冷热循环下纤维混凝土与高强钢筋间粘结强度损伤模型

通过对普通混凝土(PC)、钢纤维混凝土(SFRC)、聚丙烯纤维混凝土(PFRC)与HRB500E钢筋进行冷热循环作用后的中心拉拔试验,研究不同类型混凝土的劣化机理,分析冷热循环对PC、SFRC、PFRC的质量损失、相对动弹性模量以及粘结强度的影响。试验结果表明:冷热循环后,混凝土的质量损失和动弹性模量损失增加,钢筋与混凝土的粘结强度下降;掺入钢纤维、聚丙烯纤维的试件,其粘结强度衰减有所减弱,并且聚丙烯纤维的抑制效果更为明显。结合试验数据,对国内外的Petersen模型、Xu模型和Wu模型进行对比分析,同时考虑冷热循环对相对动弹性模量和相对粘结强度的影响,基于Weibull概率分布理论和强度衰减模型,建立了纤维混凝土与高强钢筋间粘结强度劣化模型,并通过本文数据对其进行了验证,粘结强度实测值与计算值比值的平均值为0.97,标准差为0.07,两者吻合良好,可为冷热环境下纤维混凝土结构耐久性设计提供理论参考。

Bond Strength Damage Model between Fiber Reinforced Concrete and High-Strength Steel Bars under Thermal-Cold Cycles

Through the central pull-out test of ordinary concrete (PC), steel fiber reinforced concrete (SFRC), polypropylene fiber reinforced concrete (PFRC) and HRB500E steel bars after thermal-cold cycles, the deterioration mechanism of different types of concrete was studied, and the influences of thermal-cold cycles on mass loss, relative dynamic elastic modulus and bond strength of PC, SFRC and PFRC were analyzed. The results show that the mass loss and dynamic elastic modulus loss of concrete increase, and the bond strength between reinforcement and concrete decreases after thermal-cold cycles. When steel fiber and polypropylene fiber are added into the specimen, the attenuation of bond strength is weakened, and the inhibition effect of polypropylene fiber is more obvious. Combined with the experimental data, the Petersen model, Xu model and Wu model at home and abroad are compared and analyzed. Considering the influences of thermal-coal cycles on the relative dynamic modulus of elasticity and the relative bond strength, based on Weibull probability distribution theory and strength attenuation model, a bond strength degradation model of fiber reinforced concrete and high-strength steel bar is established, which is verified by the data in this paper. The average value of the ratio between measured value and calculated value is 0.97, and the standard deviation is 0.07, which are in good agreement. The model provides a theoretical reference for the durability design of fiber reinforced concrete structures under thermal-cold environment.