ABSTRACT
A multi-scale fatigue model of concrete is established in the paper. The continuum damage mechanic is adopted as the macro-framework. Different from the ordinary empirical damage evolution law, a physical meaningful model at micro-level is used to obtain the fatigue damage accumulation. The main micro-scale mechanism for fatigue is concluded as the drift process at the micro-crack tips which explained by rate process theory. After considering the water molecules dynamic effect, the loading-unloading fatigue process will causes fluctuations of metastable interfacial state, which gives an explanation for the different damage evolution for fatigue loading and corresponding sustained loading. With the sensitivity analysis, the origination of the stochastic phenomenon in fatigue is concluded as several random variables in the constitutive model. With the probability density evolution method(PDEM), the significant scatter of fatigue results is well identified in a rational way which exhibited by the transfer of intrinsic randomness.
