Unified Damage Constitutive Model for Fiber-Reinforced Concrete at High Temperature

The mechanical behavior of fiber-reinforced concrete at high temperature is investigated, and a constitutive model considering the damage effect is developed based on the thermodynamic theory. By comparing the experimental results of steel fiber-reinforced concrete, the hardening function and yield theory of concrete at different temperatures are proposed. Meanwhile, a damage evolution model for concrete matrix at high temperature is developed by incorporating the free energy function. The influence of fibers on the concrete strength is investigated at different temperatures, and a parameter considering the deterioration of fiber properties at high temperature is introduced based on experimental observations. Theoretical predictions of the developed model are compared with the experimental data and show reasonable accuracy.