锈蚀钢筋与混凝土不协调变形量化方法及对构件受弯性能的影响

Method of quantification of incompatible strain between corroded steel rebar and concrete and its effects on flexural behavior of members

锈蚀黏结退化会引起钢筋与混凝土之间的不协调变形,导致构件受弯性能退化。提出了一种锈蚀钢筋与混凝土不协调变形量化方法,该方法将黏结退化表示成锈蚀率的函数,基于有效黏结力传递规律确定受弯构件黏结滑移区范围,进而构建黏结滑移区内整体变形关系实现对不协调变形的量化。该方法可用于锈蚀RC梁受弯承载力计算评估,能综合考虑锈蚀截面损失、黏结退化以及钢筋端锚失效等影响,具有较高的精度。研究表明:不协调变形受钢筋锈蚀和荷载的影响;锈蚀率低于7%时,构件不会出现不协调变形;锈蚀率越高,不协调变形出现时对应的荷载越低,对构件受弯承载力退化的影响越显著;锈蚀率大于15%时,不协调变形会提早出现,变形协调系数迅速趋于某一恒定值,由其引起的承载力退化量基本保持不变。

Corrosion-induced bond degradation leads to incompatible strain between steel rebar and concrete, resulting in the deterioration of flexural behavior of beams. An analytical model was proposed in this paper to quantify the incompatible strain between corroded steel rebar and concrete. The bond degradation was considered as the function of the corrosion degree of steel. The slipping region within the corroded RC beams was firstly determined based on the shifting rule of effective bond region. Then, the global deformation relationship between steel rebar and concrete within the slipping region was established to accomplish the quantification of incompatible strain. The proposed model can be employed to predict the flexural capacity of corroded RC beams. The effects of corrosion-induced area loss of steel rebar, bond degradation and the anchorage failure of steel rebar can be considered in the prediction. The proposed model is verified to have high accuracy. Results show that the incompatible strain is affected by the corrosion loss and loading state. No incompatible strain appears in the slightly corroded members until the corrosion loss exceeds 7%. Beyond this, a higher corrosion degree leads to a smaller load at the initiation of incompatible strain and more significant degradation of the flexural capacity of members. As the corrosion loss is greater than 15%, the incompatible strain appears prematurely and approaches rapidly to a constant value, but its effects on the flexural capacity remain almost unchanged.