PSI - Issue 78

Alessandro Fulco et al. / Procedia Structural Integrity 78 (2026) 2046–2053

2053

Fig. 9 Building C: a) View of the exoskeleton emerging from the envelope; b) plan and elevation of the connection system.

5. Conclusions General rules and examples of design and construction for earthquake-resistant internal and external additional systems for the seismic retrofitting/upgrading of existing structures are presented. This intervention strategy, using exoskeletons or endoskeletons, achieves high performance levels while meeting requirements such as limiting interference from internal spaces or preserving the structure. The choice of additional system type is, in fact, related to the client's requirements, and in any case, the additional structures are characterized by flexibility and modularity in terms of planimetric and elevation positioning. The distinctive feature of the additional systems is the connection system designed to transfer the floor forces in the case of exoskeletons and to decouple the masses in the case of endoskeletons. In the former case (exoskeletons), the device adopted allows the transfer of floor seismic forces between the two coupled structures without generating critical axial stresses for the existing columns. The device has elastic-plastic behavior with a threshold that can be adjusted based on the stresses transmitted to the foundation. In the second case (endoskeletons), the connection device not only allows the envelope to be decoupled from the endoskeleton with respect to coplanar seismic actions, but also allows the walls to be retained with respect to first- and second-mode mechanisms. In both strategies and in the proposed design examples, the devices are always accessible and replaceable. The use of these techniques allows for calibrating capacity enhancement interventions without affecting the existing structure and using additional resources. Endo/exoskeleton systems are also extremely effective in limiting displacements and therefore story drift, thus ensuring extremely limited impacts even on non-structural elements. Finally, the connection systems could also be dissipative and therefore designed to reduce stresses in the foundation, resulting in cost savings on the construction aspects. References Dall ’ Asta, A., Ragni, L., Tubaldi, E. (2005-2008). Design methods for existing R.C. frames equipped with buckling restrained braces and dissipative braces based on High Damping Rubber. DPC-ReLUIS Tecnologie per l ’ Isolamento ed il Controllo di Strutture ed Infrastrutture. NTC2018. Norme Tecniche per le Costruzioni D.M. 17 gennaio 2018, Consiglio Superiore dei Lavori Pubblici, GU Repubblica Italiana, Roma. Foraboschi, P., Giani, E. 2017: esoscheletri prerogative architettoniche e strutturali - prima parte advantages, limitations, and opportunities in the use of exoskeletons - first part. Structural 214 – paper 33 – ISSN 2282-3794 Fulco, A., Mezzi, M., Comodini, F. 2020: Practical procedure to assess the expected consequences of earthquakes on buildings, Procs. 17thWCEE, Sendai. Japan. Mezzi, M., Marzullo, M., Valletta, G., 2008. Synergetic action of new and existing structures in re-using a 18th century monastery. 6th International Conference on Structural Analysis of Historical Constructions, Bath, UK. Mezzi, M., Petrella,P. , 2013. Experiences from the Reconstruction After the 2009 L'Aquila Earthquake. Damage, Vulnerability, Retrofitting, ISEC-7 New Developments in Structural Engineering and Construction. Honolulu, USA Balducci, A., Castellano G., Seismic retrofitting of a RC school building through the “ Damping Towers ” system. Progettazione Sismica – Vol. 6, N. 1, Anno 2015