Thermodynamic-based elastoplasticity multiaxial constitutive model for concrete at elevated temperatures

In the current study, a multiaxial plastic-damage constitutive model for concrete at different temperatures is developed. The model is implemented in three-dimensional finite element analysis under fire conditions. Because of the complexity of the mechanical behavior of concrete at elevated temperatures, the establishment of an applicable concrete constitutive model remains challenging. The developed model combines damage mechanics and elastoplasticity theories based upon a thermodynamic theoretical framework. A fourth-order tensor is adopted to describe the unilateral effect. Pressure-dependent damage evolution is considered to characterize the behavior of concrete at highly confined stress states. Transient creep and thermal strains are included to account for the thermal response. Numerical simulations are conducted to validate the developed model; the predictions show good accuracy compared with the experimental results.