Numerical analyses of improved beam-to-column connections

This paper presents the results of non-linear finite element analyses on two types of improved steel moment-resisting connections, either reinforced with cover plates or weakened with RBS detail: the aim is to protect the potentially vulnerable beam-to-column groove welded joint by relocating the plastic hinge away from the face of the column. The investigation is based on results from experimental tests carried out on a two-storey steel frame tested at Ispra and involves the modeling of the 3-way beam-to-column joints. Numerical analyses on reinforced joints show that fracture indices decrease in the weld region and near the weld access hole respect to the unreinforced connection, but high values of the Triaxiality Index are registered in the weld at the column interface. In order to eliminate the high shear stress in the beam flange and to reduce the high triaxial stress condition at the beam flange-column flange interface, the beam flange was disconnected from the column flange. The reduced beam section detail provided both in the top and bottom beam flanges reduces the vulnerability of the connection to the occurrence of a fracture near the weld: yielding is concentrated within the reduced section of the beam where large inelastic strains are registered