Experimental and numerical behaviour of dissipative devices based on carbon-wrapped steel tubes for the retrofitting of existing precast RC structures

The 2012 Emilia earthquake (in Northern Italy) caused extensive damage to existing prefabricated reinforced concrete structures. These buildings were found being extremely vulnerable because, being designed for vertical loads only, they featured friction-based connections between structural elements, most commonly between beams and columns. Given the large diffusion of these structures, their seismic retrofit is critical. Various techniques have been proposed in the literature, in most of which friction-based connections are removed by inserting mechanical connectors that will make beam-column connections hinged. These approaches lead to a significant increase of the base shear and therefore require strengthening of columns. The paper presents dissipative devices based on carbon-wrapped steel tubes to be used as an alternative low-damage solution for the retrofit of beam-column connections. The first part of the paper presents results of experimental tests on the devices and discusses their dissipative behaviour. The succeeding parts of the paper present numerical analyses on simple structures reinforced with the proposed device. The results of the numerical study show how the introduction of the dissipative devices produces a significant reduction of forces transmitted to the structure, by comparing the seismic response of simple frame structures equipped with dissipative devices with the response of equivalent elastic systems.