Cyclic behaviour of composite joints with reduced beam sections

Some design recommendations or standards, such as FEMA-350 and Eurocode 8 Part 3, recommend reduced beam section (RBS) connections to be used in earthquake-prone zones and practical design guidelines are provided accordingly. These recommendations, however, are mainly based on research conducted on joints without floor slabs. In reality, steel beams are often connected to reinforced concrete (RC) floor slabs by shear connectors. Thus, it is important to explore the performance of RBS joints with floor slabs. In this paper, cyclic test results of four such joint specimens are reported, where concrete-filled steel tubular (CFST) columns were connected to the RBS beams by utilising through-diaphragms. To compare with the RBS joints, two reference joint specimens with or without slab were also tested. The experimental results are analysed to evaluate the influence of floor slabs on the cyclic performance of composite joints with RBS beams. It is found that composite joints with floor slabs still exhibit favourable seismic performance, and have good potential to be widely used in seismic regions. However, the presence of the floor slab should be considered in designing RBS connections.