm (GA) and particle swarm optimization (PSO), approaches enable the dynamic training architecture underlying an ANN model by optimizing the number and sizes of hidden layers as well as the weights and biases of the neurons, simultaneously. The former is termed as GA-ANN, and the latter as PSO-ANN. These techniques utilize the gradient-based optimization with Bayesian regularization that enhances the optimization process. The proposed GA-ANN and PSO-ANN methods construct the predictive ANNs from 125 available experimental datasets and present the superior performance over standard ANNs. Both the hybrid GA-ANN and PSO-ANN methods are encoded within a user-friendly graphical interface that can reliably map out the accurate ultimate axial compressive capacity of CFDST columns with various geometry and material parameters.

• Steel and Composite Structures
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• v.44 no.5
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• pp.603-617
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• 2022

Structural design, in general, is developed through trial and error technique which is guided by standards criteria and based on the intuition and experience of the engineer, a context that leads to structural over-dimensioning, with uneconomic solutions. Aiming to find the optimal design, structural optimization methods have been developed to find a balance between cost, structural safety, and material performance. These methods have become a great opportunity in the steel structural engineering domain since they have as their main purpose is weight minimization, a factor directly correlated to the real cost of the structure. Assuming an objective function of minimum weight with stress and displacement constraints provided by Brazilian standards, the present research proposes the sizing optimization and combined approach of sizing and shape optimization, through a software developed to implement the Simulated Annealing metaheuristic algorithm. Therefore, two steel plane frame layouts, each admitting four typical truss geometries, were proposed in order to expose the difference between the optimal solutions. The assessment of the optimal solutions indicates a notable weight reduction, especially in sizing and shape optimization combination, in which the quantity of design variables is increased along with the search space, improving the efficiency of the optimal solutions achieved.