• 한국주조공학회지
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• 제9권1호
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• pp.67-72
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• 1989

Solidification analysis was conducted on large steel castings and ingots by a modified finite difference method. Auto-mesh generation system was developed for improving the application of the computer analysis system to casting disign. Combined use of the prediction parameters, solidification time and temperature gradient, and an auxiliary parameter, shrinkage potential, were used to predict the formation of shrinkage defects. Several examples on the prediction of shrinkage cavity by this method were campared with the experimental reslts. It was found that a quantitative design of large steel castings and ingots can be made by the computer aided analysis of solidification process.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.494-497
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• 2006

The objectives of this study are to develop and evaluate the Neural Network algorithm which can predict the inelastic shortening such as the creep strain and the drying shrinkage strain of reinforced concrete members using the previous test data. New learning algorithms for the prediction of creep strain and the drying shrinkage strain are proposed focusing on input layer components and a normalization method for input data and their validity is examined through several test data. In Neural Network algorithm, the main input data to be trained are the compressive strength of the concrete, volume to surface ratio, curing condition, relative humidity, and the applied load. The results show that the new algorithms proposed herein successfully predict creep strain and the drying shrinkage strain.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.656-661
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• 1998

This paper presents a method of statistical analysis and sensitivity analysis of creep and shrinkage effects in PSC box girder bridges. The statistical and sensitivity analyses are performed by using the numerical simulation of Latin Hypercube sampling. For each sample, the time-dependent structural analysis is performed to produce response data, which are then statistically analyzed. The probabilistic prediction of the confidence limits on long-term effects of creep and shrinkage is then expressed. Three measures are examined to quantify the sensitivity of the outputs to each of the input variables. These are rank correlation coefficient(RCC), partial rank correlation coefficient(PRCC) and standardized rank regression coefficient(SRRC) computed on the ranks of the observations. Probability band widens with time, which indicates an increase of prediction uncertainty with time. The creep model uncertainty factor and the relative humidity appear as the most dominant factors with regard to the model output uncertainty.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.674-679
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• 1998

In designing the prestressed concrete box-bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of the time-dependent characteristics. In this study, the creep test was carried out for four curing ages of concrete which were applied to the prestressed concrete structure at a construction site, and the results of test were compared to the values of creep prediction by the design code. Also the creep test of step-wise incremental stresses were performed and were compared to analytical methods.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.179-180
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• 2023

In this study, the performance of the prediction model was compared and analyzed using DNN and LSTM learning models to predict the amount of dry shrinkage of the concrete. As a result of the analysis, DNN model had a high error rate of about 51%, indicating overfitting to the training data. But, the LSTM learning model showed a relatively higher accuracy with an error rate of 12% compared to the DNN model. Also, the Pre_LSTM model which preprocess data, showed the performance with an error rate of 9% and a coefficient of determination of 0.887 in the LSTM learning model.

• 한국건축시공학회지
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• 제17권1호
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• pp.31-37
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• 2017

최근에는 공사기간을 단축하기 위해서 데크플레이트 외에 half PC 슬래브의 사용도 점차적으로 증가하고 있는 실정이다. PC 슬래브 위에 후타설되는 topping concrete 의 건조수축 변형이 PC 슬래브에 의해 구속을 받게 되므로 topping concrete 에 건조수축에 의한 균열이 발생할 수 있다. 따라서 half PC 슬래브의 품질을 향상시키고 내구성능을 증가시키기 위해서 건조수축에 의한 half PC 슬래브의 거동을 사전에 정확히 예측하는 것이 중요하다. 하지만 아직까지 half PC 슬래브의 수축거동 예측에 관한 연구결과가 없는 실정이므로 본 연구에서는 half PC 슬래브를 대상으로 건조수축거동을 관찰하였으며, 크리프특성을 고려한 증분법에 의한 수축거동을 예측한 후 실측값과 비교하여 그 타당성을 검토하였다. 그 결과 건조수축의 구속작용에 의해 half PC 슬래브에 발생하는 인장변형률은 구속률 개념과 증분법을 적용하여 예측이 가능한 것으로 확인되었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.88-89
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• 2017

Curling is caused by the shrinkage difference between surface and bottom side of concrete, and the cracks can be occurred by vehicle load after curling. It is important to investigate and predict the curling behavior to minimize the quality defect of concrete due to the curling. Therefore, the experimental and analytical investigation was carried out.

• 한국주조공학회지
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• 제11권1호
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• pp.44-53
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• 1991

The proper feeding conditions for thin Al-Alloy (AA336, JIS AC8A) castings in permanent mold were investigated to eliminate microshrinkage porosity. 5mm-thick plates (200mm long, 60mm wide) were cast with increasing padding taper from 0 to 5% under different conditions : (1) constant mold temperature of $350^{\circ}C$, (2) continuous production with uniform mold thickness (10mm), (3) continuous production with a negative taper of 2.5% in mold thickness (thickness decreasing in direction to riser). The test casting were machined off to the midplane and the shrinkage porosity was examined visually. The critical padding taper which can just eliminate the shrinkage porosity was determined for each condition, i.e. : (1) 4.5% at the constant mold temperature, (2) 3.5% for continuous production with the uniform mold thickness (3) 1.5% for continuous production with the taper in mold thickness. A computer simulation by a finite difference analysis program was applied to the test casting. The liquid fraction gradient (LFG) and the temperature gradient divided by the square root of the cooling rate (G /SR) were calculated at the end of solidification and compared with the shrinkage porosity area in the castings. For the case of constant mold temperature, LFG is a better parameter to predict shrinkage porosity than G /SR and its critical value is around 11%/cm. But for the case of continuous production, neither LFG nor G /SR could be a reliable parameter. The experimental results about the critical padding taper are of practical interest for designing permanent molds and castings. The computer simulation results stimulate further research to be directed on the prediction of centerline microshrinkage porosity in continuous production.

• 한국정밀공학회지
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• 제22권11호
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• pp.210-217
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• 2005

A curl distortion induced by shrinkage during stereolithography polymerization process is analyzed with the classical lamination theory. Test parts of different layer thickness and part thickness are manufactured and their deformations are measured with CMM. Curl distortion is generated by the differential shrinkage of the layers, where the total shrinkage includes the shrinkages due to solidification and the change of temperature. It is shown that the curl distortion increases exponentially with decreasing the total thickness of the part, whose smaller layer thickness induces larger curl distortion. It is verified that only a part of the total shrinkage plays a role in generating the curl distortion.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.285-288
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• 2004

Generally, the autogenous shrinkage of high performance concrete is important in that it can lead the early cracks in concrete structures. In the previous study, The. autogenous shrinakge of HPC was found to decrease with incresing expansive additive and shrinakge reduction agent. In case of combined use, the autogenous shrinakge was more reduction than in case separate use. The purpose of this study is to derive a realistic equation to estimate the autogenous shrinakge model of high performance concrete with exapnsive agent and shrinakge reduction agent. investigated the durability of high performance concrete using expansive additive and shrinkage reducing agent. The proposed equation showed reasonably good correlation with test data on autogenous shrinakge of high performance concrete with material for shrinkage reduction.