基于扩展有限元法的混凝土断裂参数研究

Study of fracture parameters of concrete based on extended finite element method

基于扩展有限元法(XFEM),对混凝土三点弯曲梁的开裂过程进行数值模拟,获得加载全过程的荷载-裂缝口张开位移(P-CMOD)曲线以及裂缝扩展过程;对比数值模拟和试验获得的P-CMOD曲线发现,二者比较吻合,验证了数值模型的可靠性;通过XFEM和电子散斑干涉技术获得整个加载过程的断裂过程区(FPZ)长度,二者吻合程度较高,表明XFEM可用于预测FPZ长度;基于XFEM分析了初始缝高比对混凝土断裂参数的影响。结果表明:FPZ长度随着裂缝的扩展而增加,当FPZ完全发展后,其长度逐渐减小;峰值荷载时和发展完全时的FPZ长度均随初始缝高比的增大而减小;随着初始缝高比的增大,起裂韧度KIicn i基本不变,失稳韧度KIucn和临界裂缝尖端张开位移(CTODc)呈减小趋势。

Fracture behaviors in concrete beam subjected to three-point bending is numerically simulated by using the extended finite element method(XFEM). The entire load-crack mouth opening displacement(P-CMOD) curve and crack propagation are obtained. Comparisons between numerical and experimental P-CMOD curves show that numerical results agree well with the experimental results, which validate the effectiveness of numerical model. The length of the fracture process zone(FPZ) obtained from XFEM is close to that observed by the electronic speckle pattern interferometry technique, which demonstrate that the XFEM can be used to predict the length of the FPZ. Effects of the initial crack-depth ratios on fracture parameters of concrete are investigated by using XFEM. Analysis results indicate that the FPZ length increases during crack propagation while decreases after the FPZ is fully developed. The FPZ length at peak load and the fully developed FPZ length decrease as the initial crack-depth ratios increase. With the increase of the initial crack-depth ratio, the initial fracture toughness remains unchanged, while the unstable fracture toughness and the critical crack tip opening displacement tend to decrease.