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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 22, Issue 6 - Dec 2010
Volume 22, Issue 5 - Oct 2010
Volume 22, Issue 4 - Aug 2010
Volume 22, Issue 3 - Jun 2010
Volume 22, Issue 2 - Apr 2010
Volume 22, Issue 1 - Feb 2010
Selecting the target year
Seismic Performance of Reinforced Concrete Flat Plate Frames according to Gravity Shear Ratio
HwangBo, Jin ; Han, Sang-Whan ; Park, Young-Mi ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 3~10
DOI : 10.4334/JKCI.2010.22.1.003
This study evaluates the seismic performance of reinforced concrete (RC) flat plate structures relation to the gravity shear ratio. For this purpose, 3 and 7 story framed buildings were designed for gravity loads only. Subsequently, a nonlinear static pushover analysis and a nonlinear time history analysis for the prototype buildings were carried out. In the nonlinear analysis, newly propose analytical slab-column joint model was utilized to capture punching shear failure and fracture mechanism in the analysis. The analytical results showed that seismic performance of RC flat plate frame is strongly influenced by the gravity shear ratio. In particularly, in the RC flat plate frame with a large gravity shear ratio the lateral strength and maximum drift capacity decreased significantly.
Seismic Performance Improved Design of Reinforced Concrete Columns Strengthened by Steel Jackets Using Displacement-based Design
Jung, In-Kju ; Park, Moon-Ho ; Cho, Chang-Geun ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 11~18
DOI : 10.4334/JKCI.2010.22.1.011
In this study, a procedure of performance-based design for the seismic retrofit of reinforced concrete columns strengthened by steel jackets has been presented. In order to predict the target displacement of retrofitted columns, a nonlinear analysis of reinforced concrete columns retrofitted with steel jackets has been developed based on a segmental model with the fiber cross-sectional approach. The seismic displacement level of retrofitted columns is estimated both by the direct displacement-based design method and by the displacement coefficient method. In examples of seismic retrofitted columns, the current seismic retrofit procedure gives good results in improvements of displacement levels and displacement ductilities of retrofitted columns.
Prediction of Ultimate Strength and Strain of Concrete Columns Retrofitted by FRP Using Adaptive Neuro-Fuzzy Inference System
Park, Tae-Won ; Na, Ung-Jin ; Kwon, Sung-Jun ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 19~27
DOI : 10.4334/JKCI.2010.22.1.019
Aging and severe environments are major causes of damage in reinforced concrete (RC) structures such as buildings and bridges. Deterioration such as concrete cracks, corrosion of steel, and deformation of structural members can significantly degrade the structural performance and safety. Therefore, effective and easy-to-use methods are desired for repairing and strengthening such concrete structures. Various methods for strengthening and rehabilitation of RC structures have been developed in the past several decades. Recently, FRP composite materials have emerged as a cost-effective alternative to the conventional materials for repairing, strengthening, and retrofitting deteriorating/deficient concrete structures, by externally bonding FRP laminates to concrete structural members. The main purpose of this study is to investigate the effectiveness of adaptive neuro-fuzzy inference system (ANFIS) in predicting behavior of circular type concrete column retrofitted with FRP. To construct training and testing dataset, experiment results for the specimens which have different retrofit profile are used. Retrofit ratio, strength of existing concrete, thickness, number of layer, stiffness, ultimate strength of fiber and size of specimens are selected as input parameters to predict strength, strain, and stiffness of post-yielding modulus. These proposed ANFIS models show reliable increased accuracy in predicting constitutive properties of concrete retrofitted by FRP, compared to the constitutive models suggested by other researchers.
A Study on Fire Performance and Heat Transfer of HPC Column with Fiber-Cocktail in ISO Fire under Loading Condition
Kim, Heung-Youl ; Kim, Hyung-Jun ; Jeon, Hyun-Kyu ; Youm, Kwang-Soo ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 29~39
DOI : 10.4334/JKCI.2010.22.1.029
In this study, experimental test and numerical analysis were conducted to investigate the heat transfer characteristics and fiber performance of high strength concrete. The fire characteristics of the high strength concrete that couldn`t be obtained through the test due to specific requirements and restrictions were forecast using numerical analysis approach. The outcome from the numerical analysis and the test were compared to verify and improve the reliability of the analysis. A numerical analysis of 80 and 100 MPa high strength concrete cases were carried out to identify the heat transfer characteristics and fire behavior using software, ABACUS (V6.8) From the results of verification experiment, a 25~55% level of beam shrinkage reduction was observed compared to the concrete without Fiber-Cocktail, indicating the improved fire resistance performance, which appeared to be attributable to the function of Fiber-Cocktail that was able to control the heat transfer characteristics and ultimately result in enhancing the fire resistance performance.
Effects of Shore Stiffness and Concrete Cracking on Slab Construction Load I: Theory
Hwang, Hyeon-Jong ; Park, Hong-Gun ; Hong, Geon-Ho ; Im, Ju-Hyeuk ; Kim, Jae-Yo ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 41~50
DOI : 10.4334/JKCI.2010.22.1.041
Long-term floor deflection caused by excessive construction load became a critical issue for the design of concrete slabs, as a flat plate is becoming popular for tall buildings. To estimate the concrete cracking and deflection of an early age slab, the construction load should be accurately evaluated. The magnitude of construction load acting on a slab is affected by various design parameters. Most of existing methods for estimating construction load addressed only the effects of the construction period per story, material properties of early age concrete, and the number of shored floors. In the present study, in addition to these parameter, the effects of shore stiffness and concrete cracking on construction load were numerically studied. Based on the result, a simplified method for estimating construction load was developed. In the proposed method, the calculation of construction load is divided to two steps: 1)Onset of concrete placement at a top slab. 2)Removal of shoring. At each step, the construction load increment is distributed to the floor slabs according to the ratio of slab stiffness to shore stiffness. The proposed method was compared with existing methods. In a companion paper, the proposed method will be verified by the comparison with the measurements of actual construction loads.
Effects of Shore Stiffness and Concrete Cracking on Slab Construction Load II: Measurements and Comparisons
Hwang, Hyeon-Jong ; Hong, Geon-Ho ; Park, Hong-Gun ; Kim, Yong-Nam ; Kim, Jae-Yo ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 51~58
DOI : 10.4334/JKCI.2010.22.1.051
In a companion paper, a simplified method for the evaluation of the slab construction load was developed. Unlike existing methods, the proposed method includes the effects of shore stiffness and concrete cracking on the construction load. In the present study, construction loads were measured in actual flat-plate slabs. For verification, the measured shore-forces were compared with the predictions by the proposed method and existing methods. Further, the proposed method was applied to a wall-slab structure, and the prediction results were compared with the measurements. The comparison results showed that the proposed method well predicted the construction loads, furthermore it gave better predictions than the existing methods did.
Evaluation of Deformation Capacity of Slender Reinforced Concrete Walls with Thin Web
Eom, Tae-Sung ; Park, Hong-Gun ; Kim, Jae-Yo ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 59~68
DOI : 10.4334/JKCI.2010.22.1.059
In the present study, the deformation capacity of slender shear walls with thin web subject to inelastic deformation after flexural yielding was studied. Web-crushing and rebar-fracture were considered as the governing failure mechanisms of walls. To address the effect of the longitudinal elongation on web-crushing and rebar-fracture, the longitudinal elongation was predicted by using truss model analysis. The failure criteria by web-crushing and rebar-fracture were defined as a function of the longitudinal elongation. The proposed method was applied to 17 shear wall specimens with boundary columns, and the prediction results were compared with the test results. The results showed that proposed method predicted the maximum deformations and failure modes of the wall specimens with reasonable precision.
An Analytical Method for the Evaluation of Micro-cracking in Concrete Shrinkage Induced
Song, Young-Chul ; Kim, Do-Gyeum ; Moon, Jae-Heum ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 69~76
DOI : 10.4334/JKCI.2010.22.1.069
The majority of research that has been performed on cracking potential of concrete by shrinkage has assumed that concrete acts as a homogeneous material. However, with this approach, it is not able to evaluate the micro-cracking behavior in concrete due to autogenous shrinkage under unrestrained boundary condition (free boundary condition) nor to understand the cracking behavior properly because of the heterogeneous nature of concrete. To better understand the micro-cracking behavior of concrete induced by autogenous shrinkage, series of experiments were performed measuring the length change and acoustic emission energy. As an analytical approach, this research uses an object oriented finite element analysis code (OOF code) to simulate the behavior of the concrete on a meso-scale. The concrete images used in the simulations were directly obtained from mortar samples. From the experiments and simulation results, it was able to better understand the micro-cracking behaviour of concrete due to shrinking of paste phase and internal restraint by aggregates.
Numerical Investigation on Cracking of Bridge Deck Slabs with Latex Modified Concrete Overlays
Choi, Kyoung-Kyu ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 77~84
DOI : 10.4334/JKCI.2010.22.1.077
Latex modified concrete (LMC) exhibits improved material properties including high tensile strength and durability compared with conventional concrete, and hence LMC has been used as protective layers over the bridge deck slabs to increase their service life with underlying assumption of excellent bond behavior between the LMC overlay and the concrete substrate. In this study, the effect of the primary parameters of the concrete substrate (i.e., shrinkage, stiffness and cracking capacity) as well as the LMC overlay thickness on the probability of cracking of the bridge deck slabs using LMC overlays was investigated by carrying out the finite element analysis that simulated the bond behavior of LMC overlays on normal strength concrete (NSC) and HPC bridge deck slabs. Based on the results of the numerical analysis, it is concluded that the relatively high shrinkage strains and stiffness of HPC slabs can increase its probability of cracking in bridge deck slabs using LMC overlay.
Comparison of Measurement Methods and Prediction Models for Drying Shrinkage of Concrete
Yang, Eun-Ik ; Kim, Il-Sun ; Yi, Seong-Tae ; Lee, Kwang-Myong ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 85~91
DOI : 10.4334/JKCI.2010.22.1.085
In this study, the drying shrinkage strains were compared of 24~60 MPa concrete specimens subjected to various curing conditions and measurement methods were compared. And, the applicability of the test and prediction methods were investigated. According to the results, drying shrinkage was significantly reduced in 28 day curing condition. In the sealed curing case, drying shrinkage strain from demolding time was identical to the one of the standard curing case for low strength concrete, however, drying shrinkage strain was greatly increased than the standard case for high strength case because of the effect of autogenous shrinkage. The efficient measurement was possible using the embedded gage for concrete drying shrinkage, but, the measured value by contact gage was lower than the one by the embedded gage. The test results agreed with EC2 model better than the other.
Experimental Study on Blast Resistance Improvement of RC Panels by FRP Retrofitting
Ha, Ju-Hyung ; Yi, Na-Hyun ; Kim, Sung-Bae ; Choi, Jong-Kwon ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 93~102
DOI : 10.4334/JKCI.2010.22.1.093
Recently, FRP usage for strengthening RC structures in civil engineering has been increasing. Especially, the use of FRP to strengthen structures against blast loading is growing rapidly. To estimate FRP retrofitting effect under blast loading, blast tests with nine
RC panel specimens, which were retrofitted with carbon fiber reinforced polymer (CFRP), Polyurea, CFRP with Poly-urea and basalt fiber reinforced polymer (BFRP) have been carried out. The applied blast load was generated by the detonation of 15.88 kg ANFO explosive charge at 1.5 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included central deflection and strains at steel, concrete, and FRP surfaces. The failure mode of each specimen was observed and compared with a control specimen. From the test results, the blast resistance of each retrofit material was determined. The test results of each retrofit material will provide the basic information for preliminary selection of retrofit material to achieve the target retrofit performance and protection level.
Analysis of Reinforced Concrete Columns under Cyclic Loads Using a 2-Dimensional Lattice Model
Kwon, Min-Ho ; Ha, Gee-Joo ; Park, Tae-Gyu ; Cho, Chang-Geun ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 103~111
DOI : 10.4334/JKCI.2010.22.1.103
An efficient design concept for earthquake loads, which is called performance based design, has been standard design in USA, Europe and Japan since those countries experienced severe earthquake damage at end of 90`s. For general design, struttie model well predicts the strength of the disturbed region, however, it does not provide ductility information at the failure. Therefore, simple tools which are able to predict both the strength and the ductility of RC structures are in demand. 2D lattice model is introduced in this study as an analysis tool for the RC structures subject to earthquake. Experimental correlation studies indicate the 2D lattice model quite well predict the strength as well as the ductility of RC structures.
Detection of Fracture Signals of Low Prestressed Steel Wires in a 10 m PSC Beam by Continuous Acoustic Monitoring Techniques
Youn, Seok-Goo ; Lee, Chang-No ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 113~122
DOI : 10.4334/JKCI.2010.22.1.113
Corrosion of prestressing tendons and wire fractures in grouted post-tensioned prestressed concrete bridges have been considered as a serious safety problem. In bridge evaluation the condition of prestressing tendons should be inspected, and if corroded tendons are found, the loss of tendon area should be included when we calculate the ultimate strength. In the previous study, it was evaluated that continuous acoustic monitoring techniques could be considered as a reliable non-destructive method for detecting wire fractures of fully grouted post-tensioned prestressing tendons. In the present study, an experimental test was performed for detecting wire fractures of post-tensioned prestressing tendons which are prestressed lower than current design level. A 10 m prestressed concrete beam was fabricated, which included two tendons prestressed 66 percentage and 40 percentage of tensile strength, respectively. The corrosion of two tendons was induced by an accelerated corrosion equipment and the test beam was monitored by using seven acoustic sensors and a continuous acoustic monitoring system. From each prestressing tendon, two acoustic signals of wire fractures were successfully detected and source locations were estimated within 20 mm error. Based on the test results, it is considered that continuous acoustic monitoring techniques can be applied to detect low-prestressed wire fracture in fully grouted post-tensioned prestressed concrete beams.
Effect of Recycled Coarse Aggregate (RCA) Replacement Level on the Bond Behaviour between RCA Concrete and Deformed Rebars
Jang, Yong-Heon ; Choi, Ki-Sun ; You, Young-Chan ; Kim, Keung-Hwan ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 123~130
DOI : 10.4334/JKCI.2010.22.1.123
In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;
Development Length of GFRP Bars
Ha, Sang-Su ; Choi, Dong-Uk ;
Journal of the Korea Concrete Institute, volume 22, issue 1, 2010, Pages 131~141
DOI : 10.4334/JKCI.2010.22.1.131
The objective of this study was to propose a development length equation for GFRP bars. A total of 104 modified pullout tests were completed while the test variables were embedment length (15, 30,
), net cover thickness (
), top-cast bar effect, different GFRP bar types (K2KR, K3KR and AsUS), and bar diameters (10, 13, 16 mm). Average bond stresses were determined based on modified pullout test results. Two variable linear regression analysis was performed of the average bond stresses. Utilizing 5% fractile concept, a conservative development length design equation was derived. The design equation derived in this study was compared to the ACI 440 committee equation. The cross-comparison revealed that the current equation resulted in shorter development lengths than those determined by the ACI 440 equation when the net cover thickness was large (greater than
). On the other hand, when the net cover thickness was small (equal to or less than
), the development lengths required by the current equation were larger than those by the ACI equation. The bond stresses were significantly influenced by the cover thicknesses. The current equation results in development lengths that are more economical when the cover thickness is large, and more conservative lengths when the cover thickness is small than the ACI 440 committee equation.