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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 20, Issue 6 - Dec 2008
Volume 20, Issue 5 - Oct 2008
Volume 20, Issue 4 - Aug 2008
Volume 20, Issue 3 - Jun 2008
Volume 20, Issue 2 - Apr 2008
Volume 20, Issue 1 - Feb 2008
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Experimental Verification of Flexural Response for Strengthened R/C Beams by Stirrup Partial-Cutting Near Surface Mounted Using CFRP Plate
Oh, Hong-Seob ; Sim, Jong-Sung ; Ju, Min-Kwan ; Lee, Gi-Hong ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 671~679
DOI : 10.4334/JKCI.2008.20.6.671
The near surface mounted (NSM) FRP strengthening method has been conventionally applied for strengthening the deteriorated concrete structures. The NSM strengthening method, however, has been issued with the problem of limitation of the cutting depth which is usually considered as concrete cover depth. This may be related with degradation of bonding performance in long-term service state. To improve the debonding problem, in this study, the Stirrup partial-cutting NSM (SCNSM) strengthening method using CFRP plate was newly developed. SCNSM strengthening method can be effectively applied to the deteriorated concrete structure without any troubles of insufficient cutting depth. To experimentally verify the structural behavior, the flexural test of the concrete beam by using the SCNSM strengthening method was conducted with the test variable as the strengthening length (32%, 48%, 70%, 80%, 96% of span length). In the result of the test, the NSM and SCNSM strengthened specimen showed similar structural behavior with load-deflection, mode of failure. Additionally, there was no apparent structural degradation by the stirrup partial-cutting. Consequently, it was evaluated that the SCNSM strengthening method can be useful for seriously damaged concrete structures that is hard to apply the conventional NSM strengthening method for increasing the structural capacity.
Standardization of Temperature Measurement System for Stable and Reliable Infrared Thermographical Image
Yoon, Se-Hyun ; Chung, Lan ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 681~687
DOI : 10.4334/JKCI.2008.20.6.681
This study presents a technique to quantitatively measure the corrosion level of a reinforcing bar using infrared thermography system. We found out electric heating method having an important effect on thermal data in previous study. This study purposed an efficient way for grip standardization to reduce constriction resistance problem, and providing reliable thermal data using infrared thermographic method. Using vise type earth clamp, the surface resistance of rebar was smaller than that of traditional plier type earth clamp through temperature-distribution relationship. Also this study contains experiments with toque wrench to improve heating contact problem.
Evaluation of Alkali-Silica Reactivity for Aggregates in Korea according to Test Methods
Yun, Kyong-Ku ; Kim, Seong-Kwon ; Hong, Seung-Ho ; Han, Seung-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 689~696
DOI : 10.4334/JKCI.2008.20.6.689
The purpose of this study was to evaluate the alkali-silica reactivity for aggregates in Korea according to test methods: accelerated mortar bar test (AMBT) by ASTM C 1260; chemical test by KS F 2545 (ASTM C 289). The results are as follows: The AMBT (ASTM C 1260) results showed that two (2) igneous rocks (two mica granite and felsite), three (3) sedimentary rocks (arkose, red sandstone and shale), two (2) metamorphic rock (slate and vitric tuff), one (1) mineral (quartz) showed more expansion than 0.1% at 14 days. But, some sedimentary rocks and metamorphic rocks expanded more than 0.1% at 28 days even though they were less than 0.1% at 14 days. Therefore, it is necessary to extend the experimental dates more than 14 days to evaluate the possibility of alkali-aggregate reactivity. The chemical test (KS F 2545) results showed that five (5) igneous rocks (andesite, diabase, granite porphyry, muscovite granite and diorite) were indicative of potentially deleterious expansion, while two (2) igneous rocks (diorite porphyry and quartz porphyry) were possible indicative of expansion, and three (3) igneous rocks (biotite granite, two mica granite and felsite) were indicative of innocuous reactivity. The above results showed that the results from chemical method (KS F 2545) and AMBT (ASTM C 1260) had little relationship.
Analytical Method on PSC I Girder with Strengthening of External Tendon
Park, Jae-Guen ; Lee, Byeong-Ju ; Kim, Moon-Young ; Shin, Hyun-Mock ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 697~704
DOI : 10.4334/JKCI.2008.20.6.697
This paper presents an analytical prediction of Nonlinear characteristics of prestressed concrete bridges by strengthened of externally tendon considering construction sequence, using unbonded tendon element and beam-column element based on flexibility method. Unbonded tendon model can represent unbounded tendon behavior in concrete of PSC structures and it can deal with the prestressing transfer of posttensioned structures and calculate prestressed concrete structures more efficiently. This tendon model made up the several nodes and segment, therefore a real tendon of same geometry in the prestressed concrete structure can be simulated the one element. The beam-column element was developed with reinforced concrete material nonlinearities which are based on the smeared crack concept. The fiber hysteresis rule of beam-column element is derived from the uniaxial constitutive relations of concrete and reinforcing steel fibers. The formulation of beam-column element is based on flexibility. Beam-column element and unbonded tendon element were be involved in A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), that were used the analysis of RC and PSC structures. The proposed numerical method for prestressed concrete structures by strengthened of externally tendon is verified by comparison with reliable experimental results.
Structural Layout Design for Concrete Structures Based on the Repeated Control Method by Using Micro Lattice Truss Model
Choi, Ik-Chang ; Ario, Ichiro ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 705~712
DOI : 10.4334/JKCI.2008.20.6.705
This study carried out simulation for structural layout design for concrete structures by using the models of the ground structure method. The micro lattice truss is modeled as assemblage of a number of unit cells. The progress of analysis repeat to undergo finite element analysis to feed-back results of stress to the stiffness of each member. Through the repeated this analysis, truss model is represented to form the topological materials and the structural shape with the use of the local stress condition without mathematical optimum tools. It is successful to analyse the shape-layout problem as numerical samples on the lattice truss model.
A Study on Chloride Threshold Level of Polymer Inhibitive Coating Containing Calcium Hydroxide
Song, Ha-Won ; Lee, Chang-Hong ; Lee, Kewn-Chu ; Ann, Ki-Yong ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 713~719
DOI : 10.4334/JKCI.2008.20.6.713
Various types of coatings have been developed for use as reinforcement in concrete and to resist chloride environment. The most commonly used coatings are inhibited and sealed cement slurry coating, cement polymer compositing coating and epoxy coating. Cement slurry offers passive protection, epoxy coating offers barrier protection whereas polymer coating offers both passive protection and barrier protection. Moreover, damage during handling of the steel may result in disbondment of the epoxy coating, which would increase the risk of localized corrosion. In the present study, inhibiting technique was used to increase the calcium hydroxide content at the interface up to 20%. Calcium hydroxide provides a high buffering capacity that resists a local fall in pH and thus maintains the alkaline environment necessary to prevent chloride corrosion. This study examines the use of a calcium hydroxide coating on the steel surface to enhance the pH buffering capacity of steel-concrete interface. Finally, the chloride threshold level (CTL) of polymer inhibitive coating calcium hydroxide is evaluated.
An Experimental Study on the Early Strength Development Properties of Concrete According to Curing Condition and Used Materials
Lee, Sang-Soo ; Song, Ha-Young ; Lee, Ji-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 721~729
DOI : 10.4334/JKCI.2008.20.6.721
The purpose of this study is to investigate the engineering properties of concrete for the early strength development. As a result of reviewing it by establishing each experimental factor and level, the cement had more excellent quality performance in CHC and HESPC than OPC. This study has shown that the PC series admixture was more excellent in side of elapsed time (aging) and early strength development than PNS series admixture. In addition, there was much difference according to the curing temperature, but the early strength development showed the considerable vulnerability in curing temperature below
. To satisfy the strength requirements of 5 MPa/18 hr this study has shown that it needed the curing temperature over
to the minimum in OPC, over
in CHC, and over
in HESPC. On the other hand, as to the strength properties according to W/C, the less W/C was, the more strength development was excellent. If this study is to be used in construction filed on a basis of this result, this researcher is considered as possible of the economic execution of construction by advancing the early strength and by the reduction of construction cost according to shortening construction duration.
Fiber Orientation Impacts on the Flexural Behavior of Steel Fiber Reinforced High Strength Concrete
Kang, Su-Tae ; Kim, Yun-Yong ; Lee, Bang-Yun ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 731~739
DOI : 10.4334/JKCI.2008.20.6.731
To evaluate the fiber orientation characteristics and estimate its effect on the flexural strength of steel fiber reinforced ultra high strength concrete with directions of concrete placing, we developed an image processing technique and carried out the flexural test to quantify the effect of fiber orientation characteristics on the flexural strength as well. The image processing technique developed in this study could evaluate quantitatively the fiber orientation property by the use of dispersion coefficient, the number of fibers in a unit area, and fiber orientation. It was also found that the fiber orientation characteristics were dependent on the direction of concrete placing. Fiber orientation characteristic was revealed to strongly affect the ultimate flexural strength, while hardly affecting the first cracking strength. Theoretical model for flexural strength was applied to compare with test results, which exhibited a good agreement.
Mechanical Characteristics and Corrosion Resistance of Concrete Using Tannin Acid-Corrosion Inhibitor
Yang, Eun-Ik ; Ryu, Jong-Hyun ; Youm, Kwang-Soo ; Hwang, In-Dong ; Kim, Myung-Yu ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 741~746
DOI : 10.4334/JKCI.2008.20.6.741
Many methods have been introduced to protect the corrosion of embedded steel in RC structure. One of the methods that restrain corrosion of steel is corrosion inhibitor. The technology that delayed the progress of corrosion is developed recently by converting active rust to passive rust. However, the performance for concrete structure is not fully examined because this corrosion inhibitor is developed for normal metal product. In this study, the application of corrosion inhibitor that use tannin acid is investigated by concrete specimen. According to the results, tannin acid corrosion inhibitor does not occur reduction of workability and strength in concrete. When corrosion inhibitor is added more than 4% per cement weight, the penetration depth of chloride decrease about 10%. Also, corrosion resistance of concrete is improved because tannin acid corrosion inhibitor has an effect on converting the rust of steel into stable state. It is showed in special that the addition more than 6% is effective in corrosion resistance.
Evaluating Structural Performance of High-Strength Concrete Corbels Containing Steel and Polypropylene Fibers
Yang, Jun-Mo ; Lee, Joo-Ha ; Min, Kyung-Hwan ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 747~754
DOI : 10.4334/JKCI.2008.20.6.747
In this study, high strength concrete corbels reinforced with steel fibers and polypropylene fibers, and subjected to the vertical and horizontal loads were constructed and tested. The results showed that performance in terms of load carrying capacities, stiffness, ductility, crack width, and number of cracks was improved, as the steel fibers and polypropylene fibers were added. The polypropylene fiber reinforced concrete corbels resulted in higher ductility in presence of horizontal loads, but showed larger crack width than the steel fiber reinforced concrete corbels. And, the heads of the headed bars provided excellent end anchorage of the main tension tie reinforcement. Experimental results presented in this paper are also compared with various prediction models proposed by codes and researchers. The refined strut-and-tie model showed more accurate and conservative predictions in presence of horizontal loads, and the truss model proposed by Fattuhi provides fairly good predictions for fiber reinforced concrete corbels.
Strength Evaluation for Doubly Reinforced Composite Beams with Steel Fiber Concretes and Steel Angles
Oh, Young-Hun ; Nam, Young-Gil ; Lee, Jae-Yeon ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 755~763
DOI : 10.4334/JKCI.2008.20.6.755
The purpose of this study is to investigate the structural performance of doubly reinforced composite beams with steel fiber concretes and steel angles. For this purpose, total 6 specimens whose variables are shear span-to-depth ratio, existence of shear reinforcement, and shear reinforcement details, are made and tested. All specimens are constructed of steel fiber concretes with specified compressive strength of 30 MPa and steel fiber volumn content of 1%. From the experimental results, structural performance of doubly reinforced composite beams are evaluated in terms of strength, stiffness, ductility, and energy absorbing capacity. For the better structural performance, it is recommended that the composite beam is designed with diagonal shear reinforcement.
A Prediction of the Long-Term Deflection of RC Beams Externally Bonded with CFRP and GFRP
Kim, Sung-Hu ; Kim, Kwang-Soo ; Han, Kyoung-Bong ; Song, Seul-Ki ; Park, Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 765~772
DOI : 10.4334/JKCI.2008.20.6.765
For RC structures, long-term deformation occurs due to the inherent characteristics, which are creep and shrinkage. In terms of serviceability, it is important to limit deflection caused by the deformation to the allowable deflection. In the recent years, various repair and strengthening methods have been used to improve performance of the existing RC structures. One of the typical methods is FRP externally bonded method (EBR). Fiber reinforced polymer (FRP) has been used worldwide as repair and strengthening materials due to its superior properties. Besides, it has to offer improved strengthening performance not only under instantaneous load but sustained load. Therefore, accurate prediction method of deflection for the RC members externally bonded with FRP under sustained load is required. In this paper, three beams were fabricated. Two beams were externally strengthened with one of CFRP plate and GFRP plate respectively. Total three beams were superimposed under sustained load of 25 kN. During 470 days, deflections at midspan were obtained. Moreover, creep coefficients and shrinkage strains were calculated by using ACI-209 code and CEB-FIP code. In order to predict the deflection of the beams, EMM, AEMM, Branson's method and Mayer's method were used. Through the experiment, it was found that the specimen with CFRP plate has the most flexural capacity and Mayer's method is the most precise method to predict total long-term deflections.
A Study on the Evaluation of the Durability of Concrete Using Copper Slag Aggregates
Lee, Mun-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 773~784
DOI : 10.4334/JKCI.2008.20.6.773
Even if the exploitation of copper slag produced during the smelting process of copper as aggregate for construction purpose has been permitted since 2004 in Korea, the lack of sufficient data enabling to evaluate its long-term stability that is its durability has to date impeded its application. This study intends to investigate experimentally the durability characteristics of 18 and 27 MPa-class commercial concretes in which natural sand (fine aggregates) has been partially replaced by copper slag through accelerated and exposure tests so as to provide bases promoting the application of copper slag concrete. The experimental results revealed insignificant difference of the durability characteristics in most of the mix proportions in which 30% of natural sand was replaced by copper slag. In the case where crushed sand was adopted, tests verified similar characteristics for replacement ratio of 50%. Particularly, the results of the exposure test conducted during 8 years demonstrated that equivalent level of durability was secured compared to the case using natural sand. In the case of 18MPa-class lower grade concrete, exposure test verified also that the physical lifetime similar to 50 years could be secured until carbonation reaches cover depth of 20 mm.
Longitudinal Elongation of Slender Reinforced Concrete Beams Subjected to Cyclic Loading
Eom, Tae-Sung ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 785~796
DOI : 10.4334/JKCI.2008.20.6.785
Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions.
The Properties of Internal Temperature of Paste and Concrete according to Component Ratio Variation of Ternary System Cement
Kim, Yeon-Seung ; Kim, Dong-Hyeok ; Jee, Nam-Yong ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 797~807
DOI : 10.4334/JKCI.2008.20.6.797
For this study, the semi-adiabatic temperature rising test is accomplished by using ternary system cement (OPC, BFS, FA) reducing temperature crack. Two tests are conducted; one is for the paste test, and the other is for the concrete test. As the results of paste tests, using fly ash is better to reduce hydration temperature than doing blast furnace slag. In the case of the paste mixed ternary system cement, the more fly ash is mixed and the less blast furnace slag is used, the lower the temperature is. The less the mixture ratio of blast furnace slag is and the more the mixture ratio of fly ash is, the later the temperature rising velocity and descending velocity are. Besides, the temperature is lower if water/binder ratio is high. The use of ternary system cement has the retardation effect of temperature rising because the time to reach the maximum temperature is in the order of OPC100, binary system cement, and ternary system cement. From the test, the maximum temperature of concrete used ternary system cement is
lower than that of concrete used OPC100. Moreover, temperatures rising velocity and descending velocity of ternary system cement range
compared with OPC100. The specimen of concrete shows remarkable low internal temperature and slow temperature rising velocity and descending velocity compared with the specimen of paste because it is that temperature loss of concrete is much more than paste specimen according to aggregates.
Suggestion, Design, and Evaluation of a New Modified Double Tee Slabs
Yu, Sung-Yong ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 809~820
DOI : 10.4334/JKCI.2008.20.6.809
A new modified full scale double tee slabs with the length of nib plate - 1,500 mm were suggested, designed, and experimentally evaluated up to the loading of flexural failure. This slabs were composed of the tee section which was same to original PCI double tee and the plate section which was modified in a new shape, and the prestressing force was applied at the bottom of tee section only. This specimens were made from the domestic precast factory. The safety and serviceability of the modified nib plate with the dapped ends were evaluated up to the ultimate flexural strength of tee section. As the experimental loading increased, the flexural crackings developed first in the bottom of the slab and they changed to the increased flexural shear and inclined shear crackings in the nib and dapped portion of the double tees. The suggested modified double tee slabs failed in ductile above the design loading with many evenly distributed flexural crackings. The thickness of nib plate - 250 mm does not show any cracking under the service loading and show several minor flexural cracking up to the ultimate state of tee portion. The proposed specimens were satisfied with the strength and ductility requirements in the design code provisions in the tests. Additional experimental tests are required to reduce the depth and tensile reinforcement of nib plate concrete for the practical use of this system effectively.
Spalling and Internal Temperature Distribution of High Strength Column Member with Polypropylene Fiber Volume Fractions
Won, Jong-Pil ; Jang, Chang-Il ; Lee, Sang-Woo ; Kim, Heung-Youl ; Kim, Wan-Young ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 821~826
DOI : 10.4334/JKCI.2008.20.6.821
This study evaluated spalling and internal temperature distribution after elevated temperatures test for high strength concrete (
) column member with various polypropylene fiber volume fractions. The ISO-834 time-temperature curve was used for measurement of fire resistance properties. As the result of test, average internal temperature results indicated to low temperature in increased polypropylene fiber volume fraction. But, the highest internal temperature results show that does not difference in proportion of polypropylene fiber volume fractions.
Fire Resistance Performance for Hybrid Fiber Reinforced High Strength Concrete Column Member
Won, Jong-Pil ; Jang, Chang-Il ; Lee, Sang-Woo ; Kim, Heung-Youl ; Kim, Wan-Young ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 827~832
DOI : 10.4334/JKCI.2008.20.6.827
This study evaluated fire resistance performance for hybrid (polypropylene+steel) fiber reinforced high strength concrete column. Full-size columns were constructed and tested with or without fibers using ISO-834 fire curve. As the result of test, Control specimen occurred serious spalling and indicated rapidly internal temperature increasing. Specimen with polypropylene fiber occurred not spalling but steady internal temperature increasing. Specimen with hybrid fiber occurred not spalling as well as does not propagated temperature distribution. Therefore, hybrid fiber reinforced column specimen indicated a good fire resistance performance than other cases.
Performance Evaluation of the Stair Joints Constructed with Partial Precast Concrete System
Chang, Kug-Kwan ; Lee, Eun-Jin ; Jin, Byung-Chang ;
Journal of the Korea Concrete Institute, volume 20, issue 6, 2008, Pages 833~840
DOI : 10.4334/JKCI.2008.20.6.833
The time and cost can be reduced when applying partial precast concrete to the stair system in comparison to the cast-in-place or precast method. Because the performance of staircase which is used for evacuation can be largely different from connection types of precast concrete member, we tried to know structural behavior and performance evaluation according to each type of stair joints by experimental study. In the cast-in-place rigid joint, much reinforcement is needed in the end portion because much stress is concentrated in the middle portion. Also, in the pin joint which is used in the connection point, the maximum stress occurs in the middle point, so not only the amount of re-bar is increased but also the serviceability is largely decreased. The bolt type of semi-rigid joints proposed in this study had been increased strength and serviceability which is similar to the rigid joints. Also, its ductility was shown about 0.7 times in comparison to the rigid type and was about 2.8 times for the pin joint type. According to the classification of joint in Eurocode, it can be considered that it is one of the semi-rigid joints which are in the semi-rigid-full strength, and the structural behavior can be expected by using a model which applied to stiffness value decreased by 40 percent.