Compensation effect of the self-prestressing iron-based shape memory alloy on prestress loss: Characterization via the cracking load of slab members

Prestress loss is one of the major factors affecting the anti-cracking performance and serviceability of prestressed concrete (PC) members. To this end, this study proposes an active prestress loss compensation technique utilizing the self-prestress generated by iron-based shape memory alloy (Fe-SMA) bars. To evaluate the effectiveness of the proposed technique, six concrete thin-slab specimens were fabricated and tested under four-point bending after resistive-heating activation of the Fe-SMA bars. The experimental parameters included the number of Fe-SMA bars and the level of prestress loss. The results indicate that the incorporation of activated Fe-SMA bars significantly increased the cracking load, yield load, and ultimate load while optimizing crack distribution and post-cracking behavior of the specimens. For specimens subjected to simulated prestress loss, the recovery stress provided by the activated Fe-SMA bars remained effective after a 310-day storage period, and both the cracking load and the load corresponding to a crack width of 1.0 mm were restored to levels comparable to, or even exceeding, those of the reference specimens without prestress loss. Based on the experimental results, the effective prestress of Fe-SMA bars was estimated from the experimentally observed cracking behavior, and the calculated values showed good agreement with the experimental results. The proposed technique provides a feasible approach for compensating prestress loss and enhancing the crack resistance of prestressed concrete members.