混凝土断裂韧度及临界裂缝尖端张开位移——基于虚拟裂缝模型的分析

Fracture Toughness and Critical Crack Tip Opening Displacement of Concrete Based on Fictitious Crack Model

将虚拟裂缝模型与线弹性断裂力学相结合 ,利用楔入劈拉试件在实验中测得的最大荷载Pmax及对应的裂缝口张开位移CMODc,求得了混凝土裂缝亚临界扩展量Δac 的解析解 ,据此计算了最大尺寸为 12 0 0mm× 12 0 0mm× 2 0 0mm的楔入劈拉混凝土试件的起裂断裂韧度KsIc、失稳断裂韧度KeIc及临界裂缝尖端张开位移CTODc 研究结果表明 ,随着试件尺寸的增加 ,Δac 增大 ,但其增长幅度明显减小 ;而KsIc、KeIc、CTODc 却是与试件尺寸无关的断裂参数 因此 ,双K断裂准则可很好地描述混凝土裂缝的起裂。

Based on the fictitious crack model combined with linear elastic fracture mechanics,the precritical crack propagation length Δ a c of concrete was analytically evaluated by using the maximum load P max and critical crack mouth opening displacement CMOD c measured in experiment by means of wedge splitting specimens.According to the analytical solution of Δ a c,the initiation fracture toughness K s Ic ,unstable fracture toughness K e Ic and the critical crack tip opening displacement CTOD c of the wedge splitting concrete specimens,which the maximum size is 1200 mm×100 mm×200 mm,were analytically determined.Results show that the Δ a c value increases with the increasment of specimen size,but the increasment amplitude of Δ a c value decreases with the increasement of specimen size.The results also indicate that K s Ic ? K e Ic and CTOD c values are size independent,the double K fracture criterion can,therefore,well describe the cracking initiation and unstable fracture of concrete structures.