Experimental study on the flexural behavior of concrete beams reinforced with bundled hybrid steel/FRP bars

Abstract

Fiber-reinforced polymers (FRPs) are widely used in the strengthening of concrete structures due to their light weight, high strength, and good durability. For precast concrete structures, bundled FRP/steel bars can substantially ease the construction process. In this paper, experimental studies were conducted on five concrete beams with different types of bundled reinforcements. The test results showed that all the beams exhibited concrete crushing failure modes after the steel bar yielded, and the plastic development of the steel bar was restrained by the elastic FRP bar. As the reinforcement concentration increased, the bond behavior between the longitudinal reinforcement and the surrounding concrete decreased; the postcracking stiffness and crack quantity of the corresponding concrete beam decreased, whereas the crack width increased. Both the initial stiffness and postyield stiffness of the concrete beam with 3-bar bundles were approximately 50% of that of the beam with double-bar bundles. The displacement ductilities of all the concrete beams were greater than six. Due to the differences in the bond behavior, the ultimate displacements of the beams with 3-bar bundles and 6-bar bundles were approximately 1.6 and 1.9 times the ultimate displacement of the beam with single-bar reinforcement, respectively.