Flexural behavior of steel–concrete ultra-shallow floor beams (USFBs) with precast hollow-core slabs

•The flexural behavior of steel–concrete composite USFBs with PCHCS is investigated.•A finite element model of USFBs is developed.•A parametric study is carried out.•The plastic neutral axis position is measured.•The theoretical model underestimated the resistance of USFBs with PCHCS. This paper aims to predict the flexural behavior of steel–concrete composite ultra-shallow floor beams (USFBs) with precast hollow-core slab (PCHCS). A finite element model based on tests is developed. A parametric study is conducted, and the influence of the geometric parameters is discussed. The finite element results were compared with stress block analysis. It was concluded that the modeling with two symmetry planes offered better computational cost, and the flexural behavior of steel concrete USFBs was sensitive to dilation angles. From the parametric study, the models without steel tie bar through the web openings showed lower bending capacity. The variation of the reinforcement ratio of the concrete topping contributed to the cracking control. The plastic neutral axis position was measured, considering the mid-span vertical displacement at 10 mm, 50 mm and 100 mm. From the stress distribution it was observed that to define the resisting moment, the P.N.A. closest to the top tee can be considered. The theoretical model underestimated the resistance of USFBs with PCHCS.