• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.14 no.2
• /
• pp.237-247
• /
• 2001

강상판교는 부재수가 많고 구조적 거동이 복잡하여 재래적인 단일수준 (CSL) 알고리즘을 이용하여 최적화하는 것이 매우 어렵기 때문에 본 연구에서는 강상판교를 효율적으로 최적화하기 위해 다단계 최적설계 (MLDS) 알고리즘이 제안되었다. 강상판교를 주형과 강상판으로 나누기 위해 등위법이 사용되었고, 시스템 최적화를 위하여 설계 변수를 줄이는 분해법이 사용되었다. 효율적인 최적설계를 위해 다단계 최적설계 알고리즘은 제약조건 소거기법(Constraint Deletion)과 응력 재해석 같은 근사화 기법을 도입하였다. 변위해석을 위한 제약조건 소거기법은 교량의 최적화에 효율적인 것으로 검증되었고, 제안된 응력 재해석 기법 또한 설계민감도 해석을 필요로 하지 않으므로 매우 효율적이다. MLDS 알고리즘의 적용성과 강건성은 다양한 수치예제를 사용하여 기존의 단일수준 알고리즘과 비교하였다.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.475-485
• /
• 2000

In this study, an automated optimum design program for steel box girder bridges has been developed for the optimum design of composite steel box girder bridges. The design constraints required for the optimum design of steel box girder bridges are based on the Korean standard bridge specification. Considering characteristics of steel box girder bridges, several approximation techniques, such as artificial constraint deletion, variable linking and stress reanalysis technique etc. are also introduced to enhance the efficiency of optimization. The developed program is mainly composed of major sub-system modules including structural analysis module using commercial structural analysis program such as RM-SPACEFRAME, optimum design module, pre-process module for friendly user input, and post-processor module for office automation. In addition, in order to demonstrate the efficiency and applicability of the developed optimum design program for steel box girder bridges, a few numerical examples are applied. Based on the results of the application, it may be stated that the automatic optimum design program developed in this study can be a prototype model for the developement of optimum design program for other type of bridge.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.14 no.4
• /
• pp.505-513
• /
• 2001

In this study, an optimum design algorithm using efficient reanalysis is proposed for seismic design of Reinforced Concrete (RC) piers. The proposed algorithm for optimization of RC piers is based on efficient reanalysis technique. Considering structural behavior of RC piers, the other approximation technique such as artificial constraint deletion is introduced to increase the efficiency of optimization. The efficiency and robustness of the proposed algorithm including the proposed reanalysis technique is demonstrated by comparing it with a conventional optimization algorithm. A few of design examples are optimized to show the applicability of the proposed algorithm.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.07a
• /
• pp.787-789
• /
• 2005

최근 이동성이 중요한 요소로 차지하는 기기들이 등장하면서 플래시 메모리가 각광을 받고 있다. 플래시 메모리의 소형화, 대용량화, 저전력화, 비휘발성, 고속화 그리고 충격에 강한 장점으로 인하여 많은 응용에서 디스크를 대체할 것으로 예상된다. 하지만 이런 플래시 메모리는 데이터를 기록하기 전에 해당 블록이 미리 소거가 되어야 하는 제약 조건을 가지고 있으며 각 블록들의 최대 소거 횟수가 제한되어 있다는 한계가 있다. 이때 소거 연산이 특정 블록에 집중되어 특정 블록의 수명이 단축되는 문제점을 해결하기 위하여 블록에 대한 소거 횟수 평준화 기법(wear-leveling)이 필요하다. 기존에 제안된 소거 횟수 평준화 기법은 각 블록의 소거 횟수를 유지해야하는 비용이 필요로 하거나 플래시 메모리가 대용량일 경우에는 블록 영역을 이동시키는데 비용이 발생하는 문제가 있다. 본 논문에서는 플래시 메모리의 소거 횟수 평준화를 위하여 해당 블록의 소거 횟수에 대한 정보의 유지의 부담을 줄이고 플래시 메모리의 대용량화 및 디스크 대체 시에 효율적인 소거 횟수 평준화 기법을 제안하고, 실험을 통하여 성능의 우수함을 보인다.

• Journal of Navigation and Port Research
• /
• v.36 no.5
• /
• pp.379-385
• /
• 2012

In this paper, the stability and stabilization problems for marine vessels including surface and underwater vehicles are described. In the marine vessels, there are many and strong nonlinear parameters. These give hard design process and difficulties to us. In this article, at first we make a descriptor system representation as a controlled system to preserve the physical parameters of the system as it is. And we propose a new stability and stabilizability conditions based on the quadratic stabilization approach which gives a solution for the unreasonable problems produced by added mass. That is, the proposed conditions are not interfered with the nonsymmetric matrix constraint. And the stability condition is given by an matrix inequality such that it makes us to obtain a solution easily for something.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.569-579
• /
• 2000

An improved multi-level (IML) optimization algorithm using automatic differentiation (AD) of framed structures is proposed in this paper. For the efficiency of the proposed algorithm, multi-level optimization techniques using a decomposition method that separates both system-level and element-level optimizations, that utilizes and an artificial constraint deletion technique, are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments and frequencies with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.3
• /
• pp.237-250
• /
• 2003

Since an orthotropic steel deck bridge has large number of design variables and shows complex structural behavior, it would be very difficult and impractical to directly use a Conventional Single Level (CSL) optimization algorithm for its optimum design. Thus, in this paper, an Improved Multi Level Design Synthesis (IMLDS) optimization algorithm is proposed to improve the computational efficiency. In the proposed IMLDS algorithm, a coordination method is introduced to divide the bridge into main girders and orthotropic steel deck with preserving the characteristics of the structural behavior. For an efficient optimization of the bridge, the IMLDS algorithm incorporates the various crucial approximation techniques such as constraints deletion, Automatic Differentiation (AD), stress reanalysis, and etc. In the case of orthotropic steel deck system, optimum design problems are characterized by mixed continuous discrete variables and discontinuous design space. Thus, a modified Genetic Algorithm (GA) is also applied to optimize discrete member design for orthotropic steel deck. From the numerical example, the efficiency and convergency of the IMLDS algorithm proposed in this paper is investigated. It may be positively stated that the IMLDS algorithm will lead to more effective and practical design compared with previous algorithms.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.3
• /
• pp.65-79
• /
• 1992

This study is concerned with the optimal design of two hinged steel arches with I cross sectional type and aimed at the exact analysis of the arches and the safe and economic design of structure. The analyzing method of arches which introduces the finite difference method considering the displacements of structure in analyzing process is used to eliminate the error of analysis and to determine the sectional force of structure. The optimizing problems of arches formulate with the objective functions and the constraints which take the sectional dimensions(B, D, $t_f$, $t_w$) as the design variables. The object functions are formulated as the total weight of arch and the constraints are derived by using the criteria with respect to the working stress, the minimum dimension of flange and web based on the part of steel bridge in the Korea standard code of road bridge and including the economic depth constraint of the I sectional type, the upper limit dimension of the depth of web and the lower limit dimension of the breadth of flange. The SUMT method using the modified Newton Raphson direction method is introduced to solve the formulated nonlinear programming problems which developed in this study and tested out throught the numerical examples. The developed optimal design programming of arch is tested out and examined throught the numerical examples for the various arches. And their results are compared and analyzed to examine the possibility of optimization, the applicablity, the convergency of this algorithm and with the results of numerical examples using the reference(30). The correlative equations between the optimal sectional areas and inertia moments are introduced from the various numerical optimal design results in this study.