碳纤维布加固锈蚀钢筋混凝土梁疲劳性能试验研究

Fatigue performance of corroded RC beams strengthened with carbon fiber composite sheets

通过10根碳纤维布加固锈蚀钢筋混凝土梁和2根锈蚀钢筋混凝土梁的弯曲疲劳试验,研究了钢筋锈蚀率、碳纤维布加固量、荷载比、加固前损伤等因素对碳纤维布加固锈蚀钢筋混凝土梁弯曲疲劳性能的影响。试验结果表明,碳纤维布加固锈蚀钢筋混凝土梁的典型疲劳破坏过程仍具有三阶段发展规律,但其第二阶段在整个发展过程中所占的比例有所下降。钢筋的疲劳性能是控制加固梁疲劳破坏的主要因素,随着钢筋锈蚀率的增加,梁的疲劳寿命急剧缩短,其破坏形式为受拉钢筋脆性断裂,外贴碳纤维布加固则能明显改善锈蚀钢筋混凝土梁的弯曲疲劳性能、提高梁的疲劳寿命,避免锈蚀钢筋疲劳断裂后梁突然失去承载力。基于此,提出了采用粘贴碳纤维布提高锈蚀钢筋混凝土梁疲劳性能的设计步骤。荷载水平提高以及加固前的损伤均会降低混凝土梁的疲劳寿命,因此在钢筋混凝土结构使用过程中应尽量避免超载现象,并应及时对损伤结构进行修复、加固。

Tests were carried out for ten corroded reinforced concrete （RC） beams strengthened with carbon fiber composite sheets and two corroded RC beams under fatigue loadings, to investigate the flexural fatigue behavior of corroded RC beams and the influences of the reinforcement corrosion, the reinforcement ratio of carbon fiber composite sheets, the fatigue load level and damage status before strengthening on the fatigue behavior of RC beams. It is found that the typical fatigue failure process of corroded RC beams strengthened with carbon fiber composite sheets still follows the three-phase rule, but the percentage of the second phase in the whole process is declined. The fatigue behavior of steel bars is the main factor to control the fatigue failure of a corroded RC beam, and the fatigue life of a RC beam may be severely reduced with the increase of reinforcement corrosion. The fatigue failure of a corroded RC beam may occur in the form of brittle fracture of tension steel bars. However, after strengthened with externally bonded carbon fiber composite sheets, the flexural fatigue behavior of a corroded RC beam may be considerably improved, the fatigue life may be significantly increased and the residual bearing capacity of a corroded beam after rupture of reinforcement steel bars may be guaranteed. A design method to improve the fatigue performance of corroded RC beams with externally bonded carbon fiber composite sheets is proposed. Fatigue life of a RC beam may be severely reduced by increase of load level and the fatigue damage before the strengthening. Thus, overloading should be avoided as much as possible, and structures with damagc should be repaired and strengthened in time.