高温下FRP筋与混凝土的粘结性能

Bond behavior of FRP rebar and concrete at elevated temperature

摘要:

为研究FRP筋与混凝土在高温下的粘结性能,对表面喷砂的GFRP、BFRP筋混凝土进行了高温下的拉拔试验,得到20～350 ℃温度范围内粘结强度及滑移曲线随温度的变化规律．试验结果表明,高温下FRP筋与混凝土粘结性能的衰减集中出现在树脂的玻璃软化温度区间,结合材料热分析的试验结果,本文提出了FRP筋与混凝土的粘结强度随温度的衰减模型,该模型以树脂玻璃化温度T_g和热分解温度T_d为控制参数,具有较强的通用性并可应用于其他树脂材料和纤维类型的FRP筋中．高温中FRP筋与混凝土的粘结破坏模式为FRP主筋与喷砂层间的界面剥离破坏,根据高温下二者粘结受力的特点,本文首次提出了高温中FRP筋与混凝土的四阶段粘结滑移模型,该模型以常温下的CMR、mBEP模型为原型,通过回归高温拉拔试验的变化规律以得到模型中的各项参数．经验证该滑移模型与常温及高温拉拔试验结果具有较好的吻合性,可指导应用于FRP筋混凝土构件的抗火设计中．

Abstract:

Bond behavior of FRP rebars and concrete at elevated temperature are present in this paper. Commercially produced GFRP and BFRP rebars with sand coatings surface treatments were cast in concrete for the pullout tests, and the degradation of bond strength and bond-slip curve at the temperature ranging from 20-350 ℃ were obtained from the test. Experimental results indicated that the bond strength declined significantly during the glass transition temperature zones of epoxy resin, and a bond strength decay model at elevating temperature was proposed based on two controlled parameters of the glass transition temperature T_g and the decomposition temperature T_d of matrix. The model shown good agreement with our experimental results and other researcher's, and the model is also suitable for FRP bars with different fiber types and matrix materials. The bond failure of pullout specimens at high temperature is caused by the deboning of FRP core section and sand coatings. Based on the bond performance, the paper proposes a four stage bond-slip theoretical constitutive relationship model for FRP rebar with sandcoating surface and concrete at high temperature. The τ-s constitutive model at high temperature is based on the CMR and mBEP model, and the parameters in the model are proposed from the τ-s test results. The bond-slip constitutive relationship model at elevate temperature can be used for the analysis of fire performance of FRP reinforced concrete members.