Experimental Test Methodology for Moment Redistribution in Statically Indeterminate FRC Beams

Moment redistribution in structures is crucial for ensuring the safety, resilience, and efficiency of a building. There are few studies that address this phenomenon in fibre reinforced concrete (FRC), both with and without reinforcing bars. These studies used a two-span, one-way, continuous beam set-up, with point loads on each span. Although the system is, in theory, symmetric, the response is not symmetric due to differences in geometry, materials, and experimental errors. Therefore, a plastic hinge usually forms on only one of the two spans, in addition to the one over the central support. The asymmetric response makes the analysis cumbersome. In this paper, a different methodology for testing statically indeterminate FRC beams is presented. In it, a partially restrained support is materialized at both ends of a one-span beam. The configuration is completely described, which includes: load cells in the supports; LVDTs for midspan deflection, for the support rotation, and for crack opening displacements (COD); and Digital Image Correlation also for COD. Preliminary results of a beam tested in this configuration are shown and advantages and disadvantages are analyzed compared to the two-span, continuous beam set-up. Although the analysis of the proposed set-up is more straightforward, the rotational stiffness (κ) of the partially re-strained supports (defined as the relationship between the moment (M) and the angle of rotation (θ): κ = M/θ) should be carefully defined in the system to reflect the real behavior of FRC continuous members.