ABSTRACT
The retrofitting of steel framed buildings by means of the insertion of braces equipped with viscoelastic dissipative devices (VEDs) turned out to be very effective to improve the seismic behaviour. For a widespread application of this retrofitting technique practical design procedures are needed. To this aim, in the present work the attention is focused on a three-bay fifteen-storey steel office building with K-braces, which, originally designed for wind and gravity loads, has to be retrofitted for a low-, medium- or high-risk seismic region. Three retrofitting structural solutions are considered: additional diagonal braces; VEDs supported by the additional diagonal braces; VEDs supported by the existing K-braces. To check the effectiveness of these retrofitting techniques, a nonlinear dynamic analysis is carried out by using artificially generated accelerograms, whose response spectra match those adopted by Eurocode 8 for the subsoil class C and for different levels of the peak ground acceleration. The frame members and the VEDs are modelled, respectively, by an elastic-perfectly plastic model and a six-element generalized model. The brace deformability is also taken into account assuming a fully elastic behaviour in tension and compression.
