Behavior of geometrically-similar Basalt FRP bars-reinforced concrete beams under dynamic torsional loads

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.