Study on the flexural properties of T-shaped concrete beams reinforced with iron-based shape memory alloy rebar

Iron-based shape memory alloys (Fe-SMAs), which are emerging as a novel class of self-prestressing materials dispensed with in situ tensioning, have been studied primarily in the field of structural strengthening. In addition, the self-prestressing characteristics of the Fe-SMA rebars are extremely promising for new concrete bridges that are seriously affected by prestress loss during their service life. Therefore, the effect of self-prestress generated by embedded Fe-SMA rebar was experimentally investigated by six concrete T-beam. The influence of factors such as the activation status, prestress value, and diameter of the Fe-SMA rebar on the flexural performance was investigated. The variation laws of the cracking load, yield load, ultimate load, and stiffness were analyzed. The results illustrated that the activation of the Fe-SMA rebar had a remarkable influence on delaying beam cracking. Under the same load (130 kN), the specimens with an activated Fe-SMA rebar exhibited a remarkable reduction exceed 30% in crack width compared to those with an unactivated Fe-SMA rebar. Following the activation, the cracking load, yield load, ultimate load, and stiffness increased to varying extents,. The Fe-SMA, characterized by its remarkable ductility, exerted a beneficial influence on the deformation capability of the beams. This enhancement became notably conspicuous following Fe-SMA activation. Analysis of the cracking load and concrete strain during the activation process indicated that the prestress of the embedded Fe-SMA rebar closely approximated the values observed in the rigid confinement. The calculated flexural capacity agreed with the experimental data, and the proposed calculation method can provide a reference for subsequent research.