Seismic performance of RC beam-column joints retrofitted with steel dissipation jackets

This article presents an experimental campaign on full scale RC beam–column joints subjected to cyclic loading. A joint specimen, belonging to a 4-storey RC framed building designed to only withstand gravity loads, was firstly tested without retrofitting elements. It was then damaged and re-tested after the application of a retrofitting system named DIS-CAM. The main objective of the intervention was to increase the seismic performance of the joint in such a way as to achieve the same response as that of a joint which has been seismically designed in accordance with the Italian code for a peak ground acceleration equal to 0.25 g. A companion seismic specimen was purposely designed and tested to facilitate a direct comparison in the analysis of the effectiveness of the retrofitting technique. The paper describes the design and the execution of the retrofitting intervention which does not require particular technologies being essentially made up of steel L-profiles placed at the corners of the involved structural members, confined by stainless steel ribbons and connected at the beam–column intersection by steel dissipation elements. After the application of the retrofitting system the non-seismic specimen was tested again and its behaviour was compared with that of the seismically designed specimen. The strengthened joint shows remarkable increments in strength and deformation capacity, despite the previous damaging test, with respect to the as-built non seismic joint. Furthermore, its capacity is almost equal to that of the seismically designed joint and it does not manifest the unfavourable performance found in the latter.