• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.753-760
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• 2010

Ultra high performance concrete (UHPC), is characterized by its high compressive strength and advanced tensile behavior that is much superior to those of conventional concrete. In order to apply this new material in practice, the bond characteristics of UHPC were evaluated in this study. Pull-out tests between UHPC and deformed steel rebar were carried out according to the modified RILEM test method, and were verified by finite element analysis. From the test results showed that UHPC presents 5 to 10 times higher bond strength compared to normal strength concrete, this study suggested remarkably reduced development length and concrete cover comparing to existing specifications. The test results of 700 MPa high strength steel rebar demonstrated the applicability of high strength steel to UHPC. In addition, the transfer length measurements of seven-wire strand in UHPC specimens indicated that the transfer length limit set by the current design code is very conservative for UHPC.

• Geotechnical Engineering
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• v.12 no.3
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• pp.49-62
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• 1996

The pull-out test is a common test for detemining the strength and deformation parameters between reinforcement and soil inl the design of reinforced earth structures. It is often assumed in the interpretation of the results from the test that the mobilization of shear strength along the reinforcement is uniform. The progressive shearing at the soil-reinforcement interface during the pull-out test often leads to incorrect calculation of the shear displacement response between the reinforcement and the soil. To investigate the effect of progressive shearing during the calculation of the shear stiffness of the soil-reinforcement interface, the finite element method is used to simulate the pullout test. The reinforcement, soil and interface behaviors are modeled by rosing linear and non-linear constitutive models. Shear stiffnesses are calculated by uaiHg conventional methods. It is found that there are considerable discrepancies 13etween the calculated shear stiffnesses and the correct stiffnesses which are used in the finite element analysis. The amount of error depends on the relative stiffness between reinforcement and soil and the size of the specimen being analyzed. The finite element results are also compared with the observed response from laboratory experiments. A revised interpretation of the pull-out test results is discussed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.161-165
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• 2004

The main goal of this work is to study the effect of glass fiber volume fraction on the result of tensile test with respect to glass fiber/polypropylene(GF/PP) composites. The tensile test and failure mechanisms of GF/PP composites were investigated in the fiber volume fraction range from 10% to 30%. The tensile strength and the fracture strength increased with the increasing of the fiber volume fraction in the tested range. Fiber pull-out and debonding of this composites increased with the fiber volume fraction in thc tested range. The major failure mechanisms were classified into the debonding, the fiber pull out, the delamination and the matrix deformation.

• International Journal of Concrete Structures and Materials
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• v.5 no.1
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• pp.35-42
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• 2011

In this paper, a design equation for the punching shear capacity of steel fiber reinforced concrete (SFRC) slabs is proposed based on the Japan Society of Civil Engineers (JSCE) standard specifications. Addition of steel fibers into concrete improves mechanical behavior, ductility, and fatigue strength of concrete. Previous studies have demonstrated the effectiveness of fiber reinforcement in improving the shear behavior of reinforced concrete slabs. In this study, twelve SFRC slabs using hooked-ends type steel fibers are tested with varying fiber dosage, slab thickness, steel reinforcement ratio, and compressive strength. Furthermore, test data conducted by earlier researchers are involved to verify the proposed design equation. The proposed design equation addresses the fiber pull-out strength and the critical shear perimeter changed by the fiber factor. Consequently, it is confirmed that the proposed design equation can predict the punching shear capacity of SFRC slabs with an applicable accuracy.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.15-16
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• 2017

In this study, the flexural behavior of fiber-reinforced concrete by fiber type were evaluated. As a result, the flexural strength of the hooked steel fiber-reinforced concrete(HSFRC) was lower than that of the amorphous metallic fiber reinforced concrete(AFRC), however it was shown strain-softening behavior by the pull-out of fiber. The flexural strength and the equivalent flexural strength of polyamide fiber-reinforced concrete(PAFRC) were lower than other specimens, but the equivalent flexural strength ratio was similar to that of AFRC. The flexural behavior of the fiber-reinforced concrete was associated with the bonding and pull-out properties of the fiber and matrix depending on the fiber type.

• 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.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.833-841
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• 2010

In this report, the test results of five reinforced concrete beam-column joint subjected to cyclic load are presented. The main purpose of the research is to investigate the influence of the steel pull-out of the beam-column joints to the shear and ductile capacity of the RC beam-column assembles. In addition, the influence of the amount of beam reinforcement to the joint shear and ductile capacity is evaluated. Test results indicate that the yield penetration of steel bar increases as the joint shear strength ratio, $V_{j1}/V_{jby}$ decreases. And the slippage of the steel bars are varied according to the region of the beam-column joints. The pull-out of the steel bars of five specimens was almost the same regardless of the joint shear strength ratio, $V_{j1}/V_{jby}$. Because it was affected by not only the yield penetration of steel bar but also the axial elongation in the plastic hinge.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.149-156
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• 2003

The development and maintenance of a sound bond are essential requirements of concrete repair and replacement. The bond property of a overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified. A standard or a verified bond strength measurement method is required at field for screening, selecting materials and quality control for overlay or repair materials, but no test method has been adopted as a standard. In this study, a concrete pull off bond strength measurement method for field application is proposed and evaluated. This study compares the splitting tensile test, slant shear test, nipple pipe direct tensile test, flexural adhesion test, briquette tensile test, jumbo nail pull-out test and core pull-off test with their test procedures. From these comparison and investigation, core pull-off test is selected as a main topic of this study because of it's suitability for in situ testing, simplicities in field application and clearness at interface boundary condition. Thus, the proposed core pull off test is evaluated to be the most appropriate method for field application in a simple manner. The fracture surface and fracture mode could be easily determined by visual observation of failure surface of the field specimen. The core pull off test was found to be sensitive to surface condition and latex contents at latex modified concrete.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.168-174
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• 2001

Carbon fiber sheet(CFS) has been widely used for strengthening of the concrete building structures due to its excellent physical properties such as high strength, light weight and high durability. Bond strength or behavior, on the other hands, between carbon fiber sheet and concrete is very important in strengthening the concrete member using CFS. Therefore the bond failure mechanism between CFS and concrete should be fully verified and understood. This study is to investigate the bond strength of CFS to the concrete by the direct pull-out test and the tensile-shear test. In the direct pull-out tests, the bond strength under the various environmental conditions such as curing temperature, surface condition on concrete and water content of concrete are evaluated. Also, the effective bond length, lu and the average bond stress, $\tau$y are examined in the tensile-shear tests. Based on the test results, it is concluded that the curing temperature is the most critical element for the bond strength between CFS and concrete. And, the proper value of lu and $\tau$y is recommended with 15 cm and 9.78∼ 11.88 kgf/$\textrm{cm}^2$ respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.317-326
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• 2022

This research performed single fiber pull-out test to evaluate the effect between fineness modulus of cement composites and the fiber bond performance (bond strength and pull-out energy). A synthetic fiber (polypropylene) and a steel fiber (hooked ends type) were inserted in the middle of dog bone shape specimens which were designed with fine aggregates of F. M. 1.96, 2.69, 3.43. The experiment results showed bond strength and pullout energy of synthetic fiber are improved as fineness modulus of cement composites increases. It is considered that the frictional resistance between synthetic fiber and cement composite increases as fineness modulus of cement composite increases and consume more energy while pull out the fiber from cement composite. However bond performance of steel fiber which resist pull out by mechanical behavior is less effected on fineness modulus of cement composite. It is considered that the mechanical fixedness of hooked ends exerts a greater effect on the pullout resistance than the frictional resistance between the cement composite and the steel fiber so F. M. of fine aggregate has a relatively small effect on the pullout resistance with the steel fiber.