环境温差下FRP-混凝土界面粘结行为分析

为明确环境温差对纤维增强聚合物(FRP)加固混凝土构件的界面粘结性能的影响，基于粘结界面的双参数内聚力指数模型，建立了FRP-混凝土粘结结点在温差作用下的界面微分平衡方程，采用边界条件叠加的方法，解析推导了界面相对滑移、界面剪应力和FRP应力-应变分布计算公式。基于解析理论模型，提出了FRP-混凝土界面最大承载温差的计算方法，分析了粘结长度、温差变化和粘结层数对界面粘结性能的影响。结果表明:该文推导出的理论公式计算结果与界面试验结果吻合良好，建立的解析理论模型能够较好地预测温差作用下FRP-混凝土界面粘结行为；界面最大承载温差随粘结长度的增加存在上限值，且由于界面粘结性能的退化，FRP温度应力的最大值出现在达到界面最大承载温差之前；界面剪应力集中在粘结端部区域，受温差变化和FRP粘结层数影响较大，且当环境温差进入胶黏剂玻璃化转变区域后影响最为明显。该结论可用于强日照和高温车间等大温差环境下桥梁和建筑加固构件的温度应力分析和界面承载力评估。

STUDIES ON THE BOND PERFORMANCE OF FRP-TO-CONCRETE INTERFACES UNDER ENVIRONMENTAL TEMPERATURE DIFFERENCE

To reveal the effect of environmental temperature difference on the interfacial bond behavior of reinforced concrete members strengthened with external bonded fiber reinforcement polymer (FRP) composites, an analytical method for the bond behavior of FRP-to-concrete joints was presented. Based on the cohesive zone model (CZM), a second order differential equilibrium equation was derived. The analytical models of interface slip, bond stress and FRP stress and strain were given by the superposition solution of the boundary condition. Based on the presented theoretical models, the calculation method of the maximum temperature difference that the FRP-to-concrete interface could bear was presented. The effects of the bond length, temperature difference and the number of FRP layers on the interfacial bond behavior was investigated. The results show that the presented theoretical models were in good agreement with the test results. The theoretical models could predict well the bond behavior of FRP-to-concrete interfaces under the temperature difference. When the bond length increased, the maximum temperature difference was increased until reaching an upper limit. With the increase in the environmental temperature, the maximum FRP stress occurred before the maximum temperature difference was reached. The interfacial shear stress was concentrated in the end of the bond interface, which was significantly affected by the temperature difference and the number of FRP bond layers. When the environmental temperature entered the glass transition area of the adhesive, the interfacial shear stress was greatly changed. These results can be helpful to calculate the temperature stress and to assess the interfacial capacity for the strengthened members in bridge or building structures under environmental temperature differences, such as strong sunshine or high temperature environments.