Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korea Concrete Institute
Journal Basic Information
Journal DOI :
Korea Concrete Institute
Editor in Chief :
Volume & Issues
Volume 13, Issue 6 - Dec 2001
Volume 13, Issue 5 - Oct 2001
Volume 13, Issue 4 - Aug 2001
Volume 13, Issue 3 - Jun 2001
Volume 13, Issue 2 - Apr 2001
Volume 13, Issue 1 - Feb 2001
Selecting the target year
Development of Self Waterproofing Admixture for Concrete Using Inorganic Admixture
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 527~535
DOI : 10.22636/JKCI.2001.13.6.527
The watertight property of concrete was examined, that is affected by the sort of self waterproofing admixture and the change of the addition ratio of admixture. Various self waterproofing admixtures were made by changing the mixing ratio of silica fume, zinc stearate and silica sand. The result showed as follows. As the adding ratio of self waterproofing admixture increases, the fluidity is increased and the setting time is delayed. While compressive strength of concrete with self waterproofing admixture A which is currently using is increased until the adding ratio of self waterproofing admixture reached 18kg/㎥ and decreased over 24 kg/㎥, that with self waterproofing admixture B, C and D which are developed are higher than that of A. Absorption is decreased as the adding ratio of self waterproofing admixture and the increasing of age in concrete. Especially, when self waterproofing admixture has a lot of zinc stearate, absorption is decreased manifestly. The property of permeability is similar to that of absorption; permeability is decreased as the adding ratio of self waterproofing admixture and the increasing of age in concrete. Consequently, when the ratio of silica fume, zinc stearate and silica sand in self waterproofing admixture is 1 : 2 : 1 and addition ratio of self waterproofing admixture is 6kg/㎥, the high quality concrete is obtained comparing to the concrete with existent self waterproofing admixture.
Development of Early-Strength of High-Strength Concrete According to Curing Temperature for Application of System Form
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 536~543
DOI : 10.22636/JKCI.2001.13.6.536
Nowadays, with high-stoned and large-sized of structures, high-strength concrete is applicable to various methods. When high-strength concrete is used jointly with system form, seizing on the development of compressive strength at early age is very important in aspect of construction process. Because system form is stripped more faster than ordinary form. But, we have little data of compressive strength before system-form is stripped, and it isn't yet established that decision criterion of the time when system-form is stripped. So this paper deals with the development of compressive strength at early age before system-form is stripped. In this study, the experimental results indicate the boundary of curing temperature and mixing factor that is able to get needful early-strength in the application of slip-form method, and curing temperature must be kept over 15 degrees in winter season.
Investigation on Response Modification Factor of RC Structural Walls in Apartment Buildings
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 544~552
DOI : 10.22636/JKCI.2001.13.6.544
Korea is classified into low and moderate seismic zone from the view-point of seismic hazard level. Korean seismic provisions has been developed based on UBC and ATC 3-06. Thus, in calculation of design base shear according to Korean provisions response modification factor (R) is included in the formula of design base shear. The major role of this factor is to reduce the elastic design base shear whereby structures can behave in inelastic range during design level earthquake ground motions(mean return period of 475 yrs.). R factor is assigned according to material and structural systems. In this study, R factor for bearing wall system is considered. Most of the walls of apartment buildings in Korea resist gravity and seismic loads simultaneously so that this wall system can be classified into bearing wall system. Structural details of these walls are different from those used in Japan and U.S.. They are all rectangular in sectional shape rather than barbell in shape, and also have special lateral reinforcement details at the boundaries of a wall. In Korean seismic design provisions(1988), two different values(3.0 and 3.5) of R factor are assigned to the bearing wall systems according to the wall details. However, in updated seismic provisions(2000), only one value is assigned to R factor(3.0) irrespective of wall details. In this study, the design base shear values in Korean seismic design provisions(1988, 2000), ATC 3-06, UBC are compared. Also experimental study was carried out to evaluate the seismic performance of structural walls. For this purpose, five test specimens were made which have special details used in apartment bearing wall systems in Korea. Based on the results of this study, response modification factor for bearing wall system is discussed.
Effect of Tension, Compression and Lateral Reinforcement In Ductility Ratio in RC Flexural Members
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 553~560
DOI : 10.22636/JKCI.2001.13.6.553
The ductility capacity should be estimated for inelastic analysis and design of reinforced concrete flexural members. Therefore, to estimate the ductility capacity, the model of moment-curvature relationship of reinforced concrete flexural member is assumed in this study. The curvature, rotation, and displacement(deflection) of reinforced concrete cantilever beams are analyzed and tested. The analytical results are compared with the test results. According to the analytical and test results, the assumed model of moment-curvature relationship in this study is adequate in flexural analysis of reinforced concrete members because the analytical results are well agreed with the test results, and it is resonable to express the ductility capacity in the rotation or displacement ductility, Because the curvature ductility is the limited index in a certain section. It is investigated that the ductility capacity is proportional to lateral reinforcement and compression reinforcement and inversely proportional to tension reinforcement.
Strength and Absorption Properties of Cement Mortar Produced with Various Content of Sludge Powder at Mines
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 561~567
DOI : 10.22636/JKCI.2001.13.6.561
It is reported that a lot of sludge powder is produced during the process of manufacturing crushed fine aggregate in mines. However, there is a limitation on the its use that most of them are disposed and wasted, which cause environmental pollution. Therefore, in this paper, tests are carried out in order to recycle sludge powder as filler for cement mortar products. Kinds of aggregates and mix proportion of mortar are varied under various contents of sludge powder. According to test results, it is found that cement mortar products using sludge powder as substitution of fine aggregate about 10% have better qualities than those without sludge powder.
Resistance Curves of Propagating Cracks for Concrete Three-Point Bend Specimens
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 568~574
DOI : 10.22636/JKCI.2001.13.6.568
From measured responses of concrete three-point bend tests, the average values of the responses have been calculated. The fracture behavior of continuously propagating concrete crack has been analyzed from the average responses. The experimental parameters of this study were the initial notch sizes of 25.4㎜ and 6.4 ㎜ and the processing times of 2,000 sec. and 20 sec . The different notch sizes were used for the effects of the size of fracture process zone and specimen geometry, and the processing times for those of initial creep. However the load-point displacement rate in this study did not affect the experimental responses seriously. The average loads were calculated from the average external work of a series of tests, and average crack lengths were determined by using strain gages. Before the peak load, the resistance curve could be determined from the size of fracture process zone, but unstable crack propagation of 88㎜ occurred at the load-point displacement of 0.088∼0.154㎜ after the peak load. The average fracture energy density G
ave/ = 115 N/m occurred during the unstable crack propagation. The fracture process zones were fully developed at the crack length of 111㎜, and the sizes of fracture process zone for initial notches of 25.4㎜ and 6.4㎜ were 86㎜ and 105㎜, respectively. Average fracture energy densities of the resistance curves after full development of fracture process zone were 229 N/m for the initial notch of 25.4㎜ and 284 N/m for 6.4㎜. The values were more than twice of G
Properties of High Strength Recycled Aggregate Concrete
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 575~583
DOI : 10.22636/JKCI.2001.13.6.575
The purpose of this study is to present the method of utilizing the recycled aggregate that are obtained from waste concrete as the concrete aggregate. We manufactured the recycled aggregate concrete with compressive strength of over 300kgf/㎠ to increase its weaker strength than the normal concrete, and compared the physical features of the recycled aggregate concrete with that of the normal concrete. As a result of the study, the mechanical performances such as compressive and tensile strength were generally reduced as the mixing rate of the recycled aggregate increased; however, it was possible to manufacture the concrete with the compressive strength of 300∼600kgf/㎠ using the adequate mixing material such as unit quantity of cement, compounding water and silicafume. However, a continuous study on long-term durability performance is required to manufacture and utilize the recycled aggregate concrete for the structure.
Flexural Behavior of Dual Concrete Beams Using Fiber Reinforced Concrete at Tensile Parts
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 584~592
DOI : 10.22636/JKCI.2001.13.6.584
The cracks are developed in reinforced concrete(RC) beams at the early stage of service load because of the relatively small tensile strength of concrete. The structural strength and stiffness are decreased by reduction of tensile resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structures and decrease the tensile flexural cracks and deflections. Therefore, the RC beams used of the fiber reinforced concrete at. tensile part ensure the safety and serviceability of the concrete structures. In this work, analytical model of a dual concrete beams composed of the normal strength concrete at compression part and the high tension strength concrete at tensile part is developed by using the equilibrium conditions of forces and compatibility conditions of strains. Three groups of test beams that are formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio are tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the RC beams is increased in approximately 30%. In addition, the flexural rigidity, as used here, referred to the slope of load-deflection curves is increased and the deflection is decreased.
Design Considerations and Pull-Out Behavior of Mechanical Anchor of Reinforcement
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 593~601
DOI : 10.22636/JKCI.2001.13.6.593
In RC structure, sufficient anchorage of reinforcement is necessary for the member to produce the full strength. Generally, conventional standard hook is used for the reinforcement's anchorage. However, the use of standard hook results in steel congestion, making fabrication and construction difficult. Mechanical anchor offers a potential solution to these problems and may also ease fabrication, construction and concrete placement. In this paper, the required characteristics and the design considerations of mechanical anchor were studied. Also, the mechanical anchor was designed according to the requirements. To investigate the pull-out behavior and properness of mechanical anchorage, pull-out tests were performed. The parameters of tests were embedment length, diameter of reinforcement, concrete compressive strength, and spacing of reinforcements. The strengths of mechanical anchor were consistent with the predictions by CCD method. The slip between mechanical anchor and concrete could be controlled under 0.2mm. Therefore, the mechanical anchor with adequate embedment could be used for reinforcement's anchorage. However, it was observed that the strength of mechanical anchors with short spacing of reinforcements was greatly reduced. To apply the mechanical anchor in practice (e.g. anchorage of the beams reinforcements in beam-column joint), other effects that affect the mechanical anchor mechanism, such as confinement effect of adjacent member from frame action or effects of shear reinforcement, should be considered.
Analytical Model for Shear Strength of RS Hybrid Steel Beams with Reinforced Concrete Ends
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 602~609
DOI : 10.22636/JKCI.2001.13.6.602
A strut-and-tie model was proposed to predict the shear strength of RS beam which is a hybrid steel beam with reinforced concrete ends. The proposed model is capable of considering the concrete softening effects due to diagonal shear cracks at the embedded area of steel in concrete. It can predict tile failure strength of RS beam from the mathematical formulations which are based on equilibrium, compatibility, and the constitutive laws of cracked reinforced concrete. The previous experimental results of 15 RS beams were analyzed with the proposed model and the analytical results were also compared with formulas currently available. The comparison revealed that the proposed model can predict the strength of RS beam better than the others. The average ratio of experimental strengths to analytical results was 1.02 and the standard deviation was 0.126.
Effect of Temperature and Aging on the Relationship Between Dynamic and Static Elastic Modulus of Concrete
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 610~618
DOI : 10.22636/JKCI.2001.13.6.610
This paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model of the relationships we proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperatures of 10, 23, and 50
Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus according to cement type, temperature and aging. The proposcd relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type md temperature.
Shear Behavior of Reinforced Concrete Deep Beams with Web Openings
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 619~628
DOI : 10.22636/JKCI.2001.13.6.619
In building construction, openings of the story-height deep beams are usually required for accessibility and service lines such as air conditioning ducts, drain pipes and electric units. It is known that the main parameters affecting the load bearing capacity of deep beams with web openings are size, shape, location and reinforcements of openings. However, there have been no pertinent theories and national design codes for predicting ultimate shear strength of reinforced concrete deep beams with web openings. In this study, the shear behavior of simply supported reinforced concrete deep beams with web openings subject to concentrated loads has been scrutinized experimentally. A total of 34 specimens, the geometry of openings, its reinforcements and shear span to depth ratio, being taken as the experimental variables, has been cast and tested in the laboratory. The effects of these structural parameters on the shear strength and crack initiation and propagation have been carefully checked and analyzed. From the tests, it has been observed that the failures of all specimens were due to shear mechanism and the ultimate strength of specimens varies according to the location of openings, by which the formation of compression struts between the loading points and supports are deterred. All of the test results of specimens have been compared with the formulas proposed by previous researchers. The results were closely coincident with the formulas given by Ray and Kong's equation except for some X series specimens having a larger dimension of openings beyond the geometric limits of proposed equations.
크리프와 건조수축을 고려한 철근콘크리트 기둥과 동바리의 축력 재분배 해석법
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 629~636
DOI : 10.22636/JKCI.2001.13.6.629
To apply the research results to the design and the construction of the high rise buildings, long-term behavior of reinforced concrete structure have been widely studied. However, shoring and reshoring at early ages have not been considered in the most of studies. The removal of forms and shores has been dealt with one construction sequence. i.e. the deformation occurred at the early age before the removal of shore has been neglected. In this paper, two-dimensional frame analysis program for long-term behavior of reinforced concrete was developed. In the developed program, construction sequence including the settlement and the removal of shores is considered to predict axial force variation due to forms ,shores, and time-dependent concrete stiffness. Analysis results show that the time-dependent axial force of shores is reduced, and the redistributed axial force of the interior column is greater than the value by elastic analysis and that of the exterior column is smaller. In order to demonstrate the validity of this program, the test frame was constructed in sequence of the placement of concrete, form removal, reshoring, shore removal, and the application of additional load. The proposed program predicts experimental results well.
Finite Element Mesh Dependency in Nonlinear Earthquake Analysis of Concrete Dams
Journal of the Korea Concrete Institute, volume 13, issue 6, 2001, Pages 637~644
DOI : 10.22636/JKCI.2001.13.6.637
A regularization method based on the Duvaut-Lions viscoplastic scheme for plastic-damage and continuum damage models, which provides mesh-independent and well-posed solutions in nonlinear earthquake analysis of concrete dams, is presented. A plastic-damage model regularized using the proposed rate-dependent viscosity method and its original rate-independent version are used for the earthquake damage analysis of a concrete dam to analyze the effect of the regualarization and mesh. The computational analysis shows that the regularized plastic-damage model gives well-posed solutions regardless mesh size and arrangement, while the rate-independent counterpart produces mesh-dependent ill-posed results.