Modeling of temperature- and rate-dependent fatigue behavior of concrete capturing the thermo-viscoplastic effects on material degradation

Concrete fatigue testing is costly and time-intensive, often requiring high loading frequenciesto reduce durations, which impacts fatigue performance due to heat generation. This highlightsthe need for a robust model to capture the interaction between loading rate and temperature, aidingexperimental interpretation and enabling faster testing—an area that is not yet addressed by currentmodeling approaches. This contribution aims to introduce a unified, thermodynamically-based constitutivemodel describing concrete behavior. The model integrates viscoplastic effects with cumulativesliding damage as mechanisms driving the material degradation. Additionally, the effect of temperatureis integrated into the thermodynamic framework, coupled with viscoplastic strains, so that theintrinsic heat generation from internal friction is accounted for. Furthermore, Gibbs free energy-basedformulation facilitates the stress-driven fatigue simulations at the single material point idealization.Elementary studies examining the behavior of concrete under uniaxial compression are used to analyzethe effects of both loading-rate and thermal factors on both monotonic and fatigue behavior.