The stiffness of RC beams strengthened with prestressed CFRP sheets can be improved effectively,and the deflection of the strengthened beams will correspondingly decrease as the prestress level rises. This paper analyzes the change of flexural stiffness of RC beams strengthened with prestressed CFRP, and the effects of prestressing force on the stiffness of strengthened beams. Thus the changing progress of the loaddeflection curves is analyzed, and the deflection curve is approximately regarded as composed by three straight lines. On the basis of the straight-line bilinear method, the formula for calculating the deflection of strengthened reinforced beams using CFRP is proposed, and its results are compared with the experimental results of two experiments ( including 10 specimens). The result shows that the formula proposed in the paper coincides with the results of the experiment.%预应力碳纤维布加固钢筋混凝土梁可以有效地提高构件的抗弯刚度,并且随着预应力水平的提高,加固梁的挠度相应地减小.分析了预应力碳纤维布加固混凝土梁的抗弯刚度变化过程,及预应力对加固梁刚度的影响.由此分析了加固梁的荷载-挠度曲线的变化过程,将挠度曲线近似看作由三段直线组成,在直线双线性法的基础上提出了加固梁的挠度计算公式,按公式计算的值与两个试验(共10根试件)结果较为吻合.
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