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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
Environmental Impact Assessment of Different Concrete Mixture Proportions according to Domestic Region and Season
Seo, Eun-A ; Yang, Keun-Hyeok ; Jung, Yeon-Back ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 239~245
DOI : 10.4334/JKCI.2014.26.3.239
This study analyzed a comprehensive database including 6331 ready-mixed concrete plant mixtures to quantitatively assess the environmental impact of concrete under mixture proportions variable according to the domestic region and season. The environmental impact indicator includes global warming, photochemical oxidant creation, abiotic resource depletion, acidification, eutrophication and human toxicity, which are determined from categorization, characterization, normalization and weighting process based on Korea lifecycle inventories. The determined environmental impact indicator was also normalized by concrete compressive strength (
), which is defined as impact index, to calculate the environmental impact per unit strength of 1 MPa. The most common compressive strength of concrete used in the country is estimated to be 24 MPa and 27 MPa. For
of 24 MPa, the lowest environmental impact indicator is observed in Ulsan, whereas the highest region is Gwangju and Daegu. This difference according to domestic region is primarily resulted from by the replacement of different supplementary cementitious materials. Furthermore, the impact index of concrete with
of 24 MPa is higher by approximately 5% at wintertime than at summertime and standard season. The impact index gradually decreases with the increase of
up to 35 MPa, beyond which it remains constant.
Evaluation on Strain Properties of 60 MPa Class High Strength Concrete according to the Coarse Aggregate Type and Elevated Temperature Condition
Yoon, Min-Ho ; Choe, Gyeong-Cheol ; Lee, Tae-Gyu ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 247~254
DOI : 10.4334/JKCI.2014.26.3.247
Strain properties of concrete member which acts as an important factor in the stability of the concrete structure in the event of fire, significantly affected the characteristics of the coarse aggregate, which accounts for most of the volume. For this reason, there are many studies on concrete using artificial lightweight aggregate which has smaller thermal expansion deformation than granite coarse aggregate. But the research is mostly limited on concrete using clay-based lightweight aggregate. Therefore, in this study, the high temperature compressive strength and elastic modulus, thermal strain and total strain, high temperature creep strain of concrete was evaluated. As a result, remaining rate of high-temperature strength of concrete using lightweight aggregate is higher than concrete with general aggregate and it is determined to be advantageous in terms of structural safety and ensuring high-temperature strength from the result of the total strain by loading and strain of thermal expansion. In addition, in the case of high-temperature creep, concrete shrinkage is increased by rising loading and temperature regardless of the type of aggregate, and concrete using lightweight aggregate shows bigger shrinkage than concrete with a granite-based aggregate. From this result, it is determined to require additional consideration on a high temperature creep strain in case of maintaining high temperature like as duration of a fire although concrete using light weight aggregate is an advantage in reducing the thermal expansion strain of the fire.
Seismic Performance of T-Shaped PC Walls with Wet Cast Joint
Lim, Woo-Young ; Hong, Sung-Gul ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 255~266
DOI : 10.4334/JKCI.2014.26.3.255
This paper investigates the seismic performance of T-shaped PC walls with a new vertical connections and wet cast joint. The load-displacement relationship, strength, ductility, failure mechanism, and deformation capacity of the T-shaped PC walls subjected to cyclic loading are verified. Test parameter is diagonal reinforcement of both flange and web wall panels to transfer shear strength. The longitudinal reinforcing steel bars placed edges of walls yield first and the ultimate deformation is terminated due to premature failure of connections. And diagonal reinforcements for shear transfer in walls are effective to restrain the wall crack. The strength and displacement obtained by the cross section analysis were very similar to the experimental data.
Analytical Evaluation of Behavior of Precast PSC Box Curve Bridge Based on Design Variables
Kim, Sung-Bae ; Kim, Sung-Jae ; Park, Jeong-Cheon ; Uhm, Ki-Ha ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 267~275
DOI : 10.4334/JKCI.2014.26.3.267
Recently, the construction of curved bridge has increased, thus researchers perform the analytic studies on PSC curved bridge. However, the grid analysis method that are mostly used in the construction industry is not adequate to acquire the precise behavior evaluation of curved PSC briges. Therefore, the precise finite element analysis considering the effective variables were performed to establish the basis for the design method of curved PSC bridge by using 3D elements and bar element. The evaluated variables in this analysis were the number of girders, loading point, section figure, change of prestressing force. The results show the load carrying capacity of the 3 girder type bridge is 200% of that of the 2 girder type, and that applying load on outer girder makes the load resistance capacity and the deflection deviation of 2 girders smaller. The structural capacity of the bridge is improved when the section size is increased, but the efficiency of it is not sufficient enough compare to that of the change of prestressing forces. The change of prestressing forces shows that the camber and the load carrying capacity are linearly increased as PS force is increased. Moreover, when the PS force applied on outer girder is increased than that of inner girder, the deviation of deflection the girders decreases, thereby the stability of the bridge is enhanced.
An Experimental Study on the Rheological Properties of the Combined Self-Compacting Concrete by Quality Variations
Kwon, Yeong-Ho ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 277~285
DOI : 10.4334/JKCI.2014.26.3.277
The purpose of this study is to investigate experimentally the variation factors range having influence on the rheological properties of the combined self-compacting concrete according to materials quality, weighting error and site conditions. Two types cement (blast-furnace slag cement and belite cement), lime stone powder as binder and the optimum mix proportions in the preceded study are selected for this study. Also, variations for sensitivity test are as followings; (1) Concrete temperature 3 cases (2) Surface moisture of sand 5cases (3) Fineness modulus of sand 5cases (4) Specific surface of lime stone powder 3cases (5) Dosage of chemical admixture 5cases. Slump flow (
), 500 mm reaching time ((
), V-type flowing time (
) and U-box height (min. 300 mm) are tested for sensitivity. As test results, the variations range for quality control are as followings. (1) Concrete temperature;
) (2) Surface moisture of sand;
(3) Fineness modulus of sand;
(4) Dosage of chemical admixture;
(5) Specific surface of lime stone powder
. Compared with two types cement including based belite cement (binary type) and based slag cement (ternary type), the combined self-compacting concrete used belite cement type is most stable in the quality control because of high contents for lime stone powder and
. It is to propose a control scheme of the combined self-compacting concrete in the actual construction work.
A Study on the Thermal Crack Control of Foundation for Large Turbine
Ha, Ju-Hyung ; Cho, Yun-Gu ; Lee, Kewn-Chu ; Lim, Chang-Keun ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 287~297
DOI : 10.4334/JKCI.2014.26.3.287
Heat of hydration of mass concrete is one of the most important factors that significantly affect structural quality and construction period. Therefore, appropriate methods to control heat of hydration are essential technologies for mass concrete construction. In this study, probability of thermal cracking was checked by thermal analysis prior to the construction of a turbine foundation in a domestic power plant. Subsequently, changes of concrete mix proportion and an effective curing method were proposed to control heat of hydration of mass concrete structures. Concrete manufactured by slag cement was proposed instead of concrete produced by ordinary Portland cement, and an automated curing method was proposed to improve the curing method using typical moist curing with blanket. The automated curing method maintains the temperature difference between center and surface of concrete below a setting value by temperature monitoring. Concrete with slag cement was used for actual construction. One of two identical turbine foundations was cured by an insulated curing method, and the other was cured by the automated curing method to compare the curing methods. And then, the effects of control of heat of hydration were evaluated based on temperature/strain monitoring and crack investigations.
An Experimental Study on Flexural Behavior of Beams Reinforced with Zinc-Coated Rebar
Yang, In-Hwan ; Kim, Kyong-Chul ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 299~306
DOI : 10.4334/JKCI.2014.26.3.299
Coating is one of the methods used to solve the problem of corrosion of reinforcement in concrete structures. There are few research reported in the literature regarding the effect of zinc-coating on flexural behavior compared to epoxy coating. The objective of this study was to determine whether zinc-coated rebar adversely affects flexural behavior. Concrete beams reinforced with black or zinc-coated steel were tested in flexure. The test variables included the presence of rebar surface coating with zinc, steel ratio used and cover depth. The study concentrated on comparing crack pattern, crack width, deflection and strain. The ultimate flexural capacity of beams reinforced with zinc-coated bars was not different from that of black steel reinforced beams. The results from deflection and crack width measurements were indicative of no significant variation for the different rebar surface conditions. In addition, it was found that load-strain curve of beam reinforced with zinc-coated steel was similar to that of beam reinforced with zinc-coated steel. Therefore, the test results indicated that the use of zinc-coated rebar had no adverse effect on flexural behavior compared to the use of black rebar.
Fiber Orientation Factor on a Circular Cross-Section in Concrete Members
Lee, Seong-Cheol ; Oh, Jeong-Hwan ; Cho, Jae-Yeol ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 307~313
DOI : 10.4334/JKCI.2014.26.3.307
In order to predict the post-cracking tensile behavior of fiber reinforced concrete, it is necessary to evaluate the fiber orientation factor which indicates the number of fibers bridging a crack. For investigation of fiber orientation factor on a circular cross-section, in this paper, cylindrical steel fiber reinforced concrete specimens were casted with the variables of concrete compressive strength, circular cross-section size, fiber type, and fiber volumetric ratio. The specimens were cut perpendicularly to the casting direction so that the fiber orientation factor could be evaluated through counting the number of fibers on the circular cross-section. From the test results, it was investigated that the fiber orientation factor on a circular cross-section was lower than 0.5 generally adopted, as fibers tended to be perpendicular to the casting direction. In addition, it was observed that the fiber orientation factor decreased with an increase of the number of fibers per unit cross-section area. For rational prediction of the fiber orientation factor on a circular section, a rigorous model and a simplified equation were derived through taking account of a possible fiber inclination angle considering the circular boundary surface. From the comparison of the measured data and the predicted values, it was found that the fiber orientation factor was well predicted by the proposed model. The test results and the proposed model can be useful for researches on structural behavior of steel fiber reinforced columns with a circular cross-section.
Study on Analysis Technique Comparison and Evaluation of High Thermal Conductivity Concrete with Magnetite Aggregates and Steel Powder
Lee, Hack-Soo ; Kim, Min-Kyu ; Kwon, Seung-Jun ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 315~321
DOI : 10.4334/JKCI.2014.26.3.315
Concrete as a construction material is widely used in nuclear vessel and plant for excellent radiation shielding. However the isolation characteristics in concrete may affect adversely in the case of fire and melt-down in nuclear vessel since temperature cooling down is very difficult from outside. This study is for development of high thermal conductive concrete, and its mechanical and thermal properties are evaluated. Magnetite aggregates with volume ratio of 42.3% (maximum) and steel powder of 1.5% are replaced with normal aggregates and thermal properties are evaluated. Thermal conductivity little increases by 30% addition of magnetite but rapidly increases afterwards. Finally thermal conductivity is magnified to 2.5 times in the case of 42.3% addition of magnetite. Steel powder has a positive effect on high thermal conduction to 106~113%. Several models for thermal conduction like ACI, DEMM, and MEM are compared with test results and they are verified to reasonably predict the thermal conductivity with increasing addition of magnetite aggregates and steel powder.
Experiment of Flexural Behavior of Reinforced Concrete Beams with High Volume Fly Ash
Yoo, Sung-Won ; Lee, Hyung-Jib ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 323~329
DOI : 10.4334/JKCI.2014.26.3.323
It is known that the best way to recycle fly ash is to use in concrete. It is impossible to bury in the ground this fly ash recently, so it is trying to use high volume fly ash concrete. Nevertheless, recent main research topics are focused in the part of material only, however, it is necessary to perform the researches about elasticity modulus, stress-strain relationship and structural behavior. Therefore, in this paper, 18 test members were manufactured with 3 test variables, namely fly ash replacement ratio 0, 35, 50%, concrete compressive strength 20, 40, 60 MPa and 2 tensile steel ratio. 18 test members were tested for flexural behavior. From the test results, there were no differences between 35, 50% high volume fly ash cement concrete and ordinary concrete without fly ash(FA=0%).
Erosion Criteria for the Progressive Collapse Analysis of Reinforcement Concrete Structure due to Blast Load
Kim, Han-Soo ; Ahn, Hyo-Seong ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 335~342
DOI : 10.4334/JKCI.2014.26.3.335
In this paper, reference erosion criteria value suitable for progressive collapse analysis of RC structure due to blast load is proposed. Erosion is fundamentally a numerical technique to overcome the problems such as large numerical errors or abrupt termination of analysis and previous study has been suggested value for blast analysis. But concrete has different stress-strain curve according to strain rate. Consequently, the erosion criteria for the realistic progressive collapse simulation were suggested by comparing experiment results and numerical analysis results. Finally, the real progressive collapse of Oklahoma Federal Building was analyzed by using the median value of two values. And as a result, the analysis result is the actual collapse of the well described.
Uncertainty Analysis of Long-Term Behavior of Reinforced Concrete Members Under Axial Load
Yoo, Jae-Wook ; Kim, Seung-Nam ; Yu, Eun-Jong ; Ha, Tae-Hun ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 343~350
DOI : 10.4334/JKCI.2014.26.3.343
A probabilistic construction stage analysis using the Monte Carlo Simulation was performed to address the effects of uncertainty regarding the material properties, environmental factors, and applied forces. In the previous research, creep and shrinkage were assumed to be completely independent random variables. However, because of the common influencing factors in the material models for the creep and shrinkage estimation, strong correlation between creep and shrinkage can be presumed. In this paper, an Monte Carlo Simulation using CEB-FIB creep and shrinkage equations were performed to actually evaluate the correlation coefficient between two phenomena, and then another Monte Carlo Simulation to evaluate the statistical properties of axial strain affected by partially correlated random variables including the material properties, environmental factors, and applied forces. The results of Monte Carlo Simulation were compared with measured strains of a column on a first story in a 58-story building. Comparison indicated that the variation due to the uncertainty related with the material properties were most severe. And measured strains was within the range of mean+standard deviation.
Damping System Design for Apartment Buildings Using Equivalent Frame Model
Kim, Jong-Ho ; Lee, Myoung-Kyu ; Chun, Young-Soo ; Lee, Dong-Chul ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 351~360
DOI : 10.4334/JKCI.2014.26.3.351
The purpose of this research is to introduce the simplified equivalent frame model for the equivalent lateral force procedure, the response spectrum procedure and nonlinear procedure according to ASCE7-10 in order to reduce the time of performance and reasonably evaluate the effect of applying the damping system with the various conditions for the analysis and the variable. In this research, the seismic performance assessment and the design of the damping system were conducted through the nonlinear time history analysis based on the performance based seismic design in ASCE7-10 in regard to applying the damping system to apartment buildings which is lately issued. The optimal design based on the 75% of seismic base shear was performed for an apartment building. The seismic performance assessment were conducted to check the safety of the building, and the economic evaluation was performed by comparing the amount of resource for the optimal designed building with the amount of resource for the original building. In addition, hysteresis dampers was applied to the apartment building, and the suggested equivalent frame model was performed using the damping system design in ASCE7-10, then its control effects were proved in the full scale model of the apartment building which was used in this research.
Experimental Evaluation of the Punching Shear Strength with Lightweight Aggregate Concrete Slabs
Kim, Jung-Joong ; Moon, Ji-Ho ; Youm, Kwang-Soo ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 361~367
DOI : 10.4334/JKCI.2014.26.3.361
This paper investigates the punching shear strength of lightweight aggregate concrete (LWAC) slabs through a series of experimental study. Five full scale slabs were constructed using normal concrete and four different types of LWAC. Each lightweight aggregate (LWA) used in this study had different sources (clay, shale, or slate) and shapes (crushed or spherical shape). Based on the test results, the effect of the lightweight aggregates (LWA) on the punching shear behavior was investigated. From the test results, it was found that the punching shear failure surface of LWAC slab with spherical shape coarse aggregate was less inclined than that with crushed shape coarse aggregate, which resulted in an increase of the area of the shear failure surface. As a result, it leads to the increased punching shear strength of the slab. On the other hand, the failure surfaces of LWAC slab with crushed shape coarse aggregate and normal coarse aggregate were inclined similarly. Finally, the test results of this study were compared with the punching shear strength obtained from current design models, such as ACI and CEB-FIP, to examine the validation of current design model to predict the punching shear strength of the LWAC slab.
Composition Changes in Cement Matrix of RC Column Exposed to Fire
Kim, Jung-Joong ; Youm, Kwang-Soo ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 369~375
DOI : 10.4334/JKCI.2014.26.3.369
This study examined the changes of microstructural compositions in cement matrix according to the depth from the surface of a reinforced concrete (RC) column exposed to fire. The RC column was exposed to a standard fire for 180 minutes. After the fire test, core samples passing through the column section were obtained. Using the core samples, the remaining fractions of calcium-silicate-hydrates (C-S-H) and calcium hydroxide in cement matrix at the surface, the depth of 40 mm and 80 mm and the center (175 mm) were examined using thermal gravimetric analysis (TGA) and X-ray diffraction analysis (XRDA). Using nuclear magnetic resonance (NMR) technique, the silicate polymerization of C-S-H in cement matrix was also evaluated. The experimental results indicated that the amount of C-S-H loss at the center of column experiencing the transferred fire temperature of
has been underestimated as the TGA results showed the highest C-S-H contents are located at the depth of 80 mm, where the transferred fire temperature is
. Moreover, the destruction of silicate connections at the center was observed as similar as that at the depth of 40 mm, where the transferred fire temperature was
. This might be attributed to the temperature changes during cooling time after the fire test was neglected. Due to the relatively low thermal conductivity of concrete, the high temperature, which can affect the change of microstructure in cements, will hold longer at the center of the column than other depth.
Compressive Properties of Ultra High Strength Concrete Exposed to High Temperature
Kang, Yong-Hak ; Kang, Choong-Hyun ; Choi, Hyun-Guk ; Shin, Hyun-Jun ; Kim, Wha-Jung ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 377~384
DOI : 10.4334/JKCI.2014.26.3.377
Recently, the trend toward larger architectural structures continues and accelerates demand for Ultra High Strength Concrete (UHSC) which satisfies structural performance. However, UHSC has weakness in fire and the performance tests are required. In this paper, the change of mechanical properties of 100 MPa grade UHSC exposed to high temperatures (
) was observed to develop high temperature material model of UHSC: residual compressive strength, modulus of elasticity, property of stress-strain on monotonous loading and property of stress-strain on cyclic loading. In addition, TG/DTA and SEM Images analyses were performed to investigate chemical and physical characteristics of UHSC, and the results of this research were compared with those of previous studies. As a result, UHSC at the heating temperature of
showed a sharp decrease of residual compressive strength and modulus of elasticity. And It was shown that UHSC had a plastic behavior at more than
on the cyclic loading and revealed a same tendency in both monotonous and cyclic loading of all heating temperatures. In addition, through TG/DTA and SEM images analyses compared with those from previous studies, it was shown that the deterioration of concrete inner tissue, water evaporation and chemical reaction caused the decrease of residual compressive strength and modulus of elasticity.
Evaluation of Construction Loads of Slabs and Shores with Removing Shores and Placing Reshores
Chun, Sung-Chul ; Tak, So-Young ; Lee, Sung-Ho ; Sho, Kwang-Ho ; Ha, Tae-Hun ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 385~392
DOI : 10.4334/JKCI.2014.26.3.385
Reshoring makes slab deflect and support its own weight. The construction loads on the slabs in lower levels decrease using the reshoring. Simplified analysis proposed by ACI 347.2R-05 showed that if the reshoring is applied, construction loads on slabs and shores, and quantities of forms and shores decreased by 40%, 23%, 40%, and 50%, respectively. Shores' loads were comparatively measured on site. The measured reshore load was half of the load before removing the shores and was also lower than the measured shore load by 35%. To verify the safety of the reshoring, deflections of beams and strains of beam longitudinal bars were also measured. The maximum deflection was only L/5000 and the maximum bar strain was only 3.6% of the yield strain. Consequently, reshoring neither cause problems on the safety nor serviceability. In addition, the beam load was expected from the measured shores' loads and it coincides well with the predicted value by the simplified analysis of ACI 347.2R-05.
Behavior of Column-Foundation Joint under Vehicle Impact
Kang, Hyun-Goo ; Kim, Jin-Koo ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 393~400
DOI : 10.4334/JKCI.2014.26.3.393
Structures are often subject to vehicle collision which can be accidental or terrorist attack. Previous research shows that the damage in major columns may result in progressive collapse of a whole building. This study investigates the performance of a steel column standing on a reinforced concrete footing subjected to a vehicle collision. The size and the axial load of the steel column are determined based on the assumption that it is the first story corner column in a typical three-story building with six meter span length. The finite element model of a eight-ton single unit truck provided by the NCAC (National Crash Analysis Center) is used in the numerical analysis. The finite element analysis is performed using the LS-DYNA, and the results show that the behavior of the column subjected to car impact depends largely on the column-foundation connection detail.
Computational Optimization for RC Columns in Tall Buildings
Lee, Yunjae ; Kim, Chee-Kyeong ; Choi, Hyun-Chul ;
Journal of the Korea Concrete Institute, volume 26, issue 3, 2014, Pages 401~409
DOI : 10.4334/JKCI.2014.26.3.401
This research develops tools and strategies for optimizing RC column sections applied in tall buildings. Optimization parameters are concrete strength and section shape, the objective function for which is subject to several predefined constraints drawn from the original structural design. For this purpose, we developed new components for StrAuto, a parametric modeling and optimization tool for building structure. The components receive from external analysis solvers member strengths calculated from the original design model, and output optimized column sections satisfying the minimum cost. Using these components, optimized sections are firstly obtained for each predefined concrete strength applied to the whole floors in the project building. The obtained results for each concrete strength are comparatively examined to determine the fittest sections which will also result in the fittest vertical zoning for concrete strength. The main optimization scenario for this is to search for the vertical levels where the identical optimized sections coincide for the two different concrete strengths in concern, and select those levels for the boundaries where a concrete strength will be changed to another. The optimization process provided in this research is a product of an intensive development designed for a specific member in a specific project. Thus, the algorithm suggested takes on a microscopic and mathematical approach. However, the technique has a lot of potential that it can further be extensively developed and applied for future projects.