碳纤维布加固锈蚀钢筋混凝土梁抗弯性能研究

Flexural behavior of corroded reinforced concrete beams strengthened with carbon fiber composite sheets

利用外加电流加速锈蚀法获得锈蚀钢筋混凝土梁,粘贴碳纤维布加固后进行受弯试验,并在此基础上开展有限元分析,以研究钢筋锈蚀引起的结构性能退化以及碳纤维布加固的有效性和作用机理。结果表明,受拉主筋锈蚀导致梁的承载力与刚度均有明显退化,锈蚀严重时梁可能因钢筋拉断而破坏。锈蚀梁粘贴碳纤维布加固后,纵向碳纤维布补偿主筋面积锈损,U型箍横向约束则保证加固体系结构整体性并防止过早剥离,梁的极限承载力显著提高,刚度与变形性能亦有改善。极限承载力提高幅度随纵向碳纤维布加固量增大而增大,但加固梁破坏模式由碳纤维布拉断转变为混凝土压碎后,加固量进一步增大对承载力提高效果大幅削弱,且加固梁的变形能力逐渐变差。最终,基于试验结果分析,建立了碳纤维布加固锈蚀钢筋混凝土梁的抗弯承载力计算方法。

Corroded reinforced concrete beams were artificially prepared using galvanostatic method, and then strengthened with carbon fiber composite sheets. Finite element analysis was carried out after flexural tests of the beams, to study the structural deterioration induced by reinforcement corrosion, and to examine the strengthening effectiveness and mechanisms of the carbon fiber composite sheets. As the results indicate, corrosion of tensile steel bars leads to obvious decrease of the load-bearing capacity and flexural stiffness of RC beams, and even rupture of tensile steel bars could occur under severe corrosion. However, much more optimistic performance can be expected after strengthening, in that the ultimate load-bearing capacity can be considerably increased and flexural stiffness improved. This is because the longitudinal composite sheets compensate the section loss of corroded tensile steel bars, while structural integrity can be maintained through transverse confinement provided by U-strips and premature debonding of longitudinal composite sheets can be effectively prevented. Ultimate load-bearing capacity of strengthened beams increases with the increase of the reinforcement ratio of longitudinal composite sheets before the failure mode of the beams switches from rupture of composite sheets to crush of concrete, thereafter the enhancement effect is greatly weakened and the deformation capacity is gradually reduced. A calculation method for flexural bearing capacity of strengthened corroded RC beams was orooosed.