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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 26, Issue 6 - Dec 2014
Volume 26, Issue 5 - Oct 2014
Volume 26, Issue 4 - Aug 2014
Volume 26, Issue 3 - Jun 2014
Volume 26, Issue 2 - Apr 2014
Volume 26, Issue 1 - Feb 2014
Selecting the target year
Flow Experiments and Analysis of Highly Flowable Concrete Considering the Effect of Dosages of SP Admixture and W/C Ratios
Cho, Chang-Geun ; Kim, Wha-Jung ; Choi, Yeol ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 671~677
DOI : 10.4334/JKCI.2014.26.6.671
In this research, flow experiments and simulation of highly flowable concrete has been attempted using a viscoplastic particle method varying with dosages of SP admixture and water-cement (W/C) ratios. Rheological and flow characteristics of flowable concrete manufactured in domestic products of cement, aggregates, and SP admixtures were investigated by experimental programs varying with mix proportions. From experiment, the predictive model of rheological characteristics of flowable concrete has been newly proposed considering with the effects of the W/C ratio and the dosage of SP admixture, and the effect of mixing proportion has also been incorporated into shear stress and strain rate curve of flowable concrete in the current method. A series of L-box flow test of highly flowable concrete varying with dosages of SP admixture and W/C ratios was compared with the proposed model.
Quality Evaluation and Mix Proportion of Antiwashout Underwater Concrete with Mineral Admixture
Park, Yong Kyu ; Kim, Hyun Woo ; Yoon, Ki Woon ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 679~686
DOI : 10.4334/JKCI.2014.26.6.679
In this research, the mix proportion of the antiwashout underwater concrete with the mineral admixture was evaluated. It can reduce the amount used of the antiwashout admixture (hereinafter referred to as "AWA") and satisfy the properties of concrete. In addition, the review for the difference of the test and practical affairs were conducted. Optimized unit quantity of water of antiwashout underwater concrete and the amount used of AWA was revealed by
, 0.9%/W, respectively. In particularly, the mix design is reduced by 5% than the W/B of target strength even though the W and AWA reduced. Therefore, it will have the economical feasibility and qualities including the material separation, resistance characteristic and compressive strength, and etc. The stable value was shown in 1 point of minute passed in the measurement of the turbidity amounts using the turbidimeter after the checker insertion. However, it needs to be reviewed for the interrelationship between turbidity measuring machine and KCI-AD102 standard method. There were no significant differences of compressive strength of specimens in the water depending on the production methods.
Design Approach for Boundary Element of Flexure-Governed RC Slender Shear Walls Based on Displacement Ductility Ratio
Mun, Ju-Hyun ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 687~694
DOI : 10.4334/JKCI.2014.26.6.687
This study established a displacement ductility ratio model for ductile design for the boundary element of shear walls. To determine the curvature distribution along the member length and displacement at the free end of the member, the distributions of strains and internal forces along the shear wall section depth were idealized based on the Bernoulli`s principle, strain compatibility condition, and equilibrium condition of forces. The confinement effect at the boundary element, provided by transverse reinforcement, was calculated using the stress-strain relationship of confined concrete proposed by Razvi and Saatcioglu. The curvatures corresponding to the initial yielding moment and 80% of the ultimate state after the peak strength were then conversed into displacement values based on the concept of equivalent hinge length. The derived displacement ductility ratio model was simplified by the regression approach using the comprehensive analytical data obtained from the parametric study. The proposed model is in good agreement with test results, indicating that the mean and standard deviation of the ratios between predictions and experiments are 1.05 and 0.19, respectively. Overall, the proposed model is expected to be available for determining the transverse reinforcement ratio at the boundary element for a targeted displacement ductility ratio.
Seismic Performance of Precast Concrete Beam-Column Connections Using Ductile Rod
Lee, Sang-Jin ; Hong, Sung-Gul ; Lim, Woo-Young ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 695~705
DOI : 10.4334/JKCI.2014.26.6.695
Precast concrete (PC) beam-column connections using ductile rods are proposed for earthquake zone. An existing beam-column connection, two PC specimens designed by considering failure modes and a conventional RC specimen were tested under cyclic loading to evaluate the seismic performance. The specimens were designed to satisfy the requirements of current design code. The variables are the yield strength of longitudinal reinforcing bars of PC beams. The test results showed that the proposed system applying smaller yield strength of the longitudinal reinforcing bars at the PC beams than the ductile rods was satisfied with seismic criteria. The deformation capacity and energy dissipation capacity of the proposed PC beam-column connections were greater than those of the existing DDC system.
A Evaluation on the Field Application of High Strength Concrete for CFT Column
Park, Je Young ; Chung, Kyung Soo ; Kim, Woo Jae ; Lee, Jong In ; Kim, Yong Min ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 707~714
DOI : 10.4334/JKCI.2014.26.6.707
CFT (Concrete-Filled Tube) is a type of steel column comprised of steel tube and concrete. Steel tube holds concrete and the concrete inside tube takes charge of compressive load. This study presents structural performance of the CFT column which has 73~100 MPa high strength concrete inside. Fluidity, mechanical compression, pump pressure test in flexible pipe were conducted for understanding properties of the high strength concrete. Material properties were achieved by various experimental tests, such as slump, slump flow, air content, U-box, O-Lot, L-flow. In addition, mock-up tests were conducted to monitor concrete filling, hydration heat, compressive strength. From construction sites in Sang-am dong and University of Seo-kang, long-term behaviors could be effectively predicted in terms of ACI 209 material model considering elastic deformation, shrinkage and creep.
Progressive Collapse Analysis of Reinforced Concrete Core Structure Subjected to Internal Blast Loading
Kim, Han-Soo ; Ahn, Jae-Gyun ; Ahn, Hyo-Seong ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 715~722
DOI : 10.4334/JKCI.2014.26.6.715
In this paper, internal blast effect of reinforced concrete core structure were investigated using Ansys Autodyn, which is a specialized hydrocode for the analysis of explosion and impact. It is expected that internal blast case can give additional damage to the structure because it causes rebound of blast loads. Therefore, in this paper, the hazard of internal blast effect is demonstrated using UFC 3-340-02 criteria. In addition, analysis result of Autodyn, experimental result regarding rebound of blast load, and example of UFC 340-02 are compared to verify that Autodyn can analyze internal blast effect properly. Furthermore, progressive collapse mechanism of core structure which is one of the most important parts in high rise buildings is also analyzed using Autodyn. When internal blasts are loaded to core structure, the core structure is mostly damaged on its corner and front part of core wall from explosives. Therefore, if the damaged parts of core wall are demolished, progressive collapse of the core structure can be initiated.
Effects of the Reaction Degree of Ground Granulated Blast Furnace Slag on the Properties of Cement Paste
Kim, Dong-Yeon ; Cho, Hyeong-Kyu ; Lee, Han-Seung ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 723~730
DOI : 10.4334/JKCI.2014.26.6.723
The usage of Ground Granulated Blast Furnance Slag (GGBFS) has been increased recently. Studies on the cement hydration model incorporating GGBFS as well as the properties of cement paste done with GGBFS such as compressive strength, hydration products and hydration heat have been the subjects of many researches. However, studies on the reaction degree of GGBFS that affect the properties of cement paste incorporating GGBFS are lacking globally and specially in Korea. Thus, in this study, the reaction degree of GGBFS using the method if selective dissolution, compressive strength, the amount of chemical bound water and
were measured and analysed in accordance with water-binder ratio, replacement ratio of GGBFS, and curing temperature. The results show that the reaction degree of GGBFS, the amount of chemical bound water and
in cement paste with GGBFS were higher in conditions where the replacement ratio of GGBFS was low and both water-binder ratio and curing temperature were high. Finally, the reaction degree of GGBFS was achieved at a value between 0.3~0.4.
Impact Resistance of Steel Fiber-Reinforced Concrete Panels Under High Velocity Impact-Load
Kim, Sang-Hee ; Kang, Thomas H.K. ; Hong, Sung-Gul ; Kim, Gyu-Yong ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 731~739
DOI : 10.4334/JKCI.2014.26.6.731
This paper describes the evaluation of the impact performance of steel fiber-reinforced concrete based on high-velocity impact experiments using hard spherical balls. In this experimental study, panel specimens with panel thickness to ball diameter (h/d) ratios of 3.5 or less were tested with variables of steel fiber volume fraction, panel thickness, impact velocity, and aggregate size. Test results were compared with each other to evaluate the impact resistance. The results showed that the percentage of weight and surface loss decreased as the steel volume fraction increased. However, the penetration depth increased with up to steel fiber volume fraction of 1.5%. Particularly the results of specimens with 20 mm aggregates showed poorer performance than those with 8 mm aggregates. The results also confirmed that the impact performance prediction formulas are conservative with (h/d) ratios of 3.5 or less. Despite the conservative predictions, the modified NDRC formula and ACE formula predict the impact performance more consistently than the Hughes formula.
Evaluation of Horizontal Shear Strength of Prestressed Hollow-Core Slabs with Cast-in-Place Topping Concrete
Im, Ju-Hyeuk ; Park, Min-Kook ; Lee, Deuck-Hang ; Seo, Soo-Yeon ; Kim, Kang-Su ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 741~749
DOI : 10.4334/JKCI.2014.26.6.741
Prestressed hollow-core (PHC) slabs are structurally-optimized lightweight precast floor members for long-span concrete structures, which are widely used in construction markets. In Korea, the PHC slabs have been often used with cast-in-place (CIP) topping concrete as a composite slab system. However, the PHC slab members produced by extrusion method use concrete having very low slump, and it is very difficult to make sufficient roughness on the surface as well as to provide shear connectors. In this study, a large number of push-off tests was conducted to evaluate interfacial shear strengths between PHC slabs and CIP topping concrete with the key variable of surface roughness. In addition, the horizontal shear strengths specified in the various design codes were evaluated by comparing to the test results that were collected from literature.
Performance Based Evaluation of Concrete Material Properties from Climate Change Effect on Wind Speed and Sunlight Exposure Time Curing Condition
Kim, Tae-Kyun ; Shin, Jae-Ho ; Bae, Deg-Hyo ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 751~759
DOI : 10.4334/JKCI.2014.26.6.751
Currently, due to global warming, occurrences of extreme climate phenomena such as heat wave, heavy snow, heavy rain, super typhoon are continuously increasing all over the world. Due to these extreme climate phenomena, concrete structures and infrastructures are exposed to serious deterioration and damage. However, researches on construction technologies and standards to confront the climate change generated problems are needed presently. In order to better handle these problems, the validity of the present concrete mixture proportions are evaluated considering wind speed and sunlight exposure time based on climate change record in Seoul, Korea. The specimens cured at various wind speed and sunlight exposure time conditions were tested to obtain their compressive and split tensile strengths at various curing ages. Moreover, performance based evaluation (PBE) method was used to analyze the target strength satisfaction percentage of the concrete cured for the curing conditions. From the probabilistic method of performance evaluation of concrete performance, feasibility and usability of current concrete mix design practice for climate change conditions can be evaluated.
Experiment of Flexural Behavior of Composite Beam with Steel Fiber Reinforced Ultra High Performance Concrete Deck and Inverted-T Steel Girder
Yoo, Sung-Won ; Ahn, Young-Sun ; Cha, Yeong-Dal ; Joh, Chang-Bin ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 761~769
DOI : 10.4334/JKCI.2014.26.6.761
Ultra high performance concrete (UHPC) has been developed to overcome the low strengths and brittleness of conventional concrete. Considering that UHPC, owing to its composition and the use of steel fibers, develops a compressive strength of 180 MPa as well as high stiffness, the top flange of the steel girder may be superfluous in the composite beam combining a slab made of UHPC and the steel girder. In such composite beam, the steel girder takes the form of an inverted-T shaped structure without top flange in which the studs needed for the composition of the steel girder with the UHPC slab are disposed in the web of the steel girder. This study investigates experimentally and analytically the flexural behavior of this new type of composite beam to propose details like stud spacing and slab thickness for further design recommendations. To that goal, eight composite beams with varying stud spacing and slab thickness were fabricated and tested. The test results indicated that stud spacing running from 100 mm to 2 to 3 times the slab thickness can be recommended. In view of the relative characteristic slip limit of Eurocode-4, the results showed that the composite beam developed ductile behavior. Moreover, except for the members with thin slab and large stud spacing, most of the specimens exhibited results different to those predicted by AASHTO LRFD and Eurocode-4 because of the high performance developed by UHPC.
Structural Behavior of Hybrid Steel Fiber-Reinforced Ultra High Performance Concrete Beams Subjected to Bending
Yang, In-Hwan ; Kim, Kyoung-Chul ; Joh, Chang-Bin ;
Journal of the Korea Concrete Institute, volume 26, issue 6, 2014, Pages 771~778
DOI : 10.4334/JKCI.2014.26.6.771
This paper concerns the flexural behavior of hybrid steel fiber-reinforced ultra high performance concrete (UHPC) beams. It presents experimental research results of hybrid steel fiber-reinforced UHPC with steel fiber content of 1.5% by volume and steel reinforcement ratio of less than 0.02. This study aims at providing realistic information about UHPC beams in bending in order to establish a reasonable prediction model for flexural resistance in structural code in the future. The experimental results show that hybrid steel fiber-reinforced UHPC is in favor of cracking resistance and ductility of beams. The ductility indices range through 9.2 to 15.2, which means high ductility of UHPC. Also, the flexural capacity of beam which contains stirrups in pure bending zone is similar to that of beam which does not contain stirrups in pure bending zone. This result represents that the flexural capacity is not affected by the presence of stirrups whose spacing is 150 mm in bending zone.