中文摘要：

应用大型通用有限元软件ABAQUS，对于强度为C30、龄期为1、2、7、28d的混凝土三点弯曲梁断裂试验分别进行了数值模拟．有限元计算采用裂缝带模型理论，利用三点弯曲相关试验参数由曲线拟合所得到的双线性拉伸软化曲线，用模拟出的荷载-裂缝开口张开位移曲线（P-δm）与试验曲线做了对比，同时将不同龄期的P-δm曲线、荷载-位移曲线（P-△）进行了比较，证实了试验结果与数值模拟结果的正确性．应用线弹性断裂力学方法，结合数值模拟结果，求解出临界裂纹尖端张开位移、临界应力强度因子这两个重要参数，并与双参数模型试验结果进行了对比，得到了满意的结果．

英文摘要：

A finite element program, ABAQUS was used to simulate fracture experiment under three-point bending C30 concrete at ages of 1,2,7, and 28 d. Based on the crack band model, a bilinear strain-softeing curve was derived with the parameters determined by curve fitting for the three-point bending tests. Comparison between the simulated P-δm. curve and experimental results showed good agreement. Meanwhile, comparisons between numerical P-δm. curves and P-△ curves for concrete at different ages also showed good agreement. By applying the linear elastic fracture mechanics （LEFM） method, the critical stress intensity factor and critical crack tip opening displacement （δt） of concrete were calculated and compared with the test results. It was found that the simulation and experimental results were close to each other.