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

• 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

• 한국도로학회:학술대회논문집
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• 2008.03a
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• pp.31-38
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• 2008

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.709-712
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• 2008

RC super tall buildings are planned and constructed recently in domestic area. Concrete is characterized by time dependant material such as creep and shrinkage. For this properties of concrete, differential shortening is one of the main issues on super tall buildings construction. This study includes material research, which is performing as a pre design stage to solve differential shortening on Lotte Super Tower Jamsil core structure(50, 60, & 70 MPa). The major part of this study is composed with comparison and analysis between experimental data and predicted data on total shrinkage and total compliance which were used on design stage. Four models, ACI209R Model, Ba${\check{z}}$ant-Baweja B3 Model, CEB MC99 Model, & GL2000 Model, were employed to predict them. It also tries to seek a proper model for high strength and high performance concrete in the case of no concrete test.

• 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.

• 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.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.141-148
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• 2005

The nonlinear humidity distribution occurs due to the moisture diffusion when a concrete is exposed to an ambient air. This nonlinear humidity distribution induces shrinkage cracks on surfaces of the concrete. Because shrinkage cracks largely affect the durability and serviceability of concrete structures, the moisture diffusion in concrete must be investigated. The purpose of this paper is to propose a model of the moisture diffusion coefficient that governs moisture diffusion within concrete structures. To propose the model, numerical analysis was performed with several experiments. Because the moisture diffusion coefficient is changed with aging, especially at early ages, the proposed model includes aging effect by terms of the porosity as well as the humidity of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.303-308
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• 2000

During the past few decades, several composite steel-concrete structural systems have been used and the demand of SRC (Steel Reinforced Concrete) structure increases on the construction of coping structures. But drying shrinking of concrete which is not uniform and the additional restraining effects of encased steel in concrete may cause the crack which leads to harmful damage to structure. In this study, specimens were made to show the restraining effects of embeded-steel in concrete and the differential drying shrinkage strains at various position of concrete were measured and analysed by Compensation Line Method. The results showed that there were remarkable difference in the drying shrinkage according to 속 depth of the concrete, and the tensile stress of the concrete near to encased steel showed the significant amount of stress contrary to 속 specimen which has no embeded-steel.

• 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.