• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.241-244
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• 2004

The evaluation of Single or multi-degregation of concrete coated by high performance surface penetration agency was examined through various tests, i.e., carbonation, absorption, carbonation + chloride ion and carbonation + chemical solution according to various high performance surface penetration agencies and various compressive strengths of base concrete. The 2 types of high performance surface penetration agencies were used i.e., inorganic and alcohol soluble. And 2 types of compressive strength of base concrete were used such as 21 30. MPa. The characteristics of concrete coated high performance surface penetration agency was more improved than that of non-coated concrete, and especially, water soluble inorganic agency was most effective. And if compressive strength of base concrete was low, the improved effects would be larger.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.809-812
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• 2004

The evaluation of characteristics of concrete coated by high performance surface penetration agency was examined through various tests, i.e., compressive strength, penetration depth, water and air permeability, absorption according to various high performance surface penetration agencies and various compressive strengths of base concrete. The 4 types of high performance surface penetration agencies were used i.e., organic, inorganic, water soluble, and alcohol soluble. And 3 types of compressive strength of base concrete were used such as 21, 24 and 30 MPa. The characteristics of concrete coated high performance surface penetration agency was more improved than that of non-coated concrete, and especially, water soluble inorganic agency was most effective. And if compressive strength of base concrete was low, the improved effects would be larger.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.459-469
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• 2014

One of the most important structural components of steel structures is the column-base connections which are obliged to transfer horizontal and vertical loads safely to the reinforced concrete (RC) or concrete base. The column-base connections of steel or composite steel structures can be organized both moment resistant and non-moment resistant leading to different connection styles. Some of these connection styles are ordinary bolded systems, socket systems and embedded systems. The structures are frequently exposed to cycling lateral loading effects causing fatal damages on connections like columns-to-beams or columns-to-base. In this paper, connection of steel column with RC base was investigated analytically and experimentally. In the experiments, bolded connections, socket and embedded connection systems are taken into consideration by applying cyclic lateral loads. Performance curves for each connection were obtained according to experimental and analytical studies conducted and inelastic behavior of connections was evaluated accordingly. The cyclic lateral performance of the connection style of embedding the steel column into the reinforced concrete base and strengthening of steel column in upper level of base connection was found to be higher and effective than other connection systems. Also, all relevant test results were discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2001.11a
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• pp.28-33
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• 2001

This paper presents the results of mock up test on the manufacturing of high fluidity concrete by applying flowing methods with segregation reducing type superplasticizer(SRS). Three kinds of mock up structure are made such as. conventional concrete(A), high fluidity concrete(B) and high fluidity concrete incorporating 20% of fly ash(C). Physical and mechanical properties, temperature history of structure and nondestructive test are performed. Segregation reducing type superplasticizer is put into base concrete at field, and base concrete is also flowed at field. C mock up structure which requires 0.85% of SRS to flow base concrete shows most desirable performance at fresh state. The highest rising temperature shows the lowest at C structure among the tested structures. Strength variations before and after flowing also show the lowest values at C structures.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.253-260
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• 2010

The purpose of this paper is to investigate the behavior of concrete-filled tube columns for footing connections. Eight specimens were tested to investigate such structural behavior according to the column base type. The specimens consisted of concrete-filled steel tube columns (or bare steel tube columns), reinforced concrete footings, and base plates (or stud connectors). The specimens were subjected to lateral cyclic load. The cyclic load was applied according to a predetermined strength sequence. The results of the experiment indicated that the flexural strength of the stud-connector- type column base is higher than that of the base-plate-type column base. The structural behavior of the concrete-filled tube column base was similar to that of the bare steel column base.

• Steel and Composite Structures
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• v.44 no.1
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• pp.1-15
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• 2022

The weld quality has always been an important factor affecting the development of exposed CFT column-base joint. In this paper, a new type of exposed RCFST column-base joint is proposed, in which the high strength steel bars (USD 685) are set through the column and reinforced concrete foundation without any base plate and anchor bolts. Three specimens, the varying axial force ratio (0, 0.25 and 0.5), were tested under cyclic loadings. In addition, the bending moment capacity, energy dissipation capacity and deformation capacity of column-base joints were clarified. The experimental results indicated that the axial force ratio increases the stiffness and the bending moment and improves the energy dissipation capacity of column-base joints. This is because a large axial force can limit the slip between steel tubular and infilled concrete effectively. The specimens show stable hysteresis behavior.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.449-456
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• 2000

Remediation grouting has been widely used for the rehabilitation of various civil works like hydraulic and traffic structures. Recently there were some cases of remediation grouting for repairing old dams in korea. So this study will describe the case of remediation grouting of the concrete dam base located east-northern part of Seoul. We use Lugeon Test and Borehole Image Processing System(BIPS) for estimating the effectiveness of remediation grouting of this project. As the results of this study, we could find the lots of joints between the old concrete body and the weathered rock base. So the about 30% quantity of total cement grouts was injected at the boundary surface between concrete and rock base. And Lugeon Test and BIPS could be compared relatively because BIPS results could be presented quantitatively as well as qualitative analysis. Finally, we could find microfine cement was very effectively injected to the fine fissured concrete body compared with ordinary portland cement, but there was little injectability differences beteween microfine cement and ordinary portland cement at the large cracks or cavities were developed rock base.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.13-21
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• 2016

PURPOSES : In this study, we analyzed the compressive strength characteristics of lean base concrete in relation to changes in the outdoor temperature after analyzing the cold and hot weather temperature standards and calculated the minimum and maximum temperatures when pouring concrete. We examined the rate of strength development of lean base concrete in relation to the temperature change and derived an appropriate analysis formula for FRC base structures by assigning the accumulated strength data and existing maturity formula. METHODS : We measured the strength changes at three curing temperatures (5, 20, and $35^{\circ}C$) by curing the concrete in a temperature range that covered the lowest temperature of the cold period, $5^{\circ}C$, to the highest temperature of the hot period, $35^{\circ}C$. We assigned the general lean concrete and FRC as test variables. A strength test was planned to measure the strength after 3, 5, 7, 14, and 28 days. RESULTS : According to the results of compressive strength tests of plain concrete and FRC in relation to curing temperature, the plain concrete had a compressive strength greater than 5 MPa at all curing temperatures on day 5 and satisfied the lean concrete standard. In the case of FRC, because the initial strength was substantially reduced as a result of a 30% substitution of fly ash, it did not satisfy the strength standard of 5 MPa when it was cured at $5^{\circ}C$ on day 7. In addition, because the fly ash in the FRC caused a Pozzolanic reaction with the progress into late age, the amount of strength development increased. In the case of a curing temperature of $20^{\circ}C$, the FRC strength was about 66% on day 3 compared with the plain concrete, but it is increased to about 77% on day 28. In the case of a curing temperature of $35^{\circ}C$, the FRC strength development rate was about 63% on day 3 compared with the plain concrete, but it increased to about 88% on day 28. CONCLUSIONS : We derived a strength analysis formula using the maturity temperatures with all the strength data and presented the point in time when it reached the base concrete standard, which was 5 MPa for each air temperature. We believe that our findings could be utilized as a reference in the construction of base concrete for a site during a cold or hot weather period.

• Proceedings of the Korea Concrete Institute Conference
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• 1989.10a
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• pp.53-58
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• 1989

Thicknesses of the base concrete blocks for large machines were estimated by analyzing the resonance modes of mechanical vibrations. The vibration was produced by the mechanical impact and detected by a wideband conical transcuder. There signals were analyzed by FET and thicknesses were obtained by the peaks of frequency spectrum. The estimated thickness upto 100cm are in good agreement with the real ones. For the layered concrete block, the estimated thickness is dependent on the acoustic reflective index at the boundary of the two layers.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.99-110
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• 2007

A single slab concrete pavement has been modeled and analyzed by ABAQUS program. The stress and displacement of the JCP slab under traffic load with frictionless contact interaction between slab and base calculated by ABAQUS program have been compared with the results obtained by KENSLABS program. The results of the stresses of the two modeling show similar tendency and the difference of the two modeling is very small however the results of the displacement of the two modeling show some dissimilarity. In order to analyze the effects of material and geometric properties on the responses of slab, some varying parameters were chosen as input for the modeling. The changing parameters include the thickness and elastic modulus of the concrete slab, the thickness and elastic modulus of base and the elastic modulus of the subgrade. The contact interaction between the slab and base layer had been also studied and different friction coefficient 0, 2.5, 6.6, 7.5, 8.9 had been used to simulate the different friction interface condition. The results of the analysis showed that the responses of the concrete slab vary with the material and geometric properties of the pavement structure and the slab-base friction condition.