中文摘要：

基于虚拟裂缝模型,提出一种计算混凝土三点弯曲梁等效断裂韧度的解析方法.应用该方法计算了梁的最大荷载和临界等效裂缝长度,进而求得等效断裂韧度.在此基础上,进一步研究了等效断裂韧度和裂缝亚临界扩展量的尺寸效应.结果发现,随梁高的增加,等效断裂韧度与裂缝亚临界扩展量均增加;随初始缝高比的增加,等效断裂韧度与裂缝亚临界扩展量增加至最大值,随后不断降低.该现象从另一角度验证了边界效应理论.

英文摘要：

Based on the fictitious crack model an analytical model for predicting the effective fracture toughness of concrete for three-point bending notched beams is proposed. The model is applied to calculate the maximum affordable load, critical equivalent crack length and the equivalent fracture toughness KsⅠc of the beam. On this basis, the size effect is investigated by calculating the KsⅠc and precritical crack propagation length △ac using the proposed model. The results show that both KsⅠc and △ac increase with the beam depth. However, following the increase of the ratio of initial crack length to beam depth the KsⅠc and △ac reach the maximum and then reduce gradually. This size effect also verifies the theory of free surface effect.