Size effect of ultra‐high performance fiber reinforced concrete composite beams in shear

In this paper, a finite element model (FEM) based on a concrete damage‐plasticity approach was developed to investigate the size effect of ultra‐high performance fiber reinforced concrete (UHPFRC) and normal‐strength concrete or high‐strength concrete (NSC/HSC) composite beams. The material behavior of UHPFRC was modeled by introducing a suitable tension stiffening model to simulate the behavior of UHPFRC beams in tension. Specimens containing UHPFRC with different fiber volume content that have an overall height between 300 and 1,200 mm, a constant shear span‐effective depth ratio of 3 and no stirrups were investigated. The validity of the proposed model was established through comparisons between the experimental test results and those obtained in other studies. The results revealed that the size effect of UHPFRC members was diminished for fiber volume content higher than 1.5% due to the high ductility of UHPFRC material.