Characterization of the shear strength of steel fiber reinforced concrete beams

The application of the theory of probability and statistics for the characterization of the shear strength of steel fiber reinforced concrete beams is discussed in this paper. Such characterization is of interest considering that general design guidelines for such beams are still lacking, while on the other hand the potential range of application of the beams is known to be wide. Their use is particularly attractive in the construction of ring beams and small structural members, since problems that are normally encountered when using conventional reinforcement can be reduced. Labor reduction with respect to fabrication and placement of stirrups can lead to significant cost savings. With the aid of the powerful paired-difference t test, the expected mean difference in ultimate shear strength of two beams, with equal steel content provided for shear reinforcement but alternately reinforced with stirrups and steel fibers, is computed. The bounds of this mean are also calculated, and hence it is possible to estimate the maximum difference within prescribed statistical parameters; levels of significance. Consequently, by designing the shear requirements of a beam using the well established guidelines for reinforcement using stirrups, an estimate of the strength of a steel fiber reinforced concrete beam, equivalent to the conventional beam on the basis of volume fraction, can be made. Based on a comprehensive experimental program, the proposed difference can be used in a wide range of design situations.