高温下混凝土动态压缩行为细观数值研究

MESO-SCALE SIMULATIONS OF DYNAMIC COMPRESSIVE BEHAVIOR OF CONCRETE AT ELEVATED TEMPERATURE

结合混凝土细观非均质性,考虑高温下细观组分力学性能退化效应及率效应的影响,建立了高温作用下混凝土动态压缩破坏行为及应变率效应研究的细观尺度数值分析模型。首先对混凝土热传导行为进行模拟,进而将“结果输出”作为“初始条件”对混凝土动态力学行为进行细观模拟,模拟与已有试验结果的良好吻合验证了数值方法的可行性及准确性。在此基础上,研究了高温加热后混凝土动态单轴压缩破坏行为及细观破坏机制,揭示了高温作用对动态压缩强度放大系数的影响规律。结果表明:高温加热后,混凝土动态冲击破坏集中在力学性能薄弱的加载端;相比于应变率效应,温度退化效应对混凝土力学性能(如强度、割线模量)影响更为显著。

A meso-scale numerical analysis model of concrete which studies the dynamic compression damage behavior and the strain rate effect at elevated temperature was established, which is combined with the meso-scale heterogeneity of concrete and considers the mechanical property degradation effect and the strain rate effect of micro-components at elevated temperature. In this approach, the heat conduction behavior was simulated initially, then the "result output" was used as "initial conditions", and the dynamic compressive behavior of concrete was conducted. The good agreement between the numerical simulation results and the experimental results indicates the feasibility and the reasonableness of the presented meso-scale approach. Subsequently, the dynamic uniaxial compression damage behavior and failure mechanism on the meso-scale of concrete at elevated temperature were studied. The influence regularity of high temperature on the dynamic compressive strength increase coefficient (CDIF) was revealed. The results indicate that the damage of concrete concentrates on the loading terminal with weak mechanical properties at elevated temperature. Furthermore, the temperature degradation effect on mechanical properties of concrete (such as strength and secant modulus) is more significant compared with the strain rate effect.