Prestressed concrete beams are widely used in structures and infrastructures for their superior control effects on cross‐sectional area, cracking, and deformation. However, the fire resistance of ordinary prestressed beams is unsatisfactory due to the serious material degradation of concrete and steel, as well as the prestress loss at elevated temperatures. To achieve an acceptable fire resistance for prestressed concrete beams, the introduction of shape memory alloy (SMA) is proposed via the hybrid usage of prestressed steel and SMA bars. When the hybrid steel–SMA prestressed beam is exposed to fire, both the strength and modulus of elasticity of prestressed SMA bars will increase, which can compensate for the material degradation of prestressed steel bars. In addition, a desirable recovery stress can be generated in SMA bars at elevated temperatures and further compensate for the prestress loss of prestressed steel bars. To study the fire resistance of the proposed beam, the fitting formulae of material properties of concrete, steel, and SMA at elevated temperatures are given firstly. Then, the analytical model and working mechanism of the hybrid beam are also presented. Further, the methodology for the prediction of fire resistance, and the formulae for the calculation of beam's flexural bearing capacity and deflection, are also presented. A parametric study is further conducted to investigate the relationships between fire resistance and the area and location of prestressed SMA bars. Moreover, an optimal analysis is also established to obtain the most economical material cost of SMA bars. As a result, the proposed prestressed beam can achieve a better fire resistance in terms of both flexural bearing capacity and deflection control.

中文翻译：

---

混合钢形记忆合金预应力混凝土梁，可提高耐火性

预应力混凝土梁由于其对横截面积，裂缝和变形的卓越控制效果而被广泛用于结构和基础设施中。然而，由于混凝土和钢材的严重材料降解，以及高温下的预应力损失，普通预应力梁的耐火性不能令人满意。为了获得预应力混凝土梁的可接受的耐火性，建议通过将预应力钢和SMA钢筋混合使用来引入形状记忆合金（SMA）。当混合钢–SMA预应力梁暴露于火中时，预应力SMA钢筋的强度和弹性模量都会增加，这可以补偿预应力钢筋的材料降解。此外，SMA钢筋在高温下会产生理想的恢复应力，并进一步补偿预应力钢筋的预应力损失。为了研究所提出的梁的耐火性，首先给出了高温下混凝土，钢和SMA的材料性能的拟合公式。然后，给出了混合梁的分析模型和工作机理。此外，还给出了耐火性的预测方法，以及梁的抗弯承载力和挠度的计算公式。进一步进行了参数研究，以研究耐火性与预应力SMA钢筋的面积和位置之间的关系。此外，还建立了一种最佳分析方法，以获得最经济的SMA棒材成本。结果是，