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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
Selecting the target year
Development for Penetrative Performance Improving Agent to In Prevent Deterioration of Concrete Structures
Ryu Gum-Sung ; Koh Kyoung-Taek ; Kim Sung-Wook ; Kim Do-Gyeum ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 489~498
DOI : 10.4334/JKCI.2005.17.4.489
Recently, the deterioration of concrete structures have been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the deterioration of concretes have been taken. Among them, it has been often used that surface treatment which cut off the deterioration factors of durability by protecting the surface of concrete. The water proof and repair materials for concrete mainly use organic materials such as epoxy, these materials excel in intial bonding force and resistance to chemical agents. But they cause difference in the modulus of elasticity and the rate of shrinkage and expansion of concrete, and thus result in such problems as scaling and spatting in the progress of time. Therefore in this study it develop the performance Improving agent of concrete surface that can block a deterioration cause such as
gas, chloride ion and water from the outside and enhance waterproofing ability by reinforcing the concrete surface when applying it to concrete structures.
Strength Characteristics on Sulfuric Acid Corrosion of Recycled PET Polymer Concrete with Different Fillers
Jo Byung-Wan ; Shin Kyung-Chul ; Park Seung-Kook ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 499~504
DOI : 10.4334/JKCI.2005.17.4.499
Polymer concrete shows excellent mechanical properties and chemical resistance compared with conventional normal cement concrete. The polymer concrete Is drawing a strong interest as high-performance materials in the construction industry Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. Also the recycling of PET in polymer concrete would help solve some of the solid waste problems Posed by plastics and save energy. An objective of this paper is to estimate the damage of sulfuric acid, through investigating recycled PET polymer concrete, immersed at sulfuric acid solution for 84 days. As a result of testing, recycled PET PC, used
as filler, makes a problem of appearance and strength if they are exposed for long term at corrosion environment. On the other hand, recycled PET PC, used fly-ash as filler, had less effect on decrease in weight and strength. Recycled PET PC is excellent chemical resistance, resulting in the role of unsaturated polyester resin which consists of polymer chain structure accomplishes bond of aggregates and filler strongly. Also, recycled PET PC, used fly-ash as filler, is stronger resistance of sulfuric acid corrosion than
, because it is composed of
and very strong glassy crystal structure. Therefore, recycled PET PC, used fly-ash as filler, is available under corrosion circumstances like sewer pipe or waste disposal plant.
Seismic Behavior of High-Strength Reinforced Concrete Bridge Columns
Hwang Sun-Kyoung ; Lee Chin-Ok ; Ryu Hyo-Jin ; Yun Hyun-Do ; Lim Byung-Hoon ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 505~511
DOI : 10.4334/JKCI.2005.17.4.505
This experimental investigation was conducted to examine the seismic performance of reinforced concrete bridge columns. The columns were subjected to a constant axial load and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research were the volumetric ratios of transverse reinforcement (ps=0.96, 1.44 percent) and axial load ratios (P/Po=0.05, 0.1, 0.2) and concrete strengths (35, 60MPa). Test results showed that bridge columns with
higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behavior. For bridge columns with axial load ratio(P/Po) less than 0.2, the ratio of
, nominal moment capacity predicted by ACI 318-02 provisions, was consistently greater than 1 with approximately a
margin of safety.
Effect of Bond Action of Longitudinal Bars on Shear Transfer Mechanism in RC Beams
Kim Kil-Hee ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 513~520
DOI : 10.4334/JKCI.2005.17.4.513
The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results
Axisymmetric Modeling of Dome Tendons in Nuclear Containment Building I. Theoretical Derivations
Jeon Se-Jin ; Chung Chul-Hun ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 521~526
DOI : 10.4334/JKCI.2005.17.4.521
Prestressing tendons in a nuclear containment building dome are non-axisymmetrically arranged in most cases. However, simple axisymmetric modeling of the containment has been often employed in practice to estimate structural behavior for the axisymmetric loadings such as an internal pressure. In this case, the axisymmetric approximation is required for the actual tendon arrangements in the dome. Some procedures are proposed that can implement the actual 3-dimensional tendon stiffness and prestressing effect into the axisymmetric model. Prestressing tendons, which are arranged in 3 or 2-ways depending on a containment type, are converted into an equivalent layer to consider the stiffness contribution in meridional and hoop directions. In order to reflect the prestressing effect, equivalent load method and initial stress method are devised and the corresponding loads or stresses are derived in terms of the axisymmetric model. In a companion paper, the proposed schemes are applied into CANDU and KSNP(Korean Standard Nuclear Power Plant) type containments and are verified through some numerical examples comparing the analysis results with those of the actual 3-dimensional model.
Axisymmetric Modeling of Dome Tendons in Nuclear Containment Building II. Verification through Numerical Examples
Jeon Se-Jin ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 527~533
DOI : 10.4334/JKCI.2005.17.4.527
Axisymmetric modeling of the nuclear containment building has been often employed in practice to estimate structural behavior for the axisymmetric loadings, where the axisymmetric approximation is required for the actual non-axisymmetric tendon arrangements in the dome. In the preceding companion paper, some procedures are proposed for the domestic CANDU and KSNP type containments that can implement the actual 3-dimensional tendon stiffness and prestressing effect into the axisymmetric model. In this paper, the proposed schemes are verified through some numerical examples comparing the results of the actual 3-dimensional model with those of some axisymmetric models. The results of the proposed axisymmetric analyses show relatively good agreements with the actual structural behavior especially for the CANDU type. Also, it is shown that proper level of the prestressing in a hoop direction plays an important role to predict the actual prestressing effect in the axisymmetric dome modeling. Finally, correction factors are discussed that can revise some approximations introduced in the derivations.
Stress Distribution in Construction Joint of Prestressed Concrete Bridge Members with Tendon Couplers
Park Ki-Choul ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 535~542
DOI : 10.4334/JKCI.2005.17.4.535
Two series of experiments on the performance of beam-column joints in High-Strength Reinforced concrete frames were carried out. Main experimental parameters were : concrete strength, column axial load and amount of joint hoop reinforcement. Test result showed that the ultimate shear strength of exterior joints increased of column axial compressive force and the amount of the joint hoop reinforcements. Through the regression analysis on the 24data, the following equation is obtained
Flexural and Workable Properties of High Performance Hybrid Fiber Reinforced Concrete
Park Choon-Keun ; Noh Myung-Hyun ; Park Tae-Hyo ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 543~550
DOI : 10.4334/JKCI.2005.17.4.543
In the present work, modulus of rupture (MOR), flexural toughness properties
and workability (slump) of high performance hybrid fiber reinforced concrete (HPHFRC) mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber), and replaced with a fine mineral admixture such as silica fume (SF) are characterized through the analysis of variance (ANOVA). Data of MOR,
and slump are used as the characteristic values to estimate flexural performance and workable property of HPHFRC. Specially, an experimental design was Planned according to the fractional orthogoanl nay method to reduce experimental number of times. The experimental results show that steel fiber is a considerable significant factor in MOR and I30
. Based on the significance of experimental factors about each characteristic factors, the following evaluation can be used: Experiment factors which reduce slump most remarkably are carbon fiber, steel fiber, silica fume order.; Those that improve MOR most significantly are silica fume
, steel fiber order; Those that increase flexural toughness most distinctly are silica fume, carbon fiber, steel fiber order. It is obtained that the combination of steel fiber
, carbon fiber
and silica fume
is the experimental condition that improve MOR and flexural toughness excellently with workability ensured within the experiment.
Determination of Convection Heat Transfer Coefficient Considering Curing Condition, Ambient Temperature and Boiling Effect
Choi Myoung-Sung ; Kim Yun-Yong ; Woo Sang-Kyun ; Kim Jin-Keun ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 551~558
DOI : 10.4334/JKCI.2005.17.4.551
The setting and hardening of concrete is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the crack evolution. As a result, in order to predict the exact temperature history in concrete structures it is required to examine thermal properties of concrete. In this study, the convection heat transfer coefficient which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind, curing condition and ambient temperature. At initial stage, the convection heat transfer coefficient is overestimated by the evaporation quantity. So it is essential to modify the thermal equilibrium considered with the boiling effect. From experimental results, the convection heat transfer coefficient was calculated using equations of thermal equilibrium. Finally, the prediction model for equivalent convection heat transfer coefficient including effects of velocity of wind, curing condition, ambient temperature and boiling effects was theoretically proposed. The convection heat transfer coefficient in the proposed model increases with velocity of wind, and its dependance on wind velocity is varied with curing condition. This tendency is due to a combined heat transfer system of conduction through form and convection to air. From comparison with experimental results, the convection heat transfer coefficient by this model was well agreed with those by experimental results.
Optimum Mix Design of High-Performance Concrete for Bridge Deck Overlay by Statistical Method
Won Jong-Pil ; Seo Jung-Min ; Lee Chang-Soo ; Park Hae-Kyun ; Lee Myeong-Sub ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 559~567
DOI : 10.4334/JKCI.2005.17.4.559
The objective of this study is to optimize the use of mineral admixtures (silica fume, fly ash, and blast furnace slag) in high-performance concrete for bridge deck overlay. For this purpose, high-performance concrete, incorporating mineral admixtures, was tested for compressive strength and permeability. The Box Behnken design was used to determine the optimum mix proportions of the mineral admixtures. The optimized mix compositions were then technically evaluated. Test results are compare with the performance specification for high performance concrete overlay on bridge deck. The optimum mix proportions were shown to possess acceptable properties. Also, it is possible to save the construction and materials costs result from a reduction In actual material cost and from the use of widely avaliable truck mixers instead of mobile mixers.
A Experimental Study on the Material Charateristics of Crushed Aggregate Produced in Quarry
Baek Dong-Il ; Youm Chi-Sun ; Kim Myung-Sik ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 569~579
DOI : 10.4334/JKCI.2005.17.4.569
An investigation for long-term strength characteristics of crushed sand concrete using crushed sands produced in Yang-san, Kim-hae and Jin-hae that can be assumed to respectively represent eastern, middle and western suburbs of Busan has been carried out. Concrete is composed of
of aggregates in whole volume so the effect of aggregates quality to the characteristics of concrete is very important. Since 1980s, aggregates used in concrete have already been substituted crushed stone because of the exhaustion of natural gravel and sand. Crushed sand tends to increase in using quantity because of the prohibition of sea sand picking and deterioration of river sand. Crushed sand is blended with river sand in order to investigate the quality changes and characteristics of concrete as variation of blend ratio of crushed sand (n, 50, 70, 80, 90,
). Slump and air content were measured to investigate the properties of fresh concrete. Unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, n, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased with a passage of time and they are expected to keep on increasing in long-term age as well. The experimental results of the qualifies of crushed aggregates in each producing area, were all satisfied with Korea Standard. The results of the measurement of slump exposed that slump preferably decreased as mixing rate increased till
but it increased to mixing rate
. The air content was exposed that it decreased by micro filler phenomenon according to that crushed sand b)ended ratio increased. According to the result of measuring unit weight in age of 7, 28, 60, 90, 180days, it increased in accordance with that blended ratio of crushed aggregates increases. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 50, 90, 180days, compressive strength was highest when it is
of blended ratio.
A Study on the Hydration Reaction Model of Expansive Additive of Ettringite-Gypsum Type
Park Sun Gyu ; Takahumi Noguchi ; Kim Moo-Han ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 581~586
DOI : 10.4334/JKCI.2005.17.4.581
High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.
Seismic Performance of Reinforced Concrete Shear Wall Buildings with Piloti
Kwon Young-Wung ; Kim Min-Su ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 587~594
DOI : 10.4334/JKCI.2005.17.4.587
The purpose of seismic design is to ensure the serviceability of buildings against earthquake, which might be occurred during the service life of buildings, and to minimize the loss of life by preventing their failure under strong earthquake. The lack resistance of walls resulting from a tendency toward high-rise apartment buildings with shear walls and use of piloti would lead to a concentration of inelastic behaviors in their weak story. In this study, the seismic performance of reinforced concrete shear wall buildings haying piloti was analyzed by using the evaluation techniques which was proposed by FEMA 273 and ATC-40. The results from comparison with these two techniques are summarized as follows.; The results of elastic analysis method for seismic performance evaluation show that the effect of piloti and building height decrease performance index. In case of shear wall building, the state of insufficient shear stress governs their overall performance and it becomes evident in the case of the buildings with more than 25 stories. For the buildings of piloti, the change of mass, weak story, as well as insufficient shear stress, decrease the performance index rapidly compared with the performance index of the buildings without piloti. The results, obtained from the nonlinear static analysis using capacity spectrum method, indicate that the performance Point increases for the structure having Piloti and high story. Also, deformation limits of buildings satisfy the allowable criteria at the life safety level, but the immediate occupancy level is exceeded in buildings which have more than 25 stories.
Mechanical Properties of Porous Concrete For Pavement Using Recycled Aggregate and Polymer
Park Seung-Bum ; Yoon Eui-Sik ; Seo Dae-Seuk ; Lee Jun ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 595~602
DOI : 10.4334/JKCI.2005.17.4.595
The purpose of this study is to utilize recycled concrete aggregates as permeable pavement materials. This study evaluates mechanical properties and durability of porous concrete depending on mixing rates of recycled aggregates and polyme. As a result, void ratio and permeability coefficient of porous concrete for pavement increased a little as mixing rate of recycled aggregates increased. Void ratio and permeability coefficient increased a lot as mixing rate of polymer increased. As polymer was mixed
, national regulation of permeable concrete for pavement(
and 0.01cm/sec) was met. Compressive strength and flexural strength decreased as mixing rate of recycled aggregates increased but they increased a lot as mixing rate of polymer increased. Even when recycled aggregates were mixed
polymer mixed, national regulation of pavement concrete(18MPa and 4.5MPa) was met. In addition, regarding sliding resistance, BPN increased as mixing rate of recycled aggregates increased. But BPN decreased as polymer was mixed. Compared to crushed stone aggregates, abrasion resistance and freeze-thaw resistance decreased as mixing rate of recycled aggregates Increased. When polymer was mixed, abrasion resistance and freeze-thaw resistance improved remarkably. Compared to non-mixture,
mixture of polymer improved abrasion resistance and freeze-thaw resistance about
and 3.8times respectively.
A Seismatic Performance Analysis of Circular RC Bridge Piers I. Evaluation of Influence Parameters of Confinement Steel Ratio
Lee Dae-Hyoung ; Park Chang-Kyu ; Kim Hyun-Jun ; Chung Young-Soo ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 603~611
DOI : 10.4334/JKCI.2005.17.4.603
For the establishment of rational seismic design code for RC (reinforced concrete) bridge pier, this paper has analyzed the seismic code of RC bridge pier specified in )veil-known codes such as KHBDS (Korea Highway Bridge Design Specification), AASHTO Standard, ATC-32, Eurocode 8, NZS 3101, etc. So as to secure aseismic ductility of RC pier, transverse confinement steel ratios of those codes have been examined together with other design parameters such as strength of concrete and reinforcing steel, axial force ratio, aspect ratio, longitudinal steel ratio, etc. However, there has been arisen a doubt for the validity of those parameters. Thus, the objective of this study is to quantitatively evaluate the validity of design parameter of each code on the experimental seismic ductility for about 80 test specimens. It was concluded from this study that the axial force ratio is a dominant factor for the seismic displacement ductility. Therefore, it Is desirable that the axial force ratio be further taken into account in the corresponding seismic design formula of RC bridge pier in current KHBDS.
Strength of Recycled Concrete with Furnace Slag Cement under Steam Curing Condition
Lee Myung-Kue ; Kim Kwang-Seo ; Lee Keun-Ho ; Jung Sang-Hwa ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 613~620
DOI : 10.4334/JKCI.2005.17.4.613
There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of
. On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.
Flexural Analysis of RC Beam Considering Autogenous Shrinkage Model
Yoo Sung-Won ; Soh Yang-Sub ; Cho Min-Jung ; Koh Kyung-Taek ; Jung Sang-Hwa ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 621~628
DOI : 10.4334/JKCI.2005.17.4.621
Recently, it is noticed that autogenous shrinkage of high-performance concrete causes early crack in high performance concrete structures. The purpose of the present study is to derive a realistic equation to estimate the autogenous shrinkage of high performance concrete and to apply to structural analysis. For this purpose, several series of concrete specimens have been tested. When water-binder ratio is fixed to
, major test variables were the type and contents of mineral admixture. The autogenous shrinkage of HPC with fly ash slightly decreased than that of OPC concrete, but the use of blast furnace slag increased with the autogenous shrinkage. A prediction equation to estimate the autogenous shrinkage of HPC with mineral admixture was derived and proposed in this study. The proposed equation show reasonably good correlation with test data on autogenous shrinkage of HPC with mineral admixture. The finite element program developed in this study provides the useful tool for the flexural analysis including the autogenous shrinkage model. By this program, we know that the tensile stress considering the autogenous shrinkage of reinforced concrete structures increase
than that not considering.
Aggregate Gradation Effects on Cracking-Related Displacements in Concrete Pavement
Jeong Jin-Hoon ; Kim Nakseok ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 631~635
DOI : 10.4334/JKCI.2005.17.4.631
Aggregate gradation effects on cracking-related displacements of concrete are investigated in the laboratory using the German cracking frame. Concrete workability was assessed by use of the slump and drop tests for two different concrete mixtures consisting of gap-graded and dense-graded aggregates. Shrinkage strain, cracking frame strain, and concrete strain were measured and used to compare to strength gain and creep development. The measured and calculated strains of the different aggregate gradations were compared each other. Gradation effects on strength and stress development relative to tensile cracking at saw-cut tip were also investigated. Test results revealed that the gap-graded concrete has indicated larger shrinkage and creep strains than dense-grade concrete perhaps because of its higher volume concrete of cement mortars in the mixture.
Anchor Design to Prevent Debonding of Repair Mortar in Repaired Concrete Members
Choi Dong-Uk ; Lee Chin-Yong ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 637~643
DOI : 10.4334/JKCI.2005.17.4.637
Reinforced concrete beams or slabs are often strengthened or repaired using polymer modified cement concrete Stresses can develop in the structure by ambient temperature changes because thermal coefficients of the repair material and the existing concrete are typically different. Especially, shear stress often causes debonding of the interface. In this study, a rational procedure was developed where anchors can be designed in strengthened or repaired concrete members to prevent debonding at the interface. The current design procedure considers thicknesses and elastic moduli of the repair material and existing concrete, ambient temperature change, length, and beam-vs.-slab action. The procedure is also applicable to stresses developed by differential drying shrinkage.
Nonlinear Analysis of Reinforced and Prestressed Concrete Shells Using Layered Elements with Drilling DOF
Kim Tae-Hoon ; Choi Jung-Ho ; Kim Woon-Hak ; Shin Hyun Mock ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 645~654
DOI : 10.4334/JKCI.2005.17.4.645
This paper presents a nonlinear finite element procedure for the analysis of reinforced and prestressed concrete shells using the four-node quadrilateral flat shell element with drilling rotational stiffness. A layered approach is used to discretize, through the thickness, the behavior of concrete, reinforcing bars and tendons. Using the smeared-crack method, cracked concrete is treated as an orthotropic nonlinear material. The steel reinforcement and tendon are assumed to be in a uni-axial stress state and to be smeared in a layer. The constitutive models, which cover the loading, unloading, and reloading paths, and the developed finite element procedure predicts with reasonable accuracy the behavior of reinforced and prestressed concrete shells subjected to different types of loading. The proposed numerical method fur nonlinear analysis of reinforced and prestressed concrete shells is verified by comparison with reliable experimental results.
Effect of Moisture Loss on Development of Distresses in Concrete Pavements
Jeong Jin-Hoon ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 655~662
DOI : 10.4334/JKCI.2005.17.4.655
Evaporation of concrete influences the development of both initial transverse cracking and delamination in the concrete slab. It was suggested that spatting distress might develop in the slab where the initial transverse cracking occurred by theoretical equations and a field investigation. Thus, efforts to prevent the evaporation of concrete using proper curing methods are required to minimize the distresses of the slabs. Effective curing thickness (ECT) concept was used in this paper to evaluate various curing methods used to prevent the evaporation from concrete. Curing effectiveness quantified by the ECT of different types and amounts of curing compound under various curing conditions was investigated based on the results of laboratory tests. According to the test results, the wind speed is inferred to be a significant factor of the magnitude and continuance duration of the curing effectiveness.
Influence of Binder Type on the Chloride Threshold Level for Steel Corrosion in Concrete
Moon Han-Young ; Ann Ki-Yong ; Jung Ho-Seop ; Shin Dong-Gu ;
Journal of the Korea Concrete Institute, volume 17, issue 4, 2005, Pages 663~670
DOI : 10.4334/JKCI.2005.17.4.663
The present study concerns the influence of binder type on the chloride-induced corrosion being accompanied by the chloride threshold level (CTL), chloride transport and as their results the corrosion-free lift. Two levels of cement content,
GGBS concrete were employed. It was found that the most dominant factor to the CTL is the entrapped air void content at the steel-concrete interface, irrespective of the chloride binding capacity, binder type and acid neutralisation capacity of cement matrix. The CTL for lower interfacial air void contents was significantly increased up to
by weight of cement, whereas a same mix produced
for a higher level of voids. Because of a remarkable reduction in the diffusion fur GGBS concrete, its time to corrosion ranges from 255 to 1,250 days, while the corrosion-free life for control varies from 20 to 199 days sand for
PFA concrete from 200 to 331 days.