Finite element analysis of the effect of type, number, and installation angle of FRP sheets on improving the flexural strength of concrete beams

Using FRP material to strengthen concrete beams is one of the best methods to prevent cracks propagation in the tensile zone. In this article, a concrete beam is modeled using the finite element software Abaqus. In order to investigate the effects of type, number, and installation angle of FRPs, a total number of 25 numerical models are considered. In these models, 3 types of covers made of GFRP, CFRP, and AFRP materials, including 6 and 12 sheets, are used at the installation angles of 30, 45, 60, and 90 degrees. Also, at the bottom of the beam in all the models, FRP layers are used to prevent the growth of cracks. After applying a constant load of 60 kN on all models, the stresses produced in the beam together with displacement at the middle of the beam, are investigated. The results showed that with an equal number of sheets and equal distance of installed sheets, the effect of FRP sheets on reducing displacement is greater at an installation angle of 45 degrees compared to that of a 60-degree angle. Also, this effect is greater at an installation angle of 60-degree angle compared to that of a 90-degree angle. Furthermore, by the addition of plates, the maximum lateral strain at the middle of the beam span is reduced up to 12.5 %. Also, CFRP material had a better performance compared to the two other types of fibers. The addition of prestressed FRP sheets to the specimens increases their strength. The load increase continues to the point wherein the beam fails due to the crushing of the compressive concrete. Adding the prestressed FRP sheets to the specimens increases the strength against the ultimate load from 5.4 % to 26.4 %, compared to the beam, which has internal confinement by the inner rebars.