高温后混凝土断裂准则的能量分析

Analysis of Fracture Criterion for Post-fire Concrete with Energy Approach

借鉴常温下能量型断裂模型,结合线弹性断裂力学和虚拟裂缝区上的粘聚应力分布,以能量释放率G作为断裂性能判定参数,建立高温后混凝土裂缝扩展的双G准则.该准则采用起裂韧度GIC,ini和失稳韧度GIC,un描述裂缝发展阶段,引入粘聚韧度GIC,c建立3种韧度之间的定量关系,并通过高温后楔入劈拉法试验进行验证.最后将能量法和应力法求得的断裂韧度值进行对比,发现两者能够很好吻合.

Based on the linear elastic fracture mechanics （LEFM） and the cohesive stress on the fictitious crack, the dual-G criterion characterizing the fracture behaviour of crack propagation in post-fire concrete is proposed, where, G is in terms of the energy release rate. Two important parameters, the initial fracture toughness GIC.ini and the unstable fracture toughness GIC,un, are included to describe the crack extension at various stages. The quantitative relationship between initial fracture toughness and unstable fracture toughness is established by introducing the cohesive fracture toughness GIC,c, which is conformed by the wedge-splitting experiments on the post-fire concrete specimens. Furthermore, the fracture toughness determined by energy-based method （dual- G） and stress intensity factor （SIF） is compared, and the two parameters show a good coincide with each other.