混凝土火灾损伤本构模型研究

混凝土材料在高温作用下的力学性能研究对混凝土结构防火设计和火灾损伤评估具有重要意义。构建了混凝土火灾损伤本构模型,引入热损伤反映温度对混凝土弹性模量、抗拉强度、抗压强度等力学参数的影响,考虑到混凝土受拉和受压状态下的不同的损伤特性,将混凝土材料的损伤分为受压损伤、受拉损伤和热损伤三种。建立了损伤演化、塑性流动以及内变量演化方程,通过塑性-损伤耦合,描述了不同温度和应力状态下混凝土的应力-应变特性,证明了模型严格符合热力学定律。利用所建立的本构模型对不同温度下的混凝土单轴拉伸、压缩试验进行了模拟计算,计算结果与试验结果能较好地吻合,证明了模型的合理性。

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.