Seismic behavior and retrofit of steel moment connections considering slab effects

A series of five full-scale subassemblages were tested to investigate the contribution of the slabs and the effects of three types of retrofit methods, no weld access hole, horizontal stiffener, and cover plate. The test included one bare steel specimen and four composite specimens with floor slab. The results that emphasize the influence of the composite slab on connection behavior and specific comments on the retrofit scheme are presented. The test result indicated that the strains near the bottom flange of the composite beam connections were several times larger than those of the bare steel beam connections, resulting in a higher potential of fracture. Therefore, the slab effects are detrimental to the seismic behavior of the connection and should be considered in the design. Horizontal stiffener detail of three retrofit schemes demonstrated very good potential in improving the ductility of composite connections in existing buildings.