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이산성 연속형 최적성 규준을 이용한 PPC 구조의 최적설계프로그램 개발
한상훈,조홍동,이상근 한국전산구조공학회 1997 전산구조공학 Vol.10 No.4
본 논문에서는 이산성 연속형 최적성규준방법을 이용하여 다지간 부분프리스트레스트 콘크리트보의 최적설계 알고리즘을 유도하였고, 최적설계프로그램을 개발하였다. 목적함수로서 건설 경비는 콘크리트 경비, 긴장재 경비, 철근 경비, 그리고 거푸집 경비를 포함하였으며 이를 최소화하였다. 설계제약조건으로는 시방서상의 최대처짐제약, 휨 및 전단강도제약, 연성제약 그리고 설계변수에 대한 상.하한계제약을 고려하였다. Kuhn-Tucker 필요조건을 이용하여 최적성규준을 설계변수의 항으로 명시적으로 유도하였으며, 이때 설계변수로는 보의 유효깊이, 긴장재의 편심거리 그리고 철근비를 취하였다. 긴장재의 형상은 포물선함수로 고려하였으며, 구조물 자중의 영향은 긴장력에 의한 이차효과와 마찬가지로 실제시스템의 평형방정식에서 고려하였다. 설계변수들의 개선을 위한 반복과정과 컴퓨터프로그램을 개발하였으며, 수치예를 들어 개발된 기법의 응용성 그리고 효율성을 보였다. This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.
한상훈,변근주,김왕구 충북대학교 건설기술연구소 1982 建設技術論文集 Vol.1 No.1
The aim in this presentation is to explore the relationship between optimum design of structures and reliability of structures. In this paper, the concept of probability of failure is explained for a general structural system. The concept emphasized in the paper is the employment of probability of failure constraint in the mathematical programming problem to determine the set of design parameters which minimizes she weight of the truss structures. Specific reliability based optima for multi-member systems are shown for weakest-link structures which fail if any element fails. Several examples of optimization with failure probability constraints are presented, and then the sensitivity of optimum design to reliability level as well as parameters in the reliability analysis is discussed. The results presented indicate: 1) The results indicate the feasibility of using probability of failure constraints in solving for optimum m lti-member structural designs. 2) An important factor influencing the magnitude of the optimum design as well as its member sizes will be the choice of load and strength frequency distributions and their parameters particulary the coefficients of variation. 3) The optimum value increases with both allowable failure probability and increase in coefficients of variation. 4) The classical approach to optimum design using a safety factor to represent conservation often results in unnecessary weight and cost.
한상훈,이범석,최현수,강민수,김보라,한지아,이혜진 대한재활의학회 2015 Annals of Rehabilitation Medicine Vol.39 No.3
Objective To analyze the relationship of the change in fat mass percentage (FMP) and body mass index (BMI) with the change in obesity rate according to gender, extent of spinal cord injury (SCI) and the duration.Methods The retrospective study was conducted with medical records of 915 patients. FMP was calculated with BMI and bioelectrical impedance analysis (BIA). Statistical analysis of the relationship between FMP and gender, extent of SCI and the duration after SCI was done.Results FMP increased in relation to the duration. The mean FMP was higher in the motor complete tetraplegia group, as compared to the motor incomplete group. The rate of obesity was 69.8% with cutoff FMP values of over 22% and 35% for male and female patients, respectively. Rate of obesity was correlated with the duration after SCI and degree of paralysis. The rate of obesity was 17.1% with a cutoff value of BMI 25 kg/m2 and 51.3% with a cutoff value of 22 kg/m2. For evaluation of the diagnostic value of BMI to predict obesity according to FMP standards, a cutoff value of 25 kg/m2 showed a sensitivity level of 22.3% and specificity level of 94.9%. When the cutoff level for BMI was set at 22 kg/m2, the sensitivity and specificity were 59.3% and 67.0%, respectively.Conclusion In Korean SCI patients, FMP showed good correlation with the duration of SCI and the extent of SCI, while BMI did not. Especially in the motor complete tetraplegia group, the diagnostic value of BMI decreased as the duration after SCI increased. This study suggested that FMP could be used complementarily when evaluating the obesity of SCI patients.