A numerical model utilizing 3D mesoscale simulation methods was developed to investigate the influence of strain rate on the torsional performance of geometrically similar Basalt Fiber Reinforced Polymer bars-reinforced concrete (BFRP-RC) beams, as well as the corresponding size effects. The model incorporates concrete heterogeneity, material strain rate effects, and the dynamic bond-slip relationship between BFRP bars and concrete. The torsional performance of BFRP-RC beams with different structural sizes and stirrup ratios was analyzed under different strain rates. The study yielded the following findings: (1) The damage degree of BFRP-RC beams increases with the rising strain rate. (2) Increasing strain rate and stirrup ratio enhances the beams’ torsional strength and ductility while attenuating the size effect, albeit not eliminating it. (3) The impact of increasing strain rate on beam strength, ductility, and size effect outweighs that of increasing stirrup ratio. Finally, based on the Bažant size effect law (SEL) combined with the simulation results, a new size effect law was proposed that can quantitatively consider the effect of strain rate and stirrup ratio on the torsional strength of BFRP-RC beams.

中文翻译：

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动态扭转载荷下几何相似玄武岩 FRP 钢筋混凝土梁的性能

利用 3D 介观模拟方法开发了一个数值模型，以研究应变率对几何相似的玄武岩纤维增强聚合物钢筋混凝土 (BFRP-RC) 梁扭转性能的影响，以及相应的尺寸效应。该模型考虑了混凝土的异质性、材料应变率效应以及 BFRP 筋与混凝土之间的动态粘结滑移关系。分析了不同结构尺寸和箍筋比的BFRP-RC梁在不同应变率下的扭转性能。研究结果如下：（1）BFRP-RC梁的损伤程度随着应变率的增大而增大。 (2) 增加应变率和箍筋比可以提高梁的抗扭强度和延性，同时减弱尺寸效应，但不能消除尺寸效应。 (3) 增加应变率对梁强度、延性和尺寸效应的影响大于增加箍筋比的影响。最后，基于Bažant尺寸效应定律（SEL）并结合仿真结果，提出了一种新的尺寸效应定律，可以定量考虑应变率和箍筋比对BFRP-RC梁抗扭强度的影响。