• Smart Structures and Systems
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• v.17 no.4
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• pp.593-610
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• 2016

In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.327-330
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• 2005

In this study, the nature of brittleness, one of the main problems of GFRP(Glass Fiber Reinforced Plastic) Re-bar, is improved. Therefore, Hybrid GFRP Rod is developed by attaching FBG sensor to the new GFRP Rod with toughness, essential for flexural reinforcement of the concrete. The test was performed with specimens of Hybrid GFRP Rod. According to the test, data measured by electric gauge sensor are compared with data measured by FBG sensor.

• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.737-749
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• 2020

A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.199-205
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• 2001

This paper describes the design methodology, manufacturing process, rebar tensile and bending properties. Braidtrusion is a direct Composite fabrication technique utilizing an in-line braiding and pultrusion process. The produced Composite rebar exhibits ductile stress-strain behavior similar to that of conventional steel bar. Various rebar diameters ranging from modeling scale(3m) to full-scale prototype of 9.5mm have been produced Glass Fiber Reinforced Plastics(GFRP) rebar were successfully fabricated at $\phi$8.5mm and $\phi$9.5mm nominal diameters of soild and hollow type using a braidtrusion process. Tensile and bending specimens were tested and compared with behavior of stress-strain of GFRP rebar and steel bar.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.57-63
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• 2005

The objective of this research is to investigate the mechanical characteristics of the hybrid fiber reinforced composite rebar, which is manufactured from a braidtrusion process. Braidtrusion is a direct composite fabrication technique, utilizing in-line brading and the pultrusion process. hz order to obtain the mechanical behavior of the glass fiber, carbon fiber, and kevlar fiber, the tensile tests are carried out. The results of the fibers are compared with that of steel. Hybrid rebar specimens with various diameters, ranging from model size (3 mm) to full-scale size (9.5 mm), and various cross sections, such as solid and hollow shape, have been manufactured from the braidtrusion process. The tensile and bending tests for the case of the hybrid rebar, the conventional GFRP rebar, and the steel bar have been carried out. The results of the experiments show that the hybrid rebar is superior to the conventional GFRP rebar and the steel bar, from the viewpoint of tensile and bending characteristics.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.48-52
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• 2002

This paper describes the need for a ductile Fiber Reinforced Plastic(FRP) reinforcement for Concrete Structures. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudo-ductility Characteristic can be generated in FRP rebar. Ductile hybrid FRP bars were successfully fabricated at Ø3mm and Ø10mm nominal diameters using the braidtrusion process. Tensile and bending specimens from these bars were tested and compared with behavior of stress-strain of steel bar and GFRP rebar

• Computers and Concrete
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• v.27 no.4
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• pp.305-317
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• 2021

The bond between the concrete and bar is a main factor affecting the performance of the reinforced concrete (RC) members, and since the steel corrosion reduces the bond strength, studying the bond behavior of concrete and GFRP bars is quite necessary. In this research, a database including 112 concrete beam test specimens reinforced with spliced GFRP bars in the splitting failure mode has been collected and used to estimate the concrete-GFRP bar bond strength. This paper aims to accurately estimate the bond strength of spliced GFRP bars in concrete beams by applying three soft computing models including multivariate adaptive regression spline (MARS), Kriging, and M5 model tree. Since the selection of regularization parameters greatly affects the fitting of MARS, Kriging, and M5 models, the regularization parameters have been so optimized as to maximize the training data convergence coefficient. Three hybrid model coupling soft computing methods and genetic algorithm is proposed to automatically perform the trial and error process for finding appropriate modeling regularization parameters. Results have shown that proposed models have significantly increased the prediction accuracy compared to previous models. The proposed MARS, Kriging, and M5 models have improved the convergence coefficient by about 65, 63 and 49%, respectively, compared to the best previous model.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.13-16
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• 2008

In a tension-controlled section, all steel tension reinforcement is assumed to yield at ultimate when using the strength design method to calculate the nominal flexural strength of members with steel reinforcement arranged in multiple layers. Therefore, the tension force is assumed to act at the centroid of the reinforcement with a magnitude equal to the area of tension reinforcement times the yield strength of steel. Because FRP materials have no plastic region, the stress in each reinforcement layer will vary depending on its distance from the neutral axis. Similarly, if different types of FRP bars are used to reinforce the same member, the stress level in each bar type will vary, and the member will show different behavior from our expectation. In this study, six high-strength concrete beam specimens reinforced with conventional steels, CFRP bars, and GFRP bars as flexural reinforcements were constructed and tested. The members reinforced with hybrid reinforcements showed higher stiffness, smaller crack width, and better ductility than the members reinforced with single type of FRP bars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.199-207
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• 2018

Experimental programs were performed to evaluate the flexural performance of fiber reinforced concrete(FRC) beams using a hybrid double-layer arrangement of steel bars and fiber reinforced polymer(FRP) bars or using FRP bars only. A total of seven beam specimens were produced with type of tensile reinforcing bar(CFRP bar, GFRP bar, steel bar) and the poly vinyl alcohol(PVA) fiber mixing ratio(0.5%, 0%) as variable. An analysis method for predicting the flexural behaviors of FRC beams with hybrid arrangement of heterogeneous reinforcing bars through finite element analysis was proposed and verified. In case of the specimens with the double-layer reinforcing bars, the test results showed that the first cracking load of specimen with a double-layer arrangement of steel bars was greater by 26-34% than specimens with a hybrid double-layer arrangement of steel and FRP bars. In maximum flexural strengths, the specimen that used CFRP bars as bottom tensile reinforcing bar showed the greatest strength among the specimens with the double-layer reinforcing bars. When the maximum moment value obtained through experiments was compared with that obtained through analysis, the ratio was 1.2 on average, the standard deviation was 0.085, and the maximum error rate was 22% or less. Based on these results, the finite element analysis model proposed in this study can effectively simulate the actual behavior of the beams with hybrid double-layer reinforcing bars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.93-100
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• 2008

The use of fiber reinforced polymer (FRP) composites is significantly growing in construction and infrastructure applications where durability under harsh environmental conditions is of great concern. In order to examine the applicability of FRP rebar as a reinforcement in flexural member, flexural tests were conducted. 12 beams with different FRP materials such as CFRP, GFRP and Hybrid FRP and reinforcement ratio were tested and analyzed in terms of failure mode, moment-deflection, flexural capacity, ductility index and sectional strain distribution. The test results were also compared with the theoretical model represented in ACI 440.1R06. Test results indicate that the flexural capacity of the beams reinforced by FRP bars can be accurately predicted using the ultimate design theory. They also show that the current ACI model for computing the deflection overestimates the actual deflection of GFRP series and underestimates the deflection of CFRP series.