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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 18, Issue 6 - Dec 2006
Volume 18, Issue 5 - Oct 2006
Volume 18, Issue 4 - Aug 2006
Volume 18, Issue 3 - Jun 2006
Volume 18, Issue 2 - Apr 2006
Volume 18, Issue 1 - Feb 2006
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A Comparative Study on the Testing Methods for the Analysis of Tensile Strength of GERP Rebars
You, Young-Chan ; Park, Ji-Sun ; You, Young-Jun ; Park, Young-Hwan ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 303~312
DOI : 10.4334/JKCI.2006.18.3.303
The main objective of this experimental study is to examine the feasibilities of each testing method with various kinds of grip systems for the analysis of tensile strength of GFRP(glass fiber reinforced polymer) reinforcing bars. Three types of grip systems were examined such as resin-sleeved pipe-type grip proposed by CSA(Canadian Standard Association), frictional resistance type metal grip by ASTM(American Standard for Testing and Materials) and wedge-inserted cone-type grip normally used in prestressing tendons. Also, mechanical properties of GFRP rebars with different surface deformations were investigated for each different type of testing grip used in this study. All testing procedures including specimens preparation, set-up of test equipments and measuring devices were made according to the CSA S806-02 recommendations. From the test results, it was found that the highest tensile strengths of GFRP rebars were observed when tested by resin-sleeved grip system regardless of their different surface deformations. But tensile strengths of GFRP rebars by ASTM grip system are only 10% less than those by CSA grip system. On the other hand, CSA grip is not only difficult to prepare but also not disposable. Therefore, ASTM grip system is recommended as a practical alternative to estimate the tensile strength of GFRP rebars.
Flexural Behaviors of PSC Composite Girders in Positive Moment Regions
Kang, Byeong-Su ; Sung, Won-Jin ; Chang, Young-Kil ; Lee, Yong-Hak ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 313~320
DOI : 10.4334/JKCI.2006.18.3.313
Prestressed composite girder with concrete infilled steel tubes(PSC-CFT girder) is new type of bridge girder which enhances the resisting capacities due to the double composite action of PSC composite girder and concrete infilled tube. The flexural behaviors of PSC-CFT girder in the positive moment regions are investigated based on the experimental observations recently performed on two of 4.4m long specimens. The mechanical and structural roles and failure mechanism of the composite action are discussed through comparing the test results with those numerically predicted by the three methods of one- and three-dimensional nonlinear finite element analyses, and section analysis method.
Study on the Extension of Reinforced Concrete Slabs
Kim, Jin-Pyeng ; Kim, Sang-Sik ; Choi, Kwnag-Ho ; Jeon, Byong-Gap ; Lee, Jung-Yoon ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 321~330
DOI : 10.4334/JKCI.2006.18.3.321
In order to remodel old aged reinforced concrete buildings, it is often required to extend the residence area of the buildings by increasing the slab area. The slab area is usually extended by attaching a new slab to the existing slab with hinged joint or rigid joint. Transmission of the loads of the attached slabs to the existing slabs depends on the connecting methods, such as hinged or rigid connection. In this research, 8 specimens and 24 RC slabs connected by rigid joints were tested. The new slab was connected to the existing slab by three types of rigid joints using dowel bars and longitudinal tensile bars. Main parameters of the slabs were three types of the rigid joints, anchor length of steel bars(0, 50, 60, 100, and 120mm), development length of steel bars(100, 200, and 300mm), and the spacing of the steel bars(150, 200, 300, and 450mm). The test results indicated that the flexural strength of the RC test slabs having various types of rigid joints was approximately the same to that of the slab without any connections.
Influence of Curing Conditions on Volumetric Changes in Concrete
Lee, Kwang-Myong ; SunWoo, Joo-Yeun ; Lee, Hoi-Keun ; Khayat, Kamal H. ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 331~338
DOI : 10.4334/JKCI.2006.18.3.331
This paper presents the experimental results on volumetric changes in ordinary portland cement concrete made with various water-to-cement ratios(W/C's) ranging from 0.32 to 0.50 and cured in low different conditions. Curing regimes employed in this work were designed to exhibit autogenous and drying shrinkage as well as swelling of concrete. The concrete avoided any moist evaporation(Regime f showed only autogenous shrinkage and the lower the W/C, the feater the autogenous shrinkage. The concrete exposed to air drying conditions at
RH after 6-day water curing at
(Regime II) swelled and then started to shrink. The maximum swelling value of concrete developed in water curing was between 15 and
, and the greatest total shrinkage(autogenous+drying shrinkage) was obtained for the mixture made with W/C of 0.32. The concrete let to air drying conditions(Regime III) showed greater total shrinkage compared to the concrete cured in Regime II. The concrete exposed to air drying condition after 6-day sealed curing(Regime IV) exhibited slightly smaller total shrinkage than that of the concrete cured in Regime III. Net drying shrinkage that can be derived from the results of Regime I, III, and IV increased as the W/C increased despite of similar total shrinkage. This result indicated that drying shrinkage governs total shrinkage of high-W/C concretes. In other words, a portion of autogenous shrinkage in total shrinkage increased in low-W/C concretes. Therefore, it should be controlled in terms of cracking potential. Finally, total shrinkage of high-strength and high-performance concrete made with low W/C can be effectively reduced by appropriate early moisture curing.
Long-term Behavior of Reinforced Concrete Wall under Axial Loading
Kwon, Seung-Hee ; Kim, Yun-Yong ; Kim, Jin-Keun ; Park, Yon-Dong ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 339~346
DOI : 10.4334/JKCI.2006.18.3.339
The purpose of this study is to suggest a method to quantitatively predict long-term deformation of walls under an axial load concentrated to a part of the whole width. Four wall specimens were tested and three-dimensional finite element analyses were performed for these specimens. The finite element models established in this study were verified from the test results. On the basis of this verification, analysis parameters were selected considering various dimensions of walls and sectional area that a concentrated load is acting on, and finite element analyses for these parameters were carried out. The concept of the effective width coefficient was newly introduced as a method to predict the long-term behavior of walls, and a function that is able to optimally fit the effective width coefficients calculated from the analysis results for the selected parameters was found from regression analysis. The found function can be conveniently used in practice to predict the long-term behavior under loads concentrated to a local area of the whole width of walls.
Estimation of Displacement Responses Using the Wavelet Decomposition Signal
Jung, Beom-Seok ; Kim, Nam-Sik ; Kook, Seung-Kyu ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 347~354
DOI : 10.4334/JKCI.2006.18.3.347
In this paper we have attempted to bring the wavelet transform theory to the dynamic response conversion algorithm. This algorithm is proposed for the problem of estimating the displacement data by defining the transformed responses. In this algerian, the displacement response can be obtained from the measured acceleration records by integration without requiring the knowledge of the initial velocity and displacement information. The advantage of the wavelet transform over either a pure spectral or temporal decomposition of the signal is that the pertinent signals features can be characterized in the time-frequency plane. In the response conversion procedure using the wavelet decomposition signals, not only the static component can be extracted, but also the dynamic displacement component can be separated by the structural mode from the identified displacement response. The applicability of the technique is tested by an example problem using the real bridge's superstructure under several cases of moving load. If the reliability of the identified responses is ensured, it is expected that the proposed method for estimating the impact factor can be useful in the bridge's dynamic test. This method can be useful in those practical cases when the direct measurement of the displacement is difficult as in the dynamic studies of huge structure.
A Case Study for Deterioration due to Alkali-Silica Reaction in the Cement Concrete Pavement
Hong, Seung-Ho ; Han, Seung-Hwan ; Yun, Kyong-Ku ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 355~360
DOI : 10.4334/JKCI.2006.18.3.355
The Alkali-Silica Reaction(ASR) may cause a serious failure in the concrete pavements and structures. Several researches in some nations have conducted the continuous studies to prevent failure of the concrete structures by the ASR distress as well as the studies to manifest the mechanism. The researches on the ASR have not been performed affluently in Korea because the distress due to ASR has seldom been reported literarily. In this study, we tried to set up the systematic scheme practically for verifying the cause of distress due to ASR by using the visual inspections in field, the chemical method, petrographic analysis, and Electron Dispersive X-ray Spectrometer(EDX) method of Scanning Electron Microscopy(SEM) in laboratory. The chemical method, petrographic method using SEM, and X-ray method were used to verify the cause of pattern crack on the surface and internal crack in the plain concrete pavement. It can be concluded that the distress of a specific site in plain concrete pavement was mainly due to ASR. The chemical method, the petrographic method and EDX method using SEM may be the effective tools for verifying the cause of AAR distresses.
Prediction of Flexural Capacities of Steel-Fiber Reinforced Concrete Beams
Kim, Woo-Suk ; Kwak, Yoon-Keun ; Kim, Ju-Bum ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 361~370
DOI : 10.4334/JKCI.2006.18.3.361
The results of previous tests by many researchers have been compiled to evaluate the flexural strength of steel-fiber reinforced concrete beams. Existing prediction equations for flexural strength of such beams were examined, and a new equation based on mechanical and empirical observations, was proposed. In other words, the constitutive models for steel fiber reinforced concrete(SFRC) were proposed, which incorporate compressive and tensile strength. A steel model might also exhibit stain-hardening characteristics. Predictions based on the model are compared with the experimental data. For the collection of tests, a variation of the Henager equations, modified to apply to fiber-reinforced concrete beams, provided reliable estimates of flexural strength. The proposed equations accounted for the influence of fiber-volume fraction, fiber aspect ratio, concrete compressive strength and flexural steel reinforcement ratio. The proposed equations gave a good estimation for 129 flexural specimens evaluated.
A Study on the Performance Development of Sewage Concrete by Application of Antibiotics
Kim, Moo-Han ; Kim, Gyu-Yong ; Khil, Bae-Su ; Cho, Bong-Suk ; Lee, Eui-Bae ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 371~378
DOI : 10.4334/JKCI.2006.18.3.371
Recently sewage facilities mainly consisted of concrete structures are being deteriorated seriously by biodeterioration originated from sulfur-oxidizing bacteria. In this study, to prevent biochemical corrosion of the sewer concrete, antibiotics which prevent growth of sulfur-oxidizing bacteria were developed and antimicrobial performance of it was investigated. After that, to consider applicability of antibiotics to concrete, physical properties of concrete covered with antibiotics were investigated. As a results of the study, it was proved that the antimicrobial performance of antibiotics was available. Also compressive strength and bond strength of concrete didn't closely connected with antibiotics, and resistance to abrasion, water absorption, air permeability, carbonation, salt damage and chemical attack of concrete was improved remarkably by covering with it.
Shear Behavioral Model based on Shear Deformation Compatibility in Reinforced Concrete Members
Kim, Woo ; Rhee, Chang-Shin ; Jeong, Jae-Pyong ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 379~388
DOI : 10.4334/JKCI.2006.18.3.379
This paper presents a model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. Based on the relationship between shear and bending moment in beams subjected to combined shear and bending, the behavior of a beam is explicitly divided into two base components of the flexural action and the tied arch action. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. The results may confirm the rationale of the proposed behavioral model.
Strength Prediction Equations for High Strength Concrete by Schmidt Hammer Test
Kwon, Young-Wung ; Park, Song-Chul ; Kim, Min-Su ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 389~395
DOI : 10.4334/JKCI.2006.18.3.389
For the assessment of exsiting concrete structures, it is important to get the real strength of concrete. The load test or core test has many problems due to cost time, easiness, structural damage, and reliability and so on. Thus, various non-destructive test and statistical analysis techniques for strength assessment have been developed. As a result the real strength of concrete can be obtained by both direct and indirect test. In this study, a series of experimental tests of core strength and Schmidt hammer tests on 3, 7, 14, 28, 90, 180, 365, and 730 days' were done for predicting the compressive strength of high strength concrete with 65.0MPa of 28-days' strength. Each experimental results was analyzed by simple regression analysis. Then, reliability level and error rate between the proposed equations and the existing ones was examined. However, the application of the exsisting equations was inadequate to high strength concrete, because they were conducted under normal strength concrete. Therefore, the following compressive strength equations were proposed for predicting the compressive strength of high strength concrete by Schmidt hammer test. The proposed equations by Schmidt hammer test are as follows.
Drying Shrinkage of Concrete Combining Expansive Additives and Shrinkage Reducing Agent
Han, Cheon-Goo ; Han, Min-Cheol ; Song, Seung-Heon ; Yoon, Seob ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 397~404
DOI : 10.4334/JKCI.2006.18.3.397
This paper investigates experimentally the effect of combined addition of expansive additive and shrinkage reducing agent(SRA) on setting time, compressive strength and drying shrinkage of concrete. An increase of EA and SRA content leads to a reduction in flowability, which causes the increase of superplasticizer dosage, while air content increases. For setting time, in spite of increased superplasticizer dosage, with the increase of EA and SRA, setting time shortens. This is due to the presence of alkali ion by SRA and the faster formation of ettringite. At dosage of 5.0% of EA, concrete has the highest compressive strength and above that dosage, compressive strength decreased. On the contrary, the increase of SRA dosage results in a decrease in compressive strength. Combined addition of EA of 5.0% and SRA of 1.0% shows a comparable strength with control concrete. For drying shrinkage, as expected, the increase of EA and SRA dosage leads to reduction of drying shrinkage markedly. Moreover, combined addition of EA and SRA has better drying shrinkage reduction effect than individual use of EA and SRA by as much as
. Optimal combination of EA and SRA is fixed at 5.0% of EA and 0.5% of SRA based on the consideration of the effect of EA and SRA on fresh state, compressive strength and shrinkage of concrete.
Strength Prediction Model of Interior Flat-Plate Column Connections according to Design Parameters
Lee, Do-Bum ; Park, Hong-Gun ; Lee, Li-Hyung ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 405~414
DOI : 10.4334/JKCI.2006.18.3.405
In the present study, a numerical analysis was performed for interior connections of continuous flat plate to analyze the effect of design parameters such as column section shape, gravity load and slab span on the behavioral characteristics of the connections. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases and gravity load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. And as the slab span loaded with relatively large gravity load increases, the negative moment around the connection increases and therefore the strength of connection against unbalanced moment decreases. By considering the effect of design parameters on the strength of the connections, the effective shear strength to calculate the torsional moment capacity of connection was proposed and the effectiveness of the proposed shear strength was verified.
The Quality of Crushed Sand by Dry Production Process and Its Influence on Properties of Concrete
Park, Cho-Bum ; Baek, Chul-Woo ; Kim, Ho-Su ; Ryu, Deuk-Hyun ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 415~423
DOI : 10.4334/JKCI.2006.18.3.415
As the shortage of natural & good quality aggregate for concrete, it is needed development of alternative aggregate. At the present time, the crushed sand is widely used among the alternation aggregate, and the usage of crushed sand will be increased more and more. Generally, crushed sud is produced with wet process in domestic, but some manufacturing companies which are handicapped with local restrict are produced by dry process. In this study, analyzing the facilities of dry crushed sand, the quality properties of dry crushed sand was done by Korean Industrial Standards. Based on the quality results of dry crushed sand, the experiment of concrete with the dry crushed sand which is substitute for sea sand was done. As the results of basic qualities, the amount of 0.08 mm sieve passing ratio was over KS criteria, and the fineness modulus was higher than sea sand, and the other physical properties of dry crushed sand was similar to sea sand. The results of concrete experiment, according to the substitutive ratio of dry crushed sand is increased, the slump and air content of concrete was decreased by increase of fine particles of dry crushed sand, and the unit weight content, compressive & tensile strength of concrete were increased on the contrary. The physical properties of concrete used dry crushed sand were showed same tendency without relation to W/B. Consequently, if the fine particle contents of dry crushed sand was lower, it is judged that dry crushed sand is no problem to use for concrete aggregate and the amount of usage will be increased.
Horizontal Cracks in Continuously Reinforced Concrete Pavement Structures
Kim, Seong-Min ; Cho, Byoung-Hooi ; Kwon, Soon-Min ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 425~429
DOI : 10.4334/JKCI.2006.18.3.425
Horizontal cracks at the mid-depth of concrete slabs were observed at a section of the continuously reinforced concrete pavement(CRCP) structures on the Korea Highway Corporation's Test Road. To investigate the existence and the extent of horizontal cracks in the concrete slab, a number of cores were taken from the section of CRCP. To identify the causes of horizontal cracks, numerical analyses were conducted. Several variables relative to design, material, and environment were considered in the studies to evaluate possible causes of horizontal cracking. A numerical model of CRCP was developed using the finite element discretization, and the shear and normal tensile stress distributions in CRCP were investigated with the model. Numerical analysis results show that the maximum shear and normal tensile stresses develop near the depth of steel bars at transverse cracks. If those maximum stresses reach the strength of concrete, horizontal cracks occur. The maximum stresses become higher as the environmental loads, coefficient of thermal expansion of concrete, and elastic modulus of concrete increase.
A Experimental Study on the Evaluation of Deteriorated Concrete Member Exposed One Side at High Temperature
Lee, Joong-Won ; Choi, Kwang-Ho ; Hong, Kap-Pyo ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 431~438
DOI : 10.4334/JKCI.2006.18.3.431
The determination of the depth of deteriorated concrete is one of the main problems in the structural assessment of concrete structures that have been subjected to a fire. This information is particularly important in order to optimize the future operations of repair/strengthening, or in decision-making concerning a possible demolition. The purpose of this study is to propose evaluation technique of damaged depth of concrete exposed at high temperature. In order to evaluate damaged depth of core picked at member under fire, the 24 specimens have been made with variables of concrete strength(20 MPa, 40 MPa, 60 MPa) and heating exposure condition in 600 and 800 for 2 hours. Color change analysis and water absorption after heating have been measured and split tensile stress test was performed to ka the residual compressive strength against the depth of specimen. The results show that the deeper of the depth from heating face, water absorption ratio is smaller and residual stress ratio is larger and the color of heated face is changed to red color. Using this technique at damage evaluation of fired structure, We evaluate damaged depth of member under fire and determine the reasonable strengthening range.
Applicability of Hyblid FRP Reinforcing Bar for Self-diagnosis of Concrete Fracture
Park, Seok-Kyun ; Kim, Dae-Hoon ;
Journal of the Korea Concrete Institute, volume 18, issue 3, 2006, Pages 439~445
DOI : 10.4334/JKCI.2006.18.3.439
For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of hybrid FRP(having electrical property) reinforced concrete has been tested. Then after examining change in the value of electrical resistance of carbon fiber in CFRP(non-hybrid type), CFGFRP and CFAFRP(hybrid type) before and after the occurrence of cracks and fracture in non-hybrid and hybrid FRP reinforced concrete at each flexural weight-stage, the correlations of each factors(the changes in electrical resistance and load as a function of strain, deflection) were analyzed. As the results, it is clarified that when the carbon fiber tows fracture, the electrical resistance of it increase largely, and afterwards hybrid FRP composites can be resist the load due to the presence of the reinforced fiber, for example, glass fiber or aramid fiber tows. Therefore, it can be recognized that hybrid FRP(including carbon fiber) reinforcing bar could be applied for self-diagnosis of fracture in reinforced FRP concrete fracture.