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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
Selecting the target year
Influence of Openings on the Structural Behavior of Shear Walls with Slabs
Choi, Youn-Cheul ; Choi, Hyun-Ki ; Choi, Chang-Sik ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 3~11
DOI : 10.4334/JKCI.2008.20.1.003
An experimental investigation was conducted with half-scale representations of the reinforced concrete shear walls with the opening subjected to cyclic loads. Specimens were half scale representations of a one-story wall in the apartment built in 1980. The area ratio of the opening section, as well as the size and critical section of coupling slabs, were decided based on results from a previous researches. The test result of WS-0.23 specimen, which has artificial damages to install the opening, the strength of the wall decreased due to the opening. It is apparent that influence of cutting reinforcing bars and decrease of effective section area lead to early first yield of the reinforcing bars before the allowable limit of drift ratio of the shear walls was reached. Therefore, proper reinforcing method is needed to prevent this. The decrease of strength of the shear walls by installation of openings shows a great deal of difference compared to previous researches. This is because flexural capacity of the slabs is working as coupling elements for the shear walls. The critical section of coupling slabs that works as coupling elements for shear walls was a little different from the results of previous researches.
Development of Deterioration Prediction Model and Reliability Model for the Cyclic Freeze-Thaw of Concrete Structures
Cho, Tae-Jun ; Kim, Lee-Hyeon ; Cho, Hyo-Nam ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 13~22
DOI : 10.4334/JKCI.2008.20.1.013
The initiation and growth processes of cyclic ice body in porous systems are affected by the thermo-physical and mass transport properties, as well as gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and the deterioration by the accumulated damages are hard to identify in tests. In order to predict the accumulated damages by cyclic freeze-thaw, a regression analysis by the response surface method (RSM) is used. The important parameters for cyclic freeze-thawdeterioration of concrete structures, such as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing, are used to compose the limit state function. The regression equation fitted to the important deterioration criteria, such as accumulated plastic deformation, relative dynamic modulus, or equivalent plastic deformations, were used as the probabilistic evaluations of performance for the degraded structural resistance. The predicted results of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw show very good agreements with the experimental results. The RSM result can be used to predict the probability of occurrence for designer specified critical values. Therefore, it is possible to evaluate the life cycle management of concrete structures considering the accumulated damages due to the cyclic freeze-thaw using the proposed prediction method.
An Experimental Verification of the Moment Redistribution in Continuous Reinforced Concrete Members Depending on Bond Condition of Reinforcement
Yoon, Hyeong-Jae ; Lee, Seung-Bae ; Kim, Sang-Sik ; Kim, Kang-Su ; Jang, Su-Yuon ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 23~33
DOI : 10.4334/JKCI.2008.20.1.023
The moment redistribution in continuous reinforced concrete beams is very feasible phenomenon, by which the efficiency and the economy in designing reinforced concrete members can be enhanced. However, to understand the structural behavior by moment redistribution phenomenon, it is desirable to verify its mechanism experimentally considering tension stiffening effect, the relationship of moment redistribution and beam deflection, crack pattern, and effective stiffness. Six reinforced concrete continuous beam specimens were fabricated, and each specimen had a dimension of 250 mm
350 mm and 7,000 mm long. The location of de-bonding was taken as the primary test parameter to investigate tension stiffening effect. The moment redistribution ratio of the specimens was different depending on the position of de-bonding, and in particular no moment redistribution was observed when de-bonding exist at both ends, the maximum negative moment region and the maximum positive moment region.
Design of Flat Plate Systems Using the Modified Equivalent Frame Method
Park, Young-Mi ; Oh, Seung-Yong ; Han, Sang-Whan ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 35~41
DOI : 10.4334/JKCI.2008.20.1.035
In general, flat plate systems have been used as a gravity load resisting system (GLRS) in building. Thus, this system should be constructed with lateral force resisting system (LFRS) such as shear walls and brace frames. GLRS should retain the ability to undergo the lateral drift associated with the LFRS without loss of gravity load carrying capacity. And flat plate system can be designed LFRS as ordinary moment frame with the special details. Thus, flat plate system designed as GLRS or LFRS should be considered internal forces (e.g., unbalanced moments) and lateral deformation generated in vicinity of slab joints render the system more susceptible to punching shear. ACI 318 (2005) allows the direct design method, equivalent frame method under gravity loads and allows the finite-element models, effective beam width models, and equivalent frame models under lateral loads. These analysis methods can produce widely different result, and each has advantage and disadvantages. Thus, it is sometimes difficult for a designer to select an appropriate analysis method and interpret the results for design purposes. This study is to help designer selecting analysis method for flat plate system and to verify practicality of the modified equivalent frame method under lateral loads. This study compared internal force and drift obtained from frame methods with those obtained from finite element method under gravity and lateral loads. For this purposes, 7 story building is considered. Also, the accuracy of these models is verified by comparing analysis results using frame methods with published experimental results of NRC slab.
The Time Dependent Deflection Characteristics and Evaluation of Reinforced Recycled Aggregate Concrete Beams
Ji, Sang-Kyu ; Yun, Hyun-Do ; Kim, Sun-Woo ; Lee, Eon-Young ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 43~50
DOI : 10.4334/JKCI.2008.20.1.043
This paper presents experimental and analytical results on the long-term behavior of the reinforced recycled aggregate concrete beams under sustained loading. In this experimental program, three beams with different conditions of aggregates replacement (natural aggregate 100%, recycled coarse aggregate 100%, recycled fine aggregate 50%) were subjected to the sustained flexural loading that was a half of the nominal flexural capacity over a period of 1 year. The beam were designed with net span of 2,000 mm and rectangular cross-section of 170 mm width and 170 mm effective depth. The beams were instrumented and monitored to observe the change in the long-term behavior due to creep and shrinkage of concrete under sustained loading. The predictions of long-term deflection by ACI code, Branson, Mayer, Neville, EMM and AEMM were compared with the experimental results. From the experimental results, the reinforced concrete beams with recycled aggregates showed the same performance as that of a beam with natural aggregate. The proposed method to predict the long-term deflections of reinforced recycled aggregate concrete beams gives a good estimation for experimental results.
Rapid Seismic Vulnerability Assessment Method for Generic Structures
Jeong, Seong-Hoon ; Choi, Sung-Mo ; Kim, Kang-Su ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 51~58
DOI : 10.4334/JKCI.2008.20.1.051
Analytical probabilistic vulnerability analysis requires extensive computing effort as a result of the randomness in both input motion and response characteristics. In this study, a new methodology whereby a set of vulnerability curves are derived based on the fundamental response quantities of stiffness, strength and ductility is presented. A response database of coefficients describing lognormal vulnerability relationships is constructed by employing aclosed-form solution for a generalized single-degree-of-freedom system. Once the three fundamental quantities of a wide range of structural systems are defined, the vulnerability curves for various limit states can be derived without recourse to further simulation. Examples of application are given and demonstrate the extreme efficiency of the proposed approach in deriving vulnerability relationships.
A Study on Fracture Behavior for FRP Composite Girder Filled with Concrete
Kwak, Kae-Hwan ; Chung, Sang-Mo ; Sung, Bai-Kyung ; Jang, Hwa-Sup ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 59~66
DOI : 10.4334/JKCI.2008.20.1.059
This study is about manufacturing and producing girder, which is an essential component of bridge structure, in a composite of FRP + concrete. This has a higher competitive power in price than steel girder. The girder used in this study is made of glass fiber which has a lower elastic modulus than steel and thus has some technical limitations such as excessive deflection compared to steel girder and lack of production facilities in FRP production companies to make a large-section component material. Thus, this study suggested a section of a new module that will allow for applying a large section in order to solve the technical difficulties mentioned above and to secure low stiffness of FRP, developed a new FRP+concrete composite girder that is filled with the appropriate amount of concrete. To identify the structural behavior of this FRP+concrete composite girder, experiments were conducted to measure its flexural strength according to the difference in the strength of confined concrete and the existence of stud. The results of the flexural strength test confirmed the composite effect from confining concrete and the effect of increase in strength proportional to the strength of concrete. In developing FRP+concrete composite girder, NDT study was also conducted to analyze the interface characteristics of concrete and FRP.
Rheology Control of Cement Paste for Applying ECC Produced with Slag Particles to Self-Consolidating and Shotcreting Process
Park, Seung-Bum ; Kim, Jeong-Su ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 67~75
DOI : 10.4334/JKCI.2008.20.1.067
An engineered cementitious composite produced with slag particles (Slag-ECC) had been developed based on micromechanical principle. Base grain ingredients were properly selected, and then the mixture proportion was optimized to be capable of achieving robust tensile ductility in the hardened state. The rheological design is performed in the present study by optimizing the amount of admixtures suitable for self-consolidating casting and shotcreting process in the fresh state. A special focus is placed on the rheological control which is directly applicable to the construction in field, using prepackaged product with all pulverized ingredients. To control the rheological properties of the composite, which possesses different fluid properties to facilitate two types of processing (i.e., self-consolidating and shotcreting processing), the viscosity change of the cement paste suspensions over time was initially investigated, and then the proper dosage of the admixtures in the cement paste was selected. The two types of mixture proportion were then optimized by self-consolidating & shotcreting tests. A series of self-consolidating and shotcreting tests demonstrated excellent self-consolidation property and sprayability of the Slag-ECC. The rheological properties altered through this approach were revealed to be effective in obtaining Slag-ECC hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension, allowing the readily achievement of the desired function of the fresh Slag-ECC. These ductile composites with self-consolidating and shotcreting processing can be broadly utilized for a variety of applications, e.g., in strengthening seismic resistant structures with congested reinforcements, or in repairing deteriorated infrastructures by shotcreting process.
Durability Prediction for Concrete Structures Exposed to Chloride Attack Using a Bayesian Approach
Jung, Hyun-Jun ; Zi, Goang-Seup ; Kong, Jung-Sik ; Kang, Jin-Gu ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 77~88
DOI : 10.4334/JKCI.2008.20.1.077
This paper provides a new approach for predicting the corrosion resistivity of reinforced concrete structures exposed to chloride attack. In this method, the prediction can be updated successively by a Bayesian theory when additional data are available. The stochastic properties of model parameters are explicitly taken into account into the model. To simplify the procedure of the model, the probability of the durability limit is determined from the samples obtained from the Latin hypercube sampling technique. The new method may be very useful in designing important concrete structures and help to predict the remaining service life of existing concrete structures which have been monitored.
Fundamental Study of Fire-Proof Characteristics of High Strength Concrete Using Meta-Kaolin and Waste Tire Chip
Lee, Mun-Hwan ; Lee, Sea-Hyun ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 89~97
DOI : 10.4334/JKCI.2008.20.1.089
By replacing the meta-kaolin with cement and the waste tire chip with fine aggregate separately, the high strength concrete is protected from the spalling in fire and the method to constrain the temperature increase of steel bar within the concrete and the basic properties of the high strength concrete mixed with the material are reviewed. As the result, meta-kaolin increases the self fire proof characteristics of the concrete, the waste tire chip can share the internal expanding pressure so it can be deleted. In detail, using the meta-kaolin about the cement in 4
8% of weight ratio about the cement and the waste tire chip under the grade scope of 0.6
3 mm in 5
10% of weight ratio about the sand is very effective to prevent the spalling.
Predicting Actual Strength of Shear Reinforcement Using Effective Stirrup Concept
Kwon, Ki-Yeon ; Yang, Jun-Mo ; Lee, Joo-Ha ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 99~107
DOI : 10.4334/JKCI.2008.20.1.099
This paper presents the prediction of the actual strength of shear reinforcement on the basis of the concept of effective stirrups. The prediction method incorporating the shear cracking angle was proposed with the estimation by the Modified Compression Field Theory (MCFT). To check the validity of the method, discussion of the current ACI 318-05 and comparison of 39 test results from the literature including author's retrospective test data were made. The influencing factors of compressive concrete strength and type of shear-reinforcement were also investigated. Furthermore, two full-scale beam specimens shear-reinforced with headed bars were tested to demonstrate the applicability of the proposed method.
A Study on Influences of Waterproofing Admixtures for Concrete on Self-Healing Properties of Hardened Cement Paste
Kim, Jae-Young ; Byun, Seung-Ho ; Ma, Sang-Jun ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 109~116
DOI : 10.4334/JKCI.2008.20.1.109
This study was performed to get information of self-healing mechanism in cement system and the influence of waterproofing admixtures for concrete on self-healing property. For testing, cement paste specimens cured for 7, 14 and 28 days were prepared and crushed into plate-shape pieces. Screened specimens with thickness not more than 1mm were covered with wet rags and cured in a plastic container for 7 and 28 days. After stopping hydration process of the specimens by treatment with acetone, the surfaces of specimens have been contacted with wet rags were analyzed by XRD, DSC, SEM and EDX. The analysis results showed that cement paste has self-healing property and this property is mainly affected by water. Self-healing in cement system is more effective and faster at an early stage of hydration as there is enough content of unreacted cement to make an additional hydration in this period. The results of this study also showed that waterproofing admixtures for concrete have a considerable effect on self-healing of cement pastes; i.e., they improved self-healing effect of cement and, especially, the specimen using admixture C has shown a lot of needle-like or fibrous hydration products which are estimated as ettringite. It is supposed that these ettringite products are effective to enhance self-healing in cement system.
An Experimental Study on the Flexural Behavior of Deck Plates with Metal Lath and Mortar
Kim, Sung-Bae ; Kim, Sung-Jin ; Seo, Dong-Min ; Kim, Sang-Seup ;
Journal of the Korea Concrete Institute, volume 20, issue 1, 2008, Pages 117~125
DOI : 10.4334/JKCI.2008.20.1.117
In the domestic construction industry field nowadays, the usage of deck plates is currently increasing due to the lack of construction workers and the rised in construction cost. However, using deck plates manufactured by thin zinc galvanization in underground structures is criticised because it can lead to increase in maintenance cost caused by rust generation and water leakage. As a solution for this particular problem, deck plates created by Lath and Mortar instead of zinc galvanized steel sheets were developed. This paper deals with the experimental study on flexural behavior of deck plate using metal lath and mortar. Seventeen fullscale specimens were constructed and tested with different type of truss, the diameter of the top and bottom bar, and the thickness of slab. Tests results show that LAMO deck displayed equal performance such as zinc galvanized steel sheets.