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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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Experiments on the Detection of Delamination in FRP Reinforced Concrete
Rhim, Hong-Chul ; Jung, Hang-Chul ; Woo, Sang-Kyun ; Song, Young-Chul ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 3~9
DOI : 10.4334/JKCI.2007.19.1.003
With a growing concern about the state of infrastructure worldwide, the demand for the development of reliable nondestructive testing techniques (NDT) is ever increasing. Among possible NDT techniques, microwave method is proven to be effective in fast and non-contact inspection of concrete structures and inclusions inside concrete. It is also found that the microwave method has a potential in detecting the delamination between fiber reinforced polymers (FRP) plate and concrete. On the other hand, ultrasonic method can be another way to find the delamination. In this paper, the research work needed for the development of a reliable microwave method and ultrasonic method is studied in the measurements of concrete specimens reinforced with FRP. Concrete specimens are made with FRP and artificial delamination inside. A microwave measurement system with hom antennas with high center frequency and broad frequency bandwidth are used to image inside concrete specimens for the detection of debonding between concrete and FRP. Also, ultrasonic method is used for the same condition. Both results are compared with each other.
Static Behavior Analysis of Spillway Pier for Dam Safety Evaluation
Jang, Bong-Seok ; Lim, Jeong-Yeul ; Lee, Myung-Kue ; Lee, Hyung-Jun ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 11~18
DOI : 10.4334/JKCI.2007.19.1.011
Seismic performance evaluation for dam safety evaluation has been continually conducted. However the behavior analysis for the spillway pier which is known as the weak point of dam is seldom reported. Therefore, this study performed the static loading tests for a prototype structures as elementary tests for the final seismic performance evaluation of dam safety. The prototype of pier structure has 1/20 scale and it adopts to strength model. And cracking loads and ultimate loads of real structures are calculated through numerical analysis using commercial FEM program (ABAQUS). The results of this study show some difference between the results of prototype tests and the results of numerical analysis. Also, the ultimate and cracking loads can be estimated through the prototype loading test and numerical analysis.
Limited-Ductile Seismic Design and Performance Assessment Method of RC Bridge Piers Based on Displacement Ductility
Park, Chang-Kyu ; Chung, Young-Soo ; Lee, Dae-Hyoung ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 19~26
DOI : 10.4334/JKCI.2007.19.1.019
Until recently Korea is considered to be immune from the earthquake hazard because it is located for away from the active fault. However, we have noticed that recent strong earthquakes inflicted enormous losses on human lives and nation's economy all over the world. Hence, there has been raised the importance of the earthquake resistant design for various infrastructures. In this research, new methodologies for the seismic design and performance assessment of reinforced concrete(RC) bridge pier were proposed from experimental results of 82 circular RC bridge piers and 54 rectangular RC bridge piers tested in domestic and aboard. New seismic design method was based on the concept of the limited ductile design, which could be practically used for low or moderate seismic regions like Korea. Further study for the seismic safety of RC bridge piers was carried out to enhance the seismic performance of aged RC bridge piers, which were designed and constructed before implementing the 1992 seismic design provision in Korea. New formula for the seismic performance assessment of RC bridge piers was proposed and practically used for the decision on the need of repair and retrofit of many aged RC bridge piers.
Minimum Curing Time Prediction of Early Age Concrete to Prevent Frost Damage
Pae, Su-Won ; Yi, Seong-Tae ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 27~37
DOI : 10.4334/JKCI.2007.19.1.027
The purpose of this study is to propose a method to predict the minimum curing time of early age concrete required to prevent frost damage. Tests were performed to examine major factors, which affect the compressive strength of concrete frozen at early ages and investigate the source of frost damage at early age concrete. The results from the tests showed that the loss rate of compressive strength decreases as the beginning time of frost damage was delayed and water-cement ratio was lower. In addition, the test results also showed that concrete made with type III cement was less susceptible to frost damage than concrete made with ordinary Portland cement and frost damage occurred through the formation of ice lenses. When early age concrete is being damaged by frozen, a phase transition into ice of free water presented at the capillary pores of the concrete gives a reason for the decrease of compressive strength. Accordingly, the frost resistance of fresh concrete can be determined based on the saturation degree of the capillary pores. The method to predict the minimum curing time was suggested using the concept of critical saturation degree of the capillary pores.
Performance Evaluation of Repair Material and Method for Reinforced Concrete Structure by Long Term Exposure Experiment
Kim, Moo-Han ; Kim, Gyu-Yong ; Cho, Bong-Suk ; Kim, Young-Duck ; Kim, Young-Sun ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 39~46
DOI : 10.4334/JKCI.2007.19.1.039
In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast and normal atmosphere is accumulated and analyzed. Investigating and evaluating the result of exposure test during 30 months of exposure age under the coastal and normal atmosphere environment, carbonation depth and chloride-ion penetration depth very little penetrated than cover depth. It seems reasonable to conclude that main cause of Corrosion of reinforcing bar are chloride-ion and macro cell from the result of corrosion area and corrosion velocity. Therefore, it is considered to be applied as the fundamental data on the performance evaluation and quality control standards of repair material and method through continuous exposure test in the future.
Evaluation of the Mechanical Properties of Field-Cast Shotcrete and Long-Term Durability by Combined Deterioration Test
Ma, Sang-Joon ; Jang, Phil-Sung ; Kim, Dong-Min ; Choi, Jae-Seok ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 47~56
DOI : 10.4334/JKCI.2007.19.1.047
Recently, tunnels are increasingly constructed in this country with the increased construction of highways, high-speed railways and subways. Shotcrete is one of the major processes in the tunnel construction. Many problems, however, exist in the current shotcrete practice. The purpose of the study is, therefore, to explore the trobles in the current shotcreting practice, and to develop high-quality silica fume shotcrete. For the purpose of security a long-term durability of shotcrete, this study conducted combined deterioration tests. In this study, a combined deterioration test in consideration of a variety of deterioration factors were proceeded. Especially, micro-silica fume that was used frequently in overseas because of a outstanding strength-promotion effect was applied to combined deterioration test, and a long-term durability of shotcrete was investigated according to additions mixing. As a result of test, the shotcrete mixed Micro-silica fume showed a good deterioration quality compared with the other mixes. And is shows that the Micro-silica fume has an outstanding strength-promotion effect and is effective to secure a long-term durability of shotcrete by means of decreasing a deterioration caused by steel fiber mixed.
Effect of Micro-Cracks on Chloride Ions Penetration of Concrete: Phonomenological Model
Yoon, In-Seok ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 57~65
DOI : 10.4334/JKCI.2007.19.1.057
Over the past few decades, considerable numbers of studies on the durability of concrete have been carried out extensively. A lot of improvements have been achieved especially in both measuring techniques as well as modeling of ionic flows. However, the majority of these researches have been performed on sound uncracked concrete, although most of in-situ concrete structures have more or less micro-cracks. It is only recent approach that the attention has shifted towards the influence of cracks and crack width on the penetration of chloride into concrete. The penetration of chlorides into concrete through the cracks can make a significant harmful effect on reinforcement corrosion. On the other hand, a general acceptable crack width of 0.3 mm has been recognized for keeping the serviceability of concrete structures in accordance with a lot of codes. However, there seems to be rare established description to explain the critical crack width in terms of the durability of concrete. To make a bad situation worse, there is little agreement on critical crack width among a few of literatures for this issue. Critical crack width is still controversial problem. Nevertheless, since the critical crack width is important key for healthy assessment of concrete structures exposed to marine environment, it should be established. The objective of this study is to define a critical crack width. The critical crack width in this study is designed for a threshold crack width, which contributes to the first variation of chloride diffusion coefficient in responsive to the existence of cracks. A simple solution is formulated to realize the quantifiable parameter, chloride diffusion coefficient for only cracked zone excluding sound concrete. From the examination on the trend of chloride diffusion coefficient of only cracked zone for various crack widths, a critical crack width is founded out.
Experimental Study of Concrete Beam with FRP Plank as Formwork and Reinforcement
Yoo, Seung-Woon ; Bae, Han-Ug ; Oliva, Michael ; Bank, Lawrence ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 67~74
DOI : 10.4334/JKCI.2007.19.1.067
We perform an experimental study of concrete beam with pultruded fiber reinforced polymer(FRP) plank using as a permanent formwork and the tensile reinforcement. A satisfactory bond at the interface between the smooth surface of the pultruded plank and the concrete must be developed for the FRP plank and the concrete to act as a composite structural member. Two kinds of aggregate were bonded to the FRP plank using a commercially available epoxy. No additional flexural or shear reinforcement was provided in the beams. For comparison we test two types of control specimen. One control did not have any aggregate bonded to the FRP plank and the other control had infernal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. The experimental results were compared to current ACI 318 (2005) and ACI 440 (2006) code predictions. This study demonstrates that the FRP plank has the potential to serve as formwork and reinforcing for concrete structures.
A Study on the Compressive Strength Prediction of Crushed Sand Concrete by Non-Destructive Method
Kim, Myung-Sik ; Baek, Dong-Il ; Kim, Kang-Min ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 75~81
DOI : 10.4334/JKCI.2007.19.1.075
Percentage that aggregate of materials that concrete composed about
of whole volume, therefore influence that quality of aggregate gets in concrete characteristics are very important. Schmidt hammer and ultra-sonic velocity method are commonly used for crushed sand concrete compressive strength test in a construction field. At present, various equations for prediction of strength are present, which have been used in a construction field. The purpose of this study is to evaluate the correlation between prediction strength by present equations and destructive strength to test specimen, and find out which is a suitable equation for the construction site, a strength test was carried out destructive test by means of core sampling and traditional test. The experimental parameters were concrete age, curing condition, and strength level. It is demonstrated that the correlation behavior of crushed sand concrete strength in this study good due to the perform analysis of correlation between core, destructive strength and non-destructive strength.
Shear Behavior of Reinforced Concrete Beams Strengthened with Unbonded-Type Wire Rope Units
Kim, Sun-Young ; Byun, Hang-Yong ; Sim, Jae-Il ; Chung, Heon-Soo ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 83~90
DOI : 10.4334/JKCI.2007.19.1.083
The present study reports a simple unbonded-type shear strengthening technique for reinforced concrete beams using wire rope units. Fifteen beams failed in shear were repaired and strengthened with wire rope units, and then retested to failure. Influence of the prestressing force, orientation and spacing of wire rope units on the shear behavior of strengthened beams having shear span-to-depth ratios of 1.5, 2.5, or 3.25 were investigated. Test results showed that beams strengthened with wire rope units exhibited a higher shear strength and a larger post-failure deformation than the corresponding original beams. Inclined wire rope units was more effective for shear strength enhancement than vertical wire rope units. The increase of the prestressing force in wire rope units causes the decrease of the principal tensile stress in concrete, as a result, the diagonal tensile cracking strength of strengthened beams was higher than that of the corresponding original beams. Shear capacity of strengthened beams is compared with predictions obtained from ACI 318-05 and EC 2. Shear capacity of strengthened beams having shear span-to-depth ratio below 2.5 is reasonably predicted using ACI 318-05 formula. On the other hand, EC 2 overestimates the shear transfer capacity of wire rope units for beams having shear span-to-depth ratio above 2.5.
Seismic Fragility Analysis of RC Bridge Piers in Terms of Seismic Ductility
Chung, Young-Soo ; Park, Chang-Young ; Park, Ji-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 91~102
DOI : 10.4334/JKCI.2007.19.1.091
Through lessons in recent earthquakes, the bridge engineering community recognizes the need for new seismic design methodologies based on the inelastic structural performance of RC bridge structures. This study represents results of performance-based fragility analysis of reinforced concrete (RC) bridge. Monte carlo simulation is performed to study nonlinear dynamic responses of RC bridge. Two-parameter log-normal distribution function is used to represent the fragility curves. These two-parameters, referred to as fragility parameters, are estimated by the traditional maximum likelihood procedure, which is treated each event of RC bridge pier damage as a realization of Bernoulli experiment. In order to formulate the fragility curves, five different damage states are described by two practical factors: the displacement and curvature ductility, which are mostly influencing on the seismic behavior of RC bridge piers. Five damage states are quantitatively assessed in terms of these seismic ductilities on the basis of numerous experimental results of RC bridge piers. Thereby, the performance-based fragility curves of RC bridge pier are provided in this paper. This approach can be used in constructing the fragility curves of various bridge structures and be applied to construct the seismic hazard map.
Strength and Ductility of Steel Fiber Reinforced Composite Beams without Shear Reinforcements
Oh, Young-Hun ; Nam, Young-Gil ; Kim, Jeong-Hae ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 103~111
DOI : 10.4334/JKCI.2007.19.1.103
Experimental study was carried out to investigate the structural performance of composite beams with steel fiber concrete and angle. For this purpose, seven specimens composed of two RC beams with or without steel fiber and five composite beams with steel fiber and angle were constructed and tested. All specimens had no web shear reinforcement. Main variables for the specimens were tensile reinforcement ratio and fiber volume fraction. Based on the test results, structural performance such as strength, stiffness, ductility and energy dissipation capacity was evaluated and compared with the predicted strength. The prediction of flexure and shear strength gives a good relationship with the observed strength. The strength, ductility and energy dissipation capacity are increased, as the fiber volume fraction is increased. Meanwhile, high tensile reinforcement ratio resulted in the reduction of ductility and energy dissipation capacity for the composite beams.
A Study on the Performace Evaluation of Antimicrobial Concrete Using Liquid Reinforcing Antibiotics
Kim, Gyu-Yong ; Kim, Moo-Han ; Lee, Eui-Bae ; Cho, Bong-Suk ; Khil, Bae-Su ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 113~120
DOI : 10.4334/JKCI.2007.19.1.113
In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Also, as little pore volume and closed structure of antimicrobial concrete were observed, watertightness of it was verified. Finally artificial accelerating test for biochemical corrosion was proposed, and its suitability was experimentally proved.
Strength and Deformation Capacities of Short Concrete Columns with Circular Section Confined by GFRP
Cho, Soon-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 1, 2007, Pages 121~130
DOI : 10.4334/JKCI.2007.19.1.121
To investigate the enhancement in strength and deformation capacities of concrete confined by FRP composites, tests under axial loads were carried out on three groups of thirty six short columns in circular section with diverse GFRP confining reinforcement. The major test variables considered include fiber content or orientation, wrap or tube type by varying the end loading condition, and continuous or discontinuous confinement depending on the presence of vortical spices between its two halves. The circumferential FRP strains at failure for different types of confinements were also investigated with emphasis. Various analytical models capable of predicting the ultimate strength and strain of the confined concrete were examined by comparing to observed results. Tests results showed that FRP wraps or tubes provide the substantial increase in strength and deformation, while partial wraps comprising the vertical discontinuities fail in an explosive manner with less increase in strength, particularly in deformation. A bilinear stress-strain response was observed throughout all tests with some variations of strain hardening. The failure hoop strains measured on the FRP surface were less than those obtained from the tensile coupons in all tests with a high degree of variation. In overall, existing predictive equations overestimated ultimate strengths and strains observed in present tests, with a much larger scatter related to the latter. For more accuracy, two simple design- oriented equations correlated with present tests are proposed. The strength equation was derived using the Mohr-Coulomb failure criterion, whereas the strain equation was based on entirely fitting of test data including the unconfined concrete strength as one of governing factors.