复杂应力状态对混凝土梁外贴FRP条带抗剪贡献的影响

INFLUENCE OF CONCRETE STRESS STATE ON SHEAR CONTRIBUTION OF FRP STRIPS ON RC BEAMS

FRP剥离是外贴FRP抗剪加固混凝土梁主要的破坏模式之一。以往研究中往往简单的将面内剪切试验得到的FRP-混凝土界面粘结滑移关系应用于外贴FRP抗剪加固梁的剥离承载力计算。外贴FRP抗剪加固梁中FRP下的混凝土的应力状态与面内剪切试验情况有较大差别,这对FRP-混凝土界面的力学性能具有较大的影响。因此,以往的方法高估了FRP条带的抗剪贡献。该文研究了混凝土多轴应力状态对FRP-混凝土界面性能的影响,并根据试验研究结果,提出了U形FRP加固混凝土梁中FRP剥离应变的折减系数。与试验结果的对比计算分析表明:使用该折减系数修正后的设计公式更加合理。

FRP （fibre reinforced polymer） debonding is one of the major failure modes for reinforced concrete beams shear-strengthened with external FRP strips. Currently, the properties of the FRP-concrete interface based on pull-off tests are adopted in the capacity prediction of FRP shear-strengthened reinforced concrete beams. However, the concrete layers underneath FRP strips in these two cases are in different stress states, and so are the behaviours of the FRP-concrete interfaces. As a result, the FRP shear contribution may be over-estimated. This effect is examined in this paper, and a reduction factor accounting for the effect of the complex stress state in U jacketed RC beams is proposed based on test results from literature. A comparison with test results shows that better agreement is achieved using the proposed factor to modify FRP shear contribution.