Integrating near-surface mounted SMA and externally bonded CFRP for concrete beams strengthened in flexure

This study aims to develop a new hybrid strengthening approach for reinforced concrete beams by integrating near-surface mounted shape memory alloys (SMAs) and externally bonded carbon fiber reinforced polymers (CFRPs). Due to the superelasticity and shape memory effect of SMAs, the proposed strengthening can enhance the flexural strength of concrete beams without compromising ductility. The recovery behavior of deformed SMA wires was studied to determine the optimal prestrain level that can achieve the highest recovery stress. Afterward, the flexural performance of concrete beams strengthened with SMA, CFRP and both was investigated by performing three-point tests. The results show that integrating SMA and CFRP has more influence on increasing the ultimate moment than the cracking moment and leads to a more significant improvement in the ultimate moment than individually utilizing SMA and CFRP. Besides, the effect of the integrated approach on enhancing the ductility is more notable than increasing the ultimate moment. The ultimate moment was analytically calculated, and the calculations show reasonable agreement with experimental results. The effects of the SMA and CFRP amount on the ultimate moment were also clarified through a parametric study.