有弱界面的CFRP抗弯加固中U型箍防剥离研究

Effectiveness of U-Strips to Prevent CFRP Debonding in Strengthened RC Beams with Weak Interfaces

锈蚀钢筋混凝土梁置换保护层或直接粘贴CFRP加固时,可能因新老混凝土结合面或锈胀裂缝产生水平削弱面。设计了9根加固梁,研究弱界面对CFRP剥离的影响及传统U型箍约束的有效性。结果发现,2种弱界面均使加固梁的整体受力性能受到削弱,局部剥离破坏更易发生,且界面越弱,剪切传递能力越差。U型箍约束能够防止纵向CFRP发生脆性剥离破坏,保证其有效参与受力。然而弱界面仍有可能导致局部保护层剥离,纵向CFRP易过早拉断。实际应用中,宜适度降低纵向CFRP的容许拉应变,并采取更为严格的约束和锚固措施。

Weak interfaces may be induced during the process of substituting the damaged cover by corroded RC beams or strengthening directly with CFRP. The two possible causes are the combination between the new-old concrete and expansive cracks. In this study, nine strengthened beams were designed to investigate the effects of weak interface on CFRP debonding along with the effectiveness of conventional confinement provided by U-strips. The test results showed the structural integrity of strengthening system was impaired considerably by both types of weak interfaces. Furthermore, it easily led to CFRP debonding failure. Weaker the interface was, the less ability transfer shear forces are. Debonding failure could be effectively prevented by U-strips. Meanwhile, consequently flexural CFRP sheets performed mainly well. However, local cover delamination and premature rupture of flexural CFRP may still occur due to the effects of the weak interface. Therefore, the allowable tensile strain of flexural CFRP must be reduced, and stricter measures of confinement and anchorage must be taken in application.