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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 21, Issue 6 - Dec 2009
Volume 21, Issue 5 - Oct 2009
Volume 21, Issue 4 - Aug 2009
Volume 21, Issue 3 - Jun 2009
Volume 21, Issue 2 - Apr 2009
Volume 21, Issue 1 - Feb 2009
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Tensile Deformation Characteristics of ECC Predicted with a Modified Fiber Bridging Curve
Kim, Jeong-Su ; Lee, Bang-Yeon ; Kim, Jin-Keun ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 541~548
DOI : 10.4334/JKCI.2009.21.5.541
A theoretical prediction model of fiber bridging curve was established based on the assumption that fibers are uniformly distributed on the crack surface. However, the distance between fibers and their orientation with respect to crack surface can greatly affect the prediction of fiber bridging curve. Since, the shape of fiber bridging curve is a critical factor for predicting the tensile stress-strain relationship of ECC, it is expected that the assumption of uniform distribution of fiber may cause a significant error when predicting the tensile behavior of ECC. To overcome this shortcoming, a new prediction method of stress-strain relation of ECC is proposed based on the modified fiber bridging curve. Only effective fibers are taken into account considering the effects of their orientation and distance between them. Moreover, the approach for formulating the tensile stress-strain relation is discussed, where a procedure is presented for obtaining important parameters, such as the first crack strength, the peak stress, the displacement at peak stress, tensile strain capacity, and the crack spacing. Subsequent uniaxial tensile tests were performed to validate the proposed method. It was found that the predicted stress-strain relations obtained based on the proposed modified fiber bridging curve exhibited a good agreement with experimental results.
Development of Wide Connection Method for Vertical Joints of Precast Concrete Walls
Choi, Eun-Gyu ; Shin, Yeong-Soo ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 549~556
DOI : 10.4334/JKCI.2009.21.5.549
This research analyzed the structural efficiency and application by improving the 100 mm width vertical joint to 150 mm and developing three connection methods to reduce the difficulty in assembling and handling PC walls. Moreover, nonlinear finite analysis was used for analyzing. From the analysis results, when double width connection was applied, the PC wall showed larger load capacity and ductility due to the steel bar sharing loads efficiently. Moreover, as the dimension of loops and the number of bars increased, the maximum load capacity increased as well. Also, among the double width connections, the largest capacity showed in the order of welding, ring and C type loop. However, in case of welding type loop connection, the ring type loop is more stable due to changes in different site conditions. Therefore, thorough quality control of welding is necessary.
Experimental Study on the Properties of Solid Material Made by Autoclave Curing according to CaO/SiO
Ratio and W/B
Kang, Cheol ; Kang, Ki-Woong ; Kim, Jin-Man ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 557~563
DOI : 10.4334/JKCI.2009.21.5.557
This study is on the properties of inorganic porous calcium silicate material made from silica powder through the autoclaving curing, the results of this study should be utilized fundamental data for the development of noise reduction porous solid material using siliceous byproduct generated by various manufacture process. For the manufacture of autoclave curing specimen, various calcareous materials used and siliceous materials used silica powder. In this study, properties in density and compressive strength according to the change of W/B and C/S ratio, microscopy for the shape of pore, SEM and XRD for the examination of hydrate after autoclave curing are carried out respectively. The test results shown that the more slurry density decrease, the more W/B increase at the fresh state, this tendency shown similar to in hardened state. Among the specimens of C/S ratio, the compressive strength of C/S ratio of 0.85 gave the highest the compressive strength. In the results of XRD, tobermorite generated by autoclaving curing was created all of specimens regardless of C/S ratio. To ascertain pore structure, we compared with existing porous calcium silicate product(ALC, organic sound absorbing porous material). The results of microscope observation, pore structure of specimen of this study was similar to that of existing inorganic sound absorbing foam concrete. therefore, we could conformed a possibility of sound absorbing porous solid material on the basis of the results.
Material Characteristic of POFA Concrete and Its Application to Corrosion Resistance Evaluation
Lee, Chang-Hong ; Song, Ha-Won ; Ann, Ki-Yong ; Ismail, Mohamed Abdel ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 565~572
DOI : 10.4334/JKCI.2009.21.5.565
In this study, corrosion resistance of palm oil fuel ash (POFA) concrete as a blended concrete is evaluated by using electrochemical technique. The POFA is an industrial byproduct obtained from fuel ash after extracting palm oil from palm-tree. In order to obtain basic material characteristics of the POFA concrete, tests on compressive strength, slump, weight loss, bleeding and expansion ratio were carried out the early-aged POFA concrete. On the other hand, durability characteristics, both chloride penetration and carbonation depth test, were also conducted. Finally, corrosion resistance were evaluated by applying electro-chemical artificial crack healing technique, and the tests on the impressed voltage characteristic, galvanic current and linear polarization resistance. From the experimental results, it was found that long-term strength, bleeding, lower slump ratio, expansion ratio, chloride penetration, carbonation and corrosion resistance were improved by using the POFA due to activated pozzolanic reaction. It can be also mentioned that POFA concrete has a potential to be used as a cementitious binder for green-recycling resources.
Fiber Distribution Characteristics and Flexural Performance of Extruded ECC Panel
Lee, Bang-Yeon ; Han, Byung-Chan ; Cho, Chang-Geun ; Kwon, Young-Jin ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 573~580
DOI : 10.4334/JKCI.2009.21.5.573
This paper presents the mix composition, production method, and curing condition applied to the extruded ECC(Engineered Cementitious Composite) panel which are able to exhibit multiple cracking and potential pseudo strain-hardening behavior. In addition to the production technique of extruded ECC panel, the effect of fiber distribution characteristics, which are uniquely created by applying extrusion process, on the flexural behavior of the panel is also focussed. In order to demonstrate fiber distribution, a series of experiments and analyses, including image processing/analysis and micro-mechanical analysis, was performed. The optimum mix composition of extruded ECC panel was determined in terms of water matrix ratio, the amount of cement, ECC powder, and silica powder. It was found that flexural behavior of extruded ECC panel was highly affected by the slight difference in mix composition of ECC panel. This is mainly because the difference in mix composition results in the change of micro-mechanical properties as well as fiber distribution characteristics, represented by fiber dispersion and orientation. In terms of the average fiber orientation, the fiber distribution was found to be similar to the assumption of two dimensional random distribution, irrespective of mix composition. In contrast, the probability density function for fiber orientation was measured to be quite different depending on the mix composition.
Experimental Study on the Bond Capacity of RC Beams Using Electric Arc Furnace Oxidizing Slag Aggregates
Ryu, Deug-Hyun ; Lim, Ji-Young ; Lee, Yong-Jun ; Kim, Sang-Woo ; Kim, Kil-Hee ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 581~588
DOI : 10.4334/JKCI.2009.21.5.581
An amount of electric arc furnace slag, by-products generated in iron manufacture, is being increased. Therefore, it is required to recycle the electric arc furnace slag. Currently, it is possible to use the electric arc furnace slag as the aggregates of the concrete through the insurance of volume stability but not in the past because of the expansibility of f-CaO and f-MgO. In this study, simple beam tests via Ichinose method were performed to estimate the bond properties of reinforced concrete (RC) beams using the electric arc furnace slag. The results of the test showed that the showed that specimens using the electric arc furnace oxidizing slag aggregates have similar or more bond capacity relative to the specimen of natural aggregates. Especially, bond capacity of the specimens using the slag aggregates was almost one and a half times higher than a specimen using natural aggregates.
Assessment of the Damage in High Performance Fiber-Reinforced Cement Composite under Compressive Loading Using Acoustic Emission
Kim, Sun-Woo ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 589~597
DOI : 10.4334/JKCI.2009.21.5.589
High Performance Fiber-reinforced Cement Composite (HPFRCC) shows the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior of HPFRCC and understand the micro-mechanism of cement matrix with reinforcing fiber. This study is devoted to the investigation of the AE signals in HPFRCC under monotonic and cyclic uniaxial compressive loading, and total four series were tested. The major experimental parameters include the type and volume fraction of fiber (PE, PVA, SC), the hybrid type and loading pattern. The test results showed that the damage progress by compressive behavior of the HPFRCC is a characteristic for the hybrid fiber type and volume fraction. It is found from acoustic emission (AE) parameter value, that the second and third compressive load cycles resulted in successive decrease of the amplitude as compared with the first compressive load cycle. Also, the AE Kaiser effect existed in HPFRCC specimens up to 80% of its ultimate strength. These observations suggested that the AE Kaiser effect has good potential to be used as a new tool to monitor the loading history of HPFRCC.
Generalized Analysis of RC and PT Flat Plates Using Limit State Model
Kang, Thomas H.K. ; Rha, Chang-Soon ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 599~609
DOI : 10.4334/JKCI.2009.21.5.599
This paper discusses generalized modeling schemes for both reinforced concrete (RC) and post-tensioned (PT) flat plate buildings. In this modeling approach, nonlinear behavior due to slab flexure, moment and shear transfer at slab-column connections, and punching shear was included along with linear secant stiffness of each member or connection that accounts for concrete cracking. This generalized model was capable of simulating all different scenarios of slab-column connection failures such as brittle punching, flexure-shear interactive failure, and flexural failure followed by drift-induced punching. Furthermore, automatic detection of drift-induced punching shear and subsequent backbone curve modifications were realistically modelled by incorporating the limit state model, in which gravity shear versus drift capacity relations were adopted. The validation of the model was conducted using one-third scale two-story by two-bay RC and PT flat plate frames. The comparisons revealed that the model was robust and effective.
Sulfate Attack Resistance and Microstructural Observations of Cement Matrix Exposed to a Low Temperature Condition
Lee, Seung-Tae ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 611~617
DOI : 10.4334/JKCI.2009.21.5.611
This paper reports an experimental study on the damage mechanism and resistance of Type I portland cement mortar and paste samples exposed to 5% sodium sulfate solution with different solution temperatures; namely,
. The resistance of mortar samples was evaluated using expansion, compressive strength and flexural strength measurements. Some microstructural observations such as x-ray diffraction, differential scanning calorimetry and scanning electron microscopy were also introduced to elucidate reactants formed by sulfate attack, especially in a low temperature condition. From the results, it was found that the degree of damage in the mortar samples was significantly associated with the temperature of sulfate solution. Low temperature of the sulfate solution led to the formation of thaumasite in mortar and paste samples, and subsequently a poor resistance to sulfate attack. Thus, it is noted that when concrete structures are exposed to sulfate media in the condition of a cold region or whether, special care should be taken.
Estimation Method of Creep Coefficient in Concrete Structures
Park, Jong-Bum ; Park, Jung-Il ; Chang, Sung-Pil ; Cho, Jae-Yeol ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 619~628
DOI : 10.4334/JKCI.2009.21.5.619
To predict the time-dependent behavior of concrete structures, the models which describe the time-dependent characteristics of concrete, i.e. creep and shrinkage are required. However, there must be significant differences between the displacements that are obtained using the given creep and shrinkage models and the measured displacements, because of the uncertainties of creep and shrinkage model itself and those of environmental condition. There are some efforts to reduce these error or uncertainties by using the model which are obtained from creep test for the concrete in construction site. Nevertheless, the predicted values from this model may be still different from the actual values due to the same reason. This study aimed to propose a method of estimating the creep coefficient from the measured displacements of concrete structure, where creep model uncertainty factor was considered as an error factor of creep model. Numerical validation for double composite steel box and concrete beam showed desirable feasibility of the presented method. Consideration of the time-dependent characteristics of creep as one of the error factors make it possible to predict long-term behaviors of concrete structures more realistically, especially long-span PSC girder bridges and concrete cable-stayed bridges of which major problem is the geometry control under construction and maintenance.
Sensitivity Analysis of Generalized Parameters on Concrete Creep Effects of Composite Section
Yon, Jung-Heum ; Kim, Eui-Hun ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 629~638
DOI : 10.4334/JKCI.2009.21.5.629
In this paper, the existing formulas of the step-by-step method were generalized for effective estimation of responses of complicated composite sections due to long-term deformation of concrete. The initial transformed section properties of the composite section were derived from material and section properties of concrete section and sections which confine the longterm deformation of concrete. The transformed section properties at each step were derived from the effective modulus of elasticity considered the creep coefficient variation. Improved formulas of the step-by-step method for generalized responses were derived by introducing 5 generalized parameters. The formulas can be more simplified by applying constant increment of creep coefficient at each step. The constant increment of creep coefficient at each step can also reduce computing time and make equal computing error of each step. The generalized responses for axial elastic strain of concrete section were most sensitive to the area rate of concrete section, and the ratio of the second moment of the confining section area was more sensitive than that of the concrete section. Those for elastic curvature of concrete section were most sensitive to the ratio of the second moment of concrete section area.
An Experimental Study on Relation between Chloride Diffusivity and Microstructural Characteristics for GGBS Concrete
Kim, Tae-Sang ; Jung, Sang-Hwa ; Choi, Young-Cheol ; Song, Ha-Won ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 639~647
DOI : 10.4334/JKCI.2009.21.5.639
In order to evaluate the durability of reinforced concrete structures under chloride attack from sea water and frost damage, it is important to analyze both the microstructural characteristics of concrete and its diffusion resistance of concrete against chloride ingress. In this study, a relation between micro-pore structures of concrete obtained by the Mercury Intrusion Porosimetry and accelerated chloride diffusivity as well as long term chloride diffusivity were studied for ground granulated blast furnace slag(GGBS) concrete. Different water-cement ratio of 40, 45, 50% and different unit cement concrete of 300, 350, 400 or 450 kg/
of the GGBS concrete along with OPC concrete were used and freeze and thawing, and the change in diffusivity and microstructure were observed for both GGBS concrete and damaged GGBS concrete due to rapid freezing and thawing.
Behavior of Internally Confined Hollow RC Columns
Han, Taek-Hee ; Won, Deok-Hee ; Yi, Gyu-Sei ; Kang, Young-Jong ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 649~660
DOI : 10.4334/JKCI.2009.21.5.649
A nonlinear column model of an internally confined hollow (ICH) reinforced concrete (RC) column was suggested and a parametric study was performed. The suggested column model considered the confining effect and the material nonlinearity of concrete. To verify the suggested column model, its analysis results were compared with the test results from previous researchers and a quasi static test performed in this study. They showed that the suggested column model was reasonable and had acceptable accuracy. The results from parametric studies showed that the thickness of the internal tube, concrete strength, and the hollow ratio of the ICH RC column affected its behavior.
Stiffness Reduction Factor for Post-Tensioned Flat Plate Slabs under Lateral Loads
Park, Young-Mi ; Park, Jin-Ah ; Han, Sang-Whan ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 661~668
DOI : 10.4334/JKCI.2009.21.5.661
Effective beam width model(EBWM) has been used for analysis of post-tensioned(PT) flat plate slab frames under lateral loads. The accuracy of this model in predicting lateral drifts and unbalanced moments strongly depends on the estimated effective stiffness of PT flat plate slabs. As moments on the slab due to lateral loads increases, cracks occur which leads to stiffness reduction in slabs. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for EBWM. For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis using the stiffness ratio of the reduced width of slab to the effective width of EBWM with respect to the level of slab moments, an equation for calculating stiffness reduction factor for slab is proposed. For verifying the accuracy of the proposed equation, this study compared with the test result of the PT flat plate frame. It is shown that the EBWM with the proposed equation predicts the actual stiffness of the PT specimen which varied according to the level of applied moment.
Effect of Aggregate Size on the Shear Capacity of Lightweight Concrete Continuous Beams
Yang, Keun-Hyeok ; Mun, Ju-Hyun ;
Journal of the Korea Concrete Institute, volume 21, issue 5, 2009, Pages 669~677
DOI : 10.4334/JKCI.2009.21.5.669
Twenty-four beam specimens were tested to examine the effect of the maximum aggregate size on the shear behavior of lightweight concrete continuous beams. The maximum aggregate size varied from 4 mm to 19 mm and shear span-to-depth ratio was 2.5 and 0.6 in each all-lightweight, sand-lightweight and normal weight concrete groups. The ratio of the normalized shear capacity of lightweight concrete beams to that of the company normal weight concrete beams was also compared with the modification factor specified in ACI 318-05 for lightweight concrete. The microphotograph showed that some unsplitted aggregates were observed in the failure planes of lightweight concrete beams, which contributed to the enhancement of the shear capacity of lightweight concrete beams. As a result, the normalized shear capacity of lightweight concrete continuous beams increased with the increase of the maximum aggregate size, though the increasing rate was lower than that of normal weight concrete continuous beams. The modification factor specified in ACI 318-05 was generally unconservative in the continuous lightweight concrete beams, showing an increase of the unconservatism with the increase of the maximum aggregate size. In addition, the conservatism of the shear provisions of ACI 318-05 was lower in lightweight concrete beams than in normal weight concrete beams.