• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.183-190
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• 2006

From the result of this research above, it may be summed up as follows. As a summary of results from each experiment, as the test body reinforced with the carbon rods was embedded inside the concrete section and made it possible uniform movement, this study has shown that it had excellent characteristics in improving the flexural strength and ductility. Also, it was considered as the carbon-steel sheet composite plate was to exert the strength more if it would complement the adherence with the concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.215-216
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• 2023

Leakage in the structure due to the irregular flow of groundwater in the underground structure penetrates into internal spaces such as underground parking lots and basement through underground walls, which is expensive in terms of maintenance of the building. In this study, various composite waterproofing methods installed on the outer walls of underground structures were selected to evaluate the structural performance of composite specimens due to bending behavior through experiments and analysis on bending test behavior on concrete attachment surfaces.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.483-491
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• 2008

The effectiveness of a new fiber-steel composite plate designed specifically to be used for strengthening of reinforced concrete members has been investigated. Twelve reinforced concrete beams were tested. Seven of the beams were strengthened with carbon fiber-steel composite plate(CSP), four of the beams were strengthened with glass fiber-steel composite plate(GSP), and one beam was used as a control specimen. The experimental results showed that new strengthening system controls the premature debonding and provides a more ductile failure mode than other conventional strengthening systems. The observed ductility ratios were $3.01\sim3.81$ and $3.55\sim4.95$ for strengthened beam with CSP and GSP, respectively. The maximum load was increased by 115% and 107% for strengthened beam with CSP and GSP, respectively, comparing with control beam. In addition, experimental and analytical results were well agreed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.175-186
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• 2013

Based on Model Code 2010, flexural and residual strength, flexural toughness of SFRC with design strength of 60 MPa are evaluated. For comparisons, SFRC with design strength 40 MPa was tested. Distribution of steel fibers in crack surface of specimens was evaluated by visual inspection. The used steel fibers were hooked fibers with aspect ratio of 64, 67 and 80. In all specimens, mix ratio of steel fibers was 0.5% Vol. In results, only SFRC with the highest aspect ratio satisfied requirements specified in Model Code 2010. The results demonstrated that the use of high aspect ratio will provide enough flexural toughness for high strength concrete. Also, it is found that low slump of high strength concrete can help to enhance isotropic fiber distribution.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.458-466
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• 2020

The purpose of this experimental research is to evaluate the compressive and tensile behaviors of high performance hybrid fiber reinforced concrete(HPHFRC) using amorphous steel fiber(ASF) and polyamide fiber(PAF). For this purpose, the HPHFRCs using ASF and PAF were made according to their total volume fraction of 1.0% for target compressive strength of 40MPa and 60MPa, respectively. And then the compressive and tensile behaviors such as the compressive strength, compressive toughness, direct tensile strength, and stress-strain characteristics under compressive and tensile tests were estimated. It was observed from the test results that the compressive strength of HPHFRC was slightly decreased than that of plain concrete, but the compressive toughness, compressive toughness ratio, and direct tensile strength of HPHFRC increased significantly. Also, it was revealed that the plain concrete showed brittle fracture after the maximum stress from the stress-strain curves, but HPHFRC showed strain softening.

• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.5-13
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• 1996

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.11-18
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• 2012

Deterioration and weakening is advanced in compliance with flowing of time and the change of environment in RC structures. Consequently, strength and serviceability decreases, finally, the life of infrastructure shortens and safety characteristics decreases. Accordingly, in this study, a new method to develop a strengthening method using the vacuum impregnation, which increases durability of the infrastructure occurred the safety reduction due to the performance degradation and increases the life of infrastructure by improving the durability compared to the existing method, was planned. For flexural tests, the maximum strength was a low-end order from high order as follows: (1) vacuum impregnation with 2 fold reinforcement, (2) fiber sheet 2 fold reinforcement, (3) vacuum impregnation with 1 fold reinforcement, (4) fiber sheet 1 fold reinforcement, and (5) nothing. Also, for confirmation results about durability, when the fiber reinforcement is being exposed to the inferior environment, the remaining tensile strength exceeded of 90% or more for all environments. This is because the reinforcement used in this research shows the excellent resistance in severe environment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.75-87
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• 1993

Four series of fiber reinforced concrete deep beams without shear reinforcement were tested to determine their cracking shear strengths and ultimate shear capacities. Results of tests on 20 reinforced concrete deep beams (including 16 containing steel fibers) are reported. Three parameters were varied in the study, namely, the concrete compressive strength, volume fraction of fibers, and the shear span to depth ratio. The effects of fiber incorporation on failure modes, deflections. strains, cracking shear strength, and ultimate shear strength have been examined. Resistance to shear stresses have been found to be improved by the inclusion of fibers. Based on these investigations, a method of computing the shear stress of steel fiber reinforced concrete deep beam is suggested. The comparisons between computed values and experimentally observed values are shown to validate the proposed theoretical treatment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.215-223
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• 2013

An experimental research on the possibility of using fiber reinforced concrete precast tunnel segments instead of traditional reinforced concrete(RC) segment has been performed in europe. This solution allows removing the traditional reinforcement with several advantages in terms of quality and cost reduction. Full-scale bending tests were carried out in order to compare the behaviour of the segments under flexural actions on both rebar reinforced concrete and rebar-fiber reinforced elements. The test results showed that the fiber reinforced concrete can substitute the traditional reinforcement; in particular the segment performance is improved by the fiber presence, mainly in terms of crack.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.4
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• pp.261-283
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• 2023

This study aimed to review the performance stability of PET (Polyethylene terephthalate) fiber reinforcing materials among the synthetic fiber types for which the application of performance reinforcing materials to fiber-reinforced concrete is being reviewed by examining short-term and long-term performance changes. To this end, the residual performance was analyzed after exposing the PET fiber to an acid/alkali environment, and the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture by age were analyzed, and the surface of the PET fiber collected from the concrete specimen was examined using a scanning microscope (SEM). The changes in were analyzed. As a result of the acid/alkali environment exposure test of PET fiber, the strength retention rate was 83.4~96.4% in acidic environment and 42.4~97.9% in alkaline environment. It was confirmed that the strength retention rate of the fiber itself significantly decreased when exposed to high-temperature strong alkali conditions, and the strength retention rate increased in the finished yarn coated with epoxy. In the test results of the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture, no reduction in flexural strength was found, and the equivalent flexural strength result also did not show any degradation in performance as a fiber reinforcement. Even in the SEM analysis results, no surface damage or cross-sectional change of the PET reinforcing fibers was observed. These results mean that no damage or cross-section reduction of PET reinforcing fibers occurs in cement concrete environments even when fiber-reinforced concrete is exposed to high temperatures in the early stage or depending on age, and the strength of PET fibers decreases in cement concrete environments. The impact is judged to be of no concern. As the flexural strength and equivalent flexural strength according to age were also stably expressed, it could be seen that performance degradation due to hydrolysis, which is a concern due to the use of PET fiber reinforcing materials, did not occur, and it was confirmed that stable residual strength retention characteristics were exhibited.