• Journal of the Korean Society of Safety
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• v.26 no.4
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• pp.80-86
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• 2011

Structural optimization algorithm of steel box girder bridges using improved higher-order approximate reanalysis technique is proposed in this paper. The proposed approximation method is a generalization of the convex approximation method. The order of the approximate reanalysis for each function is analytically adjusted in the optimization process. This self-adjusted capability makes the approximate structural analysis values conservative enough to maintain the optimum design point of the approximate problem. The efficiency of proposed optimazation algorithm, compared with conventional algorithm, is successfully demonstrated in the steel box girder bridges. The efficiency and robustness of proposed algorithm is also demonstrated in practical steel box girder bridges.

• Journal of Korean Society for Quality Management
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• v.18 no.2
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• pp.25-32
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• 1990

This paper presents an approximate algorithm for computing Fault-tree probabilities. The method is essentially composed of three steps. In the first step, a Fault-tree is converted into a network form. In the second step, We change the network into a parallelized diagram. In the third step, the approximate fault-tree probability is calculated from the parallelized diagram. In this paper, in order to verify the method two hypothetical Fault-tree is used by examples. The results show that the method is very useful, even though it is an approximate technique, since it needs not to search the minimal cut sets and has the simple computing rontines.

• Structural Engineering and Mechanics
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• v.3 no.4
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• pp.359-372
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• 1995

This study presents an efficient method for optimum design of plate and shell structures, when the design variables are continuous or discrete. Both sizing and shape design variables are considered. First the structural responses such as element forces are approximated in terms of some intermediate variables. By substituting these approximate relations into the original design problem, an explicit nonlinear approximate design task with high quality approximation is achieved. This problem with continuous variables, can be solved by means of numerical optimization techniques very efficiently, the results of which are then used for discrete variable optimization. Now, the approximate problem is converted into a sequence of second level approximation problems of separable form and each of which is solved by a dual strategy with discrete design variables. The approach is efficient in terms of the number of required structural analyses, as well as the overall computational cost of optimization. Examples are offered and compared with other methods to demonstrate the features of the proposed method.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.205-220
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• 2014

This paper is concerned with the modification of multidisciplinary feasible formulation for MDO problems using the integrated coupled approximate models. A drawback of conventional MDFs is the numerical difficulty in decomposing the design variables and deriving the coupled equations of state. To overcome such a drawback of conventional methods, the coupling in analysis and design is resolved by approximating the state variables in each discipline by the response surface method and by modifying the optimization formulation using the corresponding integrated coupled approximate models. The validity, reliability and effectiveness of the proposed method are illustrated and verified through two optimization problems, a mathematical MDF problem and the multidisciplinary optimum design of suspension unit of wheeled armored vehicle.

• Tribology and Lubricants
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• v.35 no.5
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• pp.310-316
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• 2019

This paper presents two methods for designing a high-speed air spindle operated over the rotational speed of 50,000 rpm. The first method is an approximate method, which assumes a symmetric spindle shape even though it is not symmetric in reality. The second is an analysis of rotordynamics using beam and solid models. The approximate method can be used to calculate the bearing load capacities, stiffness and damping coefficients, stability of the shaft system, and response of the forced excitation from the unbalanced mass. Designers can use this method to determine the dimensions of the desired spindle at the first stage of the design. The more detailed behavior of the spindle can be calculated using the rotordynamics theory using beam and solid models based on the Finite Element Method. In this paper, a spindle, with two air bearings, one motor at the end, and two air thrust bearings, is newly developed. The solutions from the two rotordynamics theories are compared with the solution obtained using the approximate method. The three calculations are in agreement, and the procedure for the design of a spindle system, supported on the externally pressurized air bearings, ispresented and discussed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.7
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• pp.690-695
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• 1991

The ability to linearize a nonlinear system by feedback and coordinate change reduces to finding an integrating factor for a one-form which is determined from the system dynamics. Utilizing Taylor series expansion of this one-form, we characterize approximate linearizabilitu. A constructive method is derived for approximate linearization up to order 2.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.601-605
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• 1991

In this paper an approximate solution method for the large-scale Traveling Salesman Problem(TSP) is presented. The method start with the subdivision of the problem domain into a number of clusters by considering their geometries. The clusters have limited number of nodes so as to get local solutions. They are linked to give the least path which covers the whole domain and become TSPs with start- and end-node. The approximate local solutions in each cluster are obtained by using geometrical property of the cluster, and combined to give an overall-approximate solution for the large-scale TSP.

• Water Engineering Research
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• v.4 no.4
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• pp.175-185
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• 2003

A numerical model to analyze dam break flows has been developed based on approximate Riemann solver. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using finite volume method and the numerical flux are reconstructed with weighted averaged flux (WAF) method. The developed model is verified. The first verification problem is about idealized dam break flow on wet and dry beds. The second problem is about experimental data of dam break flow. From the results of the verifications, very good agreements have been observed

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1603-1611
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• 2010

The comparative study of regression-model-based approximate optimization techniques used in the strength design of an automotive knuckle component that will be under bump and brake loading conditions is carried out. The design problem is formulated such that the cross-sectional sizing variables are determined by minimizing the weight of the knuckle component that is subjected to stresses, deformations, and vibration frequency constraints. The techniques used in the comparative study are sequential approximate optimization (SAO), sequential two-point diagonal quadratic approximate optimization (STDQAO), and approximate optimization based on enhanced moving least squares method (MLSM), such as CF (constraint feasible)-MLSM and Post-MLSM. Commercial process integration and design optimization (PIDO) tools are utilized for the application of SAO and STDQAO. The enhanced MLSM-based approximate optimization techniques are newly developed to ensure constraint feasibility. The results of the approximate optimization techniques are compared with those of actual non-approximate optimization to evaluate their numerical performances.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.333-338
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• 1998

Deflections due to warping are frequently ignored in design calculation. For thin member, shrinkage deflection results in important and objectionable additions to the dead load deflection. Thus it may be desirable to consider warping effects due to shrinkage for thin member. Some methods for computing shrinkage curvature have been proposed by many researchers. The approximate methods widely used in the recent years are the equivalent tensile force method. Miller's method and Branson's method (an empirical method based on Miller's approach extended to include doubly reinforced beams). These method were somewhat oversimplified and could be too conservative in the case of well cured concrete structure. In this paper, the approximate method for computing shrinkage curvature are reviewed and new approximate method based on the Age-Adjusted Effective Modulus method is proposed.