Retrofitting of Reinforced Concrete Beams with Steel Fiber Reinforced Composite Jackets

In the present study, a new method for retrofitting reinforced concrete beam is introduced in which steel-concrete composite jackets containing steel fiber is used. For this purpose, 75% of the peripheral surface of reinforced concrete beams was initially reinforced using steel plates and bolts, and steel fiber reinforced concrete was used between the steel plates and the peripheral surfaces of the beam. Thus, due to the relatively high tensile strength of concrete reinforced with steel fibers, not only the cross-section and moment of inertia of the beam will increase, but the tensile strength of the beam will also increase. The variables studied were steel fiber value (0, 1 and 2% by volume of concrete) and type of retrofitting (concrete jacket, steel-concrete composite jacket, and carbon fiber reinforced polymer (CFRP) sheet). Thus, 8 reinforced concrete beams were constructed and their response to four-point loading was compared by examining the parameters such as crack load, yield load, ultimate load, ductility, stiffness, and energy absorption capacity. The results showed that steel fiber-reinforced composite jackets delay the formation of the first crack in concrete and the yield of steel rebars with confinement and they result in an increase in energy absorption capacity of the beams by 89 to 129% depending on the amount of steel fiber. On the other hand, the use of steel-concrete composite jackets, due to their higher flexural stiffness, exhibits higher flexural capacity compared to steel-reinforced concrete jackets and CFRP sheets. They have a much better performance in terms of ductility.