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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 11, Issue 6 - Dec 1999
Volume 11, Issue 5 - Oct 1999
Volume 11, Issue 4 - Aug 1999
Volume 11, Issue 3 - Jun 1999
Volume 11, Issue 2 - 00 1999
Volume 11, Issue 1 - 00 1999
Selecting the target year
Bond Characteristics of High-Strength Light-Weight Concrete
Shin, Sung-Woo ; Lee, Kwang-Soo ; Choi, Myung-Shin ; Kim, Hyun-Sik ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 77~77
Recently, it is increased the use of High-Strength Light-Weight Concrete(HLC) in the high-rise buildings and mega-structures. But there are a few research on the bond behavior of HLC, so it need to study about that. The present study was performed to investigate the bond characteristics of HLC. Major test variables include concrete compressive strength(f'c), concrete cover(c), bond length (
), and bar diameter(
). Test results indicate that the bond stress of HLC is increased with the increment of
and concrete cover, bond stress is decreased with increment of bond length and bar diameter. And the final failure mode such as splitting or pullout failure is significantly affected by the concrete cover to bar diameter ratios(C/
). Test results were compared with ACI code and other proposed equations. The bond stress of HLC is higher than that of normal-strength normal-weight concrete, but lower than that of high-strength normal-weight concrte. Considering the present test results, modification factor(
= 1.3) of bond length in ACI 318-95 code for light-weight concrete is may have to be reviewed to apply to HLC.
on Cement-flyash Paste and the Strength Development of Concrete
Lee, Chin-Yong ; Bae, Sung-Yong ; Song, Jong-Taek ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 85~85
It was investigated to evaluate the characteristics of cement-flyash paste which was affected the replacement level, curing method and chemical admixtures. The strength of cement-flyash paste was lower than that of cement paste only and the differences increased with increasing the replacement level. However, in steam curing, the strength of cement-flyash pastes was improved and specially, the early strength was effectively increased. The inclusion of
increased the early strength of cement-flyash paste. In addition, the strength of concrete including 30% of fly ash and
has improved and obtained the highest strength compared to other concrete mixes.
Size Effect of Compressive Strength of Concrete for the Cylindrical Specimens Considering Strength Level
Kim, Hee-Sung ; Jin, Chi-Sub ; Eo, Seok-Hong ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 95~95
The reduction phenomena of concrete compressive strength with the size of specimens have been extensively investigated, but till now the adequate analysis technique is not fixed. The existing research results show that the bigger the member size, the smaller the strength. This means the nonlinear fracture mechanics theory is needed in order to analyze the fracture behaviors of concrete and the size effect. There is a few model equations that is to predict the size effect of compressive strength of standard and non-standard cylindrical specimen. However, theses equations did not considered the difference of fracturing mechanism which depends on the strength level. In this paper, model equations to predict compressive strength of concrete considering the size effect and strength level are suggested. The size effect model suggested in this paper shows good prediction compared with the existing test data of various concrete size and strength level.
Strengthening Effects of Slabs by Aramid Fiber Sheet
Yeon, Kyu-Seok ; Kang, Young-Sug ; Kim, Hyung-Woo ; Lee, Youn-Su ; Kim, Nam-Gil ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 105~105
This study was conducted to evaluate the structural behaviors of Aramid fiber sheet reinforced slabs. Seven concrete slabs with
were made for this experiment one slab with out being reinforced completely loaded until failure and the maximum load was obtained from this test. 70% of the maximum load was applied to 3 Aramid fiber sheet reinforced slabs after cracking and to the rest of 3 Aramid fiber sheet reinforced slabs without loading and cracking. Test results shows that maximum loading flexural rigidity and ductility for the Araimid fiber sheet reinforced slabs after initial cracking are similar as those for the Armied fiber sheet reinforced slabs without loading and cracking.
An Experimental Study on the Properties of Admixtures for Concrete
Bae, Su-Ho ; Chung, Young-Soo ; Park, Kwang-Su ; Lee, Joon-Gu ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 115~115
The purpose of this experimental research is to investigate the properties of workability and strength of the concrete containing admixtures such as silica fume, fly ash, ground granulated blast-furnace slag, and rice husk ash. For this purpose, the workability and the strength of the concrete containing each admixture were tested and analyzed according to the unit weight of binder and the replacement ratio of each admixture. As a result, considering their workability and strength, the existence of minimum binder weight and optimum replacement ratio of concrete containing admixture to plain concrete were obtained for each admixture.
Verification of Proposed Design Equation for Stress Evaluation of Unbonded Tendons
Lim, Jae-Hyung ; Moon, Jeong-Ho ; Lee, Li-Hyung ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 127~127
In the previous study in relation to the current study, a test program for the verification of the proposed design equation was carried with fourteen prestressed concrete beams with unbonded tendons. Experimental results were compared with the computed results by the proposed design equations. The previous design equations are ACI code, AASHTO LRFD code, the analysis equation with the strain compatibility, Harajli/Kanj' design equation, Chakrabarti' design equation. As a result of comparative studies, it turned out that the proposed design equation could predict the ultimate tendon stress with comparatively high accuracy.
The Similitude of Material for Small-Scale Model Mix Proportion of Concrete Pavement
Ko, Young-Zoo ; Lee, Yeoung-Woo ; Bae, Ju-Seong ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 139~139
The objective of this study is to provide the information on the small-scale model mix proportion when the behavior of prototype concrete pavement is studied through small-scale model experiments. However it is difficult to obtain a model material to simulate the prototype concrete by scaling the individual components according to the laws of similitude. In this paper, the stress-strain behavior in uniaxial compression is used as a means to correlate material similitude between the prototype and the model concrete. Based on the results of experiments, we compared the stress-strain curves of prototype and model concrete mixes using a nondimensional basis. In order to simulate the stress-stain curves of prototype concrete, it is important that various mix proportions of model concrete selected properly which are varied from aggregate grading, cement-aggregate and sand-aggregate ratio.
Behavior of Concrete Columns Confined by Carbon Fiber Sheets under a Constant Axial Force with Reversed Cyclic Lateral Loading
Chun, Sung-Chul ; Park, Hyung-Chul ; Ahn, Jae-Hyen ; Park, Chil-Lim ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 147~147
An investigation was conducted into the flexural behavior of earthquake damaged reinforced concrete columns repaired with carbon fiber sheets. Six column specimens were tested to failure under reversed cyclic loading. Two columns were specimens for control with no sheets and tested. These columns were repaired with carbon fiber sheets and retested to evaluate the effect of the confinement of the carbon fiber on the damaged column. Another two columns were repaired and tested with no pre-cyclic loading. The test specimens were designed to model single bent under a constant axial force with reversed cyclic lateral loading. Carbon fiber sheets were used to repair damaged concrete columns in the critically stressed areas near the column footing joint and the physical, mechanical properties of carbon fiber sheets are described. The performance of repaired columns in terms of their hysteretic response is evaluated and compared to those of the original columns. The results indicate that the repaire technique with carbon fiber sheets is highly effective. Both flexural strength and displacement ductility of repaired columns were higher than those of the original columns.
Size Effect for Flexural Compressive Strength of Concrete
Kim, Jin-Keun ; Yi, Seong-Tae ; Yang, Eun-Ik ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 157~157
When the ultimate strength of a concrete flexural member is evaluated, the effect of member size is usually not considered. For various types of loading, however, the strength always decreases with the increment of member size. In this paper the size effect of a flexural compression member is investigated by experiments. For this purpose, a series of C-shaped specimens subjected to axial compressive load and bending moment was tested using three different sizes of specimens with a compressive strength of 528 kg/
. According to test results the size effect on flexural compressive strength was apparent, and more distinct than that for uniaxial compressive strength of cylinders. Finally a model equation was derived using regression analyses with experimental data.
A study on Development of Methods to Rehabilitate the Damaged Prestressed Concrete beam Using Glass Fiber
Kang, Won-Ho ; Han, Man-Yop ; Lee, Taek-Sung ; Rhu, Young-Min ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 167~167
Many composite girder bridges have been constructed for about thirty five years. Nowadays they are aged or deteriorated because of the increase in traffic and vehicle loads. In this study, the effect of strengthening with glass fiber sheet is investigated to estimate the possibility for applying to damaged prestressed concrete bridges. One normal and eight cracked specimens which had been preloaded were tested. The cracked specimens were strengthened with either external prestressing or bonding glass fiber sheet, or using both methods. The results showed that the maximum loads are almost same for both methods. So it seems that the strengthening with glass fiber sheet can be used for strengthening damaged prestressed concrete girders. It is important that proper devices should be selected to prevent glass fiber sheet from premature bonding failure below its maximum load, which is similar to end anchorage problem in external prestressing method. It is proved that the devices proposed in this paper have sufficient anchoring capability to increase load carrying capacity.
Analytical Study on Interface Debonding of Reinforced Concrete Beams Strengthened with Carbon Fiber Sheet(CFS)
Sim, Jong-Sung ; Bae, In-Hwan ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 177~177
The purpose of this study is to analyze the interface debonding of RC beams strengthened by carbon fiber sheet(CFS). The behavior of damaged RC beams strengthened with CFS is analytically investigated next using linear elastic fracture mechanics(LEFM) approach and the finite element method. The study includes an investigation of the separation mode by interface fracture of the strengthening materials due to the interfacial shear and normal stresses. The numerical method is presented to obtain the value of interfacial fracture parameter such as the strain energy release rate. Based on the results of this study, it is found that the critical case occurs when the interfacial cracks occur within a short region of the flexural crack. The CFS strengthening has not an adequate factor of safety against interfacial debonding of CFS. Furthermore, for the thicknesses of the adhesive studied[1mm~3mm], it is no noticeable effect on the strain energy release rate.
An Experimental Study on the Structural Behavior of Concrete Columns Confined with Welded Reinforcement Grids
Choi, Chang-Sik ; Saatcioglu, Murat ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 187~187
An experimental investigation was conducted to study the structural behavior of concrete columns confined with welded grids. The full-scale columns with different volumetric ratio, spacing and arrangement of welded reinforcement grids were tested under simulated seismic loading. The columns were subjected to constant axial compression of approximately 20% or 40% of their capacities accompanied by incrementally increasing lateral deformation reversals. The results indicate that the welded reinforcement grid can be used effectively as confinement reinforcement provided that the steel used, have sufficient ductility and the welding process employed does not alter the strength and elongation characteristics of steel. The grids improved the structural performance of columns, which developed lateral drift ratios in excess of 3% with the spacing and volumetric ratio of transverse reinforcement similar to those required by the ACI 318-95 Building Code. Drift capacity further increased when grids with larger number of cells were used. Furthermore, the use of grids reduced congesting of reinforcement while the dimensional accuracy provided perfect support to longitudinal reinforcement.
A Study on the Prediction of the Strength and Axial Strain of High-Strength Concrete Columns Confined by Tie Reinforcement
Park, Hoon-Gyu ; Jang, Il-Young ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 197~197
The use of high-strength concrete which permits smaller cross sections, reduced dead loads, and longer spans has been getting more popular in tall buildings. However, there has been little research on behavior of high-strength concrete columns laterally reinforced with square ties and subjected to compressive loading. With the addition of transverse reinforcement which lead to triaxial compressive state, ductility behavior of high-strength column member shall be increased. In this study, rational quality and quantity evaluations were made to investigate the ultimate strength and strain ductility by confinement effect of tie reinforced high-strength concrete columns subject to uniaxial loads. Concrete failure theory at the triaxial compressive state and statistical results based on conventional experimental data were applied for this propose. Up to 185 columns, tested under monotonically increasing concentric loading, were evaluated in terms of strength and strain ductility. Analytical results show that confinement stress, maximum compressive strength, and increase of strain equations were developed with the consideration of concrete strength, yield strength, spacing, volumetric ratio, and configurations of tie reinforcement.
Steel Fiber Reinforcing Effect Analysis of Slab Panel Structure and Assessment Technics of Toughness
Jeon, Chan-Ki ; Park, Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 209~209
This paper is aimed to evaluate the effectiveness of flexural toughness of slab panel structures(
) reinforced by steel fiber instead of wire mesh. Steel fiber used in this study is double hooked Dramix type fiber. And the fiber length is 60mm, diameter is 0.8mm, Various assessment methods of toughness index are used to estimate the proper effectiveness. In this experimental study, we find that Johnston, JCI-SF4 and EFNARC method are more effective to assess the flexural toughness of slab panels than the others. And the steel fiber is very effective alternative material to reinforce slab panel structures instead of wire mesh. Fiber volume fraction of 0.5~0.75% is more useful than the others in enhancing the post-peak energy absorption and toughness index by Johnston's
assessment method. And the slab panels reinforcing with steel fiber are more resistant to crack propagation than wire mesh reinforcing slabs.
Effect of Impressed Current System for Corrosion Protection of Rebars in Concrete
Moon, Han-Young ; Kim, Seong-Soo ; Kim, Hong-Sam ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 221~221
Corrosion of rebars can occur if there are cracks, moisture and availability of oxygen or carbonation proceeds, chloride penetrates and diffuses in concrete. Once rebars in concrete corrodes, subsequently accompanied with scaling, spalling in concrete cover. As a result of them, the RC structure is seriously deteriorated. In this study, theoretical review and experiments for cathodic protection(CP) have been performed to control corrosion of rebars in concrete contained chlorides and pre-crack. For CP the impressed current system was applied, the protection effect was investigated when rebars was directly contacted with salt water due to crack and open to much chlorides in concrete. In order to investigate the effect of protection, when CP was energized for 1 year, half-cell potential, potential-decay with current density, corrosion ratio, etc. were measured. With the cathodic protection by impressed current system, the depolarized values of all specimen were met NACE Standard, the effect of 34~84% of the ratio of corrosion area and 84~86% of cross-section reduction were calculated.
An Experimental Study on the Properties of Compressive Strength of Fly Ash Replaced Antiwash out Underwater Concrete Considering Marine Environment
Kwon, Joong-Hyen ; Jung, Hee-Hyo ; Moon, Je-Kil ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 231~231
When the concrete is cast at the sea, there are lots of restrictions in the working process being different from in land, and the concrete is suffered from the physical and chemical action in terms of marine environment. The compressive strength was measured after antiwash out underwater concrete mixed with fly ash had been cast and cured in order to produce the endurable high performance concrete, and then its characteristic was discussed by comparing one cured in air with in fresh water, and the effect of fly ash usage under the properly controled sea water temperature of
was also covered. The present work showed that the proper usage of fly ash was obtained at the condition of around 10% of substituted binder weight under the structure required the early age strength, and at the condition of over 40% if considering its durability and economy.
Realistic Estimation Method of Compressive Strength in Concrete Structure
Oh, Byung-Hwan ; Yang, In-Hwan ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 241~241
To estimate the compressive strength of concrete more realistically, relative large number of data are necessary. However, it is very common in practice that only limited data are available. The purpose of the present paper is therefore to propose a realistic method to estimate the compressive strength of concrete with limited data in actual site. The Bayesian method of statistical analysis has been applied to the problem of the estimation of compressive strength of concrete. The mean compressive strength is considered as the random parameter and a prior distribution is selected to enable updating of the Bayesian distribution of compressive strength of concrete reflecting both existing data and sampling observations. The updating of the Bayesian distribution with increasing data is illustrated in numerical application. It is shown that by combining prior estimation with information from site observation, more precise estimation is possible with relatively small sampling. It is also seen that the contribution of the prior in determining the posterior distribution depends on its sharpness or flatness in relation to the sharpness or flatness of the likelihood function. The present paper allows more realistic determination of concrete strength in site with limited data.
Corrosion and Bond Strength Characteristics of Anti-Corrosive Cement Coated Reinforcements
Oh, Byung-Hwan ; Lee, Jong-Ryul ; Cho, Yun-Ku ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 251~251
Recently, large scale concrete structures exposed to severe environments are increasingly built in various locations, The corrosion may severely affect the durability and service life of such a concrete structure. It is, therefore, necessary to develop a method to enhance the corrosion resistance of a concrete, The purpose of this paper is, therefore, to investigate the corrosion resistance and bond strength characteristics of anti-corrosive cement coated reinforcements. To this end, a comprehensive experimental study has been done to explore the corrosion and bond behavior of those coated reinforcements. The test results indicate that the anti-corrosive cement coated reinforcements do not exhibit any corrosion after corrosion tests and the bond strengths are very good as much as plain bar. It is seen that the anti-corrosive cement coated reinforcements can be efficiently used to enhance the durability of reinforced concrete structures.
An Experimental Study on Dynamic Properties of Concrete with Vibration-Mitigation Materials
Chung, Young-Soo ; Park, Yong-Goo ;
Journal of the Korea Concrete Institute, volume 11, issue 2, 1999, Pages 261~261
In these days, construction activities have caused civil petitions associated with vibration-induced damages or nuisances. Therefore, it is strongly needed to develop a remedial technique to mitigate unfavorable effects. The objective of this experimental research is to investigate material and structural dynamic characteristics of vibration-controlled concretes which have been proportionally mixed with various vibration reducing material, such as latex, rubber powder, plastic resin, polystyrofoams and etc. Normal and high strength concrete specimens are also prepared for corresponding comparison. As part of the recycling research for obsolete rubber and plastic materials, 32 concrete cylinders and 10 concrete flexural beams have been made for material and structural dynamic properties, respectively. In accordance with the resonance test on concrete cylinders, it can be concluded that concrete with vibration-reducing material have relatively larger material damping ration than normal or high strength concrete. Styrofoam is determined to be very effective vibration-reducing mixtures. From the vibration test on 10 concrete flexural beams, meamwhile, of importance observations was that material damping ratio is very smaller than structural damping ratio of corresponding specimen. But further vibration test on more flexural beams should be strongly needed by varying support conditions.