Behavior and design modification of RBS moment connections with composite beams

Reduced beam section (RBS) connections are innovative connections for steel beam composite frames. The current design procedure for RBS connections is based on bare steel beams. For RBS connections with composite beams, the potential of fracture at the beam bottom flange increases because the strains at the corresponding location increase. This paper focuses on the behavior of RBS connections with composite beams. A mathematical model of the RBS connections with composite beams is derived first. Then an amplification factor is proposed for the design of the RBS connections with composite beams. Parametric analyses based on the mathematical model are conducted to examine the influence of the slab dimension, reinforcement and the beam dimension on the amplification factor. The simplified design formula is proposed for the amplification factor based on a large number of theoretical data from the parametric analysis. Finally, the mathematical models are verified by the finite element (FE) models. It is found that the proposed design formula can give satisfactory results for considering the slab effects in the design of the RBS connections with composite beams.