基于裂缝扩展准则的K_R阻力曲线研究

STUDY ON K_R-CURVES BASED ON CRACK PROPAGATION CRITERION IN CONCRETE

根据混凝土I型裂缝扩展准则,将起裂断裂韧度作为材料参数,提出了一种新的计算混凝土结构裂缝扩展过程KR阻力曲线模型。该模型认为,裂缝扩展阻力由混凝土材料固有的抗裂能力和粘聚力提供的阻力组成并等于裂缝扩展的驱动力;应用该模型并借助有限元法计算了混凝土三点弯曲梁、楔入劈拉试件的裂缝扩展量、断裂过程区(FPZ)长度,在此基础上计算了混凝土试件的KR阻力曲线、研究了其尺寸效应,并与采用其他方法所计算的KR阻力曲线结果进行了比较。根据该文的研究结果,只要给出混凝土的弹性模量、抗拉强度和起裂断裂韧度,即可根据有限元法计算混凝土裂缝扩展过程的KR阻力曲线而无需测定混凝土试件的荷载-裂缝口张开位移等曲线。

Based on the crack propagation criterion for mode I crack,a new model to calculate KR extension resistance curves that describe the crack propagation of mode I crack in concrete was proposed by utilizing the initial fracture toughness K ini IC as a material parameter.In this model,the crack extension resistance is composed of the inherent anti-cracking performance of concrete and the resistance caused by cohesive force,and is equal to the driving force of crack extension.The FEM was applied to calculate the crack propagation length and the fracture process zone（FPZ） length in both the three-point bending beams and the wedge splitting specimens,and then corresponding KR curves were calculated and the size-effect was discussed.The results were compared with those by other methods.It is concluded that as long as the elastic modulus E,the uniaxial tensile strength ft and the initial fracture toughness K ini IC of concrete are determined without measuring P-CMOD curve,the KR curve can be obtained by utilizing FEM.