基于相场法的混凝土冻融疲劳耐久性能研究

Study on Freeze⁃Thaw Fatigue Durability of Concrete Based on Phase Field Method

为了研究混凝土在疲劳与冻融耦合作用下的性能表现,采用疲劳相场法对混凝土的性能演化进行了研究.基于随机骨料投放算法,得到一定面积分数与带界面过渡区(Interfacial Transition Zone,ITZ)的混凝土骨料模型.通过引入热力耦合疲劳相场模型,对混凝土冻融疲劳开裂的全过程进行了数值模拟研究.结果表明:冻融过程中,损伤起始于骨料角点处应力水平最高的界面过渡区;纯冻融条件下,冻融前期损伤发展比较缓慢,后期损伤迅速发展;冻融加疲劳条件下,混凝土耐久性能大大降低,寿命仅为纯冻融条件下的50%,随着冻融次数的增加,混凝土强度、弹性模量逐渐降低,且降幅增大.

In order to investigate the performance behaviour of concrete under the coupled effects of fatigue and freeze-thaw,the fatigue phase field method was used to investigate the performance evolution of concrete.The concrete aggregate model with certain area fraction and with interfacial transition zone(ITZ)was obtained by random aggregate placement algorithm.A numerical simulation of the entire process of concrete freeze-thaw fatigue cracking was conducted by introducing a thermo-mechanical coupled fatigue phase field model.The results show that during the freeze-thaw cycles,damage starts at the interface transition zone with the highest stress level at the aggregate corner.Under the condition of freeze-thaw,the damage development in the early stage of freeze-thaw is relatively slow,and the damage starts to develop rapidly in the later period.Under the condition of combined freeze-thaw cycles and fatigue,the durability of concrete is greatly reduced,and the life is only 50%of that under pure freeze-thaw conditions.With the increase of the cycles of freeze-thaw,the concrete strength,modulus of elasticity gradually decrease,with the decrease rate gradually increasing.