On the effectiveness of steel fibers as shear reinforcement

An experimental study on steel fiber-reinforced concrete (SFRC) beams subjected to shear loading tested at the University of Brescia in recent years is presented and discussed. A total of 18 full-scale experiments were carried out, aimed at investigating the effect of randomly distributed steel fibers within the concrete matrix on shear behavior. The focus was on the parameters influencing the shear response of members, including concrete class, fiber content, and mixture of different fibers. All tested members contained no conventional shear reinforcement. All SFRCs used were characterized in tension according to the provision included in the fib Model Code 2010. A useful database-with other tests published elsewhere-was developed, linking the shear strength of members to the codified residual strengths of the corresponding fiber-reinforced concrete (FRC) materials. Results show that a relatively low amount of fibers (Vf < 0.7%) can significantly increase the shear strength and ductility of concrete beams without transverse reinforcement. Moreover, visible cracking and noticeable deflections offer ample warning of impending collapse in FRC members. A critical discussion of two recent analytical models for calculating the shear strength of FRC materials is also provided.Copyright © 2013, American Concrete Institute. All rights reserved