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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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Journal DOI :
Korea Concrete Institute
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Volume & Issues
Volume 16, Issue 6 - Dec 2004
Volume 16, Issue 5 - Oct 2004
Volume 16, Issue 4 - Aug 2004
Volume 16, Issue 3 - Jun 2004
Volume 16, Issue 2 - Apr 2004
Volume 16, Issue 1 - Feb 2004
Selecting the target year
Comparison on the Behaviors of Inverted Tee and Rectangular Precast Prestressed Concrete Beams Under Combined Bending and Torsion
Seol Dong-Jae ; Park Sang-Yeol ; Yu Sung-Yong ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 733~740
DOI : 10.4334/JKCI.2004.16.6.733
This study presents the behaviors of the typical architectural precast prestressed concrete beams, inverted tee and rectangular beams, subjected to combined flexural and torsional loads. For this purpose, two inverted-tee beams were designed with a parking live load,
, and a market load
according to the currently used typical shape in the domestic building site. Also, two rectangular beams were also designed as the same bottom dimension and area, and reinforced for similar strength as in the cases of inverted tee beams. Total of four beams were tested, under combined bending and torsion, analysed and compared. Test results showed that the cracking and ultimate flexural strength of the beams decreased under torsional loading. However, two different shaped-beams had roughly the same load resisting capacity in service and ultimate states.
Analysis of Air Voids System Using Image Analysis Technique in Hardened Concrete
Yun Kyong-Ku ; Jeong Won-Kyong ; Jun In-Koo ; Lee Bong-Hak ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 741~750
DOI : 10.4334/JKCI.2004.16.6.741
Air voids in hardened concrete have an important influence on concrete durability such as freeze-thaw resistance, surface scaling resistance, and water permeability, and they have been characterized by spacing factor Linear traverse and point count methods in ASTM standard have been used in estimating an air void system in hardened concrete. However, these methods require lots of time and efforts, further they are not repeatable. Image analysis method could be utilized In estimating an air void systems in hardened concrete with a developments of microscope, digital camera and computer program. The purpose of this study was to develope image analysis method and provide a guideline by comparing the results from ASTM method and image analysis method. The concerns were at air void content and diameter distribution, air voids system as well as spacing factors. The experimental variables included air content by air entrained agent (0, 0.01,
) and depth of specimen (top, middle, bottom). The result showed that it was possible to calculate spacing factor using image analysis technique, as well as air content, air diameter distribution, and air structure. This study also contributed in developing an reasonable and repeatable image analysis method.
Alkali-Activated Coal Ash(Fly Ash, Bottom Ash) Artificial Lightweight Aggregate and Its Application of Concrete
Jo Byung-Wan ; Park Seung-Kook ; Kwon Byung-Yoon ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 751~757
DOI : 10.4334/JKCI.2004.16.6.751
Artificial lightweight aggregates and solids were manufactured with coal ash(fly ash, bottom ash). In order to apply alkali-activated coal ash(fly ash, bottom ash) artificial lightweight aggregate to concrete, several experimental studies were performed. Thus, it can be noticed the optimal mix proportion, basic characteristies, mechanical properties and environmental safety of alkali-activated coal ash(fly ash, bottom ash) solid and alkali-activated coal ash(fly ash, bottom ash) artificial lightweight aggregate. Also, the freezing-thawing test property of concrete using the alkali-activated coal ash(fly ash, bottom ash) artificial lightweight aggregate was investigated. As a result, the optimal mixing proportion of coal ash(fly ash, bottom ash) solid to make alkali-activated artificial lightweight aggregates was cement
, water glass
. Alkali-activated coal ash(fly ash, bottom ash) solid can achieve compressive strength of 36.4 MPa, at 7-days, after the paste was cured at air curing after moist curing during 24 hours in
. Alkali-activated coal ash(fly ash, bottom ash) artificial lightweight aggregate that do impregnation to polymer was improved
, and was available to concrete.
Characteristic Strength and Deformation of SFRC Considering Steel Fiber Factor and Volume fraction
Lee Hyun-Ho ; Lee Hwa-Jin ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 759~766
DOI : 10.4334/JKCI.2004.16.6.759
The addition of steel fiber with concrete significantly improves the engineering properties of structural members, notably shear strength. The purpose of this study is to determine the steel fiber shape, aspect ratio and volume fraction ratio in a point of practical usage as structural members. Steel fiber factor and volume fraction are also considered to verify the strengthening effect in member level. From the reviewing of previous researches and analyzing of consecutive material test results, the optimum shape and length of steel fiber, which can have a good strengthening effects were defined as a hooked end type and larger than 1.5 times of maximum gravel size. Analyzing the test results of strength and deformation capacity, aspect ratio 75 and volume fraction
can be having a maximum strengthening effect of steel fiber. Also steel fiber factor, tensile splitting strength, and flexural strength are found as key parameter in shear strengthening effect in member level.
A Proposal of Stress-Strain Relations Model for Recycled-PET Polymer Concrete under Uniaxial Stress
Jo Byung-Wan ; Moon Rin-Gon ; Park Seung-Kook ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 767~776
DOI : 10.4334/JKCI.2004.16.6.767
Polymer concrete shows excellent mechanical properties and chemical resistance compared with conventional normal cement concrete. The polymer concrete is drawing a strong interest as high-performance materials in the construction industry. Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. Also the recycling of PET in polymer concrete would help solve some of the solid waste problems posed by plastics and save energy. The purposed of this paper is to propose the model for the stress-strain relation of recycled-PET polymer concrete at monotonic uniaxial compression and is to investigate for the stress-strain behavior characteristics of recycled-PET polymer concrete with different variables(strength, resin contents, curing conditions, addition of silane and ages). The maximum stress and strain of recycled-PET polymer concrete was found to increase with an increase in resin content, however, it decreased beyond a particular level of resin content. A ascending and descending branch of stress-strain curve represented more sharply at high temperature curing more than normal temperature curing. Addition of silane increases compressive strength and postpeak ductility. In addition, results show that the proposed model accurately predicts the stress-strain relation of recycled-PET polymer concrete
A Study on the Charateristics of Antiwashout Underwater Concrete with Mineral Admixture
Baek Dong-Il ; Kim Myung-Sik ; Jang Hee-Suk ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 777~783
DOI : 10.4334/JKCI.2004.16.6.777
In this study, for improving of concrete properties, those are used ground granulated blast slag(GGBS) and fly ash(FA). There are some advantage to add the GGBS and FA in plain concrete. The objective of this study is to find the characteristics of fresh and hardened antiwashout underwater concrete which is followed by blended ratio of GGBS and FA. Experimental parameters were chosen that W/C was
, S/a was
and as the blended ratio of GGBS was set at 0, 10, 20, 30, 40, 50,
and FA was set at 0, 10, 15, 20, 25, 30,
in order to prove the properties of antiwashout underwater concrete can be changed by blended ratio of GGBS md FA. It was measured pH, suspension and slump flow of fresh antiwashout underwater concrete and compressive strength of hardened antiwashout underwater concrete in age of 7 days, 28 days and 56 days. The experimental results of fresh concrete show that pH, suspension and slump flow were all satisfied with KSCE (Korea Society of Civil Engineering) standard value and mix design standard value. To synthetically consider, the optimum blended ratio is about
of GGBS and FA.
A New Refined Truss Modeling for Shear-Critical RC Members (Part I) - lts derivation of Basic Concept -
Kim Woo ; Jeong Jae-Pyong ; Kim Dae-Joong ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 785~794
DOI : 10.4334/JKCI.2004.16.6.785
This paper describes a new refined truss modeling technique derived based on the well-known relationship of V=dM/dx=zdT/dx+Tdz/dx in a reinforced concrete beam subjected to combined shear and moment loads. The core of the model is that a new perspective on the shear behavior can be gained by considering the variation of the internal arm length along the span, so that the shear resistance mechanism can be expressed by the sum of two base components; arch action and beam action. The sharing ratio of these two actions is determined by accounting for the compatibility of deformation associated to the two actions. Modified Compression Field Theory and the tension-stiffening effect formula in CEB/FIP MC-90 are employed in calculating the deformations. Then the base equation of V=dM/dx has been numerically duplicated to form a new refined truss model.
Effects of Shear Span-to-depth Ratio and Tensile Longitudinal Reinforcement Ratio on Minimum Shear Reinforcement Ratio of RC Beams
Lee Jung-Yoon ; Kim Wook-Yeon ; Kim Sang-Woo ; Lee Bum-Sik ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 795~803
DOI : 10.4334/JKCI.2004.16.6.795
To prevent the shear failure that occurs abruptly with no sufficient warning, the minimum amount of shear reinforcement should be provided to reinforced concrete(RC) beams. The minimum amount of shear reinforcement of RC beams is influenced by not only compressive strength of concrete but also shear span-to-depth ratio and ratio of tensile longitudinal reinforcement. In this paper, 14 RC beams were tested in order to observe the influences of shear span-to-depth ratio, ratio of tensile longitudinal reinforcement, and compressive strength of concrete. The test results indicated that the rate of shear strength to the diagonal cracking strength of RC beams with the same amount of shear reinforcement increased as the ratio of tensile longitudinal reinforcement increased, while it decreased as the shear span-to-depth ratio increased. The observed test results were compared with the calculated results by the current ACI 318-02 Building Code and the proposed equation.
Property of tow Shrinkage High Performance Concrete depending on Mixture Proportions and Material Characteristics
Han Cheon-Goo ; Kim Sung-Wook ; Koh Kyoung-Taek ; Han Mu-Cheol ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 805~811
DOI : 10.4334/JKCI.2004.16.6.805
In this paper, effects of mixture proportion and material condition on both fundamental properties, drying and autogenous shrinkage of high performance concrete are discussed. According to the results, for the effect of mixture proportion on the fundamental properties, decrease in W/B and unit water content results in reduction of fluidity, while air content has no variation. Compressive strength exhibits an decreasing tendency with an increase in W/B and unit water content do not remarkable affect the compressive strength. For the effect of materials on the fluidity, the fluidity of low heat portland cement(LPC) is smaller than that of ordinary portland cement(OPC). The use of Polycarbonic acid based superplasticizer(PS) has more favorable effect on enhancing fluidity than Naphtalene based superplasticlzer(NS) and Melamine based superplasticizer(MS). Air content of concrete using LPC is larger than that using OPC. The effects of superplasticizer type on the air content is larger in order of MS, PS and NS. The use of LPC exhibited lower strength development at early age than OPC, whereas after 91days, similar level of compressive strength is achieved regardless of cement type. Compressive strength of concrete is not affected by SP type. For the effect of mixture proportion and materials on drying and autogenous shrinkage, an increase in W/B results in reduction of drying shrinkage and an decrease in water content leads to reduce drying shrinkage. Autogenous shrinkage is not observed until 49 days with the concrete mixture with
of W/B and
of water content. This is due to the combination effects of expansion admixture and shrinkage reducing admixture, which causes an offset of autogenous shrinkage. The use of LPC results in a reduction in autogenous shrinkage compared with OPC. SP type has little influence on the autogenous shrinkage. It is found from the results that mixture proportioning of high performance concrete incorporating fly ash, silica fume, expansion admixture and shrinkage reducing admixture is need to focus on the increase in W/B and the reduction in water content and the use of LPC and MS is also required to use to secure the stability against shrinkage properties.
Shear Strength Prediction of Reinforced Concrete Members Subjected In Axial force using Transformation Angle Truss Model
Kim Sang-Woo ; Lee Jung-Yoon ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 813~822
DOI : 10.4334/JKCI.2004.16.6.813
For the prediction of the shear strength of reinforced concrete members subjected to axial force, this paper presents a truss model, Transformation Angle Truss Model (TATM), that can predict the shear behavior of reinforced concrete members subjected to combined actions of shear, axial force, and bending moment. In TATM, as axial compressive stress increases, crack angle decreases and concrete contribution due to the shear resistance of concrete along the crack direction increases in order to consider the effect of the axial force. To verify if the prediction results of TATM have an accuracy and reliability for the shear strength of reinforced concrete members subjected to axial forces, the shear test results of a total of 67 RC members subjected to axial force reported in the technical literatures were collected and compared with TATM and existing analytical models(MCFT RA-STM and FA-STM). As a result of comparing with experimental and theoretical results, the test results was better predicted by TATM with 0.94 in average value of
in coefficient of variation than other truss models. And theoretical results obtained from TATM were not effect by steel capacity ratio, axial force, shear span-to-depth ratio, and compressive steel ratio.
Flexure-Shear Behavior of Circular Bridge Columns under Cyclic Lateral Loads
Lee Jae-Hoon ; Ko Seong-Hyun ; Lee Dae-Hyoung ; Chung Young-Soo ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 823~832
DOI : 10.4334/JKCI.2004.16.6.823
The purpose of this research is to investigate the flexure-shear behavior of bridge columns under seismic loads. Four full scale circular reinforced concrete columns were tested under cyclic lateral load with constant axial load. The selected test variables are aspect ratio(1.825, 2.5, 4.0), transverse steel configuration, and longitudinal steel ratio. Volumetric ratio of transverse hoop of all the columns is 0.0023 in the plastic hinge region. It corresponds to
of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. The columns showed flexural failure or flexure-shear failure depending on the test variables. Failure behavior and seismic performance are investigated and discussed in this paper.
A Study on the Minimum Number of Rebound Number Test and Pulse Velocity Method for Estimating Compressive Strength of Concrete
Lee Mun-Hwan ; Choi Chang-Woo ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 833~840
DOI : 10.4334/JKCI.2004.16.6.833
Among non-destructive tests for compressive strength, rebound number test and pulse velocity test are the most widely used methods. However, the non-destructive tests mostly used in Korea was developed by foreign country. Therefore, it is unreasonable to directly apply them to concrete structures in Korea. In accordance with the suggestion of Institute of Architecture in Japan for rebound number test, a compressive strength is calculated by the mean value of 20 hit points without being considered standard deviation. Furthermore, there is no regulation on the number of measurements required for measuring compressive strength by pulse velocity test. This study, therefore, reviewed the rebound number test and pulse velocity test by chi-square, and suggested the minimum number of each test. As a result, the minimum number that falls within range of reliability for rebound number test and pulse velocity test are 11 and 7, respectively. If abnormal values are processed as missing and test groups are assumed to be arrayed in cross by considering changes in quality of actual concrete structures, 20 times and 9 times are appropriate for rebound number test and pulse velocity test, respectively.
An Effect of Uplift Pressure Applied to Concrete Gravity Dam on the Stress Intensity Factor
Lee Young-Ho ; Jang Hee-Suk ; Kim Tae-Wan ; Jin Chi-Sub ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 841~850
DOI : 10.4334/JKCI.2004.16.6.841
The modeling of uplift pressure within dam, on the foundation on which it was constructed, and on the interface between the dam and foundation is a critical aspect in the analysis of concrete gravity dams, i.e. crack stability in concrete dam can correctly be predicted when uplift pressures are accurately modelled. Current models consider a uniform uplift distribution, but recent experimental results show that it varies along the crack faces and the procedures for modeling uplift pressures are well established for the traditional hand-calculation methods, but this is not the case for finite element (FE) analysis. In large structures, such as dams, because of smaller size of the fracture process zone with respect to the structure size, limited errors should occur under the assumptions of linear elastic fracture mechanics (LEFM). In this paper, the fracture behaviour of concrete gravity dams mainly subjected to uplift Pressure at the crack face was studied. Triangular type, trapezoidal type and parabolic type distribution of the uplift pressure including uniform type were considered in case of evaluating stress intensity factor by surface integral method. The effects of body forces, overtopping pressures are also considered and a parametric study of gravity dams under the assumption of LEFM is performed.
Fracture Toughness of a Center Notched Concrete Disk
Park Hyun-Jae ; Jang Hee-Suk ; Lee Seung-Hoon ; Jin Chi-Sub ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 851~858
DOI : 10.4334/JKCI.2004.16.6.851
Purpose of this paper is to determine the appropriate size of a center notched disk specimen for mode I fracture toughness
. For this purpose, mode I test results with various sizes of center notched disk were compared with the RILEM three-point-bend test ones. Compressive strength of concrete used in this paper was 44.9 MPa. Diameters of 200, 300, 400 mm, thickness of 75, 100, 125 mm, and notch length ratios an of 0.3, 0.4, 0.5, 0.6 were used for the mode I disk test. Also, diameter of 300mm thickness of 100mm, and notch length ratios a/R of 0.3, 0.4, 0.5, 0.6 were used for the mixed mode disk test. Mixed mode stress intensity factors were investigated by changing notch angles for the disk specimen. Stress intensity factors of a center notched disk were calculated with the various methods for comparison. From the test results, mode I fracture toughness calculated from the disk specimen with diameter of 300 mm, thickness of Inn and notch length ratio a/R of 0.5 was very similar to the RILEM three-point-bend test ones. And it is verified that stress intensity factors for mixed mode can be easily calculated with the disk specimen.
Diffusion of Chloride Ions in Limestone Powder Concrete
Moon Han-Young ; Jung Ho-Seop ; Kim Jong-Pil ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 859~865
DOI : 10.4334/JKCI.2004.16.6.859
In this study, the diffusion of chloride ions in cement concrete made with and without the limestone powder was investigated. In order to study the effect of the limestone powder, all mixtures were prepared at a fixed water-cementitious ratio (0.45). From the experimental results, the setting time of limestone powder concrete is faster than that of control concrete, and compressive strength of all specimens decreased with increasing replacement ratio of limestone powders. The diffusion properties of limestone powder concretes indicated a trend increasing with curing period. LSA10 and LSA20 concretes, the diffusion coefficient was smaller than that of control concrete. The addition of
limestone powder reduces the diffusion coefficient of chloride ions, irrespective of fineness levels of limestone powder.
An Experimental Study to Prevent Debonding Failure of Full-Scale RC Beam Strengthened with Multi-Layer CFS
You Young-Chan ; Choi Ki-Sun ; Kim Keung-Hwan ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 867~873
DOI : 10.4334/JKCI.2004.16.6.867
It has been known that debonding failures between CFS(Carbon Fiber Sheet) and concrete in the strengthened RC beams are initiated by the peeling of the sheets in the region of combined large moment and shear forces, being accompanied by the large shear deformation after flexural cracks. These shear deformation effects are seldom occurred in small-scale model tests, but debondings due to the large shear deformation effects are often observed in a full-scale model tests. The premature debonding failure of CFS, therefore, must be avoided to confirm the design strength of full-scale RC beam in strengthening designs. The reinforcing details, so- called 'U-Shape fiber wrap at mid-span' which wrapped the RC flexural members around the webs and tension face at critical section with CFS additionally, were proposed in this study to prevent the debonding of CFS. Other reinforcing detail, so called 'U-Shape fiber wrap at beam end' were included in this tests and comparisons were made between them.
Influence of the Quality of Recycled Aggregates on Microstructures and Strength Development of Concrete
Moon Dae-Joong ; Moon Han-Young ; Kim Yang-Bae ;
Journal of the Korea Concrete Institute, volume 16, issue 6, 2004, Pages 875~881
DOI : 10.4334/JKCI.2004.16.6.875
The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60. 1MPa, B:41.7MPa, C:25.5MPa). Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over
, but increased rapidly in the porosity of new mortar fewer than