일반철근콘크리트 보와 동일한 구조적 거동을 하는 강섬유보강 철근콘크리트 보 단면의 이론적 산정

이차돈,윤여천 中央大學校 建設環境硏究所 1995 環境科學硏究 Vol.6 No.-

The objective of this study was to develop an mathematical model which can take into account the effects of steel fiber reinforced concrete(SFRC) on the flexural and shear behavior of a reinforced steel fibrous concrete beam(RSFC beam). The model developed on the basis of the nonlinear layered finite element method and the nonlinear programming technique was successfully able to find the necessary amount of steel fibers, tensile steels and comporessive steels(if any) to constitute and equivalent RSFC beam section compared to a given conventionally reinforced concrete beam in terms of equal flexural an shear strengths as well as ductility. Using the developed model. some parametric studies were also performed in order to examine the possible replacement of conventional reinforcement with steel fibers and consequently the changes in the amount of tension, compression, and shear reinforcement for the beam made of different reinforcement ratios and concrete compressive strengths.

Simulated Annealing에 의한 3차원 철근콘크리트 골조의 실제적인 최적설계

이차돈,황정섭 중앙대학교 건설환경연구소 2001 環境科學硏究 Vol.12 No.2

3차원 철근콘크리트골조를 최적화하기 위한 최적설계 알고리즘을 Simulated Annealing(SA)에 근거하여 개발하였다. 기존 수치해석 또는 해석적인 최적화 기법에 비하여 SA는 다음과 같은 장점을 갖는다. : 이산 변수를 다를 수 있으며, 함수의 연속성이나 미분을 요구하지 않으며, SA의 국소해를 탈피하는 응력으로 인하여, 좀더 전체적인 최적해에 근접할 수 있는 확률을 가지며, 또한 구조기준에 나타난 식들을 프로그램에 포함하기가 쉽다. 본 연구의 최적화에 다음과 같은 사항들을 고려하였다 : 보나 기둥의 이산형 크기, 보의 정 및 부모멘트에 대한 철근수, 스터럽수, 기둥의 축력과 휨에 대한 상관관계에 근거한 철근수, masher and slave관계를 이용한 프로그래밍.기준에서 철근배근에 관하여 규정한 대부분의 기준을 또한 만족하도록 하였다. 개발된 알고리즘은 적절한 탐색을 거쳐 3차원 철근콘크리트 골조의 최적해를 성공적으로 찾아내었다. An optimization algorithm based on Simulated Annealing(SA) is developed for three dimensional reinforced concrete frames. SA is a branch of Stochastic optimization techniques. SA has beneficial aspects compared to conventional numerical or analytical optimization techniques in that: it can handle discrete variables, does not need continuity or derivatives of a function, has more probabilities of convergence to global minimum by its uphill capability, and is easy to include the equations in structural design cede. Considered in optimization are: discrete set of member sizes of beams and columns, number of reabars in flexure(both the positive moment and negative moment) and stirrups in shear for beams, and number of reabars in flexure and axial forces and stirrups in shear for columns, Concept of master and slave node has been adopted. Most of constraints in code regarding reinforcements are also considered in this research. With finite number of searching the developed algorithm was successful in finding optimum solutions for three dimensional reinforced concrete frame structure.

비선형 유한요소법에 의한 부착 및 비부착된 프리스트레스트 콘크리트 보의 휨 모델

이차돈,김민경,이재찬 중앙대학교 건설환경연구소 2001 環境科學硏究 Vol.12 No.2

본 연구에서는 기존의 이론 모델을 고찰하고 이들 모델의 단점을 수정, 보완하여 부착 및 비부착된 프리스트레스트보의 하중-처짐 관계를 예측할 수 있는 비선형 휨모델을 유한요소법에 근거하여 개발하는데 목적이 있다. 주어진 외력과 단면 내력간의 불균형력(unbalanced force)를 감소시키기 위하여 반복계산 형태의 수치해석 방법을 사용하게 되는데, 본 연구에서는 Newton-Raphson Method를 도입하여, 보의 하중-처짐 곡선을 예측할 수 있는 진보된 수치해석 모델을 개발하였다. 또한 비부착 프리스트레스보의 긴장재의 응력은 콘크리트와 긴장재가 부착되어 있지 않기 때분에 부재 전체길이의 변형을 고려한 해석이 이루어져야 하므로, 비부착된 프리스트레스트보의 휨 거동은 부재전체의 휨변형과 관계가 되므로 A.E Naaman이 제시한 부착감소계수(Ω)의 개념을 적용하였다. 개발된 모델은 임의의 텐돈위치와 profile, 임의 위치의 하중에 대해 적용할 수 있도록 개발되으며, 비교적 실험결과과 잘 일치하였다. In this research, various types of theoretical models and solution techniques suggested for predicting flexural behavior of prestressed concrete beam are reviewed. An analytical method based on the nonlinear layered finite element method is then developed to simulate overall load-deflection behavior of bonded and unbonded prestressed concrete beams. Emphasis is given to eveluate the stressed in unbonded tendons Based on the i￥A M ðR¿ n" Ω) suggested by A.E. naaman. The developed model can take into account various types of tendon profiles and loads. The developed model is found to predict experimental results reasonably well.

Mean Field Annealing을 이용한 평면 트러스 최적설계

이차돈 中央大學校 建設環境硏究所 1994 環境科學硏究 Vol.5 No.-

조합최적화 이론에 그 근간을 둔 Mean Field Annealing은 상호작용하는 대단한 큰 자유도(degrees of freedom)를 가진 처리 시스템을 다룰 때 사용되어지는데 물리학의 통계적 이론에 근거한 이 방법은 열평형 상태에서의 분자 시스템의 작용에 대한 간단한 해석적 근사를 이용해 최적화 문제를 간소화시킨다. 본 연구에서는 제약조건으로서 압축 및 인장에서의 항복강도, 좌굴하중, 부재상호간의 연관성(grouping in members)등을 갖는 평면트러스 최적설계를 mean field approximation에 의하여 행하였으며 그 결과 성공적으로 최적해를 산정할 수 있었다. A Mean Field Annealing(MFA), dealing with large number of interacting degrees of freedom is a branch of combinatorial optimization techniques. The MFA whose term has been originally derived from the field of thermodynamics establishes in this truss optimization problem a probabilistic criterion for acceptance or rejection of current design and iteratively improves it until the optimum design is reached. The design improvements are continuously achieved according to the cooling schedule of MFA. The method has been successfully applied to the plane truss optimization problems characterized either by simple constraints such as strength limits only or by additional complexities introduced by buckling and multiple loading conditions. Satisfactory results are obtained and some comments are made based on the observations of the performance of MFA during the optimization process.

Genetic Algorithm을 이용한 철근콘크리트보의 최적설계

안지현,이차돈 中央大學校 建設環境硏究所 1999 環境科學硏究 Vol.9 No.2

Simple Genetic Algorithm (SGA) is refined to take into account for the optimization of reinforced concrete beams under positive and negative moments. GA has beneficial aspects compared to conventional numerical or analytical optimization techniques in that ; it can handle discrete variables, does not need continuity or derivatives of a function, has more probabilities of convergence to global minimum; and is relatively easy to include the equations in structural design code. Considered in optimization are : discrete set of widths, depths and number of rebars both in positive moment and in negative moment region for beam members. In addition to the strength constraints, requirements for reinforcement arrangement including minimum cover thickness and necessary spacings between rebars in a beam section are considered. Within a reasonable and finite number of searching, the developed algorithm was able to yield optimum solutions for reinforced concrete beams.

진폐진행정도에 따른 혈청내 구리와 아연 농도의 변동

박정래,박종욱,이수일,이철호,오차재,김창원,조병만,김돈균 大韓産業醫學會 2000 대한직업환경의학회지 Vol.12 No.3

목 적 : 진폐증은 분진으로 인해 인체의 면역기전이 작용하여 폐섬유화가 진행되는 질환으로, 인체의 면역기전에 작용하는 구리와 아연은 진폐증의 병리적인 진행과정인 폐섬유화에 관여한다. 본 연구의 목적은 초기진폐증 유소견자와 진행된 진폐증 환자의 혈청 구리와 아연의 농도를 정상인과 비교함으로써 체내 구리와 아연의 농도가 진폐증의 섬유화의 진행정도에 따라 변동함을 밝히고, 이를 이용하여 폐섬유화의 진행정도를 추정할 수 있는 지표를 제시하고자 한다. 방 법 : 진폐정밀기관에 내원한 초진내 원자 100명과 진폐요양기관에 입원한 진폐증 환자 100명을 선정한 후 흥부사진소견을 ILO 분류법의 진폐진행정도에 따라 각각 세 군(Stage Vl, V2, V3 & Stage Pl, P2, P3)으로 구분한 후 각 군의 혈청구리와 아연의 농도를 비교분석하였다. 대조군으로는 폐결핵, 심근경색, 뇌경색을 경험한 적이 없는 일반인 100명을 선정하였다. 결 과 : 초진내 원자군의 혈청 구리농도는 섬유화의 진행단계에 따른 유의한 차이를 보였으며, Stage V3에서 가장 높았다. 입원환자군에서는 혈청 구리농도가 대조군과 유의한 차이를 보이지 않는데 (p=0, 152), 이는 입원환자의 불량한 영양상태와 건강상태 때문인 것으로 추정된다. 초진내원자군과 입원환자군의 혈청 아연농도는 섬유화의 진행에 따라 통계적인 차이를 보였으며, Stage V2와 Stage P2, P3에서 각각 대조군에 비해 유의하게 낮았다. 혈청 아연과 구리농도의 비또한 양군에서 섬유화의 진행에 따라 의미있게 높았는데, 섬유화가 현저히 진행된 단계 (Stage V3, Stage P2, P3)에서 대조군과 의미있는 차이를 보였다. 결 론 : 초진내 원자와 입원환자의 혈청 Cu/zrl 비는 섬유화의 진행정도가 현저할수록 대조군에 비해 유의하게 높게 나타났다. 진폐증 환자들의 혈청 Cu/zn 비는 진폐증의 폐섬유화의 진행정도를 추정함에 있어 상당히 유용한 지표로 이용될 수 있으며, 폐섬유화의 진행과정에서의 혈청 구리와 아연의 작용기전을 이용한 치료방법의 마련에도 도움이 될 것으로 판단한다. Objectives : Copper and Zinc, the trace elements of a living body, take a part in immunologic mechanism and induce the pulmonary fibrosis which is the pathologic progress of pneumoconiosis. This study was performed to assist the identification of the pathologic process of pulmonary fibrosis in pneumoconiosis. Methods : The subjects of thls study was 200 diagnosed persons as pneumoconiosis, of whom 700 persons was the visitors in the outpatients departments of pneumoconiosis and 100 admissive pneumoconiosis patients. The serum copper and zinc are measured and compared. Results : The mean serum copper concentration of visitor group was significantly higher than that of control group, and that of stage V3 subgroup of visitor group was highest because of their advanced fibrosis. But, there was not the difference of serum copper concentration between patient and control group. We thought that the reason was poor nutritional and health status of the patient. The mean of serum zinc concentration of visitor and patient control was lower than that of control group. As the degree of pulmonary fibrosis was more severe from stage Vl, V2, V3 of visitor to stage Pl, P2, P3 of patient, the mean of serum zinc concentration was lower. The ratio of serum copper/zinc of visitor and patient was higher than that of control, and that of patient was higher than that of visitor. Those results showed that the ratio of serum copper/zlnc ratio more greatly expressed the degree of progression of pneumoconiosis than only copper or zinc concentration by adjustment of nutritional and health status of the patient. Conclusions : As above study results, the degree of pulmonary fibrosis of pneumoconiosis could be estimated by means of serum copper/zinc ratio.

고온 하에서 고 강도 철근 콘크리트 보의 구조거동

신미경,신영수,이차돈,홍성걸,박재영 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

This paper deals with structural behavior of reinforced concrete beams under fire. The main purpose of this study is to investigate the effect of concrete covers and exposure time to fire on the structural behavior of the beams under high temperature condition. The structural behaviors of RC beams with ordinary and high strength concrete under high temperature are compared. For this purpose, twelve beam specimens are fabricated and experimented. Twelve specimens are exposed to the fire for 60 and 90 minutes and to the failure. The research result shows that the main variables of the test, concrete cover and exposure time to fire influence the structural behavior.

화재 피해를 입은 고 강도 철근 콘크리트 보의 보수 성능

신미경,신영수,이차돈,홍성걸,강지연 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

This paper is to evaluate practically the techniques and materials of repair for high strength concrete elements with fire damages as well as to investigate the structural behavior of beams according to pre- or post-repair after fire-damages. For this purpose, flexural specimens with high strength concrete were exposed to high temperatures by the ISO 834 specification. After natural cooling and post-fire-curing in a natural environment for 1 months, 6 specimens were loaded to failure after they were repaired with polymer cement mortar for 1 month curing.

fmGA를 이용한 하수관거정비 최적화 모델

류재나,기범준,박규홍,이차돈 대한상하수도학회 2004 상하수도학회지 Vol.18 No.2

A long-term sewer rehabilitation project consuming an enormous budget needs to be conducted systematically using an optimization skill. The optimal budgeting and ordering of priority for sewer rehabilitation projects are very important with respect to the effectiveness of investment. In this study, the sewer rehabilitation optimization model using fast-messy genetic algorithm is developed to suggest a schedule for optimal sewer rehabilitation in a subcatchment area by modifying the existing GOOSER model having been developed using simple genetic algorithm. The sewer rehabilitation optimization model using fast-messy genetic algorithm can improve the speed converging to the optimal solution relative to GOOSE , suggesting that it is more advantageous to the sewer rehabilitation in a larger-scale subcatchment area than GOOSER .

Constitutive Modeling of Confined Concrete under Concentric Loading

Lee, Cha-Don,Park, Ki-Bong,Cha, Jun-Sil Korea Concrete Institute 2001 KCI concrete journal Vol.13 No.1

The inelastic behavior of a reinforced concrete columns is influenced by a number of factors : 1) level of axial load, 2) tie spacing, 3) volumetric ratio of lateral steel, 4) concrete strength, 5) distribution of longitudinal steel, 6) strength of lateral steel, 7) cover thickness, 8) configuration of lateral steel, 9) strain gradient, 10) strain rate, 11) the effectively confined concrete core area, and 12) amount of longitudinal steel. A new constitutive model of a confined concrete is suggested in order to investigate the nonlinear behavior of the reinforced concrete columns under concentric loading. The developed constitutive model for the confined concrete takes into account the effects of effectively confined area as well as the horizontal and longitudinal distributions of the confining pressures. None of the existing models incorporated these two main effects at the same time. A total of different six constitutive models for the behavior of the confined concrete under concentric compression were compared with the sixty-one test results reported by different researchers. The superiority of the developed model in its accuracy is demonstrated by evaluating the error function, which compares the weighted averages for the sum of squared relative differences in peak compressive strength and corresponding strain, stress at strain equal to 0.015, and total area under stress-strain curve up to strain equal to 0.015.