The investigations on the influence of geometric dimension on concrete failure at normal temperature have made a fruitful progress, while the investigations on the size effect of concrete at elevated temperature approach blank. For investigating the influence of elevated temperature and dimension on static and dynamic failures of concrete, a 3D thermo-mechanical coupling method considering the meso-structural characteristics of concrete and the strain rate effect of material was established. Flexural-tensile failure analyses of concrete beams with different geometric dimensions were conducted after heat conduction analysis. The results reveal that the speed of the heat transfer is relatively fast in small-sized concrete and the heat conduction behavior quickly approaches an equilibrium state. There is a significant degradation behavior on dynamic flexural-tensile strength for concrete exposed to fire. The elevated temperature can weaken the strain rate hardening-effect of concrete. At normal temperature, the influence of geometric dimension on dynamic flexural-tensile strength can be weakened at low strain rates while there is a reverse size effect at high strain rates. At elevated temperature, with the increasing geometric dimension, the flexural-tensile strength first decreases and then increases at low strain rates while the strength increases steadily as subjected to high strain rates.

几何尺寸对常温混凝土破坏影响的研究取得了丰硕的成果，而高温下混凝土尺寸效应的研究则接近空白。为了研究高温和尺寸升高对混凝土静态和动态破坏的影响，建立了一种考虑混凝土细观结构特征和材料应变率效应的 3D 热机械耦合方法。热传导分析后，对不同几何尺寸的混凝土梁进行弯曲-拉伸破坏分析。结果表明，小尺寸混凝土的传热速度相对较快，热传导行为很快接近平衡状态。暴露于火中的混凝土的动态弯曲拉伸强度存在显着的退化行为。升高的温度会削弱混凝土的应变率硬化效应。在常温下，几何尺寸对动态弯曲拉伸强度的影响在低应变率下会减弱，而在高应变率下则存在反向尺寸效应。在升高的温度下，随着几何尺寸的增加，弯曲拉伸强度在低应变率下先降低然后增加，而在高应变率下强度稳定增加。几何尺寸对动态弯曲拉伸强度的影响在低应变率下会减弱，而在高应变率下则存在反向尺寸效应。在升高的温度下，随着几何尺寸的增加，弯曲拉伸强度在低应变率下先降低然后增加，而在高应变率下强度稳定增加。几何尺寸对动态弯曲拉伸强度的影响在低应变率下会减弱，而在高应变率下则存在反向尺寸效应。在升高的温度下，随着几何尺寸的增加，弯曲拉伸强度在低应变率下先降低然后增加，而在高应变率下强度稳定增加。