全级配混凝土单轴疲劳特性细观数值模拟

为研究全级配混凝土在等幅、变幅及阶梯重复荷载作用下的疲劳特性,揭示材料特性与疲劳应力水平对其疲劳寿命的影响规律,通过自编程序建立二维随机骨料模型,运用有限元软件和耐久性疲劳分析软件进行联合仿真,对全级配混凝土细观结构进行应力分析和疲劳分析,探讨了不同骨料分布、骨料形状及疲劳应力水平对混凝土疲劳性能的影响,并估算了疲劳寿命。结果表明:在阶梯重复荷载作用下,骨料形状和分布对混凝土疲劳寿命影响较小,而疲劳应力水平对疲劳寿命影响较大;圆形和椭圆形骨料混凝土疲劳寿命较高,多边形骨料寿命较低;在疲劳加载破坏过程中,骨料界面先起裂,然后裂纹逐渐扩展贯通,最后导致整个试件完全破坏,可见骨料界面是混凝土中的薄弱部位,其寿命直接影响整个混凝土试件的寿命。研究成果为后续混凝土疲劳性能研究提供了参考。

Mesoscopic numerical simulationon uniaxial fatigue properties of fully graded concrete

In order to study the fatigue characteristics of fully grade concrete under equal amplitude，luffing amplitude and step repeated load，and then reveal the law of the impacts from the material properties and fatigue stress levels on its fatigue life，the stress analysis and fatigue analysis on the meso structure of the fully graded concrete are made with co simulation of finite element and durability fatigue analysis software by a 2-D random aggregate model established though a self compiled program，from which the impacts from various aggregate distribution，aggregate shapes and fatigue stress levels on the fatigue properties of concrete are discussed，while the fatigue life is estimated as well. The result shows that under the step repeated load，the impacts from the aggregate shape and distribution on the fatigue life of concrete are less，but the fatigue stress level has a larger impact on the fatigue life，while the fatigue lives of circular and elliptical aggregates are higher and that of polygon aggregate is lower. During the process of fatigue loading damage，the aggregate interface cracks at first，and then the crack gradually extends through and causes a full damage of the whole specimen at last. The aggregate interface is the weak location in concrete and its life impacts the life of the whole concrete specimen. The study result provides a reference for the relevant successive study made on the fatigue property of concrete.