Torsional behavior of BFRP bars reinforced engineered cementitious composites beams without stirrup

Engineered cementitious composites (ECC) is characterized by high tensile strain capacity and tight crack width control. The combination of ECC and fiber reinforced plastic (FRP) bars is expected to have better mechanical performance. This study aims to investigate the torsional behaviors of basalt FRP (BFRP) bars reinforced ECC beams without stirrup. Seven beams with different fiber contents and water to binder ratios were prepared and tested under pure torsion. BFRP bars reinforced ECC beams without stirrup and plain ECC beam exhibit a maximum crack width of less than 0.4 mm at service state, which meets the requirements of the corresponding codes for crack width. The ECC beams possess high ultimate torque and superior ductility performance as compared with reference beam with longitudinal bars and stirrups. It is noteworthy that minimum stirrup ratio may be not necessary in the torsional design of BFRP bars reinforced ECC beams. Moreover, an empirical formula is proposed for predicting the ultimate torque. The predicted values are consistent with the experimental results, indicating the effectiveness of the proposed formula. This study provides a helpful reference for the torsional design of BFRP bars reinforced ECC beams without stirrup.