A thermo-mechanical coupling model for concrete including damage evolution

Abstract

In the current study, a coupled thermo-mechanical constitutive model of concrete was newly developed to characterize the mechanical responses of concrete at different temperatures within thermodynamics framework. The coupling thermo-mechanical contributions among thermal effect (up to 800°C), damage evolution and thermo-plastic hardening were creatively taken into account in energy potential function. The thermal damage evolution law and load induced plastic mechanical damage evolution law was developed respectively and were coupled in the dissipation function. The thermo-mechanical hardening rule was considered through adopting back stress and hardening parameters. A particular advantage of the proposed model is that fiber influence coefficients can be employed in potential functions to upgrade for modeling fiber reinforced concrete. The impact of types and volume fractions of fibers on the reinforcement mechanism was calculated in the fiber influence coefficients. Besides, an orthotropic triaxial compression model was developed for concrete and fiber reinforced concrete to predict multiaxial stress behavior at high temperature. The proposed model was coded and implemented into the Fortran program and the nonlinear behaviors of concrete and fiber reinforced concrete were predicted. Good effectiveness and accuracy have been validated through comparing the modelling results and six groups experimental results in literatures, which illustrates that the proposed model is robust and reliable. Finally, a discussed study was conducted to investigate the effect of hardening parameters and thermal effect on the yield surface.