Seismic upgrading of RC frames using new hybrid dampers with recentering capability applying the second-generation of eurocode 8

This paper investigates the seismic upgrading of existing RC frames whose design was governed by the gravity loads in earthquake-prone regions, using new hybrid energy dissipation devices with recentering capability and applying the analytical methods of the second-generation of Eurocode 8. The energy dissipation devices combine in parallel three components (viscoelastic, elastoplastic and superelastic) that control the response under frequent (viscoelastic) and severe (elastoplastic) earthquakes, and minimize the permanent deformations (superelastic). Frames representative of residential buildings having short, medium and long fundamental periods are considered. Beams, columns and joints with brittle shear failure or insufficient ductility are first upgraded, applying local measures to attain a lateral deformation capacity of 2% of story height that ensures cost-effective strengthening with the hybrid energy dissipation devices. It is shown that the RC frames seismically upgraded with the proposed approach can endure the maximum earthquake foreseen in a high seismicity region with moderate (economically feasible to repair) damage and negligible permanent deformations. It is also shown that the energy-balance-based analysis implemented in the second-generation of Eurocode 8 for displacement-dependent dampers, with elastoplastic restoring force characteristics, can be applied with some limitations to design and verify structures featuring energy dissipation devices that include a superelastic component.