Abstract
The rule of mixtures (ROM) method is often used to estimate the tensile strength of fiber reinforced polymers (FRPs) reinforcing bars (rebars). Generally, the ROM method predicts the FRP rebars’ modulus of elasticity adequately but overestimates their tensile strength. This may result from defects occurred during manufacture that prevent the used materials from exhibiting a sound performance and the shear-lag phenomenon by transmission of external forces through the surface of the rebar having a circular cross section. Due to the latter, there is a difference in fiber breaking points regarding the fibers located on the surface and fibers located at the center, and thus results in differences between the values calculated from the conventional ROM and the experimental result. In this study, for the purpose of resolving the problem, glass FRP (GFRP) rebars were shaped to have a hollow section at the center of their cross sections and were further subject to tensile strength tests. The test results were further placed under regression analysis and a modified ROM within ±5% accuracy compared to the experimental value was proposed for GFRP rebars with 13, 16, and 19 mm diameters.
Highlights
IntroductionFiber reinforced polymers (FRPs) have been mainly utilized in the aeronautical, aerospace, and automotive fields owing to their relatively high strength, lightweight, and non-corroding qualities
Fiber reinforced polymers (FRPs) have been mainly utilized in the aeronautical, aerospace, and automotive fields owing to their relatively high strength, lightweight, and non-corroding qualities.The construction sector began paying attention to FRPs in the 1950s as they were recognized as a replacing material capable of solving the problem of degradation of structural performance caused by the corrosion of steel reinforcement in concrete structures
Even if the tensile strength of bars made with glass fiber reinforced polymers (GFRPs) attains strengths of typically around 700 MPa (ISIS 2007), recent achievements have succeeded in developing glass FRP (GFRP) rebars with strengths higher than 1000 MPa [3,4]
Summary
Fiber reinforced polymers (FRPs) have been mainly utilized in the aeronautical, aerospace, and automotive fields owing to their relatively high strength, lightweight, and non-corroding qualities. In general, GFRP rebars intended to replace steel rebars have circular cross-sections with deformed or sand-coated surfaces to properly achieve the transfer of forces to the rebar in concrete. This causes the rebar to experience shear-lag where the fibers located in the periphery of the rebar cross-section receive higher stress than those located at the center. Despite the results of this study not being appropriate for application to all GFRP rebars, the GFRP rebars considered in this research were used to propose a modified ROM that considers only one variable, which was focused on the sound performance of the fiber used in the GFRP rebar (relatively higher tensile strength/fiber content than previously researched GFRP rebars). Due to the linear material feature, this model may help other researchers as an index in the design and evaluation of GRFP rebar through any method like linear interpolation
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