Damage evolution in concrete after high temperature is a complicated procedure, in which the pre-peak strain hardening behaviour, the post-peak strain softening behaviour and the impact of high temperature play key roles. Uniaxial and biaxial compression damage models of concrete considering high temperature degradation effect are proposed based on damage theory and experimental phenomena. They consider that the destruction of concrete is actually the cumulative evolution course of the two meso-damage modes, rupture and yield. High temperature changes the mechanical performance in microstructure of concrete and the generation and propagation of microcracks. It could be described by adjusting the probability distributions which characterize the mesoscopic damage evolution. The damage constitutive model is employed to determine the stress-strain behaviour of concrete under uniaxial compression, and the calculated results are compared with the experimental results under different high temperature levels. Results indicate that the proposed model can not only predict the stress-strain behaviour with acceptable accuracy in macroscopic scale, but also reveal the damage evolution mechanism in mesoscopic scale. Finally, the constitutive behaviour under biaxial compression is also simulated to investigate the influence of high temperature on biaxial stress-strain behavior and strength envelope.

高温后混凝土的损伤演化是一个复杂的过程，其中峰前应变硬化行为、峰后应变软化行为和高温影响起着关键作用。基于损伤理论和实验现象，提出了考虑高温退化效应的混凝土单轴和双轴压缩损伤模型。他们认为混凝土的破坏实际上是破裂和屈服两种细观破坏模式的累积演化过程。高温会改变混凝土微观结构的力学性能以及微裂纹的产生和扩展。它可以通过调整表征细观损伤演变的概率分布来描述。采用损伤本构模型确定了混凝土在单轴受压作用下的应力-应变行为，并将计算结果与不同高温水平下的试验结果进行了对比。结果表明，该模型不仅可以在宏观尺度上以可接受的精度预测应力-应变行为，而且在细观尺度上揭示了损伤演化机制。最后，还模拟了双轴压缩下的本构行为，以研究高温对双轴应力-应变行为和强度包络线的影响。结果表明，该模型不仅可以在宏观尺度上以可接受的精度预测应力-应变行为，而且在细观尺度上揭示了损伤演化机制。最后，还模拟了双轴压缩下的本构行为，以研究高温对双轴应力-应变行为和强度包络线的影响。结果表明，该模型不仅可以在宏观尺度上以可接受的精度预测应力-应变行为，而且在细观尺度上揭示了损伤演化机制。最后，还模拟了双轴压缩下的本构行为，以研究高温对双轴应力-应变行为和强度包络线的影响。