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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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Korea Concrete Institute
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Volume & Issues
Volume 25, Issue 6 - Dec 2013
Volume 25, Issue 5 - Oct 2013
Volume 25, Issue 4 - Aug 2013
Volume 25, Issue 3 - Jun 2013
Volume 25, Issue 2 - Apr 2013
Volume 25, Issue 1 - Feb 2013
Selecting the target year
Evaluation of Shrinkage Strain of Alkali-Activated Slag Concrete
Yang, Keun-Hyeok ; Seo, Eun-A ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 593~599
DOI : 10.4334/JKCI.2013.25.6.593
The unrestrained shrinkage strain of alkali-activated (AA) slag concrete was examined and compared with design equations specified in code provisions and empirical equations proposed by Yang et al. The main parameters investigated were the water-to-binder ratio (W/B), unit water content and fine aggregate-to-total aggregate ratio (S/a). Test results revealed that shrinkage strain of AA slag concrete is nearly proportional to the W/B ratio, whereas its time function is independent of the W/B ratio. The shrinkage strain of AA slag concrete increased significantly when the unit water content is above
, whereas it is marginally affected by the S/a ratio. The design equation of ACI 209 considerably overestimates the shrinkage behavior of AA slag concrete, whereas CEB-FIP equation tends to underestimate the shrinkage at the age more than 28 days. The empirical equation of Yang et al. is in better agreement with test results, showing that values of mean and standard deviation of error coefficients obtained from each specimen are 016 and 0.07, respectively.
Cyclic Loading Test for Shear Strength of Low-rise RC Walls with Grade 550 MPa Bars
Park, Hong-Gun ; Lee, Jae-Hoon ; Shin, Hyun-Mock ; Baek, Jang-Woon ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 601~612
DOI : 10.4334/JKCI.2013.25.6.601
In the construction of nuclear power plants using massive walls, the use of high-strength re-bars for shear design is necessary to enhance the constructability and economy. In this study, low-rise walls (aspect ratio of 1.0) with grade 550 MPa bars were tested under cyclic loading to investigate the shear capacity and deformation capacity. The test parameters were the grade of horizontal re-bars (550 MPa, 420 MPa), strength of concrete compressive strength (46 MPa, 70 MPa), horizontal/vertical reinforcement ratio, use of lateral confinement hoops, shape of cross section, and failure modes (shear failure before or after flexural yielding). The test results were compared with those of walls with grade 420 MPa bars and predicted strength by current design codes. The results showed that the shear strength of the walls with 550 MPa bars was comparable to that of the walls with 420 MPa bars though the safe margin slightly decreased. ACI 349 provides underestimated shear strength for the walls with 550 MPa bars. In case of the wall with flexural yielding, a large deformation capacity was achieved. This result indicates that the ACI 349 provisions can be safely applied to seismic design of the low-rise walls (aspect ratio of 1.0) with grade 550 MPa bars.
Evaluation of Properties of 80, 130, 180 MPa High Strength Concrete at High Temperature with Heating and Loading
Choe, Gyeong-Cheol ; Yoon, Min-Ho ; Lee, Tae-Gyu ; Lee, Seong-Hun ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 613~620
DOI : 10.4334/JKCI.2013.25.6.613
Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Because of this, standards and researches on the degradation of the mechanical properties of concrete at high temperatures have been presented. However, research data about the state that considering the loading condition and high-strength concrete is not much. Therefore, this study evaluated the high-temperature properties of high-strength concrete by loading condition and elevated temperature. The stress-strain, strain at peak stress, compressive strength, elastic modulus, thermal strain and the transient creep are evaluated under the non-loading and
loading conditions on high strength concrete of W/B 12.5%, 14.5% and 20%. Result of the experiment, decrease in compressive strength due to high temperature becomes larger as the compressive strength increases, and residual rate of elastic modulus and compressive strength is high by the shrinkage caused by loading and thermal expansion due to high temperature are offset from each other, at a temperature above
Evaluation of Half Cell Potential Measurement in Cracked Concrete Exposed to Salt Spraying Test
Kim, Ki-Bum ; Park, Ki-Tae ; Kwon, Seung-Jun ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 621~630
DOI : 10.4334/JKCI.2013.25.6.621
Several techniques for steel corrosion detection are proposed and HCP (half cell potential) technique is widely adopted for field investigation. If concrete has cracks on surface, steel corrosion is rapidly accelerated due to additional intrusion of chloride and carbon dioxide ions. This study is for an evaluation of HCP in cracked concrete exposed chloride attack. For this work, RC (reinforced concrete) beams are prepared considering 3 w/c ratios (0.35, 0.55, and 0.70) and several cover depths (10~60 mm) and various crack widths of 0.0~1.0 mm are induced. For 35 days, SST (salt spraying test) is performed for corrosion acceleration, and HCP and corrosion length of rebar are evaluated. With increasing crack width, w/c ratios, and decreasing cover depth, HCP measurements increase. HCP evaluation technique is proposed considering the effects of w/c ratios, crack width, and cover depth. Furthermore anti-corrosive cover depths are obtained through Life365 program and the results are compared with those from this study. The results shows relatively big difference in cracked concrete, however provide similar anti-corrosive conditions in sound concrete.
Analytical Study on Hybrid Precast Concrete Beam-Column Connections
Choi, Chang-Sik ; Kim, Seung-Hyun ; Choi, Yun-Cheul ; Choi, Hyun-Ki ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 631~639
DOI : 10.4334/JKCI.2013.25.6.631
Non-linear finite element analysis for newly developed precast concrete details for beam-to-column connection which can be used in moderate seismic region was carried out in this study. Developed precast system is based on composite structure and which have steel tube in column and steel plate in beam. Improving cracking strength of joint under reversed cyclic loading, joint area was casted with ECC (Engineering Cementitious Composites). Since this newly developed precast system have complex sectional properties and newly developed material, new analysis method should be developed. Using embedded elements and models of non-linear finite element analysis program ABAQUS previously tested specimens were successfully analyzed. Analysis results show comparatively accurate and conservative prediction. Using finite element model, effect of axial load magnitude and flexural strength ratio were investigated. Developed connection have optimized performance under axial load of 10~20% of compressive strength of column. Plastic hinge was successfully developed with flexural strength ratio greater than 1.2.
Minimum Torsional Reinforcement Ratio of Reinforced Concrete Members for Safe Design
Kim, KangSu ; Lee, DeuckHang ; Park, Min-Kook ; Lee, Jung-Yoon ; Ju, HyunJin ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 641~648
DOI : 10.4334/JKCI.2013.25.6.641
Current design codes regulate the minimum torsional reinforcement requirement for reinforced concrete members to prevent their brittle failure. The minimum torsional reinforcement ratio specified in the current national code and ACI318-11, however, have problems in the minimum longitudinal reinforcement ratio for torsion, the equilibrium condition in space truss model, and a marginal strength, etc. Thus, in order to overcome such shortcomings, this study presents a rational equation for minimum torsional reinforcement ratio that can provide a sufficient margin of safety in design. The minimum torsional reinforcement ratio proposed in this study was compared to the test results available in literature, and it was confirmed that it gave a proper margin of safety for all specimens studied in this paper.
Cyclic Behavior of High-Performance Fiber-Reinforced Cement Composite Coupling Beam Having Diagonal Reinforcement
Kwon, Hyun-Wook ; Jeon, Yong-Ryul ; Lee, Ki-Hak ; Shin, Myung-Su ; Han, Sang-Whan ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 649~656
DOI : 10.4334/JKCI.2013.25.6.649
Coupled shear walls can provide an efficient structural system to resist lateral force. However, the reinforcement detail for diagonally reinforced coupling beams required by ACI-318 often causes the difficulties in construction due to the reinforcement congestion and interference among reinforcement. This paper is to evaluate cyclic behavior of High-Performance Fiber-Reinforced Cement Composite (HPFRCC) coupling beams having reduced transverse reinforcement around the beam perimeter. Experimental test was conducted using three specimens having a beam aspect ratio 2.0. Test results showed that HPFRCC coupling beams with half of transverse reinforcement required by ACI-318 provided similar energy dissipation capacities compared with the coupling beams having reinforcement satisfy the requirement of ACI-318.
Basic Research of Self Compacting Concrete Using Alkali-Activated Slag Binder
Song, Keum-Il ; Shin, Gyeong-Sik ; Gong, Min-Ho ; Song, Jin-Kyu ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 657~665
DOI : 10.4334/JKCI.2013.25.6.657
The purpose of this study is the basic research of self-compacting concrete using Alkali-Activated Slag (AAS) binder in order to emphasize the durability of structures and facilitate casting the fresh concrete in field. The AAS binder emitted low carbon dioxide (
) is eco friendly material of new concept because AAS products not only emit little
during production but also reuse the industrial by-products such as ground granulated blast-furnace slag (GGBS) of the steel mill. Until now, almost of domestic and foreign research are using Ordinary Portland Cement (OPC) for self-compacting concrete, and also, nonexistent research about AAS. The self-compacting concrete must get the performance of flowability, segregation resistance, filling and passing ability. Nine concrete mixes were prepared with the main parameter of unit amount of binder (400, 500, 600
) and 3 types of water-binder (W/B) ratio. The results of test were that fresh concretes were satisfied with flowability, segregation resistance, and filling ability of JSCE. But the passing ability was not meet the criteria of EFNARC because of higher viscosity of AAS paste than OPC. This high viscosity of AAS paste enables the manufacturing of self compacting concrete, segregation of which does not occur without the using of viscosity agent. It is necessary that the development of high fluidity AAS binders of higher strength and the study of better passing ability of AAS concrete mixes in order to use self compacting AAS concrete in field.
Seismic Strengthening and Performance Evaluation of Damaged R/C Buildings Strengthened with Glass Fiber Sheet and Carbon Fiber X-Brace System
Lee, Kang-Seok ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 667~674
DOI : 10.4334/JKCI.2013.25.6.667
Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. This paper proposes a new seismic retrofit methodology combined with glass fiber sheet (GFS) and non-compression X-brace system using carbon fiber (CFXB) for reinforced concrete buildings damaged in earthquakes. The GFS is used to improve the ductility of columns damaged in earthquake. The CFXB consists of carbon fiber bracing and anchors, to replace the conventional steel bracing and bolt connection. This paper reports the seismic resistance of a reinforced concrete frame strengthened using the GFS-CFXB system. Cyclic loading tests were carried out, and the hysteresis of the lateral load-drift relations as well as ductility capacities were investigated. Carbon fiber is less rigid than the conventional materials used for seismic retrofitting, resulting in some significant advantages: the strength of the structure increased markedly with the use of CF X-bracing, and no buckling failure of the bracing was observed.
Characteristics of Excess Water Dewatered Concrete Using Permeable Liner
Jeon, Kyu-Nam ; An, Gi-Hong ; Lee, Jong-Suk ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 675~682
DOI : 10.4334/JKCI.2013.25.6.675
In this study, to enhance the quality of concrete surface by removing the surplus water, permeable liner attached the euroform was applied for manufacturing concrete specimens. Various kinds of concrete mixtures with different water to binder ratios were applied and the strength properties of the hardened concrete surfaces were evaluated at different heights. Experimental results showed that the rebound values by schmidt hammer test and the compressive strengths on the surfaces of concrete specimens were increased as proportion to the amount of mixture water which is dependent on the water to binder ratio of each concrete mixture, and more enhancements were observed on the middle and lower specimen surfaces than the upper region. SEM analysis also showed that much denser hydrate structures were observed on the specimen surfaces by the application of the permeable liner while similar hydrate formations were occurred regardless of surface treatment conditions. From the MIP test results of the concrete surfaces, it was observed that, by the application of permeable liner, the pore volume below
was decreased with a maximum of 50% resulting in the densification of pore structures.
Failure Behaviour and Shear Strength Equations of Reinforced Concrete Deep Beams
Won, Dae-Yon ;
Journal of the Korea Concrete Institute, volume 25, issue 6, 2013, Pages 683~691
DOI : 10.4334/JKCI.2013.25.6.683
Failure behaviour of deep beams is largely depend on shear span to effective depth ratio(a/d). For deep beams with
, the diagonal splitting of the web and local crushing of concrete near applied loads or supports is the most common failure mode. If the beam contains sufficient web reinforcement, area of local crushing will be increased while area of diagonal splitting is decreased. When web reinforcement above purpose, web should be reinforced both in the horizontal and vertical directions or be reinforced in perpendicular direction to diagonal cracks. For deep beams with 1.0
, the increment of shear strength by the horizontal web reinforcement are hardly expected unless amount of main bars very small that the main bars should be reached yielding state when shear failure occurs. In contrast, the vertical web reinforcement prevent the beam from being transferred to tied arch mechanism, and as a result th shear strength of beam increase. In this study, formulas based on upper bound theorem of plastic theory are proposed to predict the shear strength of reinforced concrete deep beams with
. Comparisons with other experiment results are performed, and good agreement between measured and predicted value by proposed formulas is obtained.