Among the modern techniques envisaged to improve the seismic performance of structures there is the supplementary energy dissipation, which consists in absorbing part of the seismic input energy in special devices which are not part of

the frame supporting gravity loads; this approach is aimed at preventing structural damage, increasing life-safety and achieving a desired level of performance. In the first paper of this series (Structural 237 – settembre/ottobre 2021 – paper 25) a quick and simple design procedure for the seismic retrofit of frame building by means of energy dissipating devices with non-linear, displacement dependent behaviour was presented. In this second paper a theoretical framework of the principles of energy dissipation is provided, followed by an in-depth study on the regulatory requirements established in the Italian Building Code (NTC 2018) and in the European standard EN 15129, with a focus on Displacement Dependent Devices (DDD).

Then, the contribution presents the evolution of DDD by discussing the main original research efforts as well as the most relevant drawbacks, and by presenting some practical applications of the devices currently available on the market.