Experimental and Numerical Investigation of Flexural Behaviour in Steel Fiber-Reinforced Concrete Notched Beam

This study investigates the influence of hooked-end steel fibres on the compressive and flexural behaviour of steel fibre-reinforced concrete (SFRC) using combined experimental testing and three-dimensional nonlinear finite element analysis (3D-NLFEA). Concrete mixes with fibre volume fractions V f = 0%,0.5%, 1.0 %, and 1.5% were cast and tested through standard cylinder compression and notched-beam three-point bending. Notched beams were tested under three-point bending with crack mouth opening displacement (CMOD) control in accordance with JCI-S-002-2003, and the resulting load–CMOD responses were used to calibrate a 3D plasticity–fracture finite element model. Experimentally, the addition of steel fibres increased compressive strength from 52.52 MPa (plain concrete) to 70.55 MPa at V f = 1.5%, while the peak flexural load in notched beams rose from 36.01 kN to 49.24 kN with increasing V f . SFRC mixes also exhibited markedly enhanced post-peak ductility and crack control, reflected in larger CMOD at comparable load levels and an extended descending branch of the load–CMOD curve. The calibrated 3D-NLFEA model reproduced the experimental load– displacement trends for all fiber contents with good agreement in peak load and overall curve shape, using post-cracking tensile contributions f t, fib in the range of approximately 2.15–2.60 MPa. Within the limitations of the specimen set and modelling assumptions, the results suggest that moderate fibre contents (around 1.0–1.5%) provide a favourable balance between strength enhancement and flexural toughness and offer a rational basis for defining tensile softening laws in nonlinear analysis of SFRC elements. Further studies on reinforced members and structural-scale elements are recommended before translating these findings into codified design provisions.