混凝土结构裂缝扩展全过程的新G_R阻力曲线断裂判据

The new G_R crack extension resistance as a fracture criterion for complete crack propagation in concrete structures

混凝土结构的受力特性与裂缝的发展密切相关。在对国际断裂力学领域里所提出的三种裂缝扩展阻力曲线理论加以总结的基础上,以能量为表征,基于裂缝黏聚力提出了描述混凝土结构裂缝扩展全过程的新GR阻力模型。在该模型中,裂缝扩展阻力分为三部分:一部分是基体水泥凝胶材料裂缝发展需克服的表面能,一部分是克服细骨料桥联作用的能量消耗,另一部分是粗骨料桥联闭合作用消耗的能量。文中对粗细骨料所消耗的能量进行了详细推导,得出了不同区段裂缝扩展阻力的解析计算公式。根据实测试验结果,得到了混凝土新GR阻力曲线。结果表明GR曲线是材料的基本参数,与试件尺寸无关,并建立了适用于混凝土结构裂缝扩展全过程的断裂判据。

It is well known that the mechanical performance of concrete structures is closely associated with the propagation of cracks. Three crack extension resistance theories for describing concrete fracture toughening phenomena are summarized, and based on the concept of crack cohesive force, a new analytical extension resistance model, named GR model, is proposed for investigating the resistance variation with crack propagation during fracturing in concrete. In this model, the energy approach is utilized and the crack extension resistance is decomposed into three parts： the surface energy needed to overcome in the extension of cracks in the hardened cement paste, the energy consumed to resist the cohesive traction of fine aggregate in fracture zone, and the energy dissipated to overcome the cohesive traction of coarse aggregate in fracture zone, The contribution provided by cohesive traction in the fracture zone induced by both fine aggregate and coarse aggregate to R resistance is derived in detail, An analytical formula for calculating the R resistance is developed for different ranges. From the experimental results, the typical GR curve is obtained. The result indicates that the proposed new GR extension resistance has no dependence on the size of the specimens tested, and thus is a fundamental mechanical parameter of the material. And a new fracture criterion applicable for the entire crack Dropagation Process in concrete is constructed.