重复荷载作用下CFRP布-混凝土界面黏结-滑移模型

Bond-slip Model for CFRP Sheets Externally Bonded to Concrete Under Cyclic Loading

碳纤维增强复合材料(CFRP)布-混凝土界面黏结-滑移关系是进行外贴CFRP布加固混凝土结构受力分析的基础。考虑重复应力水平、混凝土强度、CFRP布与混凝土的宽度比和CFRP布黏结长度的影响,采用梁铰式试件,进行CFRP布-混凝土界面性能试验,研究静力荷载和重复荷载作用下CFRP布-混凝土界面黏结-滑移本构关系。在已有单调荷载作用下黏结-滑移本构模型的基础上,考虑荷载水平、混凝土强度、CFRP布与混凝土宽度比等因素的影响,提出重复荷载作用下CFRP布-混凝土界面某确定位置处的黏结-滑移退化模型及模型曲线上升段斜率退化公式,并提出了CFRP布-混凝土界面剥离过程中黏结强度退化公式。研究结果表明:随着荷载循环次数的增加,CFRP布-混凝土界面黏结-滑移本构关系不断退化,界面黏结-滑移曲线上升段的斜率和黏结强度也不断降低,但对应于黏结强度的滑移量变化很小。

The bond-slip relationship between CFRP sheets and concrete is the base of stress analysis of concrete structure strengthened by CFRP sheets. In this paper, considering the influences of stress level, concrete strength, CFRP-to-concrete width ratio and bond length of CFRP sheet, the CFRP-concrete interface characteristics tests were performed using hinged beam specimens to investigate the bond-slip constitutive relationship of CFRP-concrete interface under monotonic load and cyclic load. Based on the existing constitutive bond-slip model under static load, considering the influences of load level, concrete strength, CFRP-to-concrete width ratio and so on, a bond-slip degradation model and a degradation formula of the slope of the ascending section of the model curve were proposed for a certain position of CFRP sheet-concrete interface under repeated load. In addition, a degradation formula of bond strength during the debonding process of CFRP sheet-concrete interface under repeated load was proposed. The results showed that as load cycles increased, the bond-slip constitutive relationship CFRP-concrete interface degenerated continuously, and the slope of the ascending section of the bond-slip curve and the bond strength also decreased continuously, but the change of the slip corresponding to the bond strength was very small.