• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.33 no.4
• /
• pp.334-345
• /
• 1997

Reliability-based design approaches are needed for cylindrical shell structure whose design and operational experiences are few and which are subjected to external loads of random loads. In designing new type of structure, it is very difficult to evaluate the safety factors due to lack of previous design data and operational experience. To solve the above mentioned problem, much attention is being focussed on rational reliability based design approaches. This paper deals with weight-optional reliability-based design of cylindrical shell structure subjected to structural reliability constraints taking into account of the effect of local buckling and interactive behavior between local and global buckling. Present mentioned is compared with the exiting optional design method based only on safety factors. Numerical simulation reveals that the present method leads to lighter structure (4% reduction in weight compared to the existing optimal design) with the same reliability index. For larger structures with more number of structural members and possible failure modes, the present W0RBD procedure will be an efficient tool in designing cost-effective rationalized economic design.

• Smart Structures and Systems
• /
• v.19 no.6
• /
• pp.665-678
• /
• 2017

In this paper the tuned mass-damper-inerter (TMDI) is considered for passive vibration control and energy harvesting in harmonically excited structures. The TMDI couples the classical tuned mass-damper (TMD) with a grounded inerter: a two-terminal linear device resisting the relative acceleration of its terminals by a constant of proportionality termed inertance. In this manner, the TMD is endowed with additional inertia, beyond the one offered by the attached mass, without any substantial increase to the overall weight. Closed-form analytical expressions for optimal TMDI parameters, stiffness and damping, given attached mass and inertance are derived by application of Den Hartog's tuning approach to suppress the response amplitude of force and base-acceleration excited single-degree-of-freedom structures. It is analytically shown that the TMDI is more effective from a same mass/weight TMD to suppress vibrations close to the natural frequency of the uncontrolled structure, while it is more robust to detuning effects. Moreover, it is shown that the mass amplification effect of the inerter achieves significant weight reduction for a target/predefined level of vibration suppression in a performance-based oriented design approach compared to the classical TMD. Lastly, the potential of using the TMDI for energy harvesting is explored by substituting the dissipative damper with an electromagnetic motor and assuming that the inertance can vary through the use of a flywheel-based inerter device. It is analytically shown that by reducing the inertance, treated as a mass/inertia-related design parameter not considered in conventional TMD-based energy harvesters, the available power for electric generation increases for fixed attached mass/weight, electromechanical damping, and stiffness properties.

• International Journal of Automotive Technology
• /
• v.8 no.1
• /
• pp.93-102
• /
• 2007

The frontal crash optimization of an engine room member using the response surface method was studied. The engine room member is composed of the front side member and the sub-frame. The thicknesses of the panels on the front side member and the sub-frame were selected as the design variables. The purpose of the optimization was to reduce the weight of the structure, under the constraint that the objective quantity of crash energy is absorbed. The response surface method was used to approximate the crash behavior in mathematical form for optimization procedure. To research the effect of the regression method, two different methodologies were used in constructing the response surface model, the least square method and the moving least square method. The optimum with the two methods was verified by the simulation result. The precision of the surrogate model affected the optimal design. The moving least square method showed better approximation than the least square method. In addition to the deterministic optimization, the reliability-based design optimization using the response surface method was executed to examine the effect of uncertainties in design variables. The requirement for reliability made the optimal structure be heavier than the result of the deterministic optimization. Compared with the deterministic optimum, the optimal design using the reliability-based design optimization showed higher crash energy absorption and little probability of failure in achieving the objective.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.162-164
• /
• 1994

This paper presents the optimal design method of an induction motor for electric vehicle which minimizes the weight of motor and satisfies maximum power rating at the same time. Effects of motor parameters on the dimensions and weight of motor is investigated. Optimal routine which is used in this paper is simulated annealing technique.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.9
• /
• pp.1777-1782
• /
• 2011

Brushless DC motors applied in many control systems because of the good respose characteristic and the easy control characteristic. The speed control of the BLDC motors is important in the systems. This paper has designed PSO-PID speed controller for the speed control of BLDC motors. The PSO algorithm optimized the parameters of the PID controller in the PSO-PID speed controller. The several methods obtained the optimal inertia weight of the PSO algorithm by comparison. The optimal inertia weight of the PSO algorithm optimized the PSO-PID speed controller for BLDC motors. This paper confirmed the performance of proposed PSO-PID speed controller through simulation results.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.05a
• /
• pp.172-177
• /
• 2004

This paper presents the results of the structural analysis and optimal design of frames of the UUV(Unmanned Underwater vehicle) to be operated at 6000m depth in the ocean. The structure of the UUV system can be classified into two structure, Launcher ana ROV. Frame of the launcher will be made by Galvanized Steel which has high strength and corrosion-resistant but this material has high specific gravity for tile object to be weight in the water Similarly, ROV will be made by AI6061-T6, and frame of the ROV will be fix many instruments and syntactic buoyancy materials. Before fabrication of tile frame, we performed sensitivity analysis - change in weight due to $\pm1\%$ change in design variables, for easy choice by change of dimension of the frame.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.1
• /
• pp.111-119
• /
• 2010

Many researchers have studied on the optimal seismic design with the development of the computer. So far the application structure of most researches on the optimal seismic design was almost the moment resisting frame. Because the braced frames are the representative lateral load resisting system with the moment resisting frames, it is estimated that the effect on the practice will be great if it can is provided a design guideline through the development of optimal seismic design model for the braced frames. The purpose of this study is to propose the optimal seismic design model for the inverted V-type special concentrically braced frames considering the buckling of braces. The objective functions of this are to minimize the structural weight and maximize the total dissipated energy of the structure and the constraints of this are the strength conditions for the column, beam, brace and inter-story drifts condition. To verify the proposed model, it is applied to 2D steel concentrically braced frames of 3-story and 9-story.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10b
• /
• pp.712-717
• /
• 1998

Represtressed preflex beams do not allow tensile stress under service load by introducing additional prestressing at the lower concrete of beams. In this study, optimal design of represetressed preflex beams are numerically investigated. Design variables are dimension of plate girder. Object function is the total weight of plate girder. Constraints of the stress of plate girder and upper and lower concrete flange and lower and upper bounds on the design variables are imposed. Structural analysis is performed by D.A.R.P.(Design and Analysis of Represtressed Preflex beams). For numerical optimization, ADS(Garret N. Vanderplaats) program is used. From result of application examples, optimum designs of different cases are successfully obtained. The design program developed in this study seems efficient and robust for the optimization of represtressed preflex beams.

• Structural Engineering and Mechanics
• /
• v.51 no.5
• /
• pp.707-725
• /
• 2014

In order to improve the crane-hook's performance and service life, we formulate a multi-criteria shape design problem considering practical conditions. The structural weight, the displacement at specified points and the induced matrix norm of stiffness matrix are adopted as the evaluation items to be minimized. The heights and widths of cross-section are chosen as the design variables. The design variables are expressed in terms of shape functions based on the Gaussian function. For this multi-objective optimization problem with three items, we utilize a multi-objective evolutionary algorithm, that is, the multi-objective Particle Swarm Optimization (MOPSO). As a common feature of obtained solutions, the side views are tapered shapes similar to those of actual crane-hook designs. The evaluation item values of the obtained designs demonstrate importance of the present optimization as well as the feasibility of the proposed optimal design approach.

• Journal of the Society of Naval Architects of Korea
• /
• v.32 no.4
• /
• pp.64-72
• /
• 1995

Sizing design sensitivity analysis of structures subjected to the harmonic vibration is performed using adjoint variable method. Constraint is the stress and sizing design variables are thickness, bending moment of inertia, and cross-sectional area of structures. Accurate sensitivities are computed and plotted sensitivity can be used as a design guidance tool. The accuracy of sensitivities is verified by the finite difference values. Also, optimal design of three-bar structure is performed using the computed sensitivity and feasible direction method while satisfying constraints and obtaining the minimum weight.