Mesoscale analysis of Fiber-Reinforced concrete beams

Unlike traditional concrete, steel fiber reinforcement improves durability and crack control. The current work developed an extensive numerical study, using a three-dimensional mesoscale model, to investigate the effect of steel fibers on the mechanical properties of steel fiber-reinforced concrete (SFRC) beams. The proposed model was developed using the numerical computing environment MATLAB. Concrete was simulated using solid elements with a damaged plasticity model. The steel fibers were randomly located and modeled by truss elements with an elastic-plastic material model, while the interface was represented by springs connecting the nodes of the concrete and steel fiber elements. Traction separation model behavior was assumed for the springs at the direction tangent to the fibers' major axis and elastic with high stiffness in the normal directions. The proposed model was validated using experimental results with different fiber ratios. Moreover, a parametric study was conducted to investigate the effect of steel fiber ratios and orientations as well as the effect of the beam size. Good agreement with differences of 3%-5% at the peak loads and 3%-18% at the post-peak loads were obtained. The orientation of the steel fibers had a big effect on the behavior of the SFRC beams. A 73% increase in the peak load of the SFRC beams with aligned fibers in the flexural direction was obtained relative to the random alignments. Whereas the beams with steel fibers aligned in different directions showed unchanged behavior and strength. The beams with smaller sizes experienced higher variation between realizations and higher peak stresses than those with larger sizes for all fiber ratios. A clear size effect of type II in peak stresses was obtained for beams with different fiber ratios.