冻融循环下BFRP筋与混凝土黏结滑移本构模型

Bond slip constitutive model between BFRP bars and concrete under freeze-thaw cycles

为研究冻融循环下的玄武岩纤维增强复合筋(BFRP筋)与混凝土黏结滑移本构关系,对12种不同参数的BFRP筋混凝土黏结试件进行不同次数的冻融循环试验。试验结果表明:BFRP筋混凝土黏结试件的拉拔破坏形式包括拔出破坏和劈裂破坏两种形式,试验绝大部分为拔出破坏;BFRP筋的黏结滑移完整过程由弹性段、上升段、下降段和残余应力段组成;混凝土强度越高,BFRP筋黏结应力越大,BFRP筋直径和黏结长度越大,其黏结应力越小;提出了冻融循环下BFRP筋相对黏结应力概念,以指数函数拟合了相对黏结应力与冻融循环次数的关系,冻融循环次数越大,BFRP筋相对黏结应力越低;提出了冻融循环下的BFRP筋与混凝土黏结滑移本构模型,本构曲线与试验值吻合良好,该模型也可用于未受冻融的BFRP筋与混凝土黏结滑移关系计算。

In order to study the bond slip constitutive relationship between basalt fiber reinforced ploymer bars(BFRP bars)and concrete under freeze-thaw cycles,12 kinds of BFRP bars concrete bond specimens with different parameters were tested in different freeze-thaw cycles.The test results show that the failure mode of concrete bond specimen with BFRP bars includes pull-out failure and split failure,and most of the test results are pull-out failure.The complete process of bond slip of BFRP bars is composed of micro slip section,slip section,drop section and residual stress section.The higher the concrete strength is,the greater the bond stress of BFRP bars is.The bigger the diameter and bond length of BFRP bars are,the smaller the bond stress is.The concept of the relative bond stress of BFRP bars under the freeze-thaw cycle is proposed,and the relationship between the relative bond stress and the number of freeze-thaw cycles is fitted with an exponential function.The larger the number of freeze-thaw cycles is,the lower the relative bond stress of BFRP bars is.The bond slip constitutive model of BFRP bars and concrete under freeze-thaw cycles is proposed,and the constitutive curve is in good agreement with the test value.The model is also can be used to calculate the bond slip relationship between the BFRP bars and unfrozen concrete.