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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 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
Selecting the target year
The Estimation and Comparison of Flexural Crack Width Considering Bonding Characteristics in Reinforced Concrete Members
Ko, Won-Jun ; Min, Byung-Chul ; Park, Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 579~588
DOI : 10.4334/JKCI.2006.18.5.579
In recent years, the availability of high-strength reinforcing and prestressing steels leads us to build economically and efficiently designed concrete structural members. One of critical problems faced to the structural engineers dealing with these types of structural member is controls of crack width that is used as a criterion for the serviceability in the limit state design. Especially, flexural cracking must be controlled to secure the structural safety and to improve the durability as well as serviceability of the load carving members. The proposed method utilizes the results of pure tension test in which tensile loads are applied both side of specimen, done by Ikki. The bond characteristics of deformed reinforcing bar under pure tension is considered by the area of concrete and rib area. The results of proposed method are compared with the test data and the results show that the proposed method can take into account the dimensions, variation of sectional properties, and direction of reinforcing and gives more accurate maximum bond stress and corresponding relative slip than the existing methods. the characteristics of bonding is considered by using dimensionless slip magnitude and effective reinforcement ratio. The validity of the proposed equation is verified by test experimental data.
Properties of Chemically Activated MSWI(Municipal Solid Waste Incinerator) Mortar
Jo, Byung-Wan ; Kim, Kwang-Il ; Park, Jong-Chil ; Park, Seung-Kook ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 589~594
DOI : 10.4334/JKCI.2006.18.5.589
The recycling of industrial wastes in the concrete manufacturing is of increasing interest worldwide, due to the high environmental impact of the cement and concrete industries and to the rising demand of infrastructures, both in industrialized and developing countries. The production of municipal wastes in the South Korea is estimated at about 49,902 ton per day and only 14.5% of these are incinerated and principally disposed of in landfill. These quantities will increase considerably with the growth of municipal waste production, the progressive closing of landfill, so the disposal of municipal solid waste incinerator(MSWI) ashes has become a continuous and significant issue facing society, both environmentally and economically. MSWI ash is the residue from waste combustion processes at temperature between
. And the main components of MSWI ash are
. The aim of this study is to find a way to useful application of MSWI ash(after treatment) as a structural material and to investigates the hydraulic activity, compressive strength development composition variation of such alkali-activated MSWI ashes concrete. And it was found that early cement hydration, followed by the breakdown and dissolving of the MSWI-ashes, enhanced the formation of calcium silicate hydrates(C-S-H). The XRD and SEM-EDS results indicate that, both the hydration degree and strength development are closely connected with a curing condition and a alkali-activator. Compressive strengths with values in the 40.5 MPa were obtained after curing the activated MSWI ashes with NaOH+water glass at
Seismic Behaviour of Exterior Joints in Post-Tensioned Flat Plate Systems
Han, Sang-Whan ; Kee, Seong-Hoon ; Kang, Tomas H.K. ; Cho, Jong ; Lee, Li-Hyung ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 595~602
DOI : 10.4334/JKCI.2006.18.5.595
An experimental study was conducted to investigate seismic behaviour of post-tensioned(PT) exterior slab-column connections used for the purpose to resist gravity loads only. For these, 2/3-scale, two PT post-tensioned exterior connections with two different tendon arrangement patterns and one conventional reinforced concrete(RC) exterior connection was tested under quasi-static, uni-directional reversed cyclic loading. During the lateral testing, gravity forces transferred to the column were kept constant to closely simulate a moment to shear ratio of a real building. One of the objectives of this study was to assess the necessity and/or the quantity of bottom bonded reinforcement needed to resist moment reversal which would occur under significant inelastic deformations of the adjacent lateral force resisting systems. The ACI 318 and 352 provisions for structural integrity were applied to provide the bottom reinforcement passing through the column for the specimens. Prior test results were also collected to conduct comparative studies for some design parameters such as the tendon arrangement pattern, the effect of post-tensioning forces and the use of bottom bonded reinforcement. Consequently, the impact of tendon arrangement on the seismic performance of the PT connection, that is lateral drift capacity and ductility, dissipated energy and failure mechanism, was considerable. Moreover, test results showed that the amount of bottom reinforcement specified by ACI 352. 1R-89 was sufficient for resisting positive moments arising from moment reversal under reversed cyclic loads. Shear strength of the tested specimens was more accurately predicted by the shear strength equation(ACI 318) considering the average compressive stress over the concrete(
) due to post-tensioning forces than that without considering
An Experimental Study on Flexural Behavior of RC Beams Strengthened with Hi-Strength Bars(2)
Shin, Kyung-Jae ; Kwak, Myong-Keun ; Bae, Kyu-Woong ; Oh, Young-Suk ; Moon, Jung-Ho ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 603~610
DOI : 10.4334/JKCI.2006.18.5.603
The external unbonded strengthening offers advantages in speed and simplicity of installation over other strengthening techniques. Unlike externally bonded steel plate or carbon fiber sheet, surface preparation of the concrete for installation of high-tension bar is not required and installation is not affected by environmental conditions. Anchoring pin or anchoring plate are installed at the end of beam to connect the high-tension bar to concrete beam. The deviator are used in order that supplementary external bars would follow the curvature of the tested beam. A set often laboratory tests on reinforced concrete beam strengthened using the technique are reported. The main test parameters are the section area of strengthening bar, the depth of deviator and the number of deviators. The paper provides a general description of structural behavior of beams strengthened using the technique. The test result of strengthened beam are compared with those from a reference specimen. It is shown that the reinforcing technique can provide greater strength enhancements to unstrengthened beam and that the provision of deviator enhances efficiency. The ultimate moment of specimen with two deviators was higher than that of specimens with one deviator. It is also shown that the external bars enhance strength of beams in shear.
New Approach for Shear Capacity Prediction of High Strength Concrete Beams without Stirrups
Choi, Jeong-Seon ; Lee, Chang-Hoon ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 611~620
DOI : 10.4334/JKCI.2006.18.5.611
In the shear failure mechanism of a beam, beam and arch actions always exist simultaneously. According to the shear span to depth ratio, the proportion between these two actions is varied and the contribution of these actions to shear capacity is changed. Moreover, the current codes provide recommendations based on experimental results of normal strength concrete, so the application range of concrete strength must be extended. Based on this mechanism and new requirement, a simplified analytical equation for shear capacity prediction of reinforced high strength concrete beams without stirrups is proposed. To reflect the change in the contribution between these actions, stress variation in the longitudinal reinforcement along the span is considered by use of the Jenq and Shah Model. Dowel action with horizontal splitting failure and shear friction between cracks are also taken into account. ize effect is included to derive a more precise equation. Regression analysis is performed to determine each variable and simplify the equation. And, the formula derived from theoretical approaches is evaluated by comparison with numerous experimental data, which are in broad range of concrete strength(especially in high strength concrete), shear span to depth ratio, geometrical size and longitudinal steel ratio. It is shown that the proposed equation is more accurate and simpler than other empirical equations, so a wide range of a/d can be considered in one equation.
Experimental Studies on Shear Strength of High-Strength Lightweight Concrete Beam using the Industrial by-products
Lee, Seung-Jo ; Park, Jung-Min ; Kim, Wha-Jung ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 621~630
DOI : 10.4334/JKCI.2006.18.5.621
Twelve beams made of lightweight high-strength concrete were tested to determine their diagonal cracking and ultimate shear capacities. A total of 12 beams without(4 beams) and with lightweight(8 beams) were tested in a stiff testing facility, and complete load-midspan deflection curves, including the maximum capacities portion, were obtained. The variables in the test program were concrete strength, which varied 35.4 MPa, 65.3 MPa; shear span-depth ratios a/d=1.5, 2.5, 3.5, 4.5; and tensile steel ratio between 0.57 and 2.3 percent. Also, we divided beam by diagonal tension crack and ultimate shearing strength to propose an equation. In addition, it analyzed comparison mutually applying existing proposal and guide.
was as result that AIK recommendations and Zsutty proposal decrease more than a/d=2.5, increased some in Mathey's proposal equation.
showed tendency of overestimation according to increase of tensile steel ratio and compressive strength of concrete. On the other hand,
is superior in conformability with an experiment result Zsutty's proposal among other equations. The proposal equation hew that expect
, rationally about shearing strength. Therefore, shear strength an equation is considered to be utilized usefully evaluating capacity by change of the shear span depth ratio of lightweight concrete, tensile steel ratio, and compressive strength of the concrete in this research.
Effect of Fluorine-Silicate Hybrid Based Crack Reducing Agent on the Resistance for Shrinkage Crack and Gas Permeability of Concrete
Lee, Man-Ik ; Park, Jong-Hwa ; Nam, Jae-Hyun ; Kim, Do-Su ; Kim, Jae-On ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 631~637
DOI : 10.4334/JKCI.2006.18.5.631
In this study, fundamental properties such as fresh and hardened performance of concrete mix(specification : 25-24-18) added fluorine-silicate hybrid based crack reducing agent(FS) were measured. Addition of FS ranged from 0.5% to 2.0% at intervals 0.5% based on cement weight. Adequate dosage(0.5%) of FS derived from basic properties measurements applied and compared resistance for shrinkage crack. The permeability of concrete in the absence(24-S-0.0) and presence(24-S-0.5) of evaluated at a mock-up sized concrete. Concrete added FS improved resistance for shrinkage crack and consequently crack number, length and area decreased to
compared non-added. As well, by the addition of FS, the resistance for permeability and penetration depth to concrete surface region increased 67% and 40%, respectively. Therefore it was confirmed that shrinkage crack resistance and permeability of concrete could be improved by the addition of FS.
Modeling of Shear Mechanism of RC Deep Beams Incorporating Bond Action between Re-Bar and Concrete
Kim, Kil-Hee ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 639~648
DOI : 10.4334/JKCI.2006.18.5.639
A shear experiment of one-way monotonic loading was carried out with the shear span ratio as the main experimental variable for reinforced concrete beam. Using the finite element analysis as the experimental analysis tool and the analysis method to compute the shear resistance of small shear span ratio, a new macro-model composed of crooked main strut and sub strut is proposed in consideration of the effect of bond action between re-bar and concrete based on the experimental result. The experimental finding affirmed the validity of the proposed macro-model when the shear span ratio was at or below 0.75 and confirmed that the experimental result was the most consistent with the computed analysis result when the effective factor of concrete compressive strength was set at 0.75.
Application of Powdered Superplasticizer to Improve of Slump Loss Rate in Recycled Aggregate Concrete
Yang, Keun-Hyeok ; Sim, Jae-Il ; Lee, Jae-Sam ; Chung, Heon-Soo ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 649~656
DOI : 10.4334/JKCI.2006.18.5.649
In this study, powered superplasticizer(PSP) agents to improve the slump loss rate of recycled aggregate concrete were developed. To evaluate the variation of fluidity against elapsed time and the mechanical properties, twenty four specimens whose main variables had the mixing condition of aggregates, such as natural and recycled gravels, and natural and recycled fine aggregates, were tested. The concrete slump with a liquid superplasticizer greatly decreased against the elapsed time and dropped by less than 50% of initial slump after two hours. However the concrete slump with the PSP agents hardly varied until after half an hour and maintained more than 85% of initial slump even after an hour. Also the PSP agents made the compressive, splitting tensile, and flexural strength of concrete increased and the shrinkage strain decreased. Considering the properties improvement of concrete, it can be recommended that optimum mixing amount of the PSP agents should be 5% of the amount of cement.
Evaluation on the Behaviors of Precast Concrete Beam-Column Connections for Apartments
Song, Hyung-Soo ; Yu, Sung-Yong ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 657~666
DOI : 10.4334/JKCI.2006.18.5.657
The precast concrete beam-column connectors to retrofit an apartment building were investigated experimentally. Five precast concrete beam-column connectors were considered to develop a modified model which was adapted to domestic construction conditions from the DDC(dywidag ductile connection) of Germany. Special H-shape steel hardware was used to decrease the width of column and beams for the construction of external frames in apartments. It was found that the DDC had high joint strength and ductility, however failed in inclined shear crackings in the columns. The modified one showed better behaviors in tests because they did not show critical column crackings at failure. The test result of modified one with grouting was compared to that of the one without grouting within the duct. The one with grouting showed higher strength and ductility in failure than that without grouting.
Properties of Polymer Cement Mortars under Combined Cures
Jo, Young-Kug ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 667~675
DOI : 10.4334/JKCI.2006.18.5.667
Concrete is much more easily damaged by various parameters than by the only one and performance reducing mechanism grows more complicated in that condition. In addition, the factors which really act in concrete structure tend to be activated in turn and the degradation of concrete is very rapidly progressed. The purpose of this study is to evaluate the properties of polymer cement mortars under combined cures. The polymer cement mortars are prepared with various polymer types, polymer-cement ratios and cement-fine aggregate ratio, and tested for compressive and flexural strengths, accelerated carbonation, chloride ion penetration and acid resistance test, and freezing-thawing test. The properties of polymer cement mortars under combined cures is discussed. From the test results, polymer cement mortars have superior strengths compared with plain cement mortar under combined cures. The strengths of polymer cement mortars are markedly increased at curing condition II and V, however strengths are not improved at curing condition I and IV irregardless of polymer types. The carbonation and chloride ion penetration depths of polymer cement mortars tend to decrease in curing conditions, III-C, IV-B, V-A order, and decrease with increasing polymer cement ratios. It is concluded that polymer cement ratio of 10 to 15% are considered optimum for the preparation of such polymer cement mortars.
An Advanced Assessment Strategy of Thermal Cracks Induced by Hydration Heat and Internal Restraint
Jeon, Se-Jin ; Choi, Myoung-Sung ; Kim, Young-Jin ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 677~685
DOI : 10.4334/JKCI.2006.18.5.677
Control of the temperature difference across a section is an effective strategy to minimize the hydration-heat-induced cracks for the structures where internal restraint is dominant. The domestic code, however, overestimates probability of the crack occurrence judging from the foreign codes and construction experiences of real structures. Therefore, the background of the equation presented in the domestic code was investigated step by step to examine validity of the equation, and, as a result, it was found that the equation is established on a basis of simple elastic model where the change of elastic modulus in an early age is not considered. An advanced assessment strategy was proposed taking into account the hypoelastic model which corresponds to an incremental constitutive equation. The presented procedure resulted in an increased crack index, i.e. decreased crack risk, the value of which depends on various conditions of the mix and structures. Also, a prediction equation of the temperature difference was proposed which can readily consider the effect of the curing condition and ambient temperature in a hand calculation. For further study, the assessment equation may be more classified to strictly consider the characteristics of the mix and structures if the analytical and experimental data are accumulated.
The Density and Strength Properties of Lightweight Foamed Concrete Using Stone-Powder Sludge in Hydrothermal Reaction Condition
Kim, Jin-Man ; Jeong, Ji-Yong ; Choi, Se-Jin ; Kim, Bong-Joo ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 687~693
DOI : 10.4334/JKCI.2006.18.5.687
The Stone Powder Sludge(below SPS) is the by-product from the process that translates stone power of 8mm under as crushed fine aggregate. It is the sludge as like cake that has average particle size of
, absorbing water content of 20 to 60%, and
content of 60% over. Because of high water content of SPS, it is not only difficult to handle, transport, and recycle, but also makes worse the economical efficiency due to high energy consuming to drying. This study is aim to recycle SPS as it is without drying. Target product is the lightweight foamed concrete that is made from the slurry mixed with pulverized mineral compounds and foams through hydro-thermal reaction of CaO and
. Although in the commercial lightweight foamed concrete CaO source is the cement and
source is high purity silica powder with
of 90%, we tried to use the SPS as
source. From the experiments with factors such as foam addition rate and replacement proportion of SPS, we find that the lightweight foamed concrete with SPS shows the same trends as the density and strength of lightweight foamed concrete increases according to decrease of foam addition rate. But in the same condition, the lightweight foamed concrete with SPS is superior strength and density to that with high purity silica. This trends is distinguished according to increase of replacement proportion of SPS, also the analysis of XRF shows that the hydro thermal reaction translates SPS to tobermorite. Although SPS has low
contents, the lightweight foamed concrete with SPS has superior strength and density, because it reacts well with CaO due to extremely fine particles. We conclude that it is possible to replace the high purity silica as SPS in the lightweight foamed concrete experimentally.
Stress Distribution in Concrete Pavements under Multi-Axle Vehicle Loads Obtained Using Transformed Field Domain Analysis
Kim, Seong-Min ; Shim, Jae-Soo ; Park, Hee-Beom ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 695~702
DOI : 10.4334/JKCI.2006.18.5.695
The stress distribution and the critical stresses in concrete pavements were analyzed using formulations in the transformed field domains when dual-wheel single-, tandem-, and tridem-axle loads were applied. First the accuracy of the transformed field domain analysis results was verified by comparing with the finite element analysis results. Then, the stress distribution along the longitudinal and transverse directions was investigated, and the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were studied. The effect of the tire contact pressure related to the tire print area was also studied, and the location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to multi-axle loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The number of axles did not tend to affect the critical stress ratio except for a small foundation stiffness value with which the critical stress ratio became significantly larger as the number of axles increased. The critical stress location in the transverse direction tended to move into the interior as the tire contact pressure increased, the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.
Compressive and Tensile Strength Properties of Slurry Infiltrated Fiber Concrete
Kim, Suk-Ki ; Choi, Jin-Ho ;
Journal of the Korea Concrete Institute, volume 18, issue 5, 2006, Pages 703~708
DOI : 10.4334/JKCI.2006.18.5.703
The slurry infiltrated fiber concrete(SIFCON) is recognized as one of the most promising new construction materials. Compressive and direct tensile tests are performed to investigate the mechanical property of SIFCON. Hooked-end steel fibers are used in the mix with fiber volume fraction varied from 4% to 10%. The water/cement ratio is kept constant at 0.4. The amount of silica fume added is 10% by weight of cement and 0.5% of water reducing agent is added to improve the workability of the slurry. The test results in this study show that the compressive strength of SIFCON is about 1.59 to 2.68 times in comparison with the cement paste. Tensile strength is showed the enhancement of about 2.51 to 8.77 times. It is also observed that the toughness and ductility of SIFCON are increased significantly with the increasing in fiber volume fraction.