The dynamic mechanical properties of steel fiber-reinforced concrete (SFRC) under high temperature and high strain rate were studied using a split Hopkinson pressure bar (SHPB) of 74 mm in diameter. As it is difficult to achieve constant strain rate loading in SHPB experiments with high temperature and high strain rate, this paper first presents a method for determining the strain rate under non-constant strain rate loading conditions. This method is proposed to deal with experimental data under non-constant strain rate loading conditions. Then, the influences of temperature on the ultimate compressive strength, peak strain, and failure modes of SFRC under different strain rates were analyzed and the results show that SFRC has a strain rate hardening effect. This paper also points out that there is a strain rate threshold for SFRC. If the strain rate is less than the strain rate threshold, there is a temperature softening effect. Conversely, if the strain rate is greater than the strain rate threshold, there is a temperature hardening effect. Finally, the relationship between the ultimate compressive strength and fiber volume fraction, strain rate, and temperature is presented and the prediction results are consistent with the experimental data.

中文翻译：

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温度和应变率对钢纤维混凝土力学性能的耦合影响

钢纤维混凝土 (SFRC) 在高温和高应变率下的动态力学性能使用直径为 74 mm 的分体式霍普金森压力棒 (SHPB) 进行了研究。由于高温高应变率的SHPB实验难以实现恒应变率加载，本文首先提出了一种非恒应变率加载条件下的应变率测定方法。提出这种方法来处理非恒定应变率加载条件下的实验数据。然后，分析了温度对不同应变速率下SFRC的极限抗压强度、峰值应变和破坏模式的影响，结果表明SFRC具有应变速率硬化效应。本文还指出，SFRC 存在应变率阈值。如果应变率小于应变率阈值，则存在温度软化效应。相反，如果应变率大于应变率阈值，则存在温度硬化效应。最后，给出了极限抗压强度与纤维体积分数、应变速率和温度之间的关系，预测结果与实验数据一致。