Self-monitoring and self-repairing of crack in concrete beam with constraint super-elastic SMA

Taken advantages of the characteristics of super-elasticity and restoring forces while the shape memory alloy(SMA) was excited,concrete model beams were established by embedding different pre-stretching length,different pieces of Ni-Ti SMA under martensitic state into the concrete tensile zone before the concrete casted under environmental temperature,the relationship between the resistance rate of SMA and the cracks width of beams was studied under loaded process.The impact of slip and bond between the concrete and SMA was taken into account by embedding the anchor at both ends of the beam to prevent the slip of the SMA,the influence of additional resistance coming from the anchor was taken into consideration in the process simulated.The result is in good agreement with the experimental result.It was shown that SMA increased the deformation capacity of the beam significantly,the crack closed almost completely and the deformation recovered suddenly after the SMA was excited by electrifying.The drive effect can be improved by growing in quantity of SMA.When Cracks width of beam was less than 1.5 mm,the relation between rate of change of alloy resistance and crack width of concrete beam is linear,however,the existence of residual deformation of rebar play a very negative role while recovering of the residual deformation.