Failure analysis and design recommendations on prestressed concrete beams strengthened with Fe‐<scp>SMA</scp> plates

Abstract Featuring the ability to deform spontaneously into its initial shape in response to critical temperature, shape memory alloys (SMA) are extensively utilized as innovative intelligent materials for applying prestress to reinforce existing structures. In this study, to examine the flexural behavior of prestressed concrete (PC) beams strengthened with iron‐based shape memory alloy (Fe‐SMA) plates, three‐dimensional finite element (FE) models were created in ABAQUS to simulate four‐point bending tests. The FE model was validated by comparing numerical results, including flexural behavior, load versus deflection at mid‐span, and failure mode of the beam, with experimental data. The comparison showed reliable agreement, with errors below 10%. The validated FE model was then utilized for a comprehensive parametric analysis to assess the effect of various parameters, including the cross‐sectional area, prestress level of Fe‐SMA plates and steel strands, reinforcement length of Fe‐SMA plates, concrete strength, and diameter of longitudinal rebars. The parametric analysis revealed that increasing the cross‐sectional area and prestress level of Fe‐SMA plates enhances the flexural behavior of the reinforced PC beam. Extending the reinforcement length beyond the pure bending section improved the initial deflection, but it had no significant effect on elastic stiffness, post‐cracking stiffness, crack load, or ultimate load. Balancing cost and reinforcement, an optimal reinforcement length is recommended to be one‐third of the beam. Increases in the prestress level of steel strands exhibited slight enhancement in the elastic stiffness of the beam. As the strength grade of concrete or diameter of longitudinal rebars improved, an improvement in stiffness along with a decline in initial reverse deflection was observed. Additionally, the effect of relative content between Fe‐SMA plate and steel strand or longitudinal rebars was investigated. The findings of this study provide design recommendations and valuable insights for the practical application of Fe‐SMA plates in reinforcing PC beams.