scholarly journals FLEXURAL BEHAVIOR OF FRP BARS AFTER BEING EXPOSED TO ELEVATED TEMPERATURES

2021 ◽  
Vol 18 (1) ◽  
pp. 12-19
Author(s):  
Dr. Sherif El-Gamal ◽  
Abdulrahman M. Al-Fahdi ◽  
Mohammed Meddah ◽  
Abdullah Al-Saidy ◽  
Kazi Md Abu Sohel

This research study investigates the flexural behavior of fiber reinforced polymer (FRP) bars after being subjected to different levels of elevated temperatures (100, 200 and 300°C). Three types of glass FRP bars (ribbed, sand coated, and helically wrapped) and one type of carbon FRP bars (sand coated) were used in this study. Two testing scenarios were used: a) testing specimens immediately after heating and b) keeping specimens to cool down before testing. Test results showed that as the temperature increased the flexural strength and modulus of the tested FRP bars decreased. At temperatures higher than the glass transition temperature (Tg), significant flexural strength and modulus losses were recorded. Smaller diameter bars showed better residual flexural strength and modulus than larger diameter bars. The immediately tested bars showed significant strength and modulus losses compared to bars tested after cooling. Different types of GFRP bars showed comparable results. However, the helically wrapped bars showed the highest flexural strength losses (37 and 60%) while the sand coated bars showed the lowest losses (29 and 39%) after exposure to 200 and 300℃, respectively. The carbon FRP bars showed residual flexural strengths comparable to those recorded for the GFRP bars; however, they showed lower residual flexural modulus after being subjected to 200 and 300℃.

2019 ◽  
Vol 9 (23) ◽  
pp. 5128 ◽  
Author(s):  
Yijia Sun ◽  
Yang Liu ◽  
Tao Wu ◽  
Xi Liu ◽  
Haodan Lu

Three-dimensional nonlinear finite-element (FE) models using an explicit algorithm were established to simulate the behavior of beams reinforced with glass fiber-reinforced polymer (GFRP) bars cast using lightweight aggregate concrete (LWAC) with and without steel fibers, and the progressive damage model was employed to simulate the rupture of GFRP. The developed FE model was evaluated by test results, and it exhibited good agreement with the test results in terms of moment–deflection response, serviceability performance, ultimate capacity, and failure mode. Influencing factors, including the section height, reinforcement ratio, and span length were discussed according to the established FE model. It was revealed that the reinforcement ratio corresponding to balanced failure was higher than that given by code ACI 440.1R, which confirmed the necessity of the amplification factor of a balanced reinforcement ratio to ensure concrete crushing of the beam. For specimens that failed due to concrete crushing, the increase in fiber-reinforced polymer (FRP) reinforcement ratio did not significantly improve the ultimate capacity, but it did have an obvious effect on the reduction of deflection at service load. Moreover, a greater reinforcement ratio was needed for beams when the span length increased.


2012 ◽  
Vol 182-183 ◽  
pp. 1617-1621
Author(s):  
Hong Chang Qu ◽  
Ling Ling Chen ◽  
Sheng Li Zhang

The purpose of this paper is to experimentally and theoretically study the flexural behavior of concrete beams reinforced with fiber reinforced polymer (FRP) bars. In this research, two series of concrete beams reinforced with GFRP and CFRP were tested up to failure. Beam stiffness was the same for all beams until the appearance of first cracks. Deflection at failure was identical for beams reinforced with GFRP and CFRP bars, but force at failure of CFRP reinforced beams bars was greater. The theoretical analysis for calculating deflections was carried out. The theoretical results were compared to the test results for the simply supported beam deflections, and the theoretical predictions agree well with the test results.


2015 ◽  
Vol 76 (3) ◽  
Author(s):  
Widia Wahyuni Amir ◽  
Aidah Jumahat ◽  
Jamaluddin Mahmud

This paper presents a study on the flexural properties of glass fiber reinforced polymer composites. The epoxy-nanoclay resin was milled using a three roll mill machine to produce exfoliated structure nanocomposites. The fiber laminates specimens were manufactured by vacuum bagging system. These specimens were tested in the three point bend configuration following the ASTM D7264. The flexural modulus, flexural strength and strain to failure were then determined based on the flexural test results. The results showed that flexural modulus and flexural strength increases when a certain amount of nanoclay was included in the resin system. A maximum of 80% and 37% improvement of flexural strength and flexural modulus, respectively, were found at 5 wt% nanoclay content when compared to the neat GFRP composite. The improved properties of GFRP composites were achieved mostly due to an increase on the interfacial surface areas as well as a well-dispersion of nanoclay in the GFRP composite system. The fracture surfaces of specimens after flexural test were observed under FESEM. The results showed that the compressive failure region in the fiber was a dominant failure mechanism of the specimens due to a large compressive area on the fracture surface.


2018 ◽  
Vol 7 (4) ◽  
pp. 2075 ◽  
Author(s):  
Yasmin Murad

 The use of carbon fiber reinforced polymer (CFRP) sheets is becoming a widely accepted solution for strengthening and repairing rein-forced concrete (RC) structures. To date, the behavior of RC beams, strengthened with 60˚ and 45˚ inclined CFRP sheets, has not clearly explained. An experimental program is proposed in this paper to investigate the flexural behavior of RC beams strengthened with CFRP sheets. CFRP sheets were epoxy bonded to the tension face to enhance the flexural strength of beams inducing different orientation angles of 0˚, 45˚, 60˚ and 90˚ with the beam longitudinal axis. The study shows that strengthening RC beams with CFRP sheets is highly influenced by the orientation angle of the sheets. The orientation angle plays a key role in changing the crack pattern and hence the failure mode. The influence of CFRP sheets was adequate on increasing the flexural strength of RC beams but the ductility of the beams was reduced. The best performance was obtained when strengthening RC beam obliquely using 45˚ inclined CFRP sheets where the specimen experienced additional deflection and strength of 56% and 12% respectively and the reduction in its ductility was the least. It is recom-mended to strengthen RC beams, which are weak in flexure, using 45˚ inclined CFRP sheets.  


2017 ◽  
Vol 8 (4) ◽  
pp. 392-401 ◽  
Author(s):  
Hassan A.M. Mhamoud ◽  
Jia Yanmin

Purpose This study aims to focus on the resistance to elevated temperatures of up to 700ºC of high-performance concrete (HPC) compared to ordinary Portland concrete (OPC) with regards to mass loss and residual compressive and flexural strength. Design/methodology/approach Two mixtures were developed to test. The first mixture, OPC, was used as the control, and the second mixture was HPC. After 28 days under water (per Chinese standard), the samples were tested for compressive strength and residual strength. Findings The test results showed that at elevated temperatures of up to 500ºC, each mixture experienced mass loss. Below this temperature, the strength and the mass loss did not differ greatly. Originality/value When adding a 10 per cent silica fume, 25 per cent fly, 25 per cent slag to HPC, the compressive strength increased by 17 per cent and enhanced the residual compressive strength. A sharp decrease was observed in the residual flexural strength of HPC when compared to OPC after exposure to temperatures of 700ºC.


Author(s):  
Osama A. Mohamed ◽  
Rania Khattab

The use of fiber reinforced polymer (FRP) bars to reinforce concrete beams has received significant attention in the past decade due to their corrosion resistance, high tensile strength, and excellent non-magnetic properties. Glass FRP (GFRP) reinforcing bars have gained popularity due to the relatively lower cost compared to carbon FRP (CFRP) bars. In this study, sixteen concrete beam finite element models were created using the finite element computer program ANSYS to perform linear and non-linear analyses. Twelve beams were longitudinally reinforced with GFRP bars, while the remaining four beams were reinforced with conventional steel bars as control specimens. In terms of mechanical properties, FRP reinforcing bars have lower modulus of elasticity compared to conventional reinforcing steel and remain linear elastic up to failure. This leads to lack of plasticity and a brittle failure of beams reinforced with FRP bars. The objective of this study is to investigate flexural behavior of concrete beams reinforced with GFRP reinforcing bars. Some of the parameters incorporated in the numerical analysis include longitudinal reinforcement ratio and compressive strength of concrete, both of which affect the flexural capacity of beams. It is shown in this study that replacement of traditional reinforcing steel reinforced bars by GFRP bars significantly decreases mid-span deflection and increases ultimate load. The strain distribution along GFRP longitudinal reinforcing bars is totally different from that of traditional steel bars.


2007 ◽  
Vol 345-346 ◽  
pp. 1217-1220
Author(s):  
Jung Yoon Lee

The use of fiber reinforced polymer (FRP) bars has been gaining increasing popularity in the civil engineering community due to their favorable properties such as high-strength-to-weight ratio and good corrosion resistance. In order for concrete to be FRP reinforced, there must be interfacial bond between FRP bars and concrete. The interfacial bond behavior of FRP bars to concrete is expected to vary from that of conventional steel bars, since various key parameters that influence bond performance are different. This paper presents the results of an experimental and analytical study on the interfacial surface interaction of glass fiber reinforced polymer (GFRP) bars in high strength concrete cube. The experimental program consisted of testing 54 concrete cubes prepared according to CSA S802-02 standard 1). The split specimens showed that interfacial bond failure of the steel bar occurred due to concrete crushing in front of the bar deformations, while interfacial bond failure of the GFRP bars occurred partly on the surface of the bar and partly in the concrete by peeling of the surface layer of the bar.


2021 ◽  
Vol 9 (1) ◽  
pp. 72-78
Author(s):  
Osama Daoud ◽  
Ahmed Fadul

The behavior and shear strength of concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars was investigated. Total of six reinforced concrete beams without stirrups were constructed and tested up to failure. The beams measured 1400 mm long, 150 mm wide and 300 mm deep and were tested in two-points bending with constant shear span 350 mm in all tested beams, and shear span to depth ratio a/d 1.37. The test variable was the reinforcement ratio. The test beams included three beams designed as tension control (T.C) with GFRP bars, three beams designed as compression control (C.C) with GFRP bars. The test results were compared with predictions provided by ACI 440.1R-15 design guideline and proposed equations in the literature. The test results indicated that the relatively low modulus of elasticity of FRP bars resulted in reducing shear strength. In addition, shear strength provided by ACI 440.1R-15 guideline underestimate shear strength capacity in which proposed equations in the literature had given better prediction than ACI 440.1R-15. The failure mode in T.C beams is diagonal tension by bond failure not by rupture of FRP and C.C beams is shear compression by crushing of the web in extreme fiber.  


Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1025 ◽  
Author(s):  
Fei Zhou ◽  
Jiwen Zhang ◽  
Shoutan Song ◽  
Dong Yang ◽  
Chao Wang

Material properties at elevated temperatures are important factors in the fire safety design and numerical analysis of concrete members strengthened with fiber reinforced polymer (FRP) composites. Most of the previous research mainly focused on tensile strength and elastic modulus in conventional steady state temperature tests. However, the transient state test method is more realistic for strengthening concrete structures. At the same time, the coefficient of thermal expansion of FRP composites is also one of the important factors affecting concrete members at elevated temperatures. This paper presents a detailed experimental investigation on the longitudinal thermal expansion deformation, and the mechanical properties of carbon FRP (CFRP) tendons with 8 mm diameter in the steady state and transient state. The results indicate that longitudinal deformation of CFRP tendons is negative at high temperature; in addition, the transient state test results of CFRP tendons are slightly higher than the steady state test results. The final part of this paper assesses the accuracy of different empirical models. Furthermore, a new equation calculating the properties of CFRP composites at elevated temperatures is presented with the numerical fitting technique, which is in good agreement with the experimental results.


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