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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Concrete Institute
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Korea Concrete Institute
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Volume & Issues
Volume 24, Issue 6 - Dec 2012
Volume 24, Issue 5 - Oct 2012
Volume 24, Issue 4 - Aug 2012
Volume 24, Issue 3 - Jun 2012
Volume 24, Issue 2 - Apr 2012
Volume 24, Issue 1 - Feb 2012
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Influence of Strain-Hardening Cement Composite's Tensile Properties on the Seismic Performance of Infill Walls
Cha, Jun-Ho ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 3~14
DOI : 10.4334/JKCI.2012.24.1.003
This paper describes experimental results on the seismic performance of SHCC (strain-hardening cement composite) infill wall for improving damage tolerance capacity of non-ductile frame. To investigate the effect of tensile strain capacity and cracking behavior of SHCC materials on the shear behavior of SHCC infill wall, three infill walls were fabricated and tested under cyclic loading. The test parameter in this study is a type of cement composites; concrete and SHCCs. The two types of SHCC materials were prepared for infill walls. In order to induce crack damages into the mid-span of the infill wall, each infill wall had two 100-mm-deep-notches on both sides. Test results indicated that SHCC infill walls showed superior crack control capacities and much larger drift ratios at the peak loads than RC (reinforced concrete) infill wall, as expected. In particular, due to the bridging actions of the reinforcing fibers, SHCC matrix used in this study would delay the stiffness degradation of infill wall after the first inclined cracking. Moreover, from the damage classes based on the cracks' maximum width in the infill walls, it was observed that PIW-SHD specimen possessed nearly threefold seismic capacities compared to PIW-SLD specimen. Also, from the results on the strain of diagonal reinforcements, it can be concluded that the SHCC matrix would resist a part of tensile stresses transferred along steel rebar in the infill wall.
Serviceability Verification Based on Tension Stiffening Effect in Structural Concrete Members
Lee, Gi-Yeol ; Kim, Min-Joong ; Kim, Woo ; Lee, Hwa-Min ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 15~23
DOI : 10.4334/JKCI.2012.24.1.015
This paper is about proposal of a calculation method and development of an analytical program for predicting crack width and deflection in structural concrete members. The proposed method numerically calculate stresses in steel rebar using a parabola-rectangle stress-strain curve and a modified tension stiffening factor considering the effect of the cover thickness. Based on the study results, a calculation method to predict crack width and deflection in reinforced concrete flexural members is proposed utilizing effective tension area and idealized tension chord as well as effective moment-curvature relationship considering tension stiffening effect. The calculation method was applied to the test specimens available in literatures. The study results showed that the crack width and deflections predicted by the proposed method were closed to the experimentally measured data compared the current design code provisions.
Bi-Axial Stress Field Analysis on Shear-Friction in RC Members
Kim, Min-Joong ; Lee, Gi-Yeol ; Lee, Jun-Seok ; Kim, Woo ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 25~35
DOI : 10.4334/JKCI.2012.24.1.025
For a member subjected to direct shear forces, forces are transferred across interface concrete area and resisted by shear transfer capacity. Shear-friction equations in recent concrete structural design provisions are derived from experimental test results where shear-friction capacity is defined as a function of steel reinforcement area contained in the interface. This empirical equation gave too conservative values for concrete members with large amounts of reinforcement. This paper presents a method to evaluate shear transfer strengths and to define ultimate conditions which result in crushing of concrete struts after yielding of longitudinal reinforcement perpendicular to the interface concrete. This method is based on the bi-axial stress field theory where different constitutive laws are applied in various means to gain accurate shear strengths by considering softening effects of concrete struts based on the modified compression-field theory and the softened truss model. The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with recent design code provisions. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked normal-strength concrete test.
An Experimental Study on the Influence of the Qualities of Ordinary Portland Cement on the Flowability of High Flow Concrete
Choi, Sung-Woo ; Jo, Hyun-Tae ; Ryu, Deug-Hyun ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 37~44
DOI : 10.4334/JKCI.2012.24.1.037
Recently, due to developments in construction technology, the use of high-performance concrete became popular. High-performance concrete when compared to the ordinary concrete can better satisfy required performances by using mineral admixture and superplasticizer. Various studies on the effect of admixture materials on the quality of high-performance concrete have been reported. But there exist limited number of reported results on the effect of cement qualities, which is the most important constituent material in concrete. Therefore, in this study, the relationship between the quality of cement and the flowability of high flowing concrete is investigated. Qualities of domestically produced cement were identified, and then the influence of the qualities of cement on the flowability of high flowing concrete is evaluated. The result showed that the dosage of required superplasticizer was dependent on cement fineness, to brain, free-CaO, and interstitial phase, which all trigger initial hydration process of cement. Particularly, the results showed that fineness of cement has a high impact on the dosage of the superplasticizer. For strength property of concrete, the dosage of superplasticizer had a significant effect on the early age strength, but had negligible effect in the long term strength.
Experimental Study on Bond Behavior of Retrofit Materials by Bond-Shear Test
Ha, Ju-Hyung ; Yi, Na-Hyun ; Cho, Yun-Gu ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 45~52
DOI : 10.4334/JKCI.2012.24.1.045
A variety of retrofit material such as CFRP, GFRP, and PolyUrea have been developed for strengthening RC structures and infrastructures. From previously reported research results, the capacity of strengthened concrete structures was dictated by the behavior of the interface between retrofit material and concrete. In this study, bond-shear test was carried out to estimate the bond behavior between retrofit material and concrete using a newly developed test grip. The test results of load and slip relation and energy absorption capacity of each retrofit material were obtained. These test results will provide basic information for retrofit material selection to achieve target retrofit performance.
A Study on Properties of Concrete Made of Natural and Crushed Sand in High Temperatures
Kim, Joo-Seok ; Choi, Yeol ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 53~60
DOI : 10.4334/JKCI.2012.24.1.053
The main object of this paper is to investigate the effects of high temperatures on the physical and mechanical properties of natural sand concrete(NSC) and crushed sand concrete(CSC). Test samples were exposed to high temperature ranging from
. After exposure, various tests were conducted. Color image analysis and weight losses were determined and compressive strength test and splitting tensile strength test were conducted. The results indicated that weight losses increased as exposure temperature increased with comparable decreasing rate. The results also showed that compressive strength and splitting tensile strength and modulus of elasticity decreased as exposure temperature increased. The results also showed that residual compressive strength of NSC decreased more drastically than that of CSC at
. Residual splitting tensile strength of NSC decreased more than that of CSC at
, while NSC and CSC showed comparable residual strength ratio at
Properties of Foamed Concrete According to Types and Concentrations of Foam Agent
Kim, Jin-Man ; Jeong, Ji-Yong ; Hwang, Eui-Hwan ; Shin, Sang-Chul ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 61~70
DOI : 10.4334/JKCI.2012.24.1.061
Recently, the government has been working feverously to save energy and reduce greenhouse gas emission by enacting Basic Act on Low Carbon Green Growth at the national level. Improving the insulation performance of building exterior and insulator can reduce the energy in the building sector. This study is about developing light-weight foamed concrete insulation panel that can be applied to buildings to save energy and to find the optimal condition for the development of insulation materials that can save energy by enhancing its physical, kinetic and thermal characteristics. Various experimental factors and conditions were considered in the study such as foam agent types (AES=Alcohol Ethoxy Sulfate, AOS=Alpha-Olefin Sulfonate, VS=Vegetable Soap, FP=Fe-Protein), foam agent dilution concentration (1, 3, 5%), and foam percentage (30, 50, 70%). Experiment results indicated that the surface tension of aqueous solution including foam agent, was lower when AOS was used over other foam agents. FP produced relatively stable foams in 3% or more, which produced unstable foams containing high water content and low surface tension when diluted at low concentration. Depending on foam agent types, compressive strength and thermal conductivity were similar at low density range but showed some differences at high concentration range. In addition, when concentrations of foam agent and foaming ratio increased, pore size increased and open pores are formed. In all types of foam agent, thermal conductivity were excellent, satisfying KS standards. The most outstanding performance for insulation panel was obtained when FP 3% was used.
Shear Strength Enhancement of Hollow PHC Pile Reinforced with Infilled Concrete and Shear Reinforcement
Hyun, Jung-Hwan ; Bang, Jin-Wook ; Lee, Seung-Soo ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 71~78
DOI : 10.4334/JKCI.2012.24.1.071
In order to improve the shear strength of conventional pre-tensioned spun high strength concrete (PHC) pile, concrete-infilled composite PHC (ICP) pile, a PHC pile reinforced by means of shear reinforcement and infilled concrete, is proposed. Two types of specimens were cast and tested according to KS (Korean Standards) to verify the shear strength enhancement of ICP pile. Based on the test results, it was found that the KS method was not suitable due to causing shear failure of ICP pile. However, shear strength enhancement was clearly verified. The obtained shear strength of the ICP pile was more than twice that of conventional PHC pile. In addition, the shear strength of ICP pile reinforced with longitudinal reinforcement was estimated to be more than 2.5 times greater than that of conventional PHC pile. The allowable shear force of ICP pile, which was determined by the allowable stress design process, indicated a large safety factor of more than 2.9 compared to the test results.
Influence Evaluation of Fiber on the Bond Behavior of GFRP Bars Embedded in Fiber Reinforced Concrete
Kang, Ji-Eun ; Kim, Byoung-Ill ; Park, Ji-Sun ; Lee, Jung-Yoon ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 79~86
DOI : 10.4334/JKCI.2012.24.1.079
Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume.
Influence of Blast Furnace Slag and Anhydrite on Strength of Shotcrete
Ryu, Sung-Hee ; Shin, Kyung-Joon ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 24, issue 1, 2012, Pages 87~95
DOI : 10.4334/JKCI.2012.24.1.087
This study investigated the compressive strength, flexural strength, setting time, and rebound when blast furnace slag and anhydrite, which are widely used mineral admixtures for concrete, are applied to shotcrete. When Ordinary Portland Cement (OPC) was replaced at a rate of 10% with blast furnace slag and anhydrite, the initial and final setting time requirements were all satisfied. However, when OPC was replaced at a rate of 20%, final setting was delayed, revealing that this mixture was not suitable for shotcrete. Compressive strength test results showed that the mixture with 10% OPC replacement rate met the target strength at 1 day and 28 days for permanent tunnel support usage. Particularly, the mixture designed with OPC replacement by blast furnace slag and anhydrite at rates of 5% showed the highest compressive strength. Rebound measurements revealed that this mixture exhibited excellent performance with 23% reduction in the rebound compared to the shotcrete that was produced with only OPC binder.