高温下钢筋与混凝土的黏结性能试验与分析

Experimental Study and Analysis on Bond Performance between Reinforcing Bar and Concrete under High Temperature

为研究钢筋混凝土构件在高温下的黏结性能,制作了25个中心拉拔试件及8个温度场试件,同时制作了标准立方体试块.对钢筋、标准立方体试块及中心拉拔试件分别进行室温(20℃)、100℃、200℃、400℃和600℃加温,完成了高温后钢筋抗拉强度试验、高温下标准立方体试块劈裂抗拉强度试验、温度场试验及中心拉拔试验.根据温度场试验研究结果,提出一种简易的高温下中心拉拔试验的方法,阐述不同温度下钢筋强度、混凝土抗拉劈裂强度及钢筋与混凝土黏结性能的退化规律,并从混凝土的力学性能退化角度分析了高温环境对黏结强度的影响,并以割线刚度的方法定量地研究了高温对黏结刚度的影响.试验结果表明:高温后钢筋强度在低于400℃时变化不大,高温下混凝土劈裂抗拉强度基本呈线性下降,且高温下钢筋与混凝土的黏结强度变化趋势与混凝土抗拉强度衰减趋势相近.以滑移量0.015mm为临界点,黏结刚度与温度的关系曲线呈现两种不同变化形式.

To investigate the bond performance of reinforcement and concrete components under high temperature,twenty-five central pull-out test specimens and other eight specimens for temperature field test were casted.The corresponding standard cube compressive specimens were also casted for concrete tensile splitting strength test under different temperatures.After exposed to 100℃,200℃,400℃,and 600℃,the tensile splitting strength of the cube specimens and the bond properties between rebar and concrete were tested immediately to simulated the concrete circumstance and reinforcing steel performance under high temperature.The strength of rebars which underwent temperature cycle loadings was tested after its cooling.The strength of rebar,tensile splitting strength of the cube specimens,and the bond performance between rebar and concrete under different temperatures were recorded.According to the temperature test results,a simplified test method of the bond strength between reinforcing bar and concrete under high temperature was proposed.The effect of high temperature environment on bond performance between rebar and concrete was analyzed from the perspective of the mechanical properties degradation of materials,and the influence of high temperature on bond stiffness was studied by the method of tangential bond stiffness.The experimental results show that the strength of rebar after high temperature shows little change below 400℃,the tensile splitting strength of concrete decreases linearly with temperatures and the variation trend of bond strength under high temperature is similar to the tensile strength of concrete.The results present two different relationships between bond stiffness and temperature by the slip of 0.015 mm.