Flexural strengthening of concrete beams with near-surface mounted steel-fiber-reinforced polymer composite bars: Fid-Bau Portal

Flexural strengthening of concrete beams with near-surface mounted steel-fiber-reinforced polymer composite bars

Sun, Z.Y. / Wu, G. / Wu, Z.S. / Luo, Y.B.

An experimental study on concrete beams strengthened with NSM (near-surface mounted) reinforcements under monotonic static loading is presented. The NSM reinforcements include commonly used steel bars, CFRP (carbon fiber-reinforced polymers) bars, and four different types of SFCBs (steel-FRP composite bar). The main parameters of SFCBs considered in this study have been the types of FRP used (CFRP and basalt FRP) and steel/FRP ratio. The results show that (1) the stiffness during the elastic stage and the load capacity at the ultimate state of concrete beams strengthened with NSM-SFCB could be enhanced significantly; (2) the failure modes of the two concrete beams were as follows: the concrete beam strengthened with ordinary steel bar crushed after the steel bar yielded, while the beam strengthened with CFRP bar demonstrated a debonding of concrete cover on the beam soffit without any crushing of the concrete in the compression zone; (3) the steel/FRP ratio is of vital importance for the performance of beams strengthened with NSM-SFCBs. For SFCB with a high FRP/steel ratio, debonding of the concrete cover occurred after the yielding of the SFCB inner steel bars, while for beams strengthened with NSM SFCB with lower FRP/steel ratio, concrete crushing occurred after the rupture of the SFCB outer FRP; (4) compared with NSM-CFRP bars, NSM-SFCB can achieve the same anticorrosion properties at a much lower cost, which makes SFCB a competitive material for NSM strengthening of concrete structures.