混凝土三点弯曲梁失稳韧度预测方法研究

Predicting unstable toughness of concrete based on three-point bending notched beams

基于采用起裂韧度扩展准则的三点弯曲梁断裂全过程数值模拟,研究了混凝土失稳韧度的预测方法及其受黏聚力分布的影响.该方法将起裂韧度作为裂缝起裂及扩展的判断标准,通过理论分析及数值迭代计算得到峰值荷载、临界有效裂缝长度及失稳韧度,摆脱了传统方法需要测量临界状态下的断裂参数才能得到失稳韧度的束缚.利用不同尺寸和不同最大骨料粒径的三点弯曲梁试验对本计算方法进行了验证.分析了不同黏聚力分布模型对失稳韧度及裂缝断裂全过程曲线的影响.研究表明本方法可以较好地预测混凝土失稳韧度,黏聚力分布模型对失稳韧度计算结果影响较小。

Based on numerical simulation of whole fracture process of three-point bending notched beams by initial toughness criterion, the prediction of unstable toughness of concrete and the effects of cohesive distribution on it were studied. With initial toughness taken as the criterion of crack initiation and propagation, theoretical analysis and numerical iteration were used to calculate peak load, critical crack propagation length and the unstable toughness. This method avoided the measurement of parameters on critical situation and was verified by existing experimental data of different specimen sizes and different maximum aggregate sizes.Further, the effects of cohesive distribution on unstable toughness and the whole fracture process were analyzed. The results show that the proposed method can well predict unstable toughness of concrete and the calculated unstable toughness is not sensitive to cohesive distribution.