• Computers and Concrete
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• v.24 no.2
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• pp.159-172
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• 2019

This paper presents an investigation into the flexural behavior of reinforced concrete (RC) beams retrofitted by ultra-high performance fiber-reinforced concrete (UHPFRC) layers. The experimental study has been conducted in two parts. In the first part, four methods of retrofitting with UHPFRC layers in both the up and down sides of the beams have been proposed and their efficiency in the bonding of the normal concrete and ultra-high performance fiber-reinforced concrete has been discussed. The results showed that using the grooving method and the pre-casted UHPFRC layers in comparison with the sandblasting method and the cast-in-place UHPFRC layers leads to increase the load carrying capacity and the energy absorption capacity and causes high bond strength between two concretes. In the second part of the experimental study, the tests have been conducted on the beams with single UHPFRC layer in the down side and in the up side, using the effective retrofitting method chosen from the first part. The results are compared with those of non-retrofitted beam and the results of the first part of experimental study. The results showed that the retrofitted beam with two UHPFRC layers in the up and down sides has the highest energy absorption and load carrying capacity. A finite element analysis was applied to prediction the flexural behavior of the composite beams. A good agreement was achieved between the finite element and experimental results. Finally, a parametric study was carried out on full-scale retrofitted beams. The results indicated that in all retrofitted beams with UHPFRC in single and two sides, increasing of the UHPFRC layer thickness causes the load carrying capacity to be increased. Also, increases of the normal concrete compressive strength improved the cracking load of the beams.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.55-59
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• 1995

This study was experimentally carried out to evaluate flexural creep properties of sandwich panels with polymer concrete facings. Specimen was made using polymer concrete facing and polyestyrene form core that has an excellent insulation capacity. Test results showed that, in 90 days of loading, the flexural creep was 1/292 under 40% of stresslevel and 1/780 under 60% stress level.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.793-798
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• 2002

This paper presents the analytical results on the seismic retrofit of circular bridge columns with poor lap-splice details using FRP jacket. The as-built column suffered brittle failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or ductility. The retrofitted columns using FRP jacket showed significant improvement in seismic performance due to FRP's confinement effect. FRP's confinement effect is predicted by the classical elasticity solution for the laminated circular tube manufactural with several layers, and induces the flexural failure instead of bondslip failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.959-964
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• 2002

The purpose of this study is to establish flexural behavior of high-strength concrete by means of both theoretical approach and experimental analysis of beams in which confinement stirrups have been introduced into pure bending zone. The experiment was carried out on full-scale high-strength reinforced concrete beams whose compressive strengths are 400 and 700kgf/cm$^2$, and confined with rectangular closed stirrups. The test results are reviewed in terms of flexural capacity and ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.762-767
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• 1999

This paper presents an experimental study on flexural behavior of damaged RC beams repaired with epoxy mortar system. The main test variables are repair length and depth. A series of 7 specimens was tested to show the corresponding effect of each variables on maximum load capacity, load-deflection relationship, and failure mode. The results of this study shows that flexural behavior of repaired RC beams changes as the repair length and depth is getting longer and deeper, so that the tension strength of repairing materials should be considered in the courses of repair design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1333-1337
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• 2000

The flexural vibration of laminated composite beams with active and passive constrained-layer damping has been investigated to design structure with maximum possible damping capacity. The equations of motion are derived for flexural vibrations of symmetrical, multi-layer laminated beams. The damping ratio and modal damping of the first bending mode are calculated by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations with active control.

• Earthquakes and Structures
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• v.1 no.3
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• pp.269-287
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• 2010

High-strength concrete (HSC) is becoming more popular in the construction of beams and columns of tall buildings because of its higher stiffness and strength-to-weight ratio. However, as HSC is more brittle than normal-strength concrete (NSC), it may adversely affect the flexural ductility and deformability of concrete members. Extended from a series of theoretical study conducted on flexural ductility of concrete beams, the authors would in this paper investigate the effects of some critical factors including the degree of reinforcement, confining pressure, concrete and steel yield strength on the flexural deformability of NSC and HSC beams. The deformability, expressed herein in terms of normalised rotation capacity defined as the product of ultimate curvature and effective depth, is investigated by a parametric study using nonlinear moment-curvature analysis. From the results, it is evident that the deformability of concrete beams increases as the degree of reinforcement decreases and/or confining pressure increases. However, the effects of concrete and steel yield strength are more complicated and dependent on other factors. Quantitative analysis of all these effects on deformability of beams has been carried out and formulas for direct deformability evaluation are developed. Lastly, the proposed formulas are compared with available test results to verify its applicability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.136-141
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• 1998

It is demanded to obtain the design data for bond length of the strengthening carbon fiber sheets. An objectives of this study is to provide preliminary data of rational strengthening design method which is adequate to current domestic status. The present experimental study was performed to evaluate flexural strengthening effects of steel reinforced concrete beams strengthened with carbon fiber sheets. Following conclusions can be extracted. It is revealed that the maximum load carrying capacity is increased up to 9% when the reinforced concrete beams were strengthened with 1-ply of carbon fiber sheet which is half-width of beam. The performance of reinforced concrete sections were improved due to the strengthening carbon fiber sheets on the tensile side of beams. It is believed that the strengthening length of carbon fiber sheets must be provided as (0.5l+3d) to secure the ductile capacity of above three for the flexural strengthening of reinforced concrete beams.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.133-140
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• 2018

A nonlinear finite element analysis was conducted in order to examine the moment capacity and flexural behaviour of hollow prestressed concrete filled steel tube(HCFT) piles which compose hollow PHC piles inside thin wall steel tubes. The parameters investigated in this study were various contact conditions between concrete and steel tube, thickness of concrete tube and various PC strands. A simple method is proposed to determine the ultimate flexural strength based on plastic stress distribution method. In order to verify the proposed method, calculated moment capacity of various HCFT piles are compared with the experiment and numerical analysis results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.147-156
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• 2004

The Rehabilitation and repair of structurally deteriorated, reinforced concrete structures will be highly demanded in the near future. The purpose of this study is to investigate whether damaged beams that crack and deflection are developed by bending moment are restored to the former state. In conclusion, when specimens strengthened with Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid(Carbon Fiber Reinforced Plastic-Grid) are compared with standard specimen, flexural capacity is increased and ductility and energy absorbtion capacity are similar with undamaged specimen. Therefore Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid (Carbon Fiber Reinforced Plastic-Grid) have highly efficiency as material of flexural strengthening.