Extension and validation of the triangular plate method for fiber-reinforced concrete: a comparative study against the EN 14651 three-point bending test

Concrete has high compressive strength but limited tensile capacity and deformation, leading to brittle failure. This study extends the Triangular Plate Method (TPM), originally developed for cement-based materials, to steel fiber-reinforced concrete (SFRC) and validates it against the EN 14651:2005 + A1:2007 three-point bending (TPB) test. Plain and fiber-reinforced concretes containing hooked-end steel fibers at 0.3%, 0.6%, and 0.9% were tested using equilateral triangular plates and notched beams. Load-displacement responses were used to evaluate tensile strength, ductility, and toughness. The results show that steel fibers have a limited effect on compressive strength but markedly improve post-cracking stability, tensile performance and energy absorption, particularly at fiber contents of 0.6% and above. The strong correlation between TPM and TPB toughness values demonstrates that TPM can reliably assess SFRC under biaxial bending-type stress conditions and support practical evaluation of plate-like fiber-reinforced cementitious elements.