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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 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
Selecting the target year
An Experimental Study for Improving the Durability of Concrete Bridge Decks
Suh, Jin-Won ; Rhee, Ji-Young ; Ku, Bon-Sung ; Shin, Do-Chul ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 393~399
DOI : 10.4334/JKCI.2007.19.4.393
Concrete bridge decks are directly exposed to the severe environmental conditions such as rain water and deicing chemicals resulting in the freeze-thaw action and the rebar corrosion during their service lift. These deteriorations of bridge decks shorten the service lift and consequently they are the major concerns of the maintenance. The high performance concrete (HPC) deck is proposed as the alternative to minimize the deterioration problems. To develop more durable concrete deck, the performance characteristic tests of HPC mixtures were carried out. In this study, 4 different concrete mixtures were used varying the mineral admixtures as the cement replacement; ordinary portland cement (OPC), 20% fly ash (FA),20% fly ash with 4% silica fume (FS), and 40% ground granulated blast-furnace slag (BS). The design compressive strengths of HPC specimens were 27 MPa and 35 MPa, respectively. The results showed that the compressive strength of concrete did not much affect the durability of concrete. HPC with fly ash and silica lune (FS) were turned out to have the good durability and crack resistance.
Cyclic Lond Testing for Strong Axis Joints Connected with SRC Column and RC Beams
Moon, Jeong-Ho ; Lee, Kang-Min ; Lim, Jae-Hyung ; Oh, Kyung-Hwan ; Kim, Sung-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 401~409
DOI : 10.4334/JKCI.2007.19.4.401
The objective of this research is to provide better knowledge on the behavior of strong axis SRC column-RC beam joint, supported by experimental results, that can be broadly applicable to many structures. For this purpose, firstly literature reviews and field survey were made to classify the most commonly used for these types of joints. Then, experimental program was designed and performed including 6 SRC column-RC beam joint specimens designed with various joint details. Using the experimental results obtained from the quasi-static cyclic tests, structural performances of the joints such as hysteretic curves, maximum strength capacities, strength degradation beyond the maximum strength, ductilities, and energy dissipation capacities were investigated. Test results showed that specimens with wide beam shape (RCW-P, RCW-W, RCW-F) and T beam shape (RCT-W) showed better structural performances than the bracket type specimens (HBR-L, HBR-S). These specimens also revealed to have higher strength capacities than the nominal design strength. However, H beam bracket type specimens (HBR-L, HBR-S) need further study both analytically and experimentally to verify the reason for unexpected structural performances.
Application of Headed Bars with Small Head in Exterior Beam-Column Joints Subjected to Reversed Cyclic Loads
Ha, Sang-Su ; Choi, Dong-Uk ; Lee, Chang-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 411~420
DOI : 10.4334/JKCI.2007.19.4.411
The applicability of headed bars in exterior beam-column joints under reversed cyclic loading was investigated. A total of ten pullout tests were first performed to examine pullout behavior of headed bars subjected to monotonic and cyclic loading with test variables such as connection type between head and bar stem (weld or no weld), loading methods (monotonic or cyclic loading), and head shape (small or large circular head and square head). Two full-scale beam-column joint tests were then performed to compare the structural behavior of exterior beam-column joints constructed using two different reinforcement details: i.e.
standard hooks and headed bars. Both joints were designed following the recommendations of ACI-ASCE Committee 352 for Type 2 performance: i.e. the connection is required to dissipate energy through reversals of deformation into inelastic range. The pullout test results revealed that welded head to the stem did not necessarily result in increased pullout strength when compared to non-welded head. Relatively large circular head resulted in higher peak load than smaller circular and square head. Both beam-column joints with conventional
hooks and headed bars behaved similarly in terms of crack development, hysteresis curves, and peak strengths. The joint using the headed bars showed better overall structural performance in terms of ductility, deformation capacity, and energy dissipation. These experimental results demonstrate that the headed bars using relatively small head can be properly designed far use in external beam-column joint.
Structural Performance of Reinforced Concrete Beams Strengthened with Sprayed Fiber Reinforced Polymers
Lee, Kang-Seok ; Son, Young-Seon ; Lee, Moon-Sung ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 421~431
DOI : 10.4334/JKCI.2007.19.4.421
The main purpose of this study is to develop a sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing one of the carbon or glass chopped fibers and one of the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of the sprayed FRP, this study carried out tensile tests of the material specimens, which were changed with the combinations of various variables including the length of chopped fiber and the mixture ratio of chopped fiber and resin. These variables were set to have the equal material strength, compared with that of one layer of the FRP sheet. As a result, the optimal length of glass and carbon chopped fibers was fumed out to be 38 mm, and the optimal mixture ratio between chopped fiber and resin was also turned out to be 1 : 2 from each variable. And also, the thickness of the sprayed FRP to have the equal strength to one layer of the FRP sheet was finally calculated. In is study, a series of experiments were carried out to evaluate the strengthening effects of flexural beams, shear beams and damaged beams strengthened with the sprayed FRP method, respectively. The results revealed that the strengthening effects of the flexural and shear specimens were reasonably similar to those of the FRP sheet, and the developed Sprayed FRP technique is able to be used as a strengthening scheme of existing RC building.
Experimental Study on the Static Behavior of the Spliced PSC Box Girder
Chung, Won-Seok ; Kim, Jae-Hueng ; Chung, Dae-Ki ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 433~439
DOI : 10.4334/JKCI.2007.19.4.433
The main objective of the paper is to investigate the static behavior of a prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m long full-scale spliced PSC girder is fabricated and tested to compare its static performance against a monolithic girder. The monolithic girder has the same geometric and material properties with respect to the spliced girder. This includes infernal strain, deflections, neutral axis position, and crack patterns for both girders. The test also consists of monitoring relative displacements occurring across the joints. Both the horizontal displacement (gap) and vertical displacement (sliding) are measured throughout the loading procedure. All results have been compared to those obtained from the monolithic girder. It has been demonstrated that the spliced girder offers close behavior with respect to the monolithic girder up to the crack load. Both girders exhibits ductile flexural failure rather than abrupt shear failure at joints.
An Experimental Study on Shear Behavior of Internal Reinforced Concrete Beam-Column Assembly
Lee, Jung-Yoon ; Kim, Jin-Young ; Oh, Ki-Jong ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 441~448
DOI : 10.4334/JKCI.2007.19.4.441
The beam-column assembly in a ductile reinforced concrete (RC) frames subjected to seismic loading are generally controlled by shear and bond mechanisms, both of which exhibit poor hysteretic properties. Hence the response of joints is restricted essentially to the elastic domain. The usual earthquake resistant design philosophy of ductile frame buildings allows the beams to form plastic hinges adjacent to beam-column assembly. Increased strain in these plastic hinge regions affect on joint strain to be increased. Thus bond and shear joint strength are decreased. The research reported in this paper presents the test results of five RC beam-column assembly after developing plastic hinges in beams. Main parameter of the test Joints was the amount of the longitudinal tensile reinforcement of the beams. Test results indicted that the ductile capacity of joints increased as the longitudinal tensile reinforcement of the beams decreased. In addition, both the tensile strain of the longitudinal reinforcement bars in the joint and the ductile ratio of the beam-column assemblages increased due to the yielding of steel bars in the plastic hinge regions.
Features of Critical Tensile Stresses in Jointed Concrete Pavements under Environmental and Vehicle Loads
Kim, Seong-Min ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 449~456
DOI : 10.4334/JKCI.2007.19.4.449
This research was conducted to analyze the features of the critical tensile stresses at the top and bottom of the concrete slab in the jointed concrete pavement (JCP) when subjected to both the environmental and vehicle loads. First, the stress distribution in JCP was analyzed when the system was subjected to only the environmental loads or the vehicle loads by using the finite element model of JCP. Then, the stresses were analyzed when the system was subjected to the environmental and vehicle loads at the same time. From this study, it was found that the critical tensile stresses at the slab bottom under the vehicle loads were almost constant regardless of the loading positions once the loads were applied at the positions having some distance from the transverse joint. The critical tensile stresses at the slab bottom could be obtained using the model consisting of normal springs for underlying layers by adding the critical stresses due to the environmental loads and the vehicle loads for the curled-down slab, and by subtracting the critical stress due to the environmental loads from that due to the vehicle loads for the curled-up slab. The critical tensile stresses at the top of the slab could be obtained using the model consisting of tensionless springs for underlying layers by adding the critical stress due to the environmental loads and the stress at the middle of the slab under the vehicle loads applied at the joint for the curled-up slab. An alternative to obtain the critical stresses at the top of the slab for the curled-up slab was to use the critical stresses under only the environmental loads obtained from the model having normal springs for underlying layers.
Strength Properties of Polymer-Modified Repair Mortars According to Curing Conditions and Repair Methods
Kim, Wan-Ki ; Jo, Young-Kug ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 457~465
DOI : 10.4334/JKCI.2007.19.4.457
In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.
Flexural Behavior and Analysis of RC Beams Strengthened with Prestressed CFRP Plates
Yang, Dong-Suk ; Park, Jun-Myung ; You, Young-Chan ; Park, Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 467~474
DOI : 10.4334/JKCI.2007.19.4.467
In this paper, a total of 13 beams with bonding, anchorage system, amount of prestressing and span length as variables of experiment were tested in flexural test and analyzed in finite element analysis; one control beam, two simplified FRP-boned beams, four prestressed FRP-unbonded beams and four prestressed FRP-bonded beams. Also, a nonlinear finite element analysis of beams in the flexural test is performed by DIANA program considered material nonlinear of concrete, reinforcement and the interfacial bond-slip model between concrete and CFRP plates. The failure mode of prestressed CFRP plated-beams is not debonding but FRP rupture. RC members strengthened with external bonded prestressed CFRP plates occurred 1st and 2nd debonding of the composite material. After the debonding of CFRP plates occurs in bonded system, behavior of bonded CFRP-plated beams change into that of unbonded CFRP-plated beams due to fix of the anchorage system. Also, It was compared flexural test results and analytical results of RC members strengthened with CFRF plates. The ductility of beams strengthened by CFRP plates with the anchorage system is considered high with the ductility index of above 3. Analysis results showed a good agreement with experiment results in the debonding load, yield load and ultimate load.
Evaluation of Penetrating and Reinforcing Agent for Preventing Deterioration of Concrete
Cho, Myung-Sug ; No, Jae-Myoung ; Song, Young-Chul ; Kim, Do-Gyum ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 475~482
DOI : 10.4334/JKCI.2007.19.4.475
The property and applicability of the organic-inorganic synthesized penetrating and reinforcing agent, which is developed in order to improve durability of concrete structures and prevent deterioration that may occur as service years increased, are researched with experimental works. TEOS (tetra-ethoxyorthosilicate) and acrylate monomer are synthesized by the solution polycondensation method in order to formulate silicate with sol-gel process and improve durability of concrete. Additional substances such as isobutyl-orthosilicate is supplemented in order to improve the performance of the agent. After the developed organic-inorganic penetrating reinforcing agent penetrates, a flexible impact alleviating layer is formed with organic monomers as well as the agent strengthens concrete by filling up the internal pore of concrete with stable compounds after penetration. Penetrating and reinforcing agent can be applied as an effective life management method because it makes concrete more durable against the aging factors, such as chloride ion, carbonation, freezing-thawing, and compound aging.
An Experimental Study on Thermal Prestressing Method for Strengthening Concrete Bridge
Ahn, Jin-Hee ; Kim, Jun-Hwan ; Choi, Kyu-Tae ; Kim, Sang-Hyo ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 483~490
DOI : 10.4334/JKCI.2007.19.4.483
Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for concrete bridges. However, the external post-tensioning method has some disadvantages such as stress concentration at anchorages and inefficient load carrying capability regarding live loads. Thermal prestressing method is a newly proposed method for strengthening and rehabilitation of concrete girder bridges. Founded on a simple concept of thermal expansion and contraction of steel, the method is a hybrid method of external post-tensioning and steel plate bonding, combining the merits of two methods. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect is substantiated and the FEM approach for its analysis is verified.
Development of Performance-Based Seismic Design of RC Column Using FRP Jacket by Displacement Coefficient Method
Cho, Chang-Geun ; Ha, Gee-Joo ; Bae, Su-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 491~497
DOI : 10.4334/JKCI.2007.19.4.491
In the current research, the scheme of displacement-based seismic design for seismic retrofit of concrete structures using FRP composite materials has been proposed. An algorithm of the nonlinear flexural analysis of FRP composite concrete members has been presented under multiaxial constitutive laws of concrete and composite materials. An algorithm for performance-based seismic retrofit design of reinforced concrete columns with FRP jacket has been newly introduced to modify the displacement coefficient method used in reinforced concrete structures. From applications of retrofit design, the method are easy to apply in the practice of retrofit design and give practical prediction of nonlinear seismic performance evaluation of retrofitted structures.
A Study on the Characteristic of Capillary Pore and Chloride Diffusivity by Electrical Difference of High-Strength Concrete Using Metakaolin
Kim, Nam-Wook ; Yeo, Dong-Goo ; Song, Jun-Ho ; Bae, Ju-Seong ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 499~506
DOI : 10.4334/JKCI.2007.19.4.499
According to the high demand of concrete structures with high performance, various studies have examined on the high performance concrete, especially high strength concrete. Various admixtures are required to produce high strength concrete and silica fume has been the most popular admixture. Recently, however, metakaolin, which is similar to silica fume in properties but cheaper, has been introduced to high strength concrete. In this study, high-strength concrete using metakaolin were studied of capillary pore structure by mercury intrusion porosimetry technique and the accelerated chloride diffusivity by electrical difference. In result, it was found that the pore structure improved and compressive strength increased and chloride diffusivity reduced as more metakaolin content was added. In addition, a regression analysis of
pore volume and both compression strength and chloride diffusivity revealed that each these had a high correlation of about 0.76 and 0.68.
Seismic Response of Apartment Building with Base Isolation System Consisting of Sliding-type Bearing and Lend Rubber Bearing
Chun, Young-Soo ; Yoon, Young-Ho ; Whang, Ki-Tea ; Chang, Kug-Kwan ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 507~514
DOI : 10.4334/JKCI.2007.19.4.507
This paper summarizes the results of a research on the isolate effects and economical efficiencies of seismic isolation design compared with the existing earthquake-resistant design, and presents seismic performance of the base isolation system consisting of sliding-type bearing and lead rubber bearing (LRB) compared with that consisting of the LRB only. From the results of the research, it is verified that seismic isolation is very effective to mitigate the influence of earthquake on structures and it is possible to increase the serviceability due to decrease of the floor acceleration. Also, from the point of view of reduction of story acceleration and base shear, the base isolation system consisting of sliding-type bearing and LRB is more effective than that with LRB only. In respect of economical efficiency, special care should be taken in using this method since costs which have to be paid in proportin to increased performance are high.
Influence of Column Aspect Ratio on the Hysteretic Behavior of Slab-Column Connection
Choi, Myung-Shin ; Cho, In-Jung ; Ahn, Jong-Mun ; Shin, Sung-Woo ;
Journal of the Korea Concrete Institute, volume 19, issue 4, 2007, Pages 515~525
DOI : 10.4334/JKCI.2007.19.4.515
In this investigation, results of laboratory tests on four reinforced concrete flat plate interior connections with elongated rectangular column support which has been used widely in tall residential buildings are presented. The purpose of this study is to evaluate an effect of column aspect ratio (
=side length ratio of column section in the direction of lateral loading
to the direction of perpendicular to
) on the hysteretic behavior under earthquake type loading. The aspect ratio of column section was taken as
and the column perimeter was held constant at 1200mm in order to achieve nominal vertical shear strength
uniformly. Other design parameters such as flexural reinforcement ratio
of the slab and concrete strength
was kept constant as
, respectively. Gravity shear load
was applied by 30 percent of nominal vertical shear strength
of the specimen. Experimental observations on punching failure pattern, peak lateral-load and story drift ratio at punching failure, stiffness degradation and energy dissipation in the hysteresis loop, and steel and concrete strain distributions near the column support were examined and discussed in accordance with different column aspect ratio. Eccentric shear stress model of ACI 318-05 was evaluated with experimental results. A fraction of transferring moment by shear and flexure in the design code was analyzed based on the test results.