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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 17, Issue 6 - Dec 2005
Volume 17, Issue 5 - Oct 2005
Volume 17, Issue 4 - Aug 2005
Volume 17, Issue 3 - Jun 2005
Volume 17, Issue 2 - Apr 2005
Volume 17, Issue 1 - Feb 2005
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An Experimental Study on the Flexural Behavior of Slab Repaired and Reinforced with Strand and Polymer Mortar
Yang Dong-Suk ; Hwang Jeong-Ho ; Park Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 171~177
DOI : 10.4334/JKCI.2005.17.2.171
Even though the cost associated with the repair and rehabilitation of existing structures are rapidly increasing, vast number of the repaired and rehabilitated structures do not function properly as expected during their remaining service lives. This paper focused on the flexural behavior of reinforced concrete slabs repaired and reinforced by PS strand and polymer mortar in the tension face. The slabs have the size of 700
2200 m and 700
1300 mm. Variables of experiment were space of strengthening, chipping, the number of strand, the kind of mortar in this experimental study. Attention is concentrated upon overall bending capacity, deflection, ductility and failure mode of repaired and reinforced slabs. Test results show that deflection of repaired and reinforced slabs reduced to approximately
comparison to standard slabs. Boundary cracking of chipping slab started ultimate load afterward. Concrete-mortar interface cracked 64.5 kN in repaired slab with AP mortar and 36.0 kN in repaired slab with general polymer mortar. Reinforcement effect increased with reducing space of strand. Also, Reinforcement effects are more by strand than by polymer mortar.
Influence of Carbonation for Chloride Diffusion in Concrete
Oh Byung-Hwan ; Lee Sung-Kyu ; Lee Myung-Kue ; Jung Sang-Hwa ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 179~189
DOI : 10.4334/JKCI.2005.17.2.179
Corrosion of steel due to chloride attack is a major concern in reinforced concrete structures which are located in the marine environments. In this case, Fick's 2nd law has been used for the prediction of chloride diffusion related with service life of concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation to chloride attack in concrete structures and to investigate the validity of Fick's law to chloride attack combined carbonation. The test results indicate that the chloride ion profiles from Fick's law using the diffusion coefficient of immersion tests is not reflected the effect of separation of chloride ions in carbonation region but valid in sound region in case of combined action. On the other hand, the chloride ion profiles from Fick's law using the diffusion coefficient of Tang and Nilsson's method coincide with test results under dry-wet condition but not under combined condition. The results of present study may Imply that the new method for the measurement of diffusion coefficient is required to predict the chloride ion profiles in case of combined action at early.
Shear Reinforcement for Flat Plate-Column Connections Using Lattice Bars
Ahn Kyung-Soo ; Park Hong-Gun ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 191~200
DOI : 10.4334/JKCI.2005.17.2.191
Flat plate-column connections are susceptible to brittle punching shear failure, which may result in collapse of the overall structure. In the present study, a new shear reinforcement for the plate-column connection, the lattice shear reinforcement was developed. Experimental study for the lattice shear reinforcement was performed. Shear strength and ductility of the specimens reinforced with the lattice bars were compared with those of unreinforced specimens. The test results showed that the strength and ductility of the specimens with the lattice shear reinforcement were improved by 1.37 and 9.16 times those of the unreinforced specimens, respectively. These results indicates that the lattice shear reinforcement is superior in ductility to the shear stud-rail which is popular in U.S. Based on the test results, the design method for the lattice shear reinforcement was developed.
Direct Inelastic Strut-Tie Model Using Secant Stiffness
Park Hong-Gun ; Kim Yun-Gon ; Eom Tae-Sung ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 201~212
DOI : 10.4334/JKCI.2005.17.2.201
A new strut-tie model using secant stiffness, Direct Inelastic Strut-Tie Model, was developed. Since basically the proposed design method uses linear analysis, it is convenient and stable in numerical analysis. At the same time, the proposed design method can accurately estimate the inelastic strength and ductility demands of struts and ties because it can analyzes the inelastic behavior of structure using iterative calculations for secant stiffness. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. Design examples using the proposed method were presented, and its advantages were highlighted by the comparison with the traditional strut-tie model. The Direct Inelastic Strut-Tie Model, as an integrated analysis/design method, can directly address the design strategy intended by the engineer to prevent development of macro-cracks and brittle failure of struts. Since the proposed model can analyze the inelastic deformation, indeterminate strut-tie model can be used. Also, since the proposed model controls the local deformations of struts and ties, it can be used as a performance-based design method for various design criteria.
An Estimate of Flexural Strength for Reinforce Concrete Beams Strengthened with CFRP Sheets
Park Jong-Sup ; Jung Woo-Tai ; You Young-Jun ; Park Young-Hwan ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 213~220
DOI : 10.4334/JKCI.2005.17.2.213
Carbon fiber reinforced polymer (CFRP) sheets are becoming increasingly popular for strengthening deteriorated concrete bridges due to their excellent strength and stiffness-to-weight ratio, corrosion resistance, and convenience of construction work. The purpose of this study is to compare the performance of CFRP-strengthened reinforced concrete (RC) beams and to develop a new design formula. Simple beams with 3 m span length were tested to investigate the effect of reinforcing steel ratio and CFRP-reinforcing ratio on the flexural behavior of strengthened RC beams. The test results were analyzed with the special emphasis on the failure mode, the maximum load, and the strain distribution in the section. It is shown that the strain of the strengthened beams is not linearly distributed in the section. A new design formula based on the non-linear distribution of the strain has been derived and showed that it has a good agreement with the various domestic and foreign test results.
Estimation of Shape of Voids behind Concrete Tunnel Linings Using Radar of Three Dipole Antenna Type
Park Seok-Kyun ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 221~227
DOI : 10.4334/JKCI.2005.17.2.221
The presence of voids behind tunnel linings is very likely to result in settlement or structural collapse. One proposed method of detecting such voids by non-destructive method is radar. More than effectively judging the existence of voids behind tunnel linings, this study aims to develop the analysis algorithm of radar capable of estimation of the shape of specific voids. To acquire directional information and estimate the shape of three-dimensional voids, the radar of three-dipole antenna type is used. As a foundation to this ongoing research, an investigation of microwave polarization methods using three-dipole antenna carried out with various void orientations and void geometries. As a result, it is clarified that the response of four microwave polarization modes depends on void geometry and thus there is a possibility of identifying the geometry and orientation (the shape) of specific voids using radar of three-dipole antenna type.
An Experimental Study on Behavior of Multi-Spliced Girder with Dry Joint
Kim Kwang-Soo ; Seo Bong-Won ; Park Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 229~236
DOI : 10.4334/JKCI.2005.17.2.229
To cope with increasing requirements of cost reduction, labor saving, and rapid construction, the purpose of this study is to investigate the structural behavior of PSC monolithic and spliced girders. Three tests were conducted on reduced-scale girder specimens having same type. This paper presents the result of experimental studies on the load-deflection behavior in which different joint and amount of tendon as major variables were investigated. The first one used a monolithic girder was arranged with three tendons. The second one used a spliced girder was joined with three tendons after producing five segments. And the third girder was produced in same conditions with the second girder and arranged with additional tendons. The experimental results show the difference of behavior between monolithic and spliced girders.
Variation of Application Period of Cold Weather Concrete in Korea
Han Min-Chul ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 237~245
DOI : 10.4334/JKCI.2005.17.2.237
In this paper, the changes of the period of cold weather concrete in Korea with the elapse of age are discussed to investigate the influence of elapse of age on period of cold weather concrete. The climate data of Korean Meteorological Administration(KMA) ranging from 1971 to 2000 was used. The period of cold weather concrete was calculated by following the specification of Korea Concrete Institute(KCI), American Concrete Institute(ACI) and Architectural Institute of Japan(AIJ), respectively. Previous research by the authors used the climate dada of KMA from 1961 to 1990 and research conducted by Kim M.H. used the climate data from 1931 to 1980 were also compared with the period of present paper. According to the results, in present paper, the period of cold weather concreting by KCI was calculated about 95days on average and the period by ACI was 101 days on average and the period by AIJI was 92days on average. For the variation of the period with the elapse of time, the period of cold weather concrete by KCI and ACI in present paper was shortened by as much as 5
6days compared with that of previous paper 10years ago. However, the period of cold weather concreting by AIJ did not exhibit a marked reduction in the period compared with that of previous paper by the author. But the period by Kim following AIJ exhibited a decrease in the period compared to the period by present paper by as much as 3days. For regional influence, the period of cold weather concreting in southern part of Korea was found to be much shorter than those at northern part. This may be due to the rising of mean temperature caused by global warming effect.
A Study on Fire-Resistant Performance of Concrete Using Nano-Silica Perticles
Jo Byung-Wan ; Park Jong-Bin ; Park Jong-Hwa ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 247~254
DOI : 10.4334/JKCI.2005.17.2.247
Recently, since the advanced nano technology develops unique physical and chemical properties different from those of the conventional materials. Normal concretes mixed with nano -
have been studied to improve the fire-resistance with high strength and lower heat conductivity. In this pilot study, the nano-particle contents in the specimens (
) were 0, 2, 4, and
by weight of cement, and fire-temperatures
were considered. The results show that as the nano-particle contents increases, the weight loss of concrete gradually decreases, and the compressive strength after fire-attack increases effectively.
Experimental Study for Fracture Characteristic of New Building Materials with Recycled Ash
Jo Byung-Wan ; Park Jong-Bin ; Keo Ja-Gab ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 255~261
DOI : 10.4334/JKCI.2005.17.2.255
Immense quantities of coal combustion by-products are produced every year, and only a small fraction of them are currently utilized. The purpose of this study is to investigate reused techniques of coal ash in the construction field, which may contribute to the savings of building materials and conservation of environment. From the results of the compressive strength test, the elastic modulus was experimentally proposed. Also, based on the three- point-bending test, the fracture parameters - notch sensitivity, fracture energy, and initial compliance were experimentally proposed. As a result, the strength and fracture characteristics were lower than those of concrete or mortar. Also, the study showed that the deflection at a fracture decreased as the age increased and as the notch depth rate decreased. However, it was judged that its use as a building material could be expected if further research is carried out.
An Experimental Study on the Mechanical Properties of HPFRCCs Reinforced with the Micro and Macro Fibers
Kim Moo-Han ; Kim Jae-Hwan ; Kim Yong-Ro ; Kim Young-Duck ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 263~271
DOI : 10.4334/JKCI.2005.17.2.263
HPFRCC(High Performance Fiber Reinforced Cementitious Composite) is a class of FRCCs(Fiber Reinforced Cementitious Composites) that exhibit multiple cracking. Multiple cracking leads to improvement in properties such as ductility, toughness, fracture energy, strain hardening, strain capacity, and deformation capacity under tension, compression, and bending. These improved properties of HPFRCCs have triggered unique and versatile structural applications, including damage reduction, damage tolerance, energy absorption, crack distribution, deformation compatibility, and delamination resistance. These mechanical properties of HPFRCCs become different from the kinds and shapes of used fiber, and it is known that the effective size of fiber in macro crack is different from that in micro crack. This paper reports an experimental findings on the mechanical properties of HPFRCCs reinforced with the micro fiber(PP50, PVA100 and PVA200) and macro fiber(PVA660, SF500). Uniaxial compressive tests and three point bending tests are carried out in order to compare with the mechanical properties of HPFRCCs reinforced with micro fibers or hybrid fibers such as compressive strength, ultimate bending stress, toughness, deformation capacity and crack pattern under bending, etc.,
Strength Characteristics of Concrete Subjected ta Vertical Continuous Vibration during Initial Curing Period
Kim Jong-Soo ; Jang Hee-Suk ; Kim Myung-Sik ; Kim Hee-Sung ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 273~297
DOI : 10.4334/JKCI.2005.17.2.273
In construction site, there are some occasions where concrete under initial curing is being affected by nitration from nearby vibration sources. To study these effects, in this paper, strength characteristics of concrete specimens subjected to continuous vibration up to 12 hours in vertical direction after concrete placement were observed. And through the vibration time control experiment where a number of time combinations consisted of times before and after applying vibration during initial curing period were used as experimental parameters, possibility of concrete strength improvement was investigated. From the experimental results, it could be seen that the concrete strengths were mostly decreased due to the increase of vibration velocity during initial curing period. But fluctuation ratio of concrete strength did not have any close correlations with the vibration times. And results of vibration time control experiment showed that if times before applying vibration sustains at least more than 3 hours, subsequent vibrations after that hours do not affect the concrete strength in any unfavorable ways.
Long-Term Behavior of Square CFT Columns under Concentric Load
Kwon Seung-Hee ; Kim Tae-Hwan ; Lee Tae-Gyu ; Kim Yun-Yong ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 281~290
DOI : 10.4334/JKCI.2005.17.2.281
This paper presents experimental and analytical studies on long-term behavior of square CFT columns under central axial loading. Two loading cases are considered; (1) the load applied only at the inner concrete of the column and (2) the load applied simultaneously on both the concrete and the steel tube. Four specimens of square CFT columns were tested under the two loading cases, and basic creep test for two concrete specimens was performed to find out the creep properties of the inner concrete. Three-dimensional finite element analysis models were established and verified with the experimental results. The verification shows that the prediction for the long-term behavior of actual square CFT columns is possible from the three dimensional finite element modeling considering the bond behavior between steel tube and inner concrete. Also, experimental results and numerical calculations revealed that the bond stress Induced by the confinement pressure as well as the slip between inner concrete and steel tube were increased with time In the first loading case. However, the confinement by the loading Plate was decreased with time while increasing confinement effect by the steel tube was observed over time. In contrast no confinement effects occur in the second loading case.
A Study on the Optimum Mix Proportion of the Mass Concrete Designed as Massive and Deep Structure
Kwon Yeong-Ho ; Lee Hwa-Jin ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 293~302
DOI : 10.4334/JKCI.2005.17.2.293
This study describes data from determination of the optimum mix proportion and site application of the mass concrete placed in bottom slab and side wall having a large depth and section as main structures of LNG in-ground tank. This concrete requires low heat hydration, excellent balance between workability and consistency because concreting work of LNG in-ground tank is usually classified by under-pumping, adaptation of longer vertical and horizontal pumping line than ordinary pumping condition. For this purpose, low heat Portland cement and lime stone powder as cementitious materials are selected and design factors including unit cement and water content, water-binder ratio, fine aggregate ratio and adiabatic temperature rising are tested in the laboratory and batch plant. As experimental results, the optimum unit cement and water content are selected under
separately to control adiabatic temperature rising below
and to improve properties of the fresh and hardened concrete. Also, considering test results of the confined water ratio(
p) and deformable coefficient(Ep),
of lime stone powder by cement weight is selected as the optimum replacement ratio. After mix proportions of 5cases are tested and compared the adiabatic temperature rising(
, r), tensile and compressive strength, modulus of elasticity, teases satisfied with the required performances are chosen as the optimum mix design proportions of the side wall and bottom slab concrete.
and r are proved smaller than those of another project. Before application in the site, properties of the fresh concrete and actual mixing time by its ampere load are checked in the batch plant. Based on the results of this study, the optimum mix proportions of the massive concrete are applied successfully to the bottom slab and side wall in LNG in-ground tank.
Evaluation on Steel Bar Corrosion Embedded in Antiwashout Underwater Concrete
Moon Han-Young ; Shin Kook-Jae ;
Journal of the Korea Concrete Institute, volume 17, issue 2, 2005, Pages 303~309
DOI : 10.4334/JKCI.2005.17.2.303
This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures. The three series of antiwashout underwater concrete were: concrete constituted exclusively with ordinary portland cement (OPC), concrete composed of ordinary portland cement mixed with fly-ash in
ratio (FA20), and concrete with ground granulated blast furnace slag mixed in
ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as
. On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout underwater concrete.