Novel Design Proposal for the Seismic Retrofit of Existing Buildings with Hybrid Steel Exoskeletons and Base Sliding Devices

Ljuba Sancin1, Chiara Bedon1, *, Claudio Amadio1
1 Department of Engineering and Architecture, University of Trieste, Piazzale Europa 1, 34127 Trieste, Italy

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© 2021 Sancin. et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Engineering and Architecture, University of Trieste, Piazzale Europa 1, 34127 Trieste, Italy; Tel: +39 040 558 3837; E-mail:



Existing Reinforced Concrete (RC) structures and brittle buildings are often exposed to seismic events that may have significant resistance and displacement demand compared to their actual capacity. Accordingly, an optimal retrofit intervention can ensure enhanced and safe structural performances for them. Among the techniques that have been addressed for the retrofit of existing RC frames, steel exoskeletons can notoriously improve the seismic performance of existing buildings due to their input stiffness, ductility and resistance. In this paper, the attention is focused on the interaction of steel exoskeletons with RC frames and the consequent details to achieve a more effective design of the retrofit intervention.


Based on parametric calculations, a new hybrid design concept that takes advantage of traditional steel exoskeletons with additional base sliding devices (at the foundation level of the RC frame to retrofit) is addressed in this paper.


As shown through SDOF and 2D-MDOF calculations, the definition of the optimal operational conditions (and thus mechanical configurations) for the so-assembled hybrid solution can maximize the potential of the retrofit intervention, with marked benefits in terms of ductility, resistance, and overall efficiency, ensuring very low damage in the existing building.


Given that the used base sliders are bidirectional, it is expected that the proposed solution could be efficiently extended to 3D structures, once the exoskeleton systems are optimally designed along the two principal directions of the hybrid structure to retrofit.


The potential of the hybrid approach is shown based on parametric analyses. Furthermore, general design recommendations are proposed for the hybrid solution.

Keywords: Existing Reinforced Concrete (RC) structures, Seismic retrofit, Steel exoskeletons, Coupled sliding system, Parametric analysis, Finite Element (FE) numerical analysis.