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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 20, Issue 6 - Dec 2008
Volume 20, Issue 5 - Oct 2008
Volume 20, Issue 4 - Aug 2008
Volume 20, Issue 3 - Jun 2008
Volume 20, Issue 2 - Apr 2008
Volume 20, Issue 1 - Feb 2008
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Initial Stiffness of Beam Column Joints of PCS Structural Systems
Park, Soon-Kyu ; Kim, Moo-Kyung ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 271~282
DOI : 10.4334/JKCI.2008.20.3.271
Specific joint devices composed of end-plates and through bolts are under development to assemble steel beams to PC columns efficiently by dry construction method for the PCS structural system, of which major structural components are precast concrete columns and steel beams. Seismic performance of the joint devices had been evaluated by experimental tests in the previous studies and it was showed that all the performance requirements regarding to strength deterioration, stiffness degradation and energy dissipation capacity were satisfied to the criteria of ACI requirements, but the initial stiffness was not. In order to find out possible causes of the insufficient rigidity of the joint devices and provide the proper measures to improve the performance of the joint accordingly, numerical analyses were carried out by using ABAQUS. Parameters, such as thickness of neoprene pad, conditions of surface between PC column and end-plate, magnitude of pretension forces of through bolts, stiffness of end-plate were taken into consideration. As the result, it was found that the rigidity of the PCS system was negatively affected by the magnitude of initial gaps between PC columns and end-plates, and insufficient stiffness of neoprene fillers and end plates. In order to improve the initial stiffness performance of the joints, measures such as increase of the magnitude of pretension forces on through bolts and increase of the stiffness of end-plate by reducing the bolt pitch and providing adequate stiffeners are recommended.
Durability Evaluation of Inorganic-Impregnated Concrete Exposed to Long-Term Chloride Exposure Test
Kwon, Seung-Jun ; Park, Sang-Soon ; Lho, Byeong-Cheol ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 283~290
DOI : 10.4334/JKCI.2008.20.3.283
The repair technique using surface impregnation of reactive compound is so effective for deteriorated concrete structures that many researches are recently focused on these works. Particularly, inorganic impregnant is regarded as ecofriendly material because there is no air-pollution during manufacturing process as well as field coating works. Furthermore, The delamination between old concrete and impregnated surface does not occur, resulting from different material characteristics. In order to evaluate the durability performance of surface-impregnated concrete, durability evaluation through the long-term exposure tests is significant, however, experiments are usually limited to the temporary and qualitative laboratorial scope. In this study, durability characteristics for inorganic and organic/inorganic impregnated concrete specimens are evaluated through longterm chloride exposure test. The specimens with 21MPa and 34MPa strength have been prepared and exposed to chloride attack in the atmospheric, tidal, and submerged conditions. Evaluation for compressive strength, chloride penetration, and electrical potential (half cell potential) for steel corrosion are performed for the specimens exposed for 2 years. From the results, no distinct strength gaining is observed but the resistance to chloride penetration and steel corrosion is evaluated to be improved through surface impregnation. The more improved resistance to chloride attack is measured in the inorganic impregnated concrete and the results from atmospheric condition show more improved resistance to chloride attack than those from submerged and tidal condition.
Permeability of Cracked Concrete as a Function of Hydraulic Pressure and Crack Width
Hyun, Tae-Yang ; Kim, Chin-Yong ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 291~298
DOI : 10.4334/JKCI.2008.20.3.291
Cracks in concrete generally interconnect flow paths and increase concrete permeability. The increase in concrete permeability due to the progression of cracks allows more water or aggressive chemical ions to penetrate into concrete, facilitating deterioration. The goal of this research is to study the relationship between crack width and water permeability of cracked concrete. Tests have been carried out as a function of hydraulic pressure (0.1
2 bar) and crack width (30
). Splitting and reuniting method was used to manufacture cracked concrete specimens with controlled crack width. Crack widths are checked by using a microscope(
100). The results show a considerable increase of water transport with crack width and hydraulic pressure. When the crack width is smaller than 50
, the crack width has little effect on concrete permeability. Due to the autogenous healing, the water flow through the crack gradually reduces with time. When crack width is 100
and hydraulic pressure increase from 0.1 bar to 0.25 bar, concrete permeability increases rapidly about 190 times according to the test results.
Shear Behavior of Reinforced Concrete Beams Strengthened with CFRP Strips
Lim, Dong-Hwan ; Nam, Min-Hee ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 299~305
DOI : 10.4334/JKCI.2008.20.3.299
The main goal of this study was to examine the shear behavior of reinforced concrete beams strengthened with CFRP strups. Seven rectangular beams were tested. The test variables were the configuration types, spacing length of CFRP strips and the amount of reinforced stirrups bars. From this experimental study, the shear capacity of beams strengthened with CFRP increased significantly compared to the beam without CFRP strip. Maximum increase of ultimate shear strength was found about 100% more than that of the beam without a CFRP strip and the CFRP strips attached in the shear region can resist the occurrence of the initial shear cracks and the propagation of major shear cracks. In this test, most of the shear strengthened beams failed suddenly due to the debonding of CFRP strips. A calculation of the shear strength of reinforced beams strengthened with CFRP strips based on the effective stresses was conducted and the comparisons were made with the test results.
Properties of Ternary or Quaternary High Strength Concrete Using Silica Fume & Meta Kaolin
Park, Cho-Bum ; Kim, Ho-Su ; Jeon, Jun-Young ; Kim, Eun-Kyum ; Ryu, Deug-Hyun ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 307~315
DOI : 10.4334/JKCI.2008.20.3.307
In this study, it is investigated the properties of high strength concrete using mineral admixture, on the purpose of use of meta kaolin for the substitutive materials to silica fume which is so expensive. The plain mixtures are 3 degrees which are ordinary portland cement, blast furnace slag cement and OPC included fly ash 20%, and silica fume and meta kaolin are substituted for the each plain mixtures in the range of 20%. The results of experiment showed as follows. In case of silica fume was only used, the viscosity and slump flow of fresh concrete were much decreased, on the contrary air content increased. But as usage of meta kaolin increased, to being increase the viscosity of fresh concrete, slump flow increased and air content and usage of super-plasticizer were decreased. Accordingly the workabilities of concrete were against tendency between silica fume and meta kaolin. The compressive strength, velocity of ultrasonic pulse and unit weight were increased according to usage of meta kaolin, the properties of hardened concrete were judged that they are affected with air content of fresh concrete, so it is very important to control air content of high strength concrete. Therefore, the use of meta kaolin is prospected to the substitutive material of silica fume, in case of using silica fume and meta kaolin, it is judged that the optimum usage of silica fume and meta kaolin is about 10% respectively, considering workability and strength of concrete.
Model for Flow Analysis of Fresh Concrete Using Particle Method with Visco-Plastic Flow Formulation
Cho, Chang-Geun ; Kim, Wha-Jung ; Choi, Yeol ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 317~323
DOI : 10.4334/JKCI.2008.20.3.317
In the current study, A model for the flow analysis of fresh and highly flowable concrete has been developed using a particle method, the moving particle semi-implicit (MPS) method. The phenomena on the flow of concrete has been considered as a visco-plastic flow problem, and the basic governing equation of concrete particle dynamics has been based on the Navier-Stokes equation in Lagrangian form and the conservation of mass. In order to formulate a visco-plastic flow constitutive law of fresh concrete, concrete is modeled as a highly viscous material in the state of non-flow and as a visco-plastic material in the state of flow after reaching the yield stress of fresh concrete. A flow test of fresh concrete in the L-box was simulated and the predicted flow was well matched with the experimental result. The developed method was well showed the flow motion of concrete particles because it was formulated to be based on the motion of visco-plastic fluid dynamics.
Performance of Hybrid Fiber Reinforced Concrete at Elevated High Temperature
Won, Jong-Pil ; Park, Kyung-Hoon ; Park, Chan-Gi ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 325~333
DOI : 10.4334/JKCI.2008.20.3.325
This study evaluated the mechanical performance, shrinkage crack and fire resistance of hybrid fiber (blended steel and polypropylene fiber with different diameter and length) reinforced concrete at elevated temperature. The compressive, splitting tensile, flexural, plastic shrinkage test were conducted to the evaluate the mechanical properties and the resistance of shrinkage crack. Also, the surface investigation, reduction rate of mass and residual compressive test were performed to evaluate the physical and mechanical properties after 400
exposure. Test results showed that the hybrid fiber reinforced concrete improved the mechanical performance, shrinkage crack and fire resistance. The reduction of performance with a temperature change were high at the temperature of
Evaluation of Structural Performance the Hollow PC Column Joint Subjected to Cyclic Lateral Load
Seo, Soo-Yeon ; Yoon, Seong-Joe ; Lee, Woo-Jin ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 335~343
DOI : 10.4334/JKCI.2008.20.3.335
In order to improve the workability in erecting Precast Concrete (PC) members and enhance the seismic resistance capacity of the joints in PC moment frames, a new PC column and its construction process are introduced in this paper. This column is manufactured by centrifugal force in keeping the hollow tube inside; the hollow is little bit wide and the grout can be poured from top to bottom after erection at site so that more compact grouting is possible in horizontal joint. The repeated cyclic loading test for four full scaled specimens was conducted to evaluate the seismic resistance capacity of the joint designed by the proposed system. For the continuity of main reinforcements in column, two connecting methods are used in designing specimens; one is to use mechanical connector and other is lab splice. From the cyclic lateral loading test, it was found that the seismic capacity of the developed PC column joint is comparable to that of monolithic joint.
Direct Inelastic Design of Reinforced Concrete Members Using Strut-and-Tie Model
Eom, Tae-Sung ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 345~356
DOI : 10.4334/JKCI.2008.20.3.345
In the previous study, direct inelastic strut-and-tie model (DISTM) was developed to perform inelastic design of reinforced concrete members by using linear analysis for their secant stiffness. In the present study, for convenience in design practice, the DISTM was further simplified so that inelastic design of reinforced concrete members can be performed by a run of linear analysis, without using iterative calculations. In the simplified direct inelastic strut-and-tie model (S-DISTM), a reinforced concrete member is idealized with compression strut of concrete and tension tie of reinforcing bars. For the strut and tie elements, elastic stiffness or secant stiffness is used according to the design strategy intended by engineer. To define the failure criteria of the strut and tie elements, concrete crushing and reinforcing bar fracture were considered. The proposed method was applied to inelastic design of various reinforced concrete members including deep beam, coupling beam, and shear wall. The design results were compared with the properties and the deformation capacities of the test specimens.
Parametric Study on Design Variables of Concrete Beam Reinforced with GFRP Rebar using Finite Element Analysis
Moon, Do-Young ; Oh, Hong-Seob ; Ahn, Kwang-Yeol ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 357~367
DOI : 10.4334/JKCI.2008.20.3.357
Parametric study of beams with reinforced with FRP rebar is conducted in this study. Using ABAQUS program, the finite element analysis model is set and calibrated with the experimental results which have been conducted by the authors. The employed design parameters are reinforcement ratio, elastic modulus of rebar, and concrete strength. The obtained results from FE analysis are investigated in terms of normalized beam stiffness. In particular, the effect of reinforcement ratio on the flexural stiffness is investigated with comparing with the model code specified on ACI 440. From the analysis results, the reinforcement ratio in beam is the first parameter affecting on the beam stiffness. In addition, its effect could be increased with higher concrete strength.
Self-Diagnosis Properties of Fracture in Reinforced Concrete Intermixed with Conductive Materials
Park, Seok-Kyun ; Cho, Sung-Dong ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 369~374
DOI : 10.4334/JKCI.2008.20.3.369
Two types of conductive materials are selected and their applicable properties are investigated so as to give the capability of self-diagnosis of fracture in composite mortar, concrete and reinforced concrete. In this study, for giving selfdiagnosis capability, the powder of cokes and milled carbon fiber as conductive materials are selected and intermixed with mortar, concrete and reinforced concrete. After examining change in the value of electric resistance before and after the occurrence of cracks at each flexural load-stage in composite mortar, concrete or reinforced concrete, the relationships of each factors (electric resistance, crack and flexural load) are analyzed. As the results, it can be recognized that conductive materials with powder of cokes and milled carbon fiber can be applied for self-diagnosis of flexural fracture in composite mortar, concrete and reinforced concrete specimen.
An Influence of Unit-Water Content Distribution in Ready-Mixed Concrete on Strength and Durability of Concrete
Woo, Young-Je ; Lee, Han-Seung ; Jung, Sang-Hwa ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 375~381
DOI : 10.4334/JKCI.2008.20.3.375
Various problems such as durability degradation may happen when extra water is added to concrete. Because of these reasons, the change of water content is managed by using rapid evaluation method of unit water content such as electric capacity method, heat drying method making use of micro wave, unit capacity mass method among various methods. Especially, in Japan, guidance for the change of water content (
10, 15, 20 kg/
etc.) were regulated and used. However, it is the real situation that the guidance which were regulated in South Korea evaluate suitability only considering production and measurement error under the circumstances which are not considering the degree of durability degradation. Therefore, this study tries to investigate the influence of addition of extra water in the concrete on the durability degradation of concrete when it was added by artificial manipulation or by management error. From the test results, a guideline of the contents of extra water for the quality control is suggested with the consideration of the degree of durability degradation and the probable error resulted from the addition of extra water. The contents of extra water for tests are set as 0, 15, 25, 35 kg/
. To examine the durability degradation of concrete, freezing and thawing, carbonation, chloride penetration and compressive strength are tested.
Bond Failure Surface of Glass Fiber Reinforced Polymer Bars
Lee, Jung-Yoon ; Yi, Chong-Ku ; Kim, Tae-Young ; Park, Ji-Sun ; Park, Young-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 383~391
DOI : 10.4334/JKCI.2008.20.3.383
The effects of concrete strength on bond-slip behavior and the failure mechanisms of glass fiber reinforced polymer (GFRP) bar embedded in concrete under direct pullout were investigated in this study. Total of twenty seven specimens were prepared by placing two different types of GFRP bars and conventional steel rebar in 25 MPa, 55 MPa, and 75 MPa concrete and tested according to CSA S806-02. The test results showed that the bond strength of the GFRP rebars as well as the steel increased with the concrete strength. However, the increase in the bond strength with respect to the concrete strength was not as significant in the GFRP series as the steel, and it was attributed to the interlaminar failure mechanism observed in the GFRP test specimens.
Investigation on the Effective Moment of Inertia of Reinforced Concrete Flexural Members Under Service Load
Lee, Seung-Bea ; Park, Mi-Young ; Jang, Su-Youn ; Kim, Kang-Su ; Kim, Sang-Sik ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 393~404
DOI : 10.4334/JKCI.2008.20.3.393
The approaches in many design codes for the estimation of the deflection of flexural reinforced concrete (RC) members utilize the concept of the effective moment of inertia which considers the reduction of flexural rigidity of RC beams after cracking. However, the effective moment of inertia in design codes are primarily based on the ratio of maximum moment and cracking moment of beam subjected to loading without proper consideration on many other possible influencing factors such as span length, member end condition, sectional size, loading geometry, materials, sectional properties, amount of cracks and its distribution, and etc. In this study, therefore, an experimental investigation was conducted to provide fundamental test data on the effective moment of inertia of RC beams for the evaluation of flexural deflection, and to develop a modified method on the estimation of the effective moment of inertia based on test results. 14 specimens were fabricated with the primary test parameters of concrete strength, cover thickness, reinforcement ratio, and bar diameters, and the effective moments of inertia obtained from the test results were compared with those by design codes, existing equations, and the modified equation proposed in this study. The proposed method considered the effect of the length of cracking region, reinforcement ratio, and the effective concrete area per bar on the effective moment of inertia, which estimated the effective moment of inertia more close to the test results compared to other approaches.
Mechanical Properties of Alkali-Activated Slag-Based Concrete Using Lightweight Aggregates
Yang, Keun-Hyeok ; Oh, Seung-Jin ; Song, Jin-Gyu ;
Journal of the Korea Concrete Institute, volume 20, issue 3, 2008, Pages 405~412
DOI : 10.4334/JKCI.2008.20.3.405
Six alkali-activated (AA) concrete mixes were tested to explore the significance and limitations of developing an environmental friendly concrete. Ground granulated blast-furnace slag and powder typed sodium silicate were selected as source material and an alkaline activator, respectively. The main parameter investigated was the replacement level of lightweight fine aggregate to the natural sand. Workability and mechanical properties of lightweight AA concrete were measured: the variation of slump with time, the rate of compressive strength development, the splitting tensile strength, the moduli of rupture and elasticity, the stress-strain relationship, the bond resistance and shrinkage strain. Test results showed that the compressive strength of lightweight AA concrete sharply decreased when the replacement level of lightweight fine aggregate exceeded 30%. In particular, the increase in the discontinuous grading of lightweight aggregate resulted in the deterioration of the mechanical properties of concrete tested. The measured properties of lightweight AA concrete were also compared, wherever possible, with the results obtained from the design equations specified in ACI 318-05 or EC 2, depending on the relevance, and the results predicted from the empirical equations proposed by Slate et al. for lightweight ordinary Portland cement concrete. The stress-strain curves of different concrete were compared with predictions obtained from the mathematical model proposed by Tasnimi. The measured mechanical properties of lightweight AA concrete generally showed little agreement with the predictions obtained from these equations.