Experimental study on flexural behavior of concrete beams reinforced by steel-fiber reinforced polymer composite bars

Experimental studies investigating the flexural behavior of six concrete beams were conducted with various reinforcements, including ordinary steel bars, steel-fiber reinforced polymer composite bars, pure fiber-reinforced polymer bars (either carbon fiber reinforced polymer bars or basalt fiber reinforced polymer bars), and hybrid bars (steel bars and basalt fiber reinforced polymer bars). The test results show the following: (a) steel-fiber reinforced polymer composite bar beams exhibit stable post-yield stiffness after the yielding of the inner steel bar of the steel-fiber reinforced polymer composite bar and concrete crushed after the rupture of the outer fiber-reinforced polymer of the steel-fiber reinforced polymer composite bar; (b) the ordinary reinforced concrete beam has the largest ductility coefficient, but the ultimate load was just approximately 31% of that of the corresponding steel-fiber reinforced polymer composite bar beams; (c) brittle shear failure was observed for both fiber reinforced polymer bar reinforced beams because of the high ultimate tensile strength of fiber-reinforced polymer bar; (d) although the steel-fiber-reinforced polymer ratio of the hybrid beam (reinforced by steel and basalt fiber reinforced polymer bars) is the same as that of the steel-fiber reinforced polymer composite bar beams, the ultimate load of hybrid beam is approximately 72% of that of the corresponding steel-fiber reinforced polymer composite bar, which is caused by the premature slip of basalt fiber reinforced polymer bar in hybrid beam where the bond stress is large; (e) by comparing coefficients of displacement ductility and energy ductility, it is demonstrated that energy ductility coefficient is more reasonable for evaluating the performance of steel-fiber reinforced polymer composite bar beams take into account of the post-yield stiffness of steel-fiber reinforced polymer composite bar beams; and (f) high initial stiffness and good ductility for steel-fiber reinforced polymer composite bar reinforced concrete beams can be obtained by adjusting the steel-fiber-reinforced polymer ratio and fiber-reinforced polymer type. Furthermore, because of the steel-fiber reinforced polymer composite bar's outer fiber-reinforced polymer, steel-fiber reinforced polymer composite bar reinforced concrete beams have a high durability.