基于损伤参数的CFRP布加固混凝土梁界面粘结滑移本构模型研究

Research on the interfacial bond-ship model of concrete beams strengthened with CFRP sheets based on the damage parameter

为了研究混凝土损伤程度对CFRP布加固混凝土梁的界面粘结滑移影响,采用CFRP布对5根具有不同损伤程度的混凝土梁进行加固,并以三分点加载方式对其开展受力性能试验研究。试验现象表明,各试验梁均发生CFRP布剥离,且剥离均由跨中向两端延伸直至CFRP布被拉断或受压区混凝土压碎。依据试验结果绘制各试验梁的CFRP布与混凝土界面粘结滑移曲线,并与现有粘结滑移模型进行对比分析,发现二者相差甚远。因此,基于试验结果,考虑混凝土梁损伤程度的影响,将损伤参数D引入到现有模型的主要参数中,推导出考虑混凝土梁已有损伤程度影响的最大粘结剪应力τmax和对应滑移量S0以及界面破坏能Gf的表达式,提出了能够反映损伤参数D的CFRP布-混凝土梁界面粘结滑移关系表达式。采用试验结果对其进行验证,两者基本吻合。

To investigate the influence of damage degree of concrete on the interfacial bond-slip constitutive relationship of concrete beams strengthened CFRP sheets,in this paper,experimental research(in which trisection-points loading method was used)is carried out on five CFRP-sheets strengthened concrete beams with different damage degrees.The experimental results show that debonding of CFRP sheets occur for each specimen,and propagate from the midspan to the free end,until fracture of the CFRP sheet or crush of concrete in compressive zone occurred.A comparison between the bond-slip curves obtained from test results for each specimen and the existing theoretical model indicates that the existing theoretical model does not agree with the test results.Thus,in this paper,based on test results,taking damage parameter D(which reflect the damage degree of concrete beams)into the expressions of the main parameters of the exiting model,the calculation formula of the maximum shear stress(τmax),the slip corresponding to the maximum shear stress(S0)and interfacial fracture energy(Gf)are proposed considering the effect of damage degree.Moreover,the expression of the interfacial bond-slip constitutive relationship of the concrete beam strengthened with CFRP-sheets is suggested considering the damage parameter(D),and is compared with test results,which indicate that the suggested model agrees well with test results.