The Role of the Depth and Width on the Shear Strength of Fiber Reinforced Concrete Beams: An Experimental Study

This paper reports recent results of an experimental campaign on Fiber Reinforced Concrete (FRC) beams under shear loading tested at the University of Brescia, focusing on the size effect issue and the role of the width on the shear strength. With the first regard, nine full scale beams, having a height varying from 500 to 1500 mm, were tested for investigating the effect of steel fibers on size effect. Concerning the effect of the width, eight shallow beams (all having depth of 250 mm) with two different width, fiber content and, also, minimum amount of classical shear reinforcements, were tested for evaluating the shear response of typical structural members utilized in Italy in residential buildings. Results show that a relatively low volume fraction of fibers can significantly increase shear bearing capacity and ductility. The latter determines visible deflection and prior warning of impending collapse, which is not possible in plain concrete beams (without transverse reinforcement). The size effect issue is substantially limited and it is observed that, with a fairly tough FRC composite, it is possible to completely eliminate this detrimental effect. Shallow beams do not show the typical brittle failure also without any shear reinforcement and the effect of fibers is even more prominent than in deep beams.