Influence of fiber orientation on flexural-based design of steel fiber-reinforced concrete slabs: Experimental and numerical program

Steel fiber-reinforced concrete (SFRC) has proven to be a suitable structural material for constructing elevated flat slabs, and several existing office and residential buildings, in which SFRC was used for these components, highlighted the positive outcomes from both technical and sustainability perspectives. However, research on the influence of fiber orientation on the flexural performance of SFRC slabs is relatively scarce despite the fact that a number of studies revealed that the use of constitutive models derived from three-point bending tests on notched beams leads to overestimations of the bearing capacity of statically indeterminate slabs. In this context, this study aims at presenting an extensive experimental program that consisted of testing three SFRC slabs (3.0 x 3.0 x 0.1 m3) subjected to point load under a statically indeterminate test configuration. The testing procedure was followed by the extraction of 88 cores in order to analyze both fiber distribution and orientation by means of a non-destructive inductive method. The results indicate that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the 150 x 150 x 600 mm3 notched reference beams tested to characterize the pre- and post-cracking flexural performance of the SFRC produced. Based on these results, a straightforward design-oriented approach to compute an orientation factor was proposed and considered to develop the constitutive law used to simulate the structural response of SFRC slabs by means of nonlinear finite element model. The numerical simulation results showed a good agreement with the experimental response, this evidencing that the orientation factor may permit to account for the differences caused by geometric and statistical scale-induced factors between both the beams used for the SFRC flexural properties characterization and slabs produced with the same SFRC.