钢筋混凝土结构锈蚀开裂模型研究

Cracking Model of Reinforced Concrete Structure due to Rebar Corrosion

为揭示钢筋混凝土结构锈蚀开裂的机理和裂缝相关参数的发展规律,对钢筋锈蚀作用下混凝土的开裂全过程进行研究,并建立混凝土锈蚀开裂模型。模型采用混凝土材料受拉指数型软化形式和黏结裂缝理论,将锈蚀开裂过程分为保护层未开裂、部分开裂和完全开裂三个阶段。推导每一阶段对应的应力状态、径向位移和裂缝状态等力学参数的表达式,获得计算混凝土保护层裂缝宽度的控制方程,并且给出求解该方程的数值计算方法。基于所建立的模型,研究裂缝从钢筋黏结表面扩展到混凝土保护层表面的全过程行为,讨论裂缝宽度、环向应力等参数的变化规律,预测混凝土保护层表面开裂时间与相应的临界锈蚀率。研究结果表明:钢筋表面和保护层表面的裂缝宽度的差值随锈蚀时间逐渐减小并最后趋于零;混凝土裂缝宽度和锈蚀率之间表现为正线性相关关系;混凝土保护层厚度与钢筋直径之比、混凝土抗拉强度和锈蚀膨胀系数等因素直接影响着保护层锈蚀开裂时间;最后,基于黏结裂缝理论建立的混凝土结构锈蚀开裂模型能够有效地预测试验值,可为钢筋混凝土结构锈蚀开裂机理研究提供依据。

A concrete corrosion cracking model was established to study the entire cracking process of corrosion-induced cracking in concrete structures,in order to analyze the influence of corrosion on mechanical parameters of concrete structures,and to predict the crack propagation of concrete structures due to the corrosion with time.The model adopted the exponential tensile softening form of concrete materials and cohesive cracking theory,and divided the concrete cracking process into three stages:elastic phase,partial cracking and completely cracking of the cover.The expressions of mechanical parameters such as stress states,radial displacement and cracking state corresponding to each stage were derived,and the governing equation of the crack width of the concrete cover was obtained,which can be solved numerically.Based on the established model,the evolution of cracks from the surface of the steel rebar to the surface of the concrete cover was studied,and the development of the crack front with time was provided.The time-to-crack of the cover of the concrete structure and the corresponding corrosion extent at the time of cracking were predicted.The results show that the crack widths on the rebar surface and the cover surface grow with time,and the difference between the two crack widths gradually decreases over time and eventually becomes very close.The concrete crack width can be expressed as a linear relation to the corrosion rate,and the time-to-crack depends mainly on the ratio of the concrete cover depth to rebar diameter,concrete tensile strength and corrosion expansion coefficient.The theoretically predicted values are in good agreement with the experimental data,thus the developed model can provide a basis for in-depth investigation of the deterioration of concrete structures due to reinforcement corrosion.