• Magazine of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.82-87
• /
• 2002

매스 콘크리트 구조물에서는 콘크리트의 타설후 시멘트의 수화반응에 의해 발생하는 수화열로 인하여 적지 않은 크기의 인장응력이 유발되어 균열이 발생할 가능성이 크다. 토목분야에서 통용되고 있는 많은 범용구조해석 프로그램들은 유한요소법을 이용하여 수화열에 의한 온도분포해석 및 열응력해석을 수행할 수 있는 기능을 내장하고 있다. 그러나, 다른 모든 구조해석들이 그러하듯이 수화열 해석 역시 해석자가 적절한 입력자료를 프로그램에 제공하지 않았을 경우 예상과는 다른 결과를 산출할 수 있다.(중략)

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.363-368
• /
• 1997

PWR 원전에서는 계획예방 정지운전시 효과적인 정지수화학 제어에 의해 일차계통 방사능 준위를 감소시키고 작업종사자의 피폭을 최소화하기 위해 정지운전 자료에 대한 보다 정확한 해석이 필요하다. 본 연구에서는 국내 PWR 원전 주기(A호기의 I 및 II주기와 B호기의 II주기)별 정지수화학 특성을 SCALP(Shutdown chemistry CALculation Program)프로그램으로 계산하고 정지운전 기간중 일차냉각재계통에서 제거되는 방사능량에 영향을 미치는 정지수화학 특성을 주요 인자별로 평가하였다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05a
• /
• pp.369-373
• /
• 1998

증기발생기에서 부식에 의한 전열관 손상은 전열관과 관판사이의 틈새에서 대부분 발생되고 이 틈새에서의 수질환경에 좌우된다. 틈새에서는 과열도가 높아 미량의 불순물이 농축되면서 틈새수화학 (crevice chemistry)은 증기발생기 내부수 수화학과는 달라진다. 전열관 손상을 억제하기 위해서는 틈새수질을 적절히 제어하여야 하는데 이는 틈새수화학을 정확히 분석평가할 수 있는 기술을 기반으로 하여야 한다. .기존의 틈새수질을 계산하는 방법으로는 증기발생기 내부수에 비해 틈새에서 화학종들이 얼마나 농축되는지를 가정하는 농축도 (concentration factor) 방법이 있으나 가정에 의한 불확실성으로 인해 틈새수질을 정확히 해석할 수 없었다. 그러나 원전 증기발생기의 잠복불순물 방출시험 자료로부터 틈새수질을 보다 정확히 평가할 수 있는 새로운 개념의 몰비지수(molar ratio index) 방법이 최근 EPRI에서 제시되었고 EPRI 산하의 많은 발전소에서 적용중이다. 본 연구에서는 PWR 원전 증기발생기의 틈새수화학을 평가할 수 있는 기술을 개발하기 위해 잠복불순물 방출시험 자료로부터 틈새에서의 몰비지수를 계산할 수 있는 CRAP (CRevice-chemistry Analysis Program) 전산프로그램을 작성하였다 CRAP를 국내원전에 적용하여 증기발생기 및 그 틈새에서의 수화학을 평가하였다.

• Journal of the Korea Institute of Building Construction
• /
• v.14 no.5
• /
• pp.379-388
• /
• 2014

The purpose of this study is to investigate the effect of capsulated slurry phase change material (PCM) on the thermal crack in mass concrete by experimental work and FEM analysis. In this study, three conditions of samples were prepared for evaluating the level of hydration heat, i.e., a material condition, a cement paste condition and a concrete condition. Also, a compressive strength test was conducted for FEM inverse analysis. Based on the results of the experiment, exothermic function coefficients of concrete with encapsulated slurry PCM were deducted by the inverse analysis. After that, they applied to FEM analysis of the mass scale concrete structures. From the results of this experiment, $31^{\circ}C$ capsulated slurry PCM had no super cooling phenomenon in the material condition. In the cement condition, hydration heat decreased by 34.61J when PCM of 1g was mixed. In the concrete condition, PCM of 6% was deducted as the best level in hydration heat absorption. In FEM inverse analysis, rate coefficient of reaction gradually decreased when PCM mixing ratio increased. But, temperature-rise coefficient increased when PCM mixing ratio exceeded 6%. For the inversed exothermic function coefficients applying to large scale concrete structures, a thermal cracking index increased by 0.05 when PCM of 1% was mixed.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.3
• /
• pp.137-148
• /
• 1995

In this study, a program for evaluation of heat transfer and thermal stress of mass concrete is developed and verified by 2-experiments (internally and externally restricted). Furthermore, the result of the program is compared with those of ADINA-T and ADINA. As a result of the comparison, the proposed method produces comparable results with those from the popular programs (ADIIVA-T and ADINA) and shows the usefulness of the developed program for the evaluation of thermal stresses of mass concrete in both internally and externally restricted structures.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.2
• /
• pp.121-132
• /
• 1997

The thermal behavior of' concrete can be ch;lracterized from a knowledge of concrete ternperatu1.e at early ages, environmental conditions, and cement hydration in the mixture. 'l'o account for thost. interactions, a computer model was developed for prwlicting the temperature pr.ol'ile in hnrdcning c o n c r c t ~ st.r~icture in terms of material and tmvironmcntal factors. The cerncnt hydration cha~.acteristics such as the activating energy, total heat 1ihei.atr.d. anti th\ulcorner degree of' hydration. can represent the internal heat gc,neration. In this study. th(> activating c1ncrgy and the tlcgree of' hydration curve were determined well fmm the rnortn~. compressive strength tests while total amount of heat liberated was determined by tht> isothermal calorimctcr method. The main purpose of' this study is to correlate measured tt>mperaturr distributions in a concrete st1,ucture during thc hardening process with the ~ c s u l t s computed f'ro~n theoretical considrl.ations. Using twodimensional heat transfer model, first. the importance of several parameters will be identified by a parametric analysis. Then, the tcmpcmture distribution of thc cylindrical concrete specimen in the laboratory was mensuwti and compared with that yielded by thc theoretical considel.ations.

• Magazine of the Korea Concrete Institute
• /
• v.4 no.3
• /
• pp.101-111
• /
• 1992

매스콘크리트 구조물에서의 시멘트 수화열은 구조물의 균열을 발생시킬 만큼 큰 내부온도를 발생시킨다. 따라서 매스콘크리트 구조물에서의 설계와 시공단계에서 내부온도응력을 예측할 수 있다면 이와같은 균열로 인한 구조물의 피해를 예방할 수 있을 것이다. 그리고 수화열에 의한 온도증가는 타설초기에 발생하므로 크리이프에 의한 영향도 매우크다. 따라서 온도응력해석시 크리이프와 건조수축의 영향을 고려하는 것이 구조물의 안전성과 사용성을 정확히 파악하는데 필요하다. 본 연구는 먼저 매스콘크리트의 온도이력을 유한요소법에 의해 해석하고, 작용하중이나 온도이력을 크리이프와 건조수축영향을 고려하여 콘크리트 구조물의 응력과 변형을 유한요소법에 의해 계산하였다. 본 연구에서 온도이력 계산과 콘크리트구조물의 응력과 변형의 계산을 위해 작성한 프로그램 결과를 실제 구조물의 실험결과와 비교하였을 때 양호한 결과를 얻었다.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.807-812
• /
• 2001

This paper represents the wall thinning analysis results for secondary side piping of two types of domestic nuclear power plants based on the DB establishment and F AC analysis study for NPP secondary system piping. CHECWORKS code utilized in this study has been applied world widely to wall thinning analyses for secondary side piping and its reliability has also been proved. The predicted wear rates for several piping systems of a pressurized water reactor NPP are compared with those of a pressurized heavy water reactor NPP and with the measured wear rates. On the basis of comparison results of the predicted and measured wear rates, the analysis results can be effectively applied to the development of a standard thinned pipe management program targeted all domestic nuclear power plants.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.6
• /
• pp.176-185
• /
• 1995

The heat generation of hydration of cement causes the internal temperature rise and volum& change at early age, particularly in massive concrete structures. As the results of the temperature rise and external restraint conditions, the thermal stress may induce cracks in concrete. Therefore, various techniques of the thermal stress control of the mass concrete have been wid'dy used. One of them is pipecooling which reduces the temperature of concrete with flowing water. The objective of this paper' is to develop a finite element program which is capable of simulating the temperature history considering pipe-cooling effect. The numerical results in this study are in good agreement with experimental data measured in the footing(l1 x22m). Therefore, this study may provide available method to predict the hydration temperature of concrete with pip:-cooling.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.1
• /
• pp.63-72
• /
• 2017

This research investigated the effect of solar radiation on the temperature distribution in concrete mat foundation. Zhang and Huang Model was utilized to estimate solar radiation heat at a given date and time. A one-dimensional finite element formula was derived with the fundamental laws of heat transfer and Galerkin method. Based on the formula, a one dimensional finite element analysis code was developed using MATLAB. Hydration heat analysis of mat foundation were conducted using the developed code. It was found that the solar radiation reduced the maximum temperature difference in mat foundation, and this temperature difference reduction was more prominent in case of summer season cast, a higher initial concrete temperature, and a thicker mat foundation depth. The research recommended that the solar radiation should be considered in hydration heat analysis of concrete mat foundation so as not to overestimate the maximum temperature difference in mat foundation.