Experimental testing of FRP reinforced concrete beams with steel compression reinforcement and a compression area confined with steel stirrups

Steel used as reinforcement of concrete elements may lead to durability issues. That is why in recent years steel bars are sometimes substituted with fibre reinforced polymer (FRP) bars. Although FRP has better durability, it lacks ductility, an important characteristic of load-bearing elements. The ductility of FRP reinforced concrete members may be improved by confining a compression area. In this paper nine concrete beams reinforced with FRP bars and a confined compression area were tested in a four-point bending loading scheme. Three sets of three beams were tested, each with a different level of confinement of compression area. Displacements were measured using digital image correlation techniques, which helped better understand the crack development and the progression of crushing. Results provided an important insight into the behaviour of FRP reinforced elements with a confined compression area both at ultimate load and at lower levels of load. It is concluded that confining the compression area of FRP reinforced concrete beams increases both ductility and bending moment capacity.