Hybrid fiber use on flexural behavior of ultra high performance fiber reinforced concrete beams

In this study, the flexural behavior of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) beams produced in mono and hybrid forms were investigated experimentally and numerically. Twelve doubly reinforced concrete beams were casted with four different reinforcement ratios representing low to excessive levels. The beams were produced in three groups to study the effects of mono and hybrid steel fiber usages. The first group beams of four are non-fiber beams while the second group contains only short-straight fiber of 13 mm. The last group is composed of hybrid form where the short-straight fiber of 13 mm and the long-hooked fiber of 60 mm were blended together. The beams were subjected to four-point loading, and the parameters of deflection and curvature ductilities, flexural stiffness, flexural moment capacity, cracking behavior and compressive strain were discussed. The test results indicated that the UHPFRC beams with high reinforcement ratios above the limits in current design codes provide remarkable benefits through the fibers' contribution. It can be deduced that the hybrid fiber usage showed better flexural performance, in general, comparing to the mono form. In addition, two numerical approaches were proposed to predict nominal moment capacity of the UHPFRC beams in the mono or hybrid form.