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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 19, Issue 6 - Dec 2007
Volume 19, Issue 5 - Oct 2007
Volume 19, Issue 4 - Aug 2007
Volume 19, Issue 3 - Jun 2007
Volume 19, Issue 2 - Apr 2007
Volume 19, Issue 1 - Feb 2007
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Empirical Prediction for the Compressive Strength and Strain of Concrete Confined with FRP Wrap
Lee, Dae-Hyoung ; Kim, Young-Sub ; Chung, Young-Soo ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 253~263
DOI : 10.4334/JKCI.2007.19.3.253
Previous researches showed that confined concrete with Fiber-Reinforced Plastic (FRP) sheets significantly improves the strength and ductility of concrete compared with unconfined concrete. However, the retrofit design of concrete with FRP materials requires an accurate estimate of the performance enhancement due to the confinement mechanism. The object of this research is to predict the compressive strength and strain of concrete confined with FRP wraps. For the purpose of this research, 102 test specimens were fabricated and loaded statically under uniaxial compression. Axial load, axial and lateral strains were investigated to predict the ultimate stress and strain. Also, to achieve reliability of proposed strength and strain models for FRP-confined concrete, another series of uniaxial compression test results were used. This paper presents strength and strain models for FRP-confined concrete. The proposed models to estimate the ultimate stresses and failure strains produce satisfactory predictions as compared to current design equations. In conclusion, it is proposed that the modified stress-strain model of concrete cylinders could be effectively used for the repair and retrofit of concrete columns.
Reversed Cyclic Load Tests on Deep Beam-and-Exterior Column Joints
Ko, Dong-Woo ; Lee, Han-Seon ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 265~273
DOI : 10.4334/JKCI.2007.19.3.265
The most common structural system for apartment buildings in Korea is adopted to combine structural systems: for example, a moment-resisting frame will be used for lower stories and bearing wall system for the upper stories. This type of buildings have soft and/or weak stories in lower stories, and it may lead to collapse of those buildings during the large earthquake. Reversed cyclic load tests were conducted to estimate the performance and behavioral characteristics of deep beam and exterior column Joints. Experimental parameter is the amount of transverse reinforcement (designed by ACI code and Sheikh's procedure). The results of this study are as follows: (1) The required transverse reinforcement of column designed by Sheikh's procedure requires 2.9 times larger than that designed by ACI procedure. Large amount of transverse reinforcement increase the ductility of the column. (2) Most of the lateral drift in the column is due to the flexural deformation in the joint and plastic hinge region and up-lift rotation. (3) Transverse reinforcement in the exterior column shall be required not only in the hinge region but also in the joint.
Behavior of Steel-Concrete Composite Decks for PSC Girder Bridge with Various Shear Span Lengths
Kim, Tae-Hyup ; Park, Jun-Myung ; Hong, Sung-Nam ; Park, Sun-Kyu ; Kim, Hyeong-Yeol ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 275~281
DOI : 10.4334/JKCI.2007.19.3.275
Recently, steel-concrete composite structures are widely used in bridge and building constructions. In this paper, a new type of steel-concrete composite deck with profiled steel sheeting is proposed to replace the conventional cast-in-place reinforced concrete deck. Perfobond rib shear connectors were utilized to provide horizontal shear resistance between the profiled sheeting and the concrete. To validate the effectiveness of the proposed deck system, 8 full-scale deck specimens for PSC girder bridge were fabricated. The specimens were tested with four different shear span lengths to determine the horizontal shear resistance of the deck under a static monotonic loading. For comparison purpose, two reinforced concrete decks were also fabricated and tested. The horizontal shear resistance of the proposed deck system was calculated using the m-k method.
Temperature-Dependency Thermal Properties and Transient Thermal Analysis of Structural Frames Exposed to Fire
Han, Byung-Chan ; Kwon, Young-Jin ; Kim, Jae-Hwan ; Shin, Yeong-Soo ; Choi, Eun-Gyu ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 283~292
DOI : 10.4334/JKCI.2007.19.3.283
A research projects is currently being conducted to develop a nonlinear finite element analysis methods for predicting the structural behavior of reinforced concrete frame structures, exposed to fire. As part of this, reinforced concrete frames subjected to fire loads were analyzed using the nonlinear finite-element program DIANA. Two numerical steps are incorporated in this program. The first step carries out the nonlinear transient heat flow analysis associated with fire and the second step predicts the structural behavior of reinforced concrete frames subjected to the thermal histories predicted by first step. The complex features of structural behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. A concrete material model based on nonlinear fracture mechanics to take cracking into account and plasticity models for concrete in compression and reinforcement steel were used. The material and analytical models developed in this paper are verified against the experimental data on simple reinforced concrete beams. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. Although, this study considers codes standard fire for reinforced concrete frame, any other time-temperature relationship can be easily incorporated.
Seismic Performance Preliminary Evaluation Method of Reinforced Concrete Apartments with Bearing Wall system
Chung, Lan ; Woo, Sung-Sik ; Choi, Ki-Young ; Park, Tae-Won ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 293~300
DOI : 10.4334/JKCI.2007.19.3.293
In Korea, the seismic design regulations was established since 1988 about regularity scale of structures. However, It was not established about seismic performance and evaluation method as the most existing buildings was constructed before Earthquake-Resistant Design(1988). In this study, for model structures which are 4 units of non-seismic designed apartment and 3 units of seismic designed in Korea performed seismic performance evaluation by suggested KISTC (2004). And the result compare to evaluate Capacity Spectrum Method by using MIDAS Gen and SDS. As a result, we observed that suggested KISTC's method have overestimated for shear stress and drift index. The purpose of this study provides most conformity seismic performance evaluation process and the appropriate method of calculating the seismic performance index in Korea.
Lattice Shear Reinforcement for Slab-Column Connection Subjected to Unbalanced Moment
Park, Hong-Gun ; Kim, You-Ni ; Song, Jin-Kyu ; Kim, Sun-Kyu ; Lee, Chul-Woo ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 301~312
DOI : 10.4334/JKCI.2007.19.3.301
A slab-column connection is susceptible to brittle punching shear failure, which may result in the necessity of shear reinforcement. In the present study, to investigate the earthquake resistance of newly developed lattice shear reinforcement, experimental study was performed for interior slab-column connections subjected to cyclic loading. For comparison, specimens with existing shear reinforcement method such as stud rail, shear band and stirrup were also tested. The test result showed that the structural capacity of the lattice shear reinforcement was superior to those of the existing methods and was greater than the code-specified strength. On the other hand, the existing methods did not significantly improve the shear strength of the specimens. The shear strengths of the existing methods were much less than the code-specified shear strength.
Experimental Test for Seismic Performance of PCS Structural System
Park, Soon-Kyu ; Yeo, In-Seok ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 313~322
DOI : 10.4334/JKCI.2007.19.3.313
The PCS system, which consists of precast concrete column and steel beam, is a kind of composite structural systems. In this paper, experimental study has been conducted to analyze seismic performance of bolted beam-to-column connections for the PCS system. Based on experimental results from the seismic testing of eight interior PCS specimens, it shows that behavior of PCS system is satisfactory to seismic performance criteria of ACI such as strength deterioration, stiffness degradation and energy dissipation capacity except initial stiffness. All of the specimens maintain their strength at large levels of story drift without significant loss of stiffness and show high ductility level for inelastic behavior. The energy dissipation capacity is two times greater than requirement of ACI criterion. But the initial stiffness of all specimens does not satisfy ACI criterion, and this phenomenon is similar to the other composite structural systems such as RCS, CFT system.
Development Length of GFRP Rebars Based on Pullout Test
Choi, Dong-Uk ; Ha, Sang-Su ; Lee, Chang-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 323~331
DOI : 10.4334/JKCI.2007.19.3.323
The development length equations of the GFRP rebars are suggested based on the pullout tests performed in this study. A total of 48 pullout and modified pullout tests were completed. Test variables included embedment length (L=10, 15, 20, and
), vertical and horizontal installation of the rebars, height of the rebars (H=100 and 300 mm), and cover thickness
. D13 GFRP rebars domestically developed were used in the experimental program. The average of the bond strength of all vertically installed GFRP rebars was 6.39 MPa with a 5% fractile of 4.63 MPa. A basic development length equation was derived that resulted in an equation equivalent to the one proposed in the ACI 440.1R-03. Careful reevaluation of the bond strength using the modified pullout test indicated that a modification of the design equation was necessary so that the basic development length increases by 11%. The top bar effect of the horizontally installed rebars as well as the effect of the cover thickness were determined and included in the set of suggested equations. Since the current equations were derived from testing rebars embedded in relatively low strength concrete
, they result in conservative development lengths when applied to bars embedded in higher strength concretes.
Interfacial Pullout Characteristics of Recycled PET Fiber With Hydrophilic Chemical Treatments in Cement Based Composites
Won, Jong-Pil ; Park, Chan-Gi ; Kim, Yoon-Jeong ; Park, Kyung-Hoon ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 333~339
DOI : 10.4334/JKCI.2007.19.3.333
The purpose of this study was to enhance bond performance between recycled PET (polyethylene telephthalat) fiber and cement composites through hydrophilic treatment using maleic anhydride grafted polypropylene(mPP). The mPP with various concentration of 0%, 5%, 10%, 15% and 20% to determine effect on bond behavior of recycled PET fiber were applied as experimental variables. Dog bone shaped specimens according to JCI SF-8 was applied to evaluate the bond strength and pullout energy. The results showed increased bond strength and pullout energy as concentration of mPP. Concentration of 15% mPP showed the most effective results while 20% showed reduced performance results. Because 15% mPP ensures perfect coating while 20% makes thick coating area that resulted in crack propagation and consequent separation of PET fiber and coated area during pullout load occurred. Enhancement mechanism of bond performance of recycled PET fiber and cement composites with each concentration of mPP could be conformed through investigation of microstructure of fiber surface.
Finite Element Analysis of Reinforced Concrete Hollow Columns Using Path-dependent Volume Control Method
Song, Ha-Won ; Nam, Sang-Hyeok ; Lim, Sang-Mook ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 341~350
DOI : 10.4334/JKCI.2007.19.3.341
The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependent behaviors of RC columns subjected to lateral cyclic loading or reversed cyclic loading along with compressive loading. RC shell structures and RC hollow columns are analyzed by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependent volume control method as a finite element analysis technique is verified by comparing analysis results with other data including experimental results. The validity and applicability of the modeling technique is also confirmed by the comparison.
An Experimental Study on Flexural Behavior of RC Beams Strengthened with Hi-Strength Bars(3)
Shin, Kyung-Jae ; Kim, Yoon-Jung ; Moon, Jeong-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 351~358
DOI : 10.4334/JKCI.2007.19.3.351
Unlike external bonded steel plate or carbon fiber, the external unbonded strengthening using hi-strength bar has some advantages in speed and simplicity of installation. It is not required surface preparations and not affected by environmental conditions. A set of nine laboratory tests on RC beams strengthened using the hi-tension bars are reported. Anchoring pin developed in former research is installed at the end of beam to connect the hish-tension bar to RC beam. The test results strengthened by hi-tension bars are compared with those of non-strengthened specimens. The main test parameters are the cross-sectional area of the high-tension bar, distance of stirrups and condition of supports. Test results show that the beams reinforced are superior to reference specimens, especially for the strength and deformation capacity. Also, shear resisting effect of hi-strength bar can be confirmed in the specimens which have lack of stirrups.
A Study on Analysis Technique for Chloride Penetration in Cracked Concrete under Combined Deterioration
Kwon, Seung-Jun ; Song, Ha-Won ; Byun, Keun-Joo ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 359~366
DOI : 10.4334/JKCI.2007.19.3.359
Recently, analysis researches on durability are focused on chloride attack and carbonation due to increased social and engineering significance. Generally, chloride penetration and carbonation occur simultaneously except for in submerged condition and chloride behavior in carbonated concrete is evaluated to be different from that in normal concrete. Furthermore, if unavoidable crack occurs in concrete, it influences not only single attack but also coupled deterioration more severely. This is a study on analysis technique with system dynamics for chloride penetration in concrete structures exposed to coupled chloride attack and carbonation through chloride diffusion, permeation, and carbonation reaction. For the purpose, a modeling for chloride behavior considering diffusion and permeation is performed through previous models for early-aged concrete such as MCHHM (multi component hydration heat model) and MPSFM (micro pore structure formation). Then model for combined deterioration is developed considering changed characteristics such as pore distribution, saturation and dissociation of bound chloride content under carbonation. The developed model is verified through comparison with previous experimental data. Additionally, simulation for combined deterioration in cracked concrete is carried out through utilizing previously developed models for chloride penetration and carbonation in cracked concrete. From the simulated results, CCTZ (chloride-carbonation transition zone) for evaluating combined deterioration is proposed. It is numerically verified that concrete with slag has better resistance to combined deterioration than concrete with OPC in sound and cracked concrete.
Theoretical Analysis of Critical Chloride Content in (Non)Carbonated Concrete Based on Characteristics of Hydration of Cement
Yoon, In-Seok ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 367~375
DOI : 10.4334/JKCI.2007.19.3.367
Critical chloride content for corrosion initiation is a crucial parameter in determining the durability and integrity of reinforced concrete structures, however, the value is still ambiguous. Most of the studies reporting critical threshold chloride content have involved the experimental measurement of the average amount of the total chloride content at arbitrary time. The majority of these researches have not dealt with this issue combined with carbonation of concrete, although carbonation can significantly impact on critical threshold chloride content. Furthermore, the studies have tried to define the critical chloride content within the scope of their experimental concrete mix proportion at arbitrary time. However, critical chloride content for corrosion initiation is known to be affected by a lot of factors including cement content, type of binder, chloride binding, concentration of hydroxyl ions, and so on. It is necessary to define the unified formulation to express the critical chloride content for various mix proportions of concrete. The purpose of this study is to establish an analytical formulation of the critical chloride content of concrete. In this formulation, affecting factors, such as mix proportion, environment, chemical evolution of pore solution with elapsed time, carbonation of concrete and so on are taken into account. Based on the Gouda's experimental results, critical chloride content is defined as a function of
in pore solution. This is expressed as free chloride content with mass unit to consider time evolution of
content in pore solution using the numerical simulation programme of cementitious materials, HYMOSTRUC. The result was compared with other experimental studies and various codes. It is believed that the approach suggested in this study can provide a good solution to determine the reasonable critical chloride content with original source of chloride ions, for example, marine sand at initial time, and sea water penetration later on.
Mix Design of High Performance Concrete Using Maximum Density Theory
Lee, Seung-Han ; Jung, Yong-Wook ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 377~383
DOI : 10.4334/JKCI.2007.19.3.377
In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.
Service Life Prediction of Concrete Structures Exposed to a Sulfuric Acid Environment
Jeon, Joong-Kyu ; Moon, Han-Young ; Jeon, Chan-Ki ; Song, Jong-Hwa ;
Journal of the Korea Concrete Institute, volume 19, issue 3, 2007, Pages 385~389
DOI : 10.4334/JKCI.2007.19.3.385
In this study, it was investigated the resistance of OPC, 60% GGBS, 20% PFA and 10% SF mortar specimens against sulfuric acid corrosion. As an index for degree of acid corrosion, the corrosion depth was evaluated. Then, it was found that an increase in the duration of immersion and a decrease in the pH, as expected, resulted in a more severe corrosion irrespective of binders; 60% GGBS mortar specimen was the most resistant to sulfuric acid corrosion. From the laboratory testing of sulfuric acid corrosion, an empirical prediction model was suggested as a power function of time and the pH of sulfuric acid, and was applied to an assessment of concrete structures exposed to an acidic environment. It was found that the empirical model gave a more precise prediction of sulfuric acid deterioration of concrete rather than a conventional model, mostly used for predicting carbonation of concrete.