基于能量耗散分析的混凝土随机疲劳损伤模型

基于微-细观随机断裂模型(MMSF)发展了一类混凝土随机疲劳损伤模型。该模型将MMSF中的微弹簧视为一能量耗散单元并考察了其跨尺度的能量耗散过程。在纳观尺度,引入速率过程理论描述裂纹的扩展速度,并基于裂纹层级模型和自相似假定完成从纳观尺度到微观尺度的过渡。由此建立了微弹簧在疲劳荷载作用下的多尺度耗能描述。此外,为了考虑疲劳加载中混凝土多条裂纹的相互影响,引入了包含损伤扩展效应和损伤愈合效应的疲劳损伤因子来修正耗能表达。通过与相关试验的对比,证明了该模型能反映疲劳荷载作用下混凝土的主要力学行为,如疲劳损伤三阶段特点、疲劳寿命的离散性和疲劳寿命随加载频率的变化趋势等。

Stochastic fatigue damage model for concrete based on energy dissipation analysis

In this work,a new stochastic concrete fatigue damage model is developed based on the micro-meso stochastic fracture model (MMSF).The micro-spring in the MMSF is regarded as an energy dissipation unit,and the multiscale energy dissipation process within it is investigated.At the nanoscale,the rate process theory is introduced to describe the crack expansion rate,and the scale gap between the nanoscale and the microscale is connected by a crack hierarchy model.Thus,the energy dissipation expression of microsprings under fatigue loading is established.To consider the interactions of multiple cracks,a fatigue damage function,including a damage acceleration effect and a damage healing effect,is introduced to modify the energy dissipation expression.By comparing the numerical simulation with the relevant test data,it is demonstrated that the proposed model can reflect the main mechanical behaviors of concrete under fatigue loading,including the three stages of fatigue damage,the scatter in the data of fatigue life,and the influence of loading frequency.