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RISS 인기검색어
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- 저자 : 정철원(Chulwon Jung) (검색결과 5 건)
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信賴性 設計規準에 의한 鐵筋콘크리트 部材斷面의 最適化에 관한 硏究
鄭哲源 조선대학교 국토개발연구소 1980 국토개발연구 Vol.2 No.1
This study is directed to the optimum proportioning of sections of reinforced concrete structures bsed on reliability design criteria. The reliability design criterion used in this study is the LRFD(Load and Resistance Factor Design)criterion proposed by Ellingwood. It is a Level-Ⅰ reliability design type which is mode equivalent to the Level-Ⅱ design method. Thus, the LRFD optimizations of R.C. beams and columns are formulated as nonlinear programming problems. The Lagrange multiplier method as well as the incremental linear programming method are adopted as an optimization techinques for the beam optimization problem. However, the optimization of column sections is achieved by using a heuristic optimization appoach instead of a formal numerical search algorithm. A set of design examples is solved using the FORTRAN program develooped in this study. It may be concluded that the LRFD reliability-based optimization results in significant saving in construction costs compared with the conventional strength design. Therefore it may be regarded that the LRFD criterion is more efficient and economical in design and should be adopted as a reliability-based design method in the future.
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鐵筋콘크리트 T桁橋 上部構造의 信賴性 最適化에 관한 硏究
鄭哲源 조선대학교 국토개발연구소 1981 국토개발연구 Vol.3 No.1
This study is directed for the reliability based optimum design of R.C. T-beam bridges. Reliability optimization models are developed be using both classical reliability theory and practical reliability based design criteria proposed by Ellingwood. Each reliability optimization model is formulated as a nonlinear programming problem. In the classical formulation, the reliability constraints with side limit constraints are included as the design constraints, whereas in the practical formulation, Ellingwood's LRED criteria and the ACI code requirements constitute the design constraints. Objective functions for the nonlinear programming problems are obtained by incorporating the costs of steel, concrete and formworks which are usually considered as the prime cost factors of R.C. Structures. The optimization for both formulations is achieved by using Lagrange multiplier method. Thus, two general optimization formulas for the optimum proportioning of T-beam sections are derived and the algorithms for the automatic optimum design of the T-beam superstructures are also presented.
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不規則要因으로 構成되는 鐵筋콘크리트 部材의 確率過程論에 의한 信賴解析에 關한 考察
李在煥,鄭哲源 조선대학교 국토개발연구소 1979 국토개발연구 Vol.1 No.1
This paper is a study on the reliability analysis of reinforced concrete menbers composed of various random elements by the theory of the stochastic process. Reliability analysis was performed by the theory of stochastic process when the strength and the working load of structural members were composed of serveral random elements. The results are as follows; 1) When the strength and the load were given as a function of random elements with a free distribution system, a formulation for calculating failure probability was derived according to the function form. 2) There are many difficult cases in ahich the equation derived from 1) cannot be applied, So an equation for approximate calculation of the failure probability with the extention situation of the stochastic process was derived. 3) Bu applying the equation derived from 2) to a single rectangular beam composed of the strength of reinforcement and concrete of which the random strength has a regular variable probability and the load has a function of random elements with the free distribution system, an equation was derived for calculating the failure probability of the beam. 4) By using the equation derived from 3), we analyized the reliability of the beam. The results are as follows; (1) It is necessary to take into account the probability of compressive failure in investigating the failure of the beam, and much care should be particularly taken when the coefficient of variation of the concrete strength is large. (2) The failure probability of beam with different steel ratio to concrete varies according to the value of variable codfficients of the strength of reinforcement and concrete. (3) The more influence the variation of strength has on the probability of failure, the larger the middle safety ratio becomes. (4) By this apporach of reliability analysis, the value of the failure probability of the atructure become larger as the lifetime of structure becomes longer. So, much attention should be given to the above three cases beamd whoch have a long lifetime.
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Newmark의 B法을 利用한 位相遲延의 補正方法에 關한 硏究
安鍾弼,鄭哲源 조선대학교 국토개발연구소 1979 국토개발연구 Vol.1 No.1
This paper is a study of revising amethod of phase delay in Newmark's β-method. Solutions to dynamic response are close to both the direct method and numerical integration(step-by-step integration). This paper deals with numerical integration. For the calculations used in this paper, it is first necessary for the system of the maximum natural period to be given and in phase delay of Newmark's β-method(β=1/4), we can find an applicable method of revision. In case we choose the dividedtime distance in the linear, or nonlinear weal we calculation, we must choose between the approximate degree of external force and frequency of higher degree. It this method of calculation is used, it will relax the limitations of the latter.
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