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 23, Issue 6 - Dec 2011
Volume 23, Issue 5 - Oct 2011
Volume 23, Issue 4 - Aug 2011
Volume 23, Issue 3 - Jun 2011
Volume 23, Issue 2 - Apr 2011
Volume 23, Issue 1 - Feb 2011
Selecting the target year
Optimum Combination of Carbon and Glass Fiber Composite to Obtain the Hybrid Effect
Song, Hyung-Soo ; Min, Chang-Shik ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 405~411
DOI : 10.4334/JKCI.2011.23.4.405
Using combinations of carbon and glass fiber composites normally used for strengthening of concrete structures, the hybrid effect from strengthening concrete structures using the composite is studied. To produce the hybrid effects, the specimens were made with optimum proportions of carbon fibers with glass fibers. Then, direct tensile tests were conducted on the hybrid FRP (fiber reinforced polymer) specimens. Unlike the woven fiber sheet currently used in construction sites, the FRP specimens have to be directly combined with the fibers, which make the work very complicated. Therefore, direct tensile test specimens manufacturing method based on the combination of high-tension carbon fibers and E-type glass fibers was proposed and the effects of hybridization is studied through the direct tensile test. By comparing the ductility index, the modulus of elasticity, and the stress-strain curves of the specimens, the most optimum glass to carbon fiber combination ratio for the hybrid FRP was found to be 9 to 1 with ductile K-type epoxy. The study results are discussed in detail in the paper.
Flexural Strength and Deflection Evaluation for FRP Bar Reinforced HSC Beams with Different Types of Reinforcing Bar and Fiber
Yang, Jun-Mo ; Yoo, Doo-Yeol ; Shin, Hyun-Oh ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 413~420
DOI : 10.4334/JKCI.2011.23.4.413
The test results of high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers, were compared with the prediction results of codes, guidelines and models proposed by researchers. The theoretical calculation based on the ultimate strength method of the KCI and ACI Code underestimated the ultimate moments of FRP bar-reinforced beams without fibers. The models proposed by ACI 544.4R and Campione predicted the ultimate moment capacities inaccurately for the FRP bar-reinforced beam with steel fibers, because these models do not consider the increased ultimate compressive strain of fiber reinforced concrete. Bischoff`s deflection model predicted the service load deflections reasonably well, while the deflection model of ACI Committee 440 underestimated the deflection of FRP bar-reinforced beams. Because the ACI 440 expression, used to predict member deflection, cannot directly apply to the beams reinforced with different types of reinforcing bars, an alternative method to estimate the deflections of beams with different types of reinforcing bars using the ACI 440 expression was proposed. In addition, Bischoff`s approach for computing deflection was extended to include deflection after yielding of the steel reinforcement in the beams reinforced with steel and FRP bars simultaneously.
Statistical Properties of Material Strength of Concrete, Re-Bar and Strand Used in Domestic Construction Site
Paik, In-Yeol ; Shim, Chang-Su ; Chung, Young-Soo ; Sang, Hee-Jung ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 421~430
DOI : 10.4334/JKCI.2011.23.4.421
As a fundamental study to introduce the reliability-based design code, a statistical study is conducted for the material strength data collected from domestic construction sites. In order to develop a rational design code based on statistics and reliability theory, it is essential to obtain the statistical properties of material strength. Material strength data for concrete, reinforcing bars, and prestressing strands which are used in domestic construction sites are collected and statistically analyzed. Then, the statistical properties are compared with those used in the process of the reliability-based calibration of internationally leading design codes. The statistical properties of the domestic data are such that the bias factor is relatively uniform between 1.13 and 1.20 and the coefficient of variation is below 0.10. Reinforcing bar data show difference among different manufacturers but there is not much difference among re-bar diameters. In the case of tendons, which are high strength materials, both of the domestic and foreign data show smaller values of the bias factor and the coefficient of variation than those of concrete and re-bar. Statistical distribution of all the material strength can be properly assumed as normal, log-normal, or Gumbel distribution after analyzing the classified data by individual construction site and manufacturer rather than the mixed data obtained from different sources in order to express the individual distribution of each structure.
Effect of Aggregate on Mechanical Properties of Ultra-High Strength Concrete Exposed to High Temperature
Kim, Young-Sun ; Choi, Hyoung-Gil ; Ohmiya, Yoshifumi ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 431~440
DOI : 10.4334/JKCI.2011.23.4.431
Concrete structures exposed to fire produce changes in their internal structure, resulting in their service life reduction due to the deterioration of its strength and performance capacity. The deterioration level are dependent on the temperature, exposure time, concrete mix proportions, aggregate property, and material properties. This study was performed to evaluate the thermal behavior of ultra-high strength concrete for the parameters of water to cement ratio (compressive strength), fine to total aggregate ratio, and maximum coarse aggregate size. At room temperature and
, tests of ultrasonic pulse velocity, resonance frequency, static modulus of elasticity, and compressive strength are performed using
cylindrical concrete specimens. The results showed that the residual mechanical properties of ultra-high strength concrete heated to
is influenced by variation of a water to binder ratio, fine to total aggregate ratio, and maximum coarse aggregate size.
Evaluating Early Age Shrinkage Behavior of Ultra High Performance Cementitious Composites (UHPCC) with CSA Expansive Admixture and Shrinkage Reducing Agent
Yoo, Doo-Yeol ; Park, Jung-Jun ; Kim, Sung-Wook ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 441~448
DOI : 10.4334/JKCI.2011.23.4.441
In this study, experimental tests of chemical and autogenous shrinkage were performed to evaluate the early age shrinkage behaviors of ultra high performance cementitious composites (UHPCC) with various replacement ratios of silica fume (SF), shrinkage reducing agent (SRA), expansive admixture (EA), and superplasticizer (SP). Starting time of self-desiccation, was analyzed by comparing the setting times and the deviated point of chemical and autogenous shrinkage strains. The test results indicated that both SF and SRA augment the early age chemical shrinkage, whereas SP delays the hydration reaction between cement particles and water, and reduces chemical shrinkage. About 49% of autogenous shrinkage was depleted by synergetic effect of SRA and EA. The hardening of UHPCC was catalyzed by containing EA. Self-desiccation of UHPCC occurred prior to the initial setting due to the high volume fraction of fibers and low water-binder ratio (W/B).
Applicability of Current Design Code to Class B Splice of SD600 Re-Bars
Choi, Won-Seok ; Chung, Lan ; Kim, Jin-Keun ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 449~459
DOI : 10.4334/JKCI.2011.23.4.449
An experimental study was performed to evaluate the applicability of current design code to the class B splice of SD600 reinforcing bars. Twelve simply supported beam and slab specimens with re-bar splices were tested under monotonic loading. Parameters for this test were re-bar diameter, concrete cover thickness, concrete strength, and stirrup spacing. Concrete strengths ranged 24.7~55.3 MPa. Most of the specimens were designed to satisfy the class B splice length specified by current design code. Average bar stresses resulting from this test were compared with the predictions by the KCI code provisions. Based on the result, the applicability of the current design code to SD600 re-bars were evaluated. The re-bar splices gave satisfactory performance for all D13 re-bar splices and for D22 and D32 splices with transverse reinforcement. On the basis of the test result, for D22 and the greater diameter bars, the use of either transverse reinforcement of the thicker concrete cover was recommended.
Effect of Polyvinyl Alcohol Fiber Volume Fraction on Pullout Behavior of Structural Synthetic Fiber in Hybrid Fiber Reinforced Cement Composites
Lee, Jin-Hyung ; Park, Chan-Gi ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 461~469
DOI : 10.4334/JKCI.2011.23.4.461
In this study, the effect of polyvinyl alcohol (PVA) fiber volume fraction on the pullout behavior of structural synthetic fiber in hybrid structural synthetic fiber and PVA fiber cement composites are presented. Pullout behavior of the hybrid fiber cement composites and structural synthetic fiber were determined by dog-bone bond tests. Test results found that the addition of PVA fiber can effectively enhance the structural synthetic fiber cement based composites pullout behavior, especially in fiber interface toughness. Pullout test results of the structural synthetic fiber showed the interface toughness between structural synthetic fiber and PVA fiber reinforced cement composites increases with the volume fraction of PVA fiber. The microstructural observation confirms the incorporation of PVA fiber can effectively enhance the interface toughness mechanism of structural synthetic fiber and PVA fiber reinforced cement composites.
Crack Control in Reinforced Concrete Flexural Members
Choi, Seung-Won ; Kim, Woo ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 471~478
DOI : 10.4334/JKCI.2011.23.4.471
For a practical simplicity in designing of reinforced concrete structures, the indirect crack controlling method of limiting bar spacing is adopted in KCI structural design provisions. In addition, a direct method for evaluating crack width is also provided in the appendix of the code. But there may be some mismatched results between these two crack controlling methods. In this study, limit values of maximum bar spacing calculated from KCI provisions, KCI appendix, and Frosch`s equation are examined as concrete strength, cross-section height, and concrete cover are varied, and the differences are analyzed. From the results, it becomes clear that the differences between maximum bar spacing calculated from KCI code text provisions and those from KCI code appendix provisions are too significant to be neglected. Therefore, rational crack models are suggested in order to get rid of the discrepancy between the direct and indirect control methods.
An Experimental Study on the Flexural Behavior of the Round Concrete Panels according to the Evaluation Method of Biaxial Flexural Tensile Strengths
Kim, Ji-Hwan ; Zi, Goang-Seup ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 479~486
DOI : 10.4334/JKCI.2011.23.4.479
In this study, we conducted experiment and finite element analysis on the flexural behavior of the round concrete panels according to the evaluation method of biaxial flexural tensile strengths. The Round Panel Test (RPT) and the Biaxial Flexure Test (BFT) were used to determine the biaxial flexural strength of round plain concrete panels. In order to understand the stress distribution on the panels, we measured load-strain relationship at the center of the panels` bottom surface. Test results show that fracture pattern in RPT and BFT panels are similar, and the tensile stress distribution is uniform in all directions at the center of the bottom surface of the panels for both RPT and BFT. The distribution of stresses in two test specimens coincided with the analysis result. The average biaxial flexural strength of RPT is about 29% greater than those of the BFT. The coefficient of variations (COV) of the RPT and BFT for the biaxial flexure strength is 8%, 6%, respectively, which indicates that BFT method is useful and reliable for determining biaxial flexural strengths of the concrete.
Optimum Mix Design of Alkali-Activated Cement Mortar Using Bottom Ash as Binder
Kang, Su-Tae ; Ryu, Gum-Sung ; Koh, Kyoung-Taek ; Lee, Jang-Hwa ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 487~494
DOI : 10.4334/JKCI.2011.23.4.487
In this research, the possibility of using bottom ash as a binder for the alkali-activated cement mortar is studied. Several experiments were performed to investigate the variation of the material properties according to the mix proportion. In the experimental program, the flowability and compressive strength were evaluated for various values of water/ash ratio, activator/ash ratio, sodium silicate to sodium hydroxide ratio, curing temperature, and the fineness of bottom ash as the main variables. The experimental results showed that high strength of 40 MPa or greater could be achieved in
high temperature curing condition with proper flowability. For
ambient temperature curing, the 28 days compressive strength of approximately 30MPa could be obtained although the early-age strength development was very slow. Based on the results, the range of optimized mix design of bottom-ash based alkali-activated cement mortar was suggested. In addition, using the artificial neural network analysis, the flowability and compressive strength were predicted with the difference in the mix proportion of the bottom-ash based alkali-activated cement mortar.
Calibration of Load and Resistance Factors in KCI Code Based on Domestic Data
Kim, Jee-Sang ; Kim, Jong-Ho ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 495~501
DOI : 10.4334/JKCI.2011.23.4.495
The load combinations in current KCI Design Code are determined with reference to those in ACI 318-05, which adopts the LRFD (load and resistance factor design) format. The load and resistance factors in LRFD format should be determined to meet the required levels of reliability index or probability of failure for various predetermined failure modes, which are also based on the statistical data reflecting locality and contemporary situation. However, the current KCI Design Code has been written utilizing foreign data, because of insufficiency in accrued data in Korea. This study considered the current safety levels of KCI Code based on published domestic data to evaluate appropriateness of the current KCI regulations. Based on the calibrated reliability index of the existing Code, the new resistance factors are suggested. The results presented in this paper can be considered as a basic research for establishment of unique design format for future Korean Codes.
Flexural Experiments on Reinforced Concrete Beams Strengthened with ECC and High Strength Rebar
Cho, Hyun-Woo ; Bang, Jin-Wook ; Han, Byung-Chan ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 503~509
DOI : 10.4334/JKCI.2011.23.4.503
ECC is a micro-mechanically designed cementitious composite which exhibits tightly controlled crack width and strain hardening behavior in uniaxial tension while using a moderate amount of reinforcing fiber, typically less than 2% fiber volume fraction. Recently, a variety of applications of this material ranging from repair and retrofit of structures, cast-in-place structures, to precast structural elements requiring high ductility are developed. In the present study, a retrofitting method using ECC reinforced with high strength rebar was proposed to enhance load-carrying capacity and crack control performance of deteriorated reinforced concrete (RC) beams. Six beam specimens were designed and tested under a four-point loading setup. The flexural test revealed that load-carrying capacity and crack control performance were significantly enhanced by the use of ECC and high strength rebar. This result will be useful for practical field applications of the proposed retrofitting method.
Evaluation of Strengthening Performance of Stiff Type Polyurea Retrofitted RC Slab Based on Attachment Procedure
Kim, Jang-Ho Jay ; Park, Jeong-Cheon ; Lee, Sang-Won ; Kim, Sung-Bae ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 511~520
DOI : 10.4334/JKCI.2011.23.4.511
Recent studies to improve reinforcement of structures have developed stiff type Polyurea by using highly polymized compound Polyurea, but the reinforcing effect of it appears to be merely good. To find the proper usage of Polyurea as structural reinforcement, stiff type Polyurea has developed by manipulating the ratio of the components that consist flexural type Polyurea and the developed stiff type Polyurea shows higher hardness and tensile capacity. The reinforcement effect evaluation of has been performed by the polyurea applied RC slab specimens, and the reinforcement effect of the combination of fiber sheet and polyurea has been tested. The results shows that the Polyurea applied specimens have significant improvement on hardness and ductility compare to those of unreinforced. Also, the specimens that stiff type Polyurea is sprayed on fiber sheet reinforcement has higher reinforcing effect than only sheet reinforced specimens. However, the specimens that and fiber sheet attached after polyurea applied on showed that the high toughness of fiber sheet restrains the ductile behavior of Polyurea due to the high ductility, thereby the specimen suffers the concentration of load, which leads the brittle fracture behavior.
A Study on Thermal Performance of Cement Mortar with PCM
Kim, Bo-Hyun ; Lee, Han-Seung ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 521~528
DOI : 10.4334/JKCI.2011.23.4.521
Recently, environmental concerns and issues have become great concerns for the public. Therefore, this study is conducted with the objective of preventing energy depletion and
emission. PCM (Phase Change Materials) having latent heat characteristic is mixed in mortar to find a proper mix proportion. Also, the mortar properties and performances as well as a melting point of PCM when applied to air conditioning and heating conditions in at building environments were obtained by performing experiments. Also, latent heat and heat transfer characteristics were obtained from experiments by test of thermal performance to formulate temperature gradient about amount of heat transfer of PCM content using the Fourier`s thermal equation. The study results can be used in the application of PCM in buildings and expected effect of air conditioning and heating energy.
Experimental Verification on the Structural Safety of Cantilever Beam Connected with Post-installed Adhesive Anchor Bolts
Oh, Hong-Seob ; Park, Sung-Rak ;
Journal of the Korea Concrete Institute, volume 23, issue 4, 2011, Pages 529~536
DOI : 10.4334/JKCI.2011.23.4.529
Recently, there has been a growing interest in expanded sidewalks for existing bridges. The cantilever beam system applied to expanded sidewalks for existing bridges are connected with the concrete structure by adhesive anchor bolts. However, the extended sidewalks are currently constructed without standardized regulations, which lead to excessive design of the beam spacing and installation and the construction difficulties due to the excessive over-weight. Moreover, there is only limited analysis and experiment data on the post-installed adhesive anchor bolts, so the excessive number of bolts is used for the connection. This paper deals with a method to increase the effectiveness of beam sections and anchor bolts geometry for expanded sidewalk of existing bridge. The study results showed that the failure of cantilever beam connected by adhesive anchor bolts was dominated by bond failure of interface between concrete and bolt. Also, the results indicated the possibilities of improving serviceability as well as safety of the sidewalks by changing of beam section and prestressing the bolts.