• Computational Structural Engineering
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• v.10 no.1
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• pp.62-69
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• 1997

본 고에서는 고층건물의 건설과정에서 발생하는 시간의 진행에 따른 기둥의 (장기)변형을 정확히 예측하고 이를 시공중에 보정하도록 함으로써 비구조요소의 강도와 사용을 만족시키기 위한 방법론을 제시하였다. 이 방법론은 실험적 통계치를 기초로 한 약산해법으로서 실무에 쉽게 적용할 수 있다. 52층 RC 건물에 대한 적용 결과 기둥에 발생하는 축소량에 가장 큰 영향을 미치는 것은 탄성변형이며, 건조수축의 효과가 가장 미세한 것으로 나타났다. 그러나, 2년 이상의 장기 변형이 지속될 경우 크립변형의 영향이 탄성변형에 비해 더욱 증가할 것으로 판단된다. 고층의 RC건물인 경우 기둥간 부등축소량의 최대치(=최대 시공오차)는 중간층 근처에서 발생하는 것으로 나타났다.

• Journal of the Korean Society for Railway
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• v.14 no.6
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• pp.555-561
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• 2011

This paper is designed to propose methods to both analyze and control the reasons for cracks appearing during the construction of piers. For this aim, a numerical analysis was performed to identify the properties of crack which resulted from heat of hydration and differential drying shrinkage with the key influence factors considered. The results show that the thermal cracks occurred within a few days, and the drying shrinkage cracks within a few weeks. Meanwhile, settlement shrinkage cracks occurred within a few hours. Discussing the control methods based on the time of the cracks appearing, quality control, reduction of the unit quantity of cement, and the preservation of moisture on the surface are proposed as the realistic and effective methods for preventing settlement cracks, thermal cracks, and drying shrinkage cracks respectively.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.59-68
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• 2009

Torsional behavior of concrete pavement slabs due to temperature and moisture effects is constrained by self weight and friction etc, and causes stress as the result. The stress due to humidity variation in the slab is difficult to calculate while that due to temperature variation can easily be calculated by a commercial structural analysis program. Thus, the slab behavior can be predicted more accurately if the humidity effect is converted to equivalent temperature and is used as an input of structural analysis. In this study, a concrete pavement slab was constructed and strains of the slab due to environmental loadings were measured for long-term period. Thermal strains were subtracted from the measured strains by using thermal expansion coefficient of the concrete measured in a laboratory. Shrinkage strains, the remained strains, was supposed as additional thermal strains to calculate imaginary temperature with equivalent effect of the shrinkage by dividing the shrinkage with the thermal expansion coefficient. An existing shrinkage model was modified by considering the self weight and friction to be used in another model which can convert differential shrinkage between top and bottom of the slab to equivalent temperature difference. Addition research efforts on tensile stress reduction according to steady increase in the compressive strains are warranted for more accurate stress calculation.

• 한국도로학회:학술대회논문집
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• 2008.10a
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• pp.183-188
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• 2008

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.309-314
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• 1998

The moisture diffusion and self-desiccation cause the differential drying shrinkage and autogenous shrinkage at early ages, respecitvely. Thus total shrinkage strain includes the differential drying shrinkage and self-desiccation shrinkage. Thus in this study the shrinkage strain was measured at various positions in the exposed concrete and in the sealed concrete the self-desiccation shrinkage was measured. In low-strength concrete, the differential drying shrinkage increases very rapidly, but self-desiccation shrinkage is very small. But high-strength concrete shows the reverse result. And the analytical results for differential drying shrinkage were in good agreement with the test results.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.164-171
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• 1995

Drying shrinkage and hydration heat are important factors on the initiation of the crack in con crete at early age. Therefore, the stress caused by hydration heat and drying shrinkage should be .analyzed to predict whether the crack occurrs or not. And, mechanical properties of early age concrete is also required for the predicting crack formation In this study, non-destructive test method of resonance frequency was used to find the relation between dynamic modulus and mechanical properties of concrete in early age. Test results were compared with existing equations, and a new equation based on test. results in this study and other data was also proposed

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.155-162
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• 1994

The drying shrinkage of concrete has a close relation to the water movement, Since the diffusion process of water in concrete is strongly dependent on the temperature and pore humidity, the process is highly nonlinear phenomena. It is shown that the analytical results of this study are in good agreement with experimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated quantitatively. The tensile stress which occurred in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.

• Journal of the Society of Disaster Information
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• v.6 no.1
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• pp.78-90
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• 2010

Exposure to the outside, the concrete is differential moisture distribution depending on the depth. Such a differential moisture distribution causes the differential drying shrinkage in concrete structures. This thesis is researched to compare the shrinkage of lightweight concrete depending on depth to normal concrete. It is used artificial lightweight aggregate which has 20% of pre-absorb value by lightweight concrete. When water-binder ratio is 30%, average shrinkage of lightweight concrete section decreased than normal concrete, but differential shrinkage of lightweight concrete section increased. However water-binder ratio is 40% and 50% average shrinkage and differential shrinkage of lightweight concrete section decreased than normal concrete.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.119-129
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• 2022

It is essential to control the lateral displacement and differential axial shortening of the vertical elements in high-rise buildings. The differential axial shortening can cause challenges in the serviceability and safety of non-structural and structural elements, respectively. Hence, in this study, the differential axial shortening of the vertical elements and effects of long term behaviors of concrete are analyzed in 120-story high-rise buildings via the construction sequence analysis. Consequently, the axial shortening of the vertical elements is classified into elastic, creep, and shrinkage shortening, and dominant factors to the maximum axial shortening are analyzed. In addition, the serviceability of the non -structural elements is checked with a differential axial shortening at 30 years after completion of construction, and member forces at design and construction stages in girders and outrigger walls are compared.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.291-298
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• 2002

Recently, construction of reinforced concrete tall buildings is widely increased according to the improvement of material quality and design technology. Therefore, differential shortenings of columns due to elastic, creep, and shrinkage have been an important issue. But it has been neglected to predict the Inelastic behavior of RC structures even though those deformations make a serious problem on the partition wall, external cladding, duct, etc. In this paper, analysis system for prediction and compensation of the differential column shortenings considering time-dependent deformations and construction sequence is developed using the objected-oriented technique. Developed analysis system considers the construction sequence, especially time-dependent deformation in early days, and is composed of input module, database module, database store module, analysis module, and analysis result generation module. Graphic user interface(GUI) is supported for user's convenience. After performing the analysis, the output results like deflections and member forces according to the time can be observed in the generation module using the graphic diagram, table, and chart supported by the integrated environment.