A Damage Constitutive Model for Concrete Subjected to Fire

Research on the mechanical properties of concrete subjected to high temperature fire is of great significance for fire resistance design and fire damage assessment of concrete structures. A damage constitutive model for concrete subjected to fire was established. The degradation of the mechanical parameters such as modulus of elasticity, tensile strength and compressive strength due to high temperature was considered through thermal damage variable. Furthermore, considering different damage characteristics of concrete under stress conditions of tension and compression, the damage of concrete material was divided into three types, including compression damage, tensile damage and thermal damage. The damage evolution plastic flow and internal variable evolution equation was derived. The stress-strain characteristics of concrete under different thermo-mechanical conditions were described through the plastic-damage coupling. It was proved that the model strictly obeyed the laws of thermodynamics. The constitutive model was used to simulate the uniaxial tension and compression tests of concrete at different temperatures. The obtained results are in good agreement with the tests, which proves the rationality of the model.