Can we mitigate or eliminate size effect in shear by utilizing steel fibers?

This paper reports some recent results of an experimental campaign on Fiber Reinforced Concrete (FRC) beams under shear loading tested at the University of Brescia: nine full scale beams, ha ving a height varying from 500 to 1500 mm, were tested for investigating the effect of steel fibers on key-parameters influencing the shear response of concrete members, with special emphasis on FRC toughness and size effect. All tested members contained no conventional shear reinforcement. Results show that a relatively low volume fraction of fibers can significantly increase bearing capacity and ductility. The latter determines visible deflection and prior waming of impending collapse, which is not possible in plain concrete beams (without transverse reinforcement). The size effect issue is substantially lirited and it is observed that, with a fairly tough FRC composite, it is possible to completely eliminate this detrimental effect.