Shear Behavior of Reinforced Ultrahigh Toughness Cementitious Composite Beams without Transverse Reinforcement

摘要

The shear behavior of reinforced ultrahigh toughness cementitious composite (RUHTCC) beams without transverse reinforcement was investigated in the present paper, in which UHTCC has tensile strain-hardening behavior due to the steady propagation of multiple fine cracks. A total of 15 simply supported beams were subjected to a concentrated load at midspan, of which nine beams were RUHTCC beams and six beams were RC counterpart beams. The varied parameters were shear span-effective depth ratio and longitudinal reinforcement ratio. The experimental results showed that an enhanced ultimate shear strength that was about two times larger than that of an RC beam was obtained for slender beams with use of UHTCC, whereas only a marginal improvement was obtained for short beams. All tested RUHTCC beams presented a diagonal multiple-cracking mode and a stable diagonal crack propagation process. The maximum crack width was controlled within 0.1 mm at the service state and the high postcracking shear reserve strength was obtained, which means that there is no need to limit the minimum web reinforcement ratio in the engineering design for a RUHTCC beam. On the basis of the present test and tests by other investigators, a group of empirical formulae are suggested for predicting the ultimate shear strength of fiber-reinforced beams without stirrups. A good agreement between the predicted strength and tested value was shown, with the mean and coefficient of variation of the ratio between them about 1.02 and 0.10, respectively.