• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.43-53
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• 2011

For reinforced concrete members, the bond strength is one of the important factors between two materials: concrete and reinforcing element. This study concerns the bond strength of deformed bars in artificial lightweight aggregate concrete by pull-out test. 144 cubic specimens were manufactured for the test. concrete compressive strength, size of deformed bar and embedment lengths were considered as variables in this study. Normal concrete with W/C ratio 50% specimens were tested for the comparison. Test results included the bond stress-slip responses and modes of failure. Bond strength increased with an increase of compressive strength of concrete according to W/C ratio. The equation of bond stress of polymer-modified lightweight aggregate concrete were proposed by regression analysis based on the result.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.9-16
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• 2009

For reinforced concrete members, bond strength is one of the important factors between the two materials: the concrete and the reinforcing element. The bond strength of Aramid Fiber Reinforced Polymer (AFRP) rebar was tested using the pull-out method. Presented were comparison results of the bond strength between AFRP rebar and deformed steel bars from the test. Embedded lengths and diameters of the rebar were taken into account as parameters. The bond stress-slip responses and failure modes of AFRP rebar were evaluated. It was found that the bond stress-slip responses of AFRP rebar were similar to those of deformed steel bars. As the diameter of rebar increased, the pull-out load increased. In addition, it was shown that the bond strength of an AFRP rebar was approximately 54% compared with that of a deformed steel bar.

• KCI Concrete Journal
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• v.14 no.3
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• pp.102-110
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• 2002

Results of an experimental study on the pullout behavior of the headed reinforcement are presented. A total of 48 pullout tests was performed to evaluate pullout strengths and load-displacement behaviors in pullout of the headed bars. The square steel heads had gross area of 4 $A_{b}$ and thickness of $d_{b}$ The test program consisted of three pullout test groups: Simple and Edge pullout tests using plain concrete slabs, comparison of pullout performances between the standard hooks and the headed reinforcement, and pullout tests of headed reinforcement using reinforced concrete columns. Test variables included concrete strengths ( $f_{c}$' = 27.1MPa, 39.1MPa), reinforcing bar diameters (D16~D29), embedment depths (6 $d_{b}$~12 $d_{b}$), edge conditions, column reinforcement, and single-vs.-multiple bar pullout. Test results revealed that the heads effectively provided the pullout resistances of the deformed bars in tension. The load-displacement behaviors were similar between the 90-degree hooks and the headed reinforcement. When a multiple number of headed bars installed with small head-to-head spacings was pulled out, reinforcement designed to run across the concrete failure surface in a direction parallel to the headed bars helped improve the pullout performances of the headed reinforcement.t.ement.t.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.04a
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• pp.41-48
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• 1991

In recent years, conskderable interest has developed in the fatigue strength of reinforced concrete members subjected to cyclic loading for the wide-spread adoption of ultimate strength design poecedures, the higher strength materials and the new recognition of the effect of repeated loading on structures such as bridges, concrete pavementes and offshore structures. In this study, a series of experiments is carried out to investigate the fatigue characteristics of deformed bars and underreinforced simply supported beams. The 69 reinforcing bar specimens with grade SD30 and designation of D16, D22, D25, and 24 beam specimens with D16 bars are prepared for this study. From these series of tests, it is found that I) a decrease of the bar deameter result in increased fatigue life, ii) the fatigue life of the bars embedded as main reinforcement within a concrete is more than that of bars in the air. iii) the fatigue strength at 2$\times$106 cycles of beams with steel ratio of 0.61% and 1.22% is 64.5% and 63.2% of the yielding strength, restectively. It is concluded that the low steel ratio has no significant effect on fatigue strength of underreinforced beams and the fatigue life of underreinforced concrete beams can be predicted conservatively by the fatigue life lf reinforcing bar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.240-247
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• 2010

The soil nailing system is becoming common as reinforcement method of slope face in soil. It has application to obtain slope stability method and scaffolding system. It has some troubles when the soil nailing system is applied to the downtown because it could be invaded someone's private area. Thus, in this paper, wedge type removable soil nailing system which can easily remove deformed bar in final excavation step is developed. Field pull-out test is performed to evaluate deformed bars removal and pullout resistance characteristics. According to this result, application of Wedge Type Removable Soil Nailing System is performed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.273-275
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• 2013

If the mechanical development is applied to the Nuclear Power Plant Structures instead of the standard hook development, the problem of overcrowding re-bars in the anchorage zone can be solved and the construction quality of the concrete work will be improved. But there are some problems in applying it to the NPP structures because of the restriction on the yield strength and diameter of the re-bar. After the performance evaluation test for the mechanical development, we can develop the new design equation of the mechanical development length in order to solve the limitation and apply it to NPP structures.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.325-330
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• 1995

Three types of model concrete with different mix ratios for 1/10 scale reinforced concrete model were made and tested to find the best solution for the simulation of mechanical characteristics of prototype concrete. Scaled reinforcing materials in diameter(D1.8) having similar con-figuration and mechanical properties with commercial deformed bars(D19) were prepared for 1/10 scale model tests of reinforced concrete structures. Two types of model test using D1.8 model reinforcing bars and model concrete, monotonic simple beam test and cyclic cantilever beam test, were performed to ensure and check the similitude of bond behavior between 1/10 scale model and prototype. The test results showed that the flexural behavior of 1/10 scale models can be simulated with accuracy enough for practical use in monotonic and cyclic loading test.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.299-305
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• 1995

In this study the influcence of the lateral pressure on bond behavior of reinforcing barshas been investigaed experimentally. A total of 36 specimens has been tested at the laboratory. The tests have been carried out for the uniaxial and biaxial pressures of the intensities of 0, 5, 10, 20 and 40kg/$\textrm{cm}^2$. the compressive strengths of the specimens are either 360 or 520 kg/$\textrm{cm}^2$, and two kinds of bars, round and deformed, have been used. Based on the test results, linear regression equations have been proposed, and the comparisons between test results and the regression calculations have been made.

• Journal of architectural history
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• v.23 no.6
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• pp.39-46
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• 2014

In this study, we evaluated the chemical and physical properties of structural steel, which is the most basic material for steel structures and reinforcement concrete structures in modern period. We theorized the technical data for the research of technical history of modern heritage structures by analyzing the product system and its quality control of structural steel used in modern historical heritages. The results of this study are as follow; first, the rounded bars were used in most of modern heritage structures. But in the case of Waegwan railroad bridge, the deformed bars were used in spit of not using in Japan after the great earthquake of Kantou. Second, the structural steel was good in terms of quality control, but It has brittle properties because it was not manufactured by heat treatment process.