Design Method of Lightweight Steel Exoskeletons for Seismic-Energy Upgrading of Existing RC Buildings

All over the world, the built heritage suffered a lot of damages and collapses after seismic events due to several structural deficiencies. Also, it is known the importance of limiting energy consumption in the building sector, which is one of the major sources of greenhouse gas emissions. These issues suggested an integrated approach in the building retrofit. Among the multiple techniques developed in recent years, this research focused on lightweight steel exoskeletons combined with thermal insulating panels for seismic-energy retrofitting purpose. The main focus of the paper is to develop a seismic design method for lightweight steel exoskeletons to provide an efficient guide for designers. The used system is the Resisto 5.9 seismic coat, which is made of cold-formed profiles with bolted connections having X-bracing as seismic-resistant systems. The results of the research are herein presented with the application of the proposed procedure to an existing RC 2D frame building analyzed by a FEM calculation model. Starting from the capacity curves of the existing frame, the design method allows to size the cross-section of diagonal members. Subsequently, pushover analyses are carried out on the structure reinforced with the proposed system to assess the global behavior of the building and to validate the theoretical design curve. Finally, the results derived from the proposed analysis procedure show the effectiveness of the retrofitting system to obtain the seismic upgrading of the inspected RC structure, as well as the effectiveness of the presented design method.