Design spectra for the preliminary design of elastic seismic retrofit solution from the outside

The holistic renovation of the existing building stock is now recognized as a priority in order to reach the European targets in terms of sustainability, safety, and resilience. Nevertheless, the average European renovation rate of the building stock is only 1.5%. The Building Per- formance Institute Europe identified as major barriers to the renovation of the existing build- ings the need to relocate the inhabitants, the extended downtime required during the construction works, the high cost of the interventions and the lack of adequate business mod- els fostering the renovation. This is particularly true for buildings located in seismic prone areas, which require extensive structural works to be combined with energy upgrading measures. To overcome these barriers, especially those connected to the relocation of the building functions, retrofit solutions carried out from the outside of the building are generally pre- ferred. In this work, design spectra for the preliminary design of elastic seismic retrofit solu- tions carried out from the outside are derived for reinforced concrete (RC) buildings typical of the post-WWII building stock. A parametric evaluation of the retrofitted structure is con- ducted considering a simplified 2 DOF system, and a set of design spectra are defined in or- der to simplify the design procedure and to derive the optimal retrofit parameters. Finally, a reference case study representative of a typical RC building is developed to asses and vali- date the procedure.