• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.57-66
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• 2016

In order to develop materials with a low environmental load for restoring the destroyed forest, seven types of wood-concrete hybrid laminated materials were manufactured with four softwoods, three hardwoods and concrete, and the effect of wood density on bending creep property was investigated. The bending creep curves showed a shape to considerably increase at the upper right side, and the curves were found to show a linear behavior beyond about 30 min - 1 hour, as behaviors of solid woods and wood-based materials. The initial compliances of wood-concrete hybrid-laminated materials decreased with an increase in the wood density, and those values showed 0.9 - 1.2 times of the concrete one. The creep compliances of hybrid laminated materials showed very low values, which were 0.4 - 0.8 times of the concrete ones. The relative creep were very low with a range from 8.2% to 17.0% range, which were 0.3 - 0.7 times of the concrete ones. These results indicate that these materials can be applied for restoring the destroyed forest to reduce creep deformation of the conventional concrete materials by hybrid-laminating concrete and woods.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.69-72
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• 2005

For reinforced concrete column under sustained loads, the member suffers additional lateral deflection due to creep. This deflection leads to additional bending in the member, which in turn causes the column to deflect still further. Therefore the secondary moment due to additional deflection causes an increase in primary moment and the strength of column is reduced. And also creep buckling may occur. On this study, nonlinear analysis of reinforced concrete long column including crack effects is carried out and then the strength of long column is revaluated.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.457-464
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• 2015

The alternative material for cement has been attracting attention in construction projects. Especially, the alkali activated slag(hereafter, AAS) concrete is able to use for a structural vertical member because of 40MPa of compressive strength, However, the research about time-dependent deformation such as creep which is important to strength member is insufficient. Therefore, in this study, experiments were performed with respect to time-dependent deformation including the drying shrinkage and creep deformation of AAS concrete. The creep deformed ratio of AAS concrete was more than OPC concrete by approximately 4.3% and the dry shrinkage deformation of AAS concrete was more than OPC concrete by approximately 69%. The large amount of sodium silicate, alkali activator, is added causing temperature crack than promoted drying and drying creep which is confirmed by water ration test and SEM.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.225-226
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• 2009

Day by day, concrete buildings and structure became high-rising and magnificently vast scheduled, as contributed from the development of improved equipments that suitable to specific construction works and high qualitied Material, the durability of the concrete was highly improved. The temporary elastic reduction occur at vertical members such as walls and columns under vertical loads. Specially, inelastic reduction such as creep and shrinkage occur long termly with elastic one in case of reinforced concrete members. Generally, creep and shrinkage depend on time and this is affected by concrete strength, concrete type, member size, steel ratio, and relative humidity. And elastic reduction rely on time, too because concrete is loaded before revelation of perfect strength in terms of construction conditions. So, tests on mechanical properties of concrete certainly need in order to apply to construction by forecasting an amount of reduction caused by the complex factors. Therefore, in this study the tests on creep, shrinkage are carried out to offer basic data for predicting an amount of long-term Properties at the concrete columns of an object structure, and results of the tests are described.

• Steel and Composite Structures
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• v.45 no.2
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• pp.263-279
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• 2022

With the span and arch rib size of concrete-filled steel tube (CFST) arch bridges increase, the hydration heat of pumped mass concrete inside large-size steel tube causes a significant temperature variation, leading to a risk of thermal stress-induced cracking during construction. In order to tackle this phenomenon, a hydration heat conduction model based on hydration degree was established through a nonlinear temperature analysis incorporating an exothermic hydration process to obtain the temperature field of large-size CFST. Subsequently, based on the evolution of elastic modulus based on hydration degree and early-age creep rectification, the finite element model (FEM) model and analytical study were respectively adopted to investigate the variation of the thermal stress of CFST during hydration heat release, and reasonable agreement between the results of two methods is found. Finally, a comparative study of the thermal stress with and without considering early-age creep was conducted.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.199-200
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• 2021

In the study, creep and dry shrinkage characteristics were evaluated to determine the material properties necessary for structural analysis such as column shortening and differential drying shrinkage. All the experiments were conducted in an constant temperature and humidity room. The mechanical properties as well as the specific creep and ultimate dry shrinkage values were derived. In addition the characteristics of the physical value of the high-strength fiber reinforced concrete were considered.

• KCI Concrete Journal
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• v.14 no.1
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• pp.15-22
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• 2002

Stresses that develop due to differential shrinkage between polymer modified cement mortar (PM) and Portland cement concrete (PCC) in a repaired concrete beam at early ages were investigated. Interface delamination or debonding of the newly cast repair material from the base is often observed in the field when the drying shrinkage of the repair material is relatively large. This study presents results of both experimental and analytical works. In the experimental part of the study, development of the material properties such as compressive strength, elastic modulus, interface bond strength, creep constant, and drying shrinkage was investigated by testing cylinders and beams for a three-week period in a constant-temperature chamber. Development of shrinkage-induced strains in a PM-PCC composite beam was determined. In the analytical part of the study, two analytical solutions were used to compare the experimental results with the analytically predicted values. One analysis method was of an exact type but could not consider the effect of creep. The other analysis method was rather approximate in nature but the creep effect was included. Comparison between the analytical and the experimental results showed that both analytical procedures resulted in stresses that were in fair agreement with the experimentally determined values. It may be important to consider the creep effect to estimate shrinkage-induced stresses at early ages.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.31-40
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• 1993

Many reseachers have performed extensive studies on the creep and shrinkage of concrete. Mechanism of creep and shrinkage however is not quite well-known, especially for high strength concrete. Therefore, the purpose of this study is to explore the shrinkage and creep characteristics of high strength concrete. The main variables investigated include condition of drying, reinforcement and duraton of load. The effects of drying and reinforcements are clarified and compared with various exsiting models. The present study provides useful data for the design and analysis of high stength concrete structures.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.305-311
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• 2016

This study examined the long-term inelastic characteristics, including unrestrained shrinkage and creep, of low-heat cement concrete under different ambient curing temperatures. To achieve the designed compressive strength of 42MPa, water-to-binder ratios were selected to be 27.5, 30, and 32.5% for curing temperatures of 5, 20, and $40^{\circ}C$, respectively. Test results showed that the shrinkage strains of concrete mixtures tended to decrease with the decrease in curing temperature because of the delayed evaporation of internal capillary and gel waters. Meanwhile, creep strains were higher in concrete specimens under lower curing temperature due to the occurrence of the transition temperature creep. The design models of KCI provision gave better accuracy in comparison with test results than those of ACI 209, although a correction factor for low-heat cement needs to be established in the KCI provision.