Comparison of torsional damage and size effects of BFRP- and steel-reinforced concrete beams with different stirrup ratios

Abstract

To better understand the differences in torsional performance and size effect between BFRP-reinforced concrete (BFRP-RC) beams and reinforcement concrete (RC) beams, numerical tests on the pure torsional performance of BFRP-RC and RC beams was carried out by a 3D meso-scale numerical method. The effects of beam height, stirrup ratio, and reinforcement type on torsional damage and the size effect law of beams were analyzed. Furthermore, the simulation results were compared with national codes and Jin et al.'s size effect law. The results indicate that: 1) With the beam size increase, the torsional capacity and ductility of BFRP-RC beams decrease more than that of RC deep beams. 2) Stirrups can not only improve beams' torsional strength but also weaken the torsional size effect, but the effect of BFRP stirrups is not as evident as that of steel stirrups. 3) The safety reserve of calculation results in national codes is insufficient for the torsional capacity of large-size beams. Moreover, the contribution of concrete should be reasonably considered in the pure torsional capacity of concrete members. 4) The size effect law proposed by Jin et al.'s can well describe the torsional size effect of BFRP-RC beams and RC beams.