Seismic Upgrading of an Existing Steel Structure Using Inverted Y-braces

The paper describes an application of steel eccentric bracing with vertical shear link (inverted Y-bracing) for seismic retrofitting of an existing school building. The building is located in a little village of a high seismic zone in Italy. The existing structure presented several structural defects and irregularities which required an “ad hoc” intervention of seismic upgrading for both gravity and earthquake loads. The proposed technical solution, also in agreement with the new seismic regulations, improves the seismic performance, increasing stiffness and resistance, as well as global ductility, of the lateral-force resisting system. The upgraded structure allowed satisfaction of current minimum Italian code requirements, evaluated by means of static nonlinear analysis. The paper highlights general design concepts, while also providing some details about capacity design of connections between the newly added structural elements and the existing structure. Global modelling issues and connection design offer perspectives on research needs for this type of applications.