Assessment of Orientation Factor for Flexural-Based Design of Steel Fibre Reinforced Concrete Slabs: Experimental and Analytical Investigation

Current codes and recommendations are evolving towards an approach that proposes the orientation factor to consider differences between small-scale characterization steel fibre reinforced concrete (SFRC) specimens and the real-scale elements. Moreover, several research studies revealed that the use of constitutive models derived from three-point bending tests (3PBT) on notched beams tend to overestimate the bearing capacity of statically indeterminate two-way slabs. With this in mind, an experimental programme was carried out in order to evaluate the flexural behaviour of three SFRC slabs (3.0 × 3.0 × 0.1 m3) subjected to point load under a statically indeterminate test configuration. Thereafter, 88 cores were extracted from the tested slabs with the following analysis of fibre orientation by means of a non-destructive method. The results indicated that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the reference notched beams used for the material characterization (i.e., 3PBT). Based on these results, an orientation factor was analytically computed and considered to develop the constitutive model used to predict the ultimate load of the analysed SFRC slabs by means of yield line method (YLM). The prediction showed a good agreement with the experimental response; this evidencing that the orientation factor may permit to consider the differences caused by geometric and scale-induced factors between both prismatic notched beams used for SFRC characterization and real-scale slabs produced with the same material.