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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 27, Issue 6 - Dec 2015
Volume 27, Issue 5 - Oct 2015
Volume 27, Issue 4 - Aug 2015
Volume 27, Issue 3 - Jun 2015
Volume 27, Issue 2 - Apr 2015
Volume 27, Issue 1 - Feb 2015
Selecting the target year
Seismic Performance of Steel Coupling Beam and RC Shear Wall under Lateral Cyclic Load
Lim, Woo-Young ; Hong, Sung-Gul ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 591~602
DOI : 10.4334/JKCI.2015.27.6.591
In this paper, cyclic loading test was performed to evaluate the seismic performance of the steel coupling beam and RC shear wall. The test parameter was reinforcement detail of the shear wall. For the shear wall which was designed in accordance with the current design codes, a premature bearing failure occurred at the face of the wall. On the other hand, the bearing failure of walls was prevented due to the new type of reinforcement details. Test results indicated that the vertical reinforcements were more affected to the shear strength of the coupled shear wall than the horizontal reinforcement. Based on the failure mode, concrete stress distribution above and below flanges of the embedded steel beam was proposed. Assuming proposed concrete stress distribution, load resistance was predicted and it was agree well with test data.
Evaluation on Shear Contribution of Steel Fiber Reinforced Concrete in Place of Minimum Shear Reinforcement
Kim, Chul-Goo ; Park, Hong-Gun ; Hong, Geon-Ho ; Kang, Su-Min ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 603~613
DOI : 10.4334/JKCI.2015.27.6.603
In current design codes, minimum shear reinforcement is required for reinforced concrete flexural members, and the use of steel fiber reinforced concrete is permitted to replace the minimum shear reinforcements. In the present study, to estimate the effects of shear reinforcements and fibers on shear strength, simply supported beams were tested under transverse loading. The test results showed that the shear strength was significantly increased by the use of fibers. Particularly, the effect of fiber reinforced concrete was pronounced when high-strength concrete was used. The performance of fiber reinforced concrete for minimum shear reinforcement was evaluated using results of the present study and existing tests.
Strut-and-Tie Model for Shear Strength of Reinforced Concrete Squat Shear Walls
Mun, Ju-Hyun ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 615~623
DOI : 10.4334/JKCI.2015.27.6.615
The previous strut-and-tie models (STMs) to evaluate the shear strength of squat shear walls with aspect ratio less than 2.0 do not consider the axial load transfer of concrete strut and individual shear transfer contribution of horizontal and vertical shear reinforcing bars in the web. To overcome the limitation of the existing models, a simple STM was established based on the crack band theory of concrete fracture mechanics. The equivalent effective width of concrete strut having a stress relief strip was determined from the neutral axis depth and effective factor of concrete strength. The shear transfer mechanism of shear reinforcement at the extended crack band zone was calculated from an internally statically indeterminate truss system. The shear transfer capacity of concrete strut and shear reinforcement was then driven using the energy equilibrium in the stress relief strip and crack band zone. The shear strength predictions of squat shear walls evaluated from the current models are in better agreement with 150 test results than those determined from STMs proposed by Siao and Hwang et al. Furthermore, the proposed STM gives consistent agreement with the observed trend of the shear strength of shear walls against different parameters.
Seismic Capacity of Non-seismic Designed RC Framed Building Retrofitted by CBD System
Hur, Moo-Won ; Lee, Sang-Hyun ; Chun, Young-Soo ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 625~632
DOI : 10.4334/JKCI.2015.27.6.625
In this study, a comparative analysis have been conducted to examine seismic reinforcement effect of a school building that is designed with a CBD (Channel Beam Damper) system supported by H-frame with existing non-seismic RC frame. As a result of experiment, seismic reinforcement specimen with CBD system showed hysteretic characteristics of a large ellipse with great energy dissipation ability and increased strength and stiffness, while non-seismic design specimen showed rapid reduction in strength and brittle shear failure at top and bottom of the left and right column. In addition, comparing the stiffness reduction between the two specimens, CBD system was effective in preventing the reduction of stiffness. Energy dissipation ability of specimen reinforced by CBD system was about 4.0 times higher than the non-reinforced specimen. Such enhancement in energy dissipation ability could be considered as the result of improved strength and deformation for further application in designing of seismic reinforcement.
A Study on the Bond Strength of Coated Rebar by Polymer Cement Slurry Made of EVA and Ultra High-Early Strength Cement
Hyung, Won-gil ; Jo, Young-Kug ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 633~640
DOI : 10.4334/JKCI.2015.27.6.633
Polymer cement slurry (PCS) is made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the bond strength of coated rebar by polymer cement slurry made of EVA and ultra high-early strength cement. The test pieces are prepared with EVA polymer dispersion and ultra high-early strength cement having four types of polymer-cement ratios, four types of coating thicknesses and four curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day, and coating thicknesses of
. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, and coating thickness of
is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with polymer-cement ratio of 80% or 100% and coating thickness of
at curing age of 1-day can replace epoxy-coated rebar.
Durability Assessment of High Strength Concrete with High Volume Mineral Admixture
Baek, Chul-Woo ; Kim, Hoon-Sang ; Choi, Sung-Woo ; Jo, Hyun-Tae ; Ryu, Deug-Hyun ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 641~649
DOI : 10.4334/JKCI.2015.27.6.641
The purpose of this study was to assess the durability of high-strength concrete with high volume mineral admixture (HVMAC) derived from previous studies within ternary blended concrete (TBC) and normal concrete (NC). Four durability evaluation types such as chloride penetration resistance, freezing and thawing resistance, carbonation resistance in two pre-treatment conditions, and sulfuric acid and sulfate resistance using 5% sulfuric acid (
), 10% sodium sulfate (
), and 10% magnesium sulfate (
) solution were selected and performed in this study. HVMAC showed the excellent chloride penetration resistance in any age and the freezing and thawing durability close to 100%. In addition, HVMAC affected more reduction in carbonation resistance than TBC. When the curing time was increased, to create a concrete internal organization densely improved resistance to carbonation. HVMAC also showed the most superior in sulfuric acid and sulfate resistance. As the reduction of calcium hydroxide and
to apply a large amount of admixture reduced the swelling and cracking of concrete, the strength reduction and mass change of concrete was found to be small indicated.
Shear Performance of Board-type Two-way Voided Slab
Choi, Hyeon-Min ; Park, Tae-Won ; Paik, In-Kwan ; Kim, Je-Sub ; Han, Ju-Yeon ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 651~659
DOI : 10.4334/JKCI.2015.27.6.651
Currently, social demands for long span building structures are increasing due to architectural planning purposes and economic efficiency. As a result, lighter board-type voiding materials were suggested. With the use of board-type voiding materials, a slab is able to become light weight and convenient. This process efficiently eliminates concrete where it is not required; considerably diminishing dead weight while maintaining the flexural strength of the slab. The reduction in concrete also allows for overall cost reductions and design flexibility. Also it can be ease with fixing the voided material that is composed of one body form. Although board-type voiding materials are ideal, the top and bottom concrete plates lack integrity. Because of this, test results show horizontal cracking towards the tops and bottoms of the concrete columns, or webs, connecting the slabs. The key to correcting this problem is to increase the shear strength. In order to increase the shear strength of the structure, horizontal shear area must increase. R70(100)-D-F has the largest horizontal shear area as it also shows stronger strength. As a result, shear strength (
) is dependent on the horizontal shear area (N).
. The web columns have a shear span to depth ratio (a/d) that is less than 2; which classifies it as a deep beam. In this case, however, the shear strength of the deep beams may be as much as 2 to 3 times greater than that predicated conventional equations developed for members of normal proportions. As a result,
is suggested as an extra coefficient in the equation for shear strength (
Cyclic Behavior of Slender Reinforced Concrete Coupling Beams with Bundled Diagonal Reinforcement
Han, Sang-Whan ; Yoo, Kyoung-Hwan ; Lee, Ki-Hak ; Shin, Myoung-Su ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 661~668
DOI : 10.4334/JKCI.2015.27.6.661
Coupled shear walls are effective lateral force resisting system in which coupling beams link individual walls. For improving the energy dissipation capacity of coupling beams, diagonal reinforcement details were developed. However, it is difficult to construct diagonal reinforced coupling beams due to the congestion of reinforcement in the beam. For resolving the problem, this study developed precast coupling beams with bundled diagonal reinforcement. To reduce the reinforcement congestion, bundled diagonal reinforcement were placed in the coupling beam. To evaluate the cyclic performance of coupling beams with bundled diagonal reinforcement, experimental test were conducted. For this purpose, two slender specimens with an aspect ratio of 3.5 were made and tested. It was observed that the cyclic performance of the coupling beam with bundled diagonal reinforcement was similar with that of the coupling beam with normal diagonal reinforcement placed according to design code to ACI 318-11.
Compressive Strength Development Model for Concrete Cured by Microwave Heating Form
Koh, Tae-Hoon ; Moon, Do-Young ; Bae, Jung-Myung ; Yoo, Jung-Hoon ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 669~676
DOI : 10.4334/JKCI.2015.27.6.669
Time dependent model for prediction of compressive strength development of concrete cured by microwave heating form was presented in this study. The presented model is similar to the equation which is given in ACI 209R-92 but the constants which is dependent on cement type and curing method in the presented model are modified by the regression analysis of the experimental data. Laboratory scale concrete specimens were cast and cured by the microwave heating form and drilled cores extracted from the specimens were fractured in compression. The measured core strengths are converted to standard core and in-situ strengths. These in-situ strengths are used for the regression.
A Study on the Experiment of Flexural Behavior of Composite Beam with Steel Fiber Reinforced UHPC and Inverted-T Steel Considering Compressive Strength Level
Yoo, Sung-Won ; Suh, Jeong-In ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 677~685
DOI : 10.4334/JKCI.2015.27.6.677
In a will to subdue the brittleness as well as the low tensile and flexural strengths of ordinary concrete, researches are being actively watched worldwide on steel fiber-reinforced Ultra High Performance Concrete (UHPC) obtained by admixing steel fibers in ultra high strength concrete. For the purpose of maximizing advantage of UHPC, this study removes the upper flange of the steel girder to apply an inverted T-shape girder for the formation of the composite beam. This paper intends to evaluate the behavior of the shear connectors and the flexural characteristics of the composite beam made of the inverted T-shape girder and UHPC slab using 16 specimens considering the compressive strength of concrete, the mixing ratio of steel fiber, the spacing of shear connectors and the thickness of the slab as variables. In view of the test results, it seemed that the appropriate stud spacing should range between 100 mm and 2 or 4 times the thickness of the slab. Moreover, the relative displacement observed in the specimens showed that ductile behavior was secured to a certain extent with reference to the criteria for ductile behavior suggested in Eurocode-4. The specimens with large stud spacing exhibited larger values than given by the design formula and revealed that the shear connectors developed larger ultimate strength than predicted owing to the action of UHPC and steel after non-composite behavior. Besides, the specimens with narrow stud spacing failed suddenly through compression at the upper chord of UHPC before reaching the full capacity of the shear connectors.
Determination of Water-to-Binder Ratios on the Equivalent Compressive Strength of Concrete with Supplementary Cementitious Materials
Yoon, Hyun-Sub ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 687~693
DOI : 10.4334/JKCI.2015.27.6.687
The present study proposed a k-value to determine the water-to-binder ratio of concrete using fly ash (FA) or ground granulated blast-furnace slag (GGBS) as a partial replacement of ordinary portland cement (OPC) with regard to an equivalent strength of OPC concrete. From the regression analysis using an extensive database including 7076 concrete mixes, k-values were determined for various water-to-binder ratios when the replacement ratio of OPC by the addition of FA or GGBS were below 50%. For deriving an equation to identify k-value, the relationship of concrete compressive strength and water-to-binder ratio was generalized by an exponential function. In general, k-values decreased with the increases in the addition of FA or GGBS for replacement of OPC and water-to-binder ratio. The rate in decreasing k-value against water-to-binder ratio was marginally affected by the addition of FA or GGBS, although a higher k-value was commonly obtained for GGBS concrete than for FA concrete at the same water-to-binder ratio. Consequently, the determined k-values were simplified as a function of water-to-binder ratio and the addition ratio of FA or GGBS as replacement of OPC.
A Round Robin Study of Solid Content Test and Applicability Estimation of FT-IR Analysis for Chemical Admixtures
Kim, Jin-Cheol ; Yoo, Hyeok-Jin ; Kim, Hong-Sam ; Park, Ko-Eun ;
Journal of the Korea Concrete Institute, volume 27, issue 6, 2015, Pages 695~703
DOI : 10.4334/JKCI.2015.27.6.695
Acceptance criteria for chemical admixtures of cement concrete were investigated in domestic and international specifications. The reliability was verified for solid content test method of chemical admixture examined statistical analysis by round robin test. The applicability of FT-IR spectroscopy for qualitative measurement of multi-compound chemical admixtures verified. From solid content experimental results, outlier analysed using Cochran, Grubbs and Dickson's Q test. Repeatability and reproducibility standard deviation for solid content results showed 0.25 and 0.098% respectively according to KS A ISO 5725-2 procedure, it can be confirmed reliability of test methods. FT-IR spectrum of liquefied or oven-dried chemical admixtures condition showed big differences. It is needed that the FT-IR analysis is performed on dry material. However there's no difference with the applicability of FT-IR spectroscopy for multi-compound chemical admixtures. So the utility of method analysis could not identify.