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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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Stress-Strain Behavior Characteristics of Concrete Cylinders Confined with FRP Wrap
Lee, Dae-Hyoung ; Kim, Young-Sub ; Chung, Young-Soo ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 135~144
DOI : 10.4334/JKCI.2007.19.2.135
Recently, fiber-reinforced plastic(FRP) wraps are blown as an effective material for the enhancement and rehabilitation of aged concrete structures. The purpose of this investigation is to experimentally investigate behavior of concrete cylinder wrapped with FRP materials. Experimental parameters include compressive strength of concrete cylinder, FRP material, and confinement ratio. This paper presents the results of experimental studies on the performance of concrete cylinder specimens externally wrapped with aramid, carbon and glass fiber reinforced Polymer sheets. Test specimens were loaded in uniaxial compression. Axial load, axial and lateral strains were investigated to evaluate the stress-strain behavior, ultimate strength ultimate strain etc. Test results showed that the concrete strength and confinement ratio, defined as the ratio of transverse confinement stress and transverse strain were the most influential factors affecting the stress-strain behavior of confined concrete. More FRP layers showed the better confinement by increasing the compressive strength of test cylinders. In case of test cylinders with higher compressive strength, FRP wraps increased the compressive strength but decreased the compressive sham of concrete test cylinders, that resulted in prominent brittle failure mode. The failure of confined concrete was induced by the rupture of FRP material at the stain, being much smaller than the ultimate strain of FRP material.
An Experimental Study on the Effective Strain of Reinforced Concrete Beams Strengthened by Fiber Reinforced Polymer
Hwang, Hyun-Bok ; Lee, Jung-Yoon ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 145~151
DOI : 10.4334/JKCI.2007.19.2.145
The shear failure modes of FRP strengthened concrete beams are quite different to those of the beams strengthened with steel stirrups. When the beams are externally wrapped with FRP composites, many beams fail in shear due to concrete crushing before the FRP reaches its rupture strain. In order to predict the shear strength of such beams, the effective strain of the FRP must be blown. This paper presents the results of an experimental study on the performance of reinforced concrete beams externally wrapped with FRP composites and infernally reinforced with steel stirrups. The main parameters of the tests were FRP reinforcement ratio, the type of fiber material (carbon or glass) and configuration (continues sheets or strips). The experimentally observed effective strain of the FRP was compared with the strain calculated using a proposed method.
Effect of Reinforcing Fiber Types on Lap Splice Performance of High Performance Fiber Reinforced Cementitious Composite(HPFRCC)
Jeon, Esther ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 153~161
DOI : 10.4334/JKCI.2007.19.2.153
This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length
was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to
percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.
An Experimental Study on Permeability in Elevation of Porous Concrete Using Unsaturated Polyester Resin
Lho, Byeong-Cheol ; Choi, Kyu-Hyung ; Kim, Jeong-Hoon ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 163~169
DOI : 10.4334/JKCI.2007.19.2.163
This study is focused on the proper mixture design of materials for the porous concrete with unsaturated polyester resin. The materials used in the mixture include the single-grade aggregates, unsaturated polyester resin as binder, and calcium carbonate as a filler. An experimental procedure has been carried out to select the best combination of the materials that satisfy both the required permeability and compressive strength. Various kinds of gravel size, the ratio of binder, and F/B ratios are tried to get proper mixture, and the permeability coefficient and compressive strength have been measured to find out the best combination of materials based on the proper Korean Standards. A promix design satisfied the standards of rainfall runoff reduction system with
(cm/sec) of permeability, 34 % of porosity, 11 MPa of compressive strength can be obtained.
Influence of Inclined Reinforcement around Openings on the Shear Behavior of Reinforced Concrete Continuous Deep Beams
Chung, Heon-Soo ; Sim, Jae-Il ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 171~178
DOI : 10.4334/JKCI.2007.19.2.171
Twelve reinforced concrete continuous deep beams having web openings within interior shear spans were tested to failure. All beams tested had the same geometrical dimensions. The main variables investigated were the opening size and amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the opening size and amount of inclined reinforcement on the structural behavior of the beams tested is proposed. It was observed that the load distribution, diagonal crack width, and load capacity of beams tested were greatly dependent on the effective inclined reinforcement factor which ranged from 0 to 0.171 for the test specimens. The higher this factor, the smaller the diagonal crack width and its development rate. A higher load capacity also developed in beams having effective inclined reinforcement factor above 0.077 than in the corresponding solid deep beams. A numerical technique based on the upper bound analysis of the plasticity theory is proposed to evaluate the load capacity of continuous deep beams having openings within interior shear spans. Predictions obtained from the proposed formulas are in good agreement with test results.
An Experimental Study on the Application of Measuring Method of Water Content for Quality Control of Concrete
Kim, Yong-Ro ; Choi, Il-Ho ; Jung, Yang-Hee ; Lee, Do-Bum ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 179~188
DOI : 10.4334/JKCI.2007.19.2.179
Recently, the concern on the receipt of poor ready-mixed concrete in the construction field and the durability of concrete has been increased. Based on the such background, a large number of measuring methods of water content for fresh concrete have been developed and enforced in a developed country. In this study, to investigate practicality for quality control of ready-mixed concrete among various water content measurement techniques, microwave range method, air meter method and capacitance measurement method as measuring methods of water content were selected. Then, it was evaluated estimating performance of water content according to the change of binder types, fine aggregate types, absorption ratio, water content and water-binder ratio in series I and II. Also, it was examined influence on error occurrence of water content according to change of properties of used materials in series III. Finally, based on this study, it was proposed fundamental data to utilize measurement technique of water content to quality control of ready-mixed concrete in construction field.
Behavior of Fire Resistance Engineered Cementitious Composites(FR-ECC) under Fire Temperature
Han, Byung-Chan ; Kwon, Young-Jin ; Kim, Jae-Hwan ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 189~197
DOI : 10.4334/JKCI.2007.19.2.189
Concrete tunnel lining must be designed to having the fireproof performance because the lining are sometimes exposed to very high temperature due to traffic accident. Such fire temperature may cause explosion of concrete, or collapse of tunnel structure. The purpose of this study is to obtain the fundamental fireproof behavior of fire resistance-engineered cementitious composites(FR-ECC) under fire temperature in order to use the fire protection material in tunnel lining system. The present study conducted the experiment to simulate fire temperature by employing 2 types of FR-ECC and investigated experimentally the explosion and cracks in heated surface of these FR-ECC. Employed temperature curve were hydro carbon(HC, ECl) criterion, which are severe in various criterion of fire temperature. The numerical analysis is carried out the nonlinear transient heat flow analysis and verified against the experimental data. The complex features of behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. By the use of analytical model, the concrete tunnel subjected to fire loads were analyzed and discussed. With comparison of current concrete materials and FR-ECC, the experimental and analytical results of FR-ECC shows the better fire resistance performance than the other.
Splice Strengths of Noncontact Lap Splices Using Strut-and-Tie Model
Hong, Sung-Gul ; Chun, Sung-Chul ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 199~207
DOI : 10.4334/JKCI.2007.19.2.199
Strut-and-tie models for noncontact lap splices are presented and parameters affecting the effective lap length
and the splice strength are discussed in this paper. The effective lap length along which bond stress is developed is shorter than the whole lap length. The effective lap length depends on the transverse reinforcement ratio
and the ratio of spacing to lap length
. As the splice-bar spacing becomes wider, the effective lap length decreases and, therefore, the splice strength decreases. The influence of the ratio
on the effective lap length becomes more effective when the transverse reinforcement ratio is low. Because the slope of the strut developed between splice-bars becomes steeper as the ratio
becomes lower, the splice-bar spacing significantly affects the effective lap length. The proposed strut-and-tie models for noncontact lap splices are capable of considering material and geometric properties and, hence, providing the optimal design for detailing of reinforcements. The proposed strut-and-tie model can explain the experimental results including cracking patterns and the influence of transverse reinforcements on the splice strength reported in the literature. From the comparison with the test results of 25 specimens, the model can predict the splice strengths with 11.1% of coefficient of variation.
Improved Transmission of UHSC Column Loads by Puddling of Fiber Reinforced UHSC
Lee, Joo-Ha ; Yang, Jun-Mo ; Lee, Seung-Hoon ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 209~216
DOI : 10.4334/JKCI.2007.19.2.209
This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.
The Properties of Strength and Durability of Concrete Using Early-Strength Poly Carbonic Acid Admixture
Lee, Sang-Ho ; Hong, Kyung-Sun ; Moon, Han-Young ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 217~224
DOI : 10.4334/JKCI.2007.19.2.217
This study reports the properties of high early strength & durability of concrete using PC admixture. To apply these data to construction site, we did the lab tests. The target of this study is to accomplish early strength of concrete (5.0 Mpa/18 hr), and we did the durability tests such as length change test, chloride ion penetration test, fleeting and thawing test, adiabatic test, etc. And we tested the porperties of concrete by the different factors, such as the type of admixtures, curing temperature, the amount of binder, etc. Through the test of concrete using the different type of admixture, PC type was more excellent than PNS type admixture. As a result, we made a concrete of high early strength concrete, and excellent durable concrete. According to these tests, we concluded that we can apply this type of PC admixture to the civil & construction site, and we can reduce the term of works and finally we will accomplish the economical construction.
Behavior and Ductility of Reinforced Concrete Beams Strengthened by CFRP
Kim, Jin-Yul ; Kim, Kwang-Soo ; Park, Sun-Kyu ; Lee, Young-Jae ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 225~231
DOI : 10.4334/JKCI.2007.19.2.225
In the recent construction industry, FRP is highly interesting in strengthening members of structures because it has superior material properties. This paper is an experimental study on the structural behavior of reinforced concrete beam when in using various amount of CFRP and the ductility of beams using various type of CFRP. In the experiment, when it makes an experiment using various amount of CFRP, strengthening width is more efficient than strengthening layer. The failure of CFRP strengthened beams presented brittle modes with having flexural failures. Also, It represented that most of beams classify brittle failure in the side of energy ratio. Energy ratio of CFRP sheet comparing with CFRP plate exceeds overall 50% and it represents about 70% in case of beams without strengthening layer.
Effect of Recycled PET Fiber Geometry and Length on the Plastic Shrinkage Cracking of Cement Based Composites
Won, Jong-Pil ; Park, Chan-Gi ; Kim, Hwang-Hee ; Lee, Sang-Woo ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 233~239
DOI : 10.4334/JKCI.2007.19.2.233
The main objective of this study was to evaluate the effect of recycled PET fiber made from waste PET bottle on the control of plastic shrinkage cracking of cement based composites. PET is blown as a plastic material and used in a variety products such as a beverage bottle. However, waste PET bottles are thrown after the usage, raising huge problems in terms of the environment. Thus, the research on the method to recycle the PET bottles indicates important aspects in environment and economy. The method to recycle waste PET bottles as a reinforcing fiber for cement based composites is one of effective methods in terms of the recycle of waste PET bottles. In this research, the effect of recycled PET fiber geometry and length on the control of plastic shrinkage was examined through thin slab tests. A test program was carried out to understand the influence of fiber geometry, length and fiber volume fraction. Three type of recycled PET fibers including straight, twist crimped and embossed type. Three volume fraction and two fiber length were investigated for each of the three fiber geometry. Test results indicated that recycled PET fibers are effective in controlling plastic shrinkage cracking in cement based composites. In respect to effect of length of fiber, longer fiber was observed to have efficient cracking controlling with low volume fraction in same fiber geometry while shorter fiber controled plastic shrinkage cracking efficiently as addition rate increase. Also, embossed type fibers were more effective in controlling plastic shrinkage cracking than other geometry fiber at low volume fraction. But, for high volume fraction, straight type fibers were most effective in plastic shrinkage cracking controlling in cement based composites.
Analytical Evaluations of the Retrofit Performances of Concrete Wall Structures Subjected to Blast Load
Kim, Ho-Jin ; Nam, Jin-Won ; Kim, Sung-Bae ; Kim, Jang-Ho ; Byun, Keun-Joo ;
Journal of the Korea Concrete Institute, volume 19, issue 2, 2007, Pages 241~250
DOI : 10.4334/JKCI.2007.19.2.241
In case of retrofitting a concrete structure subjected to blast load by using retrofit materials such as FRP (fiber-reinforced polymer), appropriate ductility as well as raising stiffness must be obtained. But the previous approximate and simplified models, which have been generally used in the design and analysis of structures subjected to blast load, cannot accurately consider effects on retrofit materials. Problems on the accuracy and reliability of analysis results have also been pointed out. In addition, as the response of concrete and reinforcement on dynamic load is different from that on static load, it is not appropriate to use material properties defined in the previous static or quasi-static conditions to in calculating the response on the blast load. In this study, therefore, an accurate HFPB (high fidelity physics based) finite element analysis technique, which includes material models considering strength increase, and strain rate effect on blast load with very fast loading velocity, has been suggested using LS-DYNA, an explicit analysis program. Through the suggested analysis technique, the behavior on the blast load of retrofitted concrete walls using CFRP (carbon fiber-reinforced polymer) and GFRP (glass fiber-reinforced polymer) have been analyzed, and the retrofit capacity analysis has also been carried out by comparing with the analysis results of a wall without retrofit. As a result of the analysis, the retrofit capacity showing an approximate
reduction of maximum deflection, according to the retrofit, was confirmed, and it is judged ate suggested analysis technique can be effectively applicable in evaluating effectiveness of retrofit materials and techniques.