Experimental Study on the Shear Behavior of T-Shaped Concrete Beams Strengthened with Bonded Straight Fe-SMA Plates Using Hybrid Anchorage

This study proposes a novel bonded straight iron-based shape memory alloy (Fe-SMA) plate system using hybrid anchorage for the shear strengthening of reinforced concrete (RC) T-beams and presents a comprehensive experimental evaluation of its structural performance. Unlike existing Fe-SMA shear-strengthening configurations that rely on mechanically complex anchorage or exhibit limited prestress transfer, the proposed hybrid-anchored configuration enables the reliable application of active prestressing without hydraulic anchorages while allowing flexible vertical or diagonal strengthening layouts. Fifteen specimens were tested under three-point bending to evaluate the effects of shear-span ratio ( λ = 1.0, 1.5, 2.0), activation temperature (150°C, 250°C), Fe-SMA inclination angle ( β = 90°, 45°), and bonding condition. The results demonstrate that the proposed system significantly improves the shear behavior of RC T-beams. Compared with unstrengthened specimens, activated Fe-SMA plates increased the maximum shear capacity by up to 43%, reduced internal stirrup stress, and enhanced postcracking stiffness by approximately 30%. The system also significantly improved crack-control performance, reducing the maximum diagonal crack width by more than 60% and increasing the initial cracking shear force by up to 116%, which effectively delayed crack propagation and mitigated brittle failure. Diagonal strengthening ( β = 45°), oriented perpendicular to the principal tensile stress direction, produced more uniform crack distributions and superior confinement. Bonded configurations provided additional advantages, ensuring a more uniform transfer of self-prestress and achieving shear capacity increases up to three times greater than those in unbonded specimens. The theoretical values closely matched the experimental results, confirming that the contribution of the activated Fe-SMA exceeded that of the stirrups by more than a factor of 2. Overall, the proposed bonded Fe-SMA strengthening system offers active crack control, substantial shear performance enhancement, and ease of installation, providing a practical and durable solution for upgrading existing concrete bridges and structural members.