• 한국해양공학회지
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• 제17권4호
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• pp.59-65
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• 2003

In order to achieve the desired lightweight and robust design of a structure, it is preferable to design a structure and its control system, simultaneously, which is termed the combined optimal design. A constant-cross-sectional area cantilever beam was chosen as the optimum design method, An initial load and a time-varying disturbance were applied at the free end of the beam. Sliding mode control was selected, due to its insensitivity to the disturbance, compared with other modes. It is known that the sliding mode control is robust to the disturbance and is uncertain, only if a matching condition is met, after giving a switching hyper plane. In this study, the optimum method was used for the design of the switching hyper plane, and the objective function of the optimum switching hyper plane was assumed to be the objective of the control system. The total weight of the structure was treated as a constraint, and the cross sectional areas of the beam were considered as design variables, the result being a nonlinear programming problem. To solve it, the sequential linear programming method was applied. As a result of the optimum design, the effect of attenuating vibrations has been substantially improved. Moreover, the lightweight design of the structure became possible as a result of the relationship of the weight of the structure to the control objective function.

• Journal of Advanced Marine Engineering and Technology
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• 제24권1호
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• pp.59-66
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• 2000

To investigate the optimum brazing condition, variation of bonded structure and mechanical properties of novel brazed pure Al with bonding condition (brazing temperature, time and Si/flux ratio) was studied. A basic study of the bonding mechanism was also examined. The optimum brazing condition was obtained at $590^{\circ}$ for 2 minutes and the bonded structure showed that it is composed of almost entirely eutectic Al-Si with near eutectic composition. At higher brazing temperature $630^{\circ}$, hypoeutectic Al-Si structure was observed in the bonded area and resulted in erosion of base metal. The thickness of eutectic layer formed in optimum brazing temperature increased linearly with the square root of time, showing a general diffusion controlled process. The ultimate tensile strength of bonded joint brazed at an optimum brazing condition was about 60% of base metal and its fracture surface showed a brittle mode.

• 농업과학연구
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• 제32권2호
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• pp.127-150
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• 2005

Under the WTO system, the farm size expansion or the existing korean agricultural structure should be improved to cope with farm income decrease and to continue rice cultivation for food security in the future. This study is aimed at identifying optimum farm size under trade liberalization and import and export parity price system of inputs and outputs. The optimum farm size expressed the minimum point of long run average cost is determined as 15.1ha. The farm size to be equalized as urban laborer's income of 37,361 thousand won per year was revealed 30ha. Therefore the G't recommended farm size of 6ha should be changed to 30ha and the concerned policies for agricultural structure improvement also should be changed to more flexibilitiy.

• 한국해양공학회지
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• 제24권6호
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• pp.109-113
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• 2010

We present the minimum weight optimum design of cross sectional for frame structures subject to natural frequency. The optimum design in this paper employ discrete and continuous design variables and Genetic Algorithms. In this paper, Genetic Algorithms is used in optimization process, and be used the method of Elitism and penalty parameters in order to improved fitness in the reproduction process. For 1-Bay 2-Story frame structure, in examples, continuous and discrete design variables are used, and W-section (No.1~No.64), from AISC, discrete data are used in discrete optimization. In this case, Exhaustive search are used for finding global optimum. Continuous variables are used for 1-Bay 7-Story frame structure. Two typical frame structure optimization examples are employed to demonstrate the availability of Genetic Algorithms for solving minimum weight optimum of frame structures with fundamental and multi frequency.

• 국제초고층학회논문집
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• 제3권2호
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• pp.121-145
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• 2014

The story shear force distributions of most seismic design codes generally reflect the influences of higher vibration modes based on the elastic deformations of structures. However, as the seismic design allows for the plastic behavior of a structure, the story shear force distribution shall be effective after it is yielded due to earthquake excitation. Hence this study conducted numerical analyses on the story shear force distributions of most seismic design codes to find out the characteristics of how a structure is damaged between stories. Analysis results show that the more forces are distributed onto high stories, the lower its concentration is and the more energy is absorbed. From the results, this study proposes the optimum story shear force distribution and its calculation formula that make the damages uniformly distributed onto whole stories. Consequently, the story damage distribution from the optimum calculation formula was considerably more stable than existing seismic design codes.

• Smart Structures and Systems
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• 제29권4호
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• pp.549-560
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• 2022

The optimum damping and tuning frequency ratio of the tuned mass damper-inerter (TMDI) for the base-isolated structure is obtained using the numerical searching technique under stationary white-noise and filtered white-noise earthquake excitation. The minimization of the isolated structure's mean-square relative displacement and absolute acceleration, as well as the maximization of the energy dissipation index, were chosen as the criteria for optimality. Using a curve-fitting technique, explicit formulae for TMDI damping and tuning frequency for white-noise excitation are then derived. The proposed empirical expressions for TMDI parameters are found to have a negligible error, making them useful for the effective design of base-isolated structures. The effectiveness of TMDI and its optimum parameters are influenced by the soil condition and isolation frequency, according to the comparison made of the optimized parameters and response with different soil profiles. The effectiveness of an optimally designed TMDI in controlling the displacement and acceleration response of the flexible isolated structure under real and pulse-type earthquakes is also observed and found to be increased as the inertance mass ratio increases.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.235-236
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• 2010

Since many structures in the sea environment are damaged by chloride, appropriate repair strategy is required. Therefore in the paper, optimum period for the RC structure's repair is calculated with consideration of economic efficiency. Moreover, when the concrete members are repaired with the other material such as polymer mortar forr section restoration, their expected service life also calculated to predict more accurate repair period during the life span.

• 한국항해학회지
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• 제13권2호
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• pp.75-95
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• 1989

The study presents the optimum design of B/C midship structure based on the classification society's Rule. The SUMT (Sequential Unconstrained Minimization Technique), using the Direct Search Methods (Hooke and Jeeves, Simplex) is applied to the solution of this nonlinear optimum design problem with constraints. Through the optimum designs of existing ships(60k, 186k, 220k), the amount 0.45-6.18% in weight of their midship structures are obtained on the viewpoint of minimum weight design.

• 대한조선학회논문집
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• 제42권3호
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• pp.249-258
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• 2005

Recently, the vibration reduction at a local structure such as compass deck has been continuously requested by ship owner and shipbuilder. Because crews are afflicted with vibration, severe vibration problems even bring about a damage of structure. This study conducted to get an optimized stiffener size of compass deck to reduce the vibration level and decrease the weight of structure in ship. NASTRAN external call type optimization software (OptShip) which makes use of NASTRAN as a solver is used as an optimization tool. The results indicate that the optimum design is promising for real applications.

• 한국산업융합학회 논문집
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• 제12권4호
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• pp.187-192
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• 2009

This study is performing a seismic analysis on the steel frames structure with dampers and analyzing the dynamic behavior in order to examine their efficiency and study the optimum dampers position to the seismic design steel structure. To improve the ability against an earthquake, this study performed the time history analysis. Controling an earthquake is the way to minimize the damage of the steel structure by dissipating input energy generated by an earthquake.