• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.208-215
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• 2018

The causes of column shrinkage and the codes that have been studied up to now are discussed. The documents mentioned in the code deal with the drying shrinkage, creep, compressive strength and elastic modulus of the specimen, and the elastic deformation calculated from the structural analysis. However, the deformation due to the temperature caused by the long term monitoring is less than that caused by the factors generated by the previous studies. In the previous studies, it was found that dehydration shrinkage, creep, and elastic deformation were not considered for temperature-induced deformation, while for the specimen experiments, the temperature-related items were replaced with the humidity-related terms The compensation value by the proposed equation showed error of 4.9 mm in the upper direction and 1.0mm in the lower direction when calculating column shortening, and it was found that its value by the proposed equation almost coincided with the measurement value in Site. Therefore, it is necessary to further study the temperature that can be omitted in calculating the existing column shortening, to consider the influence factors, and to supplement the criteria for the temperature measurement of the structure as well as the specimen tests.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.199-200
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• 2009

This research developed a long-term crack width prediction model based on bond characteristics that considered steel corrosion, concrete shrinkage and creep in cracking stabilized structural concrete members.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.357-360
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• 2006

Under sustained load, the stress variation occurs due to creep and shrinkage of concrete on the sections of steel-concrete composite girders. In standard specification for highway bridge, the method of stress estimation considering time effects is based on the concept of Yassumi method. In this study, comparing the analysis results using the AEMM and Yassumii method long-term behaviors, the rationality of specified requirements is checked.

• 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.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.181-188
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• 1993

In this study, a numerical method for the material nonlinear analysis of reinforced concrete shell structures including the time dependent effects due to creep and shrinkage is developed. Degenerate shell elements with the layered approach are used. The perfect or strain hardening plasticity model in compression and the linearly elastic model in tension until cracking for concrete are employed. The reinforcing bars are considered as a steel layer of equivalent thickness. Each :steel layer has an uniaxial behaviour resisting only the axial force in the bar direction. A bilinear idealization is adopted to model elasto-plastic stress-strain relationships. For the nonlinear anaysis, incremental load method combined with unbalanced load iterations for each load increment is used. To include time dependent effects of concrete, time domain is divided into several time steps which may have different length. Some numerical examples are presented to study the validity and applicability of the present method. The results are compared with experimental and numerical results obtained by other investigator.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.135-146
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• 1996

In this study, the properties of super flowing concrete containing fly ash were experimentally investigated and compared with those of ordinary concrete. Tests were carried out on five types of super flowing concrete mixes containing fly ash and three types of ordinary concrete mixes without fly ash. Flow test, 0-funnel test, box test, L type test and slump test were carried out to obtain the properties for flowability and workability of fresh concrete. The mechanical properties of hardened concrete were also investigated in terms of compressive strength, splitting tensile strength, modulus of elasticity, creep and drying shrinkage. In fresh concrete, it was found that super flowing concrete had excellent workability and flowability compared with ordinary concrete, and had self-compactable performance. Super flowing concrete *also had good mechanical properties at both early and late ages with compressive strength reaching as high as 40 MPa at 28 days. The creep deformation of super flowing concrete investigated was relatively lower than that of ordinary concrete, but drying shrinkage was much higher.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.155-162
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• 2004

An analytical method to predict the time dependent flexural behavior of composite girder is presented based on sectional analysis. The time dependent constitutive relation accounting for the early-age concrete properties including maturing of elastic modulus, creep and shrinkage is derived in an incremental format by the first order Taylor series expansion. The sectional analysis calculates the axial and curvature strains based on the force and moment equilibriums. The deflection curve of the girder approximated by the quadratic polynomial function is calculated by applying to the proper boundary conditions in the consecutive segments. Numerical applications are made for the 3-span double composite steel box girder which is a composite bridge girder filled with concrete at the bottom of the steel box in the negative moment region. The calculated results are compared with those by finite element analysis results. Close agreement is observed between the two approaches.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.357-363
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• 2016

To solve the exhaustion problem of natural aggregate which were create the high value in construction and environmental industry, recycled aggregates have considerable benefits than other materials. However, even though many researches have been conducted with recycled aggregates, building structures with recycled aggregated are rarely constructed because it has lower quality than natural aggregates have. In this study, mechanical and strain properties of recycled aggregates concrete containing steel fibers have been reviewed in order to complement performance of recycled aggregates concrete. As results, recycled aggregates concrete showed lower compressive strength and elastic modulus than plain concrete. But, recycled aggregates concrete containing steel fibers showed equivalent performance with plain concrete. In review of drying shrinkage and creep coefficient, recycled aggregates concrete containing steel fibers showed similar behavior with plain concrete in the range of 0.5 Vol.% fiber content rate by internal restraint effect, moisture transport restraint effect and strength enhancement effect of steel fiber. Therefore, it is considered that mixing steel fibers with concrete is the effective method as a active application plan for recycled aggregates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.113-123
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• 2012

The technology developed for the decrease of applying loads and self-weight of a structure is to improve conventional Foam Cement Banking Method (FCB) by applying mixed slurry of bottom ash, cement and foams. Since the foam-mixed concrete, which is a major material of the Bottom ash-mixed Light weight concrete Banking method (BLB) developed, contains mineral admixture such as cement, the behavior shows time-dependent deformation and deterioration of durability due to environmental exposure. Thus, this study is subject to figure out the characteristics of long-termed behavior and durability of the developed method by carrying out experiments for schemed parameters, which are considered to be factors affecting mainly on concrete's characteristics from mechanical analysis. As results of tests, it was found that the developed concrete offers higher resistance than conventional foamed concrete in terms of long-termed behaviors associated with drying shrinkage and creep, and durability problems of freeze-thaw and carbonation processes, especially with addition of bottom ash.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.521-529
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• 2002

A restraint coefficient for creep and dry shrinkage deformation of concrete in a composite section was derived to calculate the residual stress, and an equation for the loss rate of the pre-compression force was proposed. The derived restraint coefficient was computed by using the transformed section properties for the age-adjusted effective modulus of elasticity. The long-term behavior of complicate composite sections could be analyzed easily with the restraint coefficient. The articles of the current design code was examined for PSC and steel composite sections. The dry shrinkage strains of $150 ~ 200$\times$10^{-6}$ for the computations of the statically indeterminate force and the expansion joint could be under-estimated for less restrained sections such as the reinforced concrete. The dry shrinkage strain of $180$\times$10^{-6}$ for the computation of residual stress in the steel composite section was unreasonably less value. The loss rate of 16.3% of the design code for the PSC composite section in this study was conservative for the long-term deformation of the ACI 205 but could not be used safely for that of the Eurocode 2. For pre-compressed concrete slab in the steel composite section, the loss rate of prestressed force with low strength reinforcement was much larger than that with high strength tendon. The loss rate of concrete pre-compression increased, while that of pre-tension decreased due to the restraint of the steel girder.