• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.205-210
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• 2000

An optimum design algorithm of PSC box girder bridges using design sensitivity analysis is proposed in this paper. For the efficiency of the proposed algorithm, approximated reanalysis techniques using design sensitivity analysis are introduced. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses is proposed. A design sensitivity analysis of structural response is executed by automatic differentiation(AD). The efficiency and robustness of the proposed algorithm, compared with conventional algorithm, is successfully demonstrated in the numerical example.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.675-676
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• 2006

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.93-102
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• 2000

Substructuring-based hierarchical approach for design analysis and optimization of structural frames is presented in this study. The conceptual framework of this method is in the hierarchical modeling for design processes as well as structural systems and the methodology combining substructuring analysis and multilevel optimization. Mathematical models for analysis and synthesis are established on the common basis of substructuring systems. Modularized behavioral analysis, design sensitivity analysis and optimization are linked and integrated on the mathematical and structural basis of substructuring. Substructures are coordinated with the active constraints for system level and the weight ratio criteria. Numerical examples for test frames show the validity and effectiveness of the present approach.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.219-231
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• 2014

We develop a preliminary design optimization procedure in this paper regarding the wing planform in a solar-powered high-altitude long-endurance unmanned aerial vehicle. A high-aspect-ratio wing has been widely adopted in this type of a vehicle, due to both the high lift-to-drag ratio and lightweight design. In the preliminary design, its characteristics need to be addressed correctly, and analyzed in an appropriate manner. In this paper, we use the three-dimensional Euler equation to analyze the wing aerodynamics. We also use an advanced structural modeling approach based on a geometrically exact one-dimensional beam analysis. Regarding the structural integrity of the wing, we determine detailed configuration parameters, specifically the taper ratio and the span length. Next, we conduct a multi-objective optimization scheme based on the response surface method, using the present baseline configuration. We consider the structural integrity as one of the constraints. We reduce the wing weight by approximately 25.3 % from that in the baseline configuration, and also decrease the power required approximately 3.4 %. We confirm that the optimized wing has sufficient flutter margin and improved static longitudinal/directional stability characteristics, as compared to those of the baseline configuration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.317-324
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• 2008

Optimum design for general or complex structures are required to the need of many numbers of structural analyses. However, current computational environment with single processor is not capable of generating a high-level efficiency in structural analysis and design process for complex structures. In this paper, a virtual parallel computing system communicated by an internet of personal computers and workstation is constructed. In addition, a routine executing Pro/E, ANSYS and optimization algorithm automatically are adopted in the distributed process technique of sequential approximate optimization for the purpose of enhancing the flexibility of application to general structures. By employing the distributed processing technique during structural analysis using commercial application, total calculation time could be reduced, which will enhance the applicability of the proposed technique to the general complex structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.277-287
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• 2009

Recently, the high-strength steel of 400~600MPa tensile strength is producing in the country. Use of high-strength steel member in the design of high-rise buildings is expected to increase the efficiency of structural design in the aspect of structure material weight and cost, however it has been used only a narrow extent. No efficient design method to use high-strength steel in the design of high-rise buildings has been developed. Therefore, in this study structural cost optimization technique that can minimize the structural material cost of high-rise buildings using high-strength steels is developed. The efficiency of the technique is evaluated by comparing the experience-based design for 6 high-rise building examples. As a result, the proposed techniques can save 7~21% of structural material cost compared with experienced-based design. And also, the rough guideline for effective use of high-strength steels in the structural design of high-rise buildings is introduced on the basis of results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.786-790
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• 2002

In this study, structural optimum design was applied to the girder of magnet over head crane. The optimization was carried out using ANSYS Code for the deadweight of girder, especially focused on the thickness of its upper, lower, side and reinforced plates. The weight could be reduced up to around 15% with constraints of its deformation, stress, natural frequency and buckling strength. The structural safety was also verified by the buckling analysis of its panel structure. It might be thought to be very useful to design the conventional structures for the weight save through the structural optimization. The objective function and restricted function were estimated by the orthogonal array, and the sensitivity analysis of design variable fur that was operated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.786-792
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• 2009

Topology optimization is to find the optimal material distribution of the specified design domain minimizing the objective function while satisfying the design constraints. Since the genetic algorithm (GA) has its advantage of locating global optimum with high probability, it has been applied to the topology optimization. To guarantee the structural connectivity, the concept of compliance pattern is proposed and to improve the convergence rate, small number of population size and variable probability in genetic operators are incorporated into GA. The rank sum weight method is applied to formulate the fitness function consisting of compliance, volume, connectivity and checkerboard pattern. To substantiate the proposed method design examples in the previous works are compared with respect to the number of function evaluation and objective function value. The comparative study shows that the compliance pattern based GA results in the reduction of computational cost to obtain the reasonable structural topology.

• 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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.683-690
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• 2007

Topology optimization techniques have been developed as a very efficient design tool and utilized for design engineering processes in many industrial sections during the past decade. And topology optimization has become the focus into structural optimization design up to now. Recently, thermally actuated compliant mechanisms have a wide range of applications. In this research, the thermo-elastic problem is a coupled problem which has to consider heat transfer analysis and structural analysis. Hence, the thermo-elastic problem has to deal with heat transfer material properties and structural material properties at the same time. The numerical examples are presented. From the results, it was shown that in terms of the displacement after optimization. Moreover, this paper compared thermo-system, elastic-system with thermo-elastic system and was shown a good result of topology optimization while thermo-elastic system was used.