碳纤维复合材料-混凝土界面梁铰式疲劳试验与分析

Fatigue analysis of CFRP-concrete interface based on modified beam tests

外贴碳纤维增强复合材料（CFRP）-混凝土的界面抗疲劳性能是影响重复荷载作用下外贴CFRP加固混凝土梁加固效果的关键因素之一。基于梁铰式疲劳试验，对CFRP布-混凝土界面抗疲劳性能进行研究。试验结果表明：在黏结长度大于有效黏结长度时，重复荷载作用下CFRP布-混凝土界面的破坏过程可以分为初始刊离形成、剥离缓慢发展、剥离快速发展3个阶段，分别约占疲劳寿命的0～10％、10％～90％和90％～100％；在其他条件相同的情况下，提高混凝土强度或增加黏结长度可提高疲劳寿命，而随着CFRP布与混凝土宽度比的增大，疲劳寿命降低。基于试验结果，提出了考虑应力比（循环荷载作用下CFRP布的谷值应力与峰值应力之比）、混凝土强度、CFRP布与混凝土宽度比、黏结长度4个影响因素的CFRP布-混凝土界面的疲劳寿命曲线，并在传统疲劳寿命预测方法基础上，提出了考虑多因素的CFRP-混凝土界面疲劳寿命预测方法。

The fatigue behavior of the CFRP-to-concrete interface is one of the important factors that control the mechanical performance of CFRP-strengthened concrete beams subjected to cyclic loading. The fatigue endurance of CFRP sheet-concrete interface was investigated based on modified beam fatigue tests. The test results indicate that, for specimens in which the bonded zones are longer than the effective bond length, the fatigue failure process of the CFRP sheet-concrete interface can be divided into three main stages. The first stage is associated with debonding initiation for the first 10% of the fatigue life; the second stage corresponds to slow debonding propagation for the following 80% of the fatigue life ; and the third stage involves the unstable debonding failure for remaining 10% of the fatigue life. It is also found that, the fatigue life of the CFRP sheet-concrete interface can be enhanced with an increase in either the concrete strength or bond length, but decreased with an increase in CFRP sheet-to-concrete width ratio. The S-N relation for the CFRP-to-concrete interface was obtained considering four variables, namely, the ratio of minimum stress to maximum stress, loading range, concrete strength, CFRP sheet-to-concrete width ratio, and bond length. And a prediction method of CFRP-concrete interfaces fatigue lives considering many factors was proposed based on the traditional method.