Experimental investigation on flexural performance of concrete beams strengthened with SMA-GFRP-ECC smart composite materials

The structural performance improvement of concrete members is by far a crucial theoretical issue for engineers, and the development of modern smart and composite materials makes it possible to gradually enhance the durability design of the concrete structure. In this study, six beams of the same size and reinforcement ratio, the proposed composite beam (SMA-GFRP-ECC) and five comparative beams (RC, R-ECC, SS-ECC, GFRP-ECC, SMA-ECC), were designed and tested under low-cycle unidirectional cyclic loading and unloading conditions. The energy dissipation capacity, displacement ductility, residual deformation, and self-repairing performance of each concrete beam were evaluated. Afterward, a concise calculation model for the studied composite beam is deduced and developed based on the existing relevant constitutive models and concrete assumptions. The test results indicate that compared with RC beams, the composite reinforced ECC beams show obvious multi-cracking and smaller crack width during the loading process and have good bending ductility. The innovative SMA-GFRP-ECC beam is capable of a high bearing capacity, ductility, and damage self-repairing. The new proposed beam has more than 80% of the maximum crack width recovery capacity during unloading. Hence, the proposed SMA-GFRP-ECC beam is a rather good first attempt of strengthened beams, combining the advantages of SMA, GFRP, and ECC.