Design for seismic upgrading of existing RC frames by friction dampers

Nowadays, many buildings with RC framed structure need to be seismically upgraded. The insertion of steel braces equipped with friction dampers within the framed structure is a promising seismic upgrading technique. In fact, steel braces and friction dampers reduce the storey drift demand providing additional lateral stiffness and energy dissipation. Furthermore, friction dampers cap the forces transmitted by braces avoiding that the upgrading system overload the existing structure. In this paper a design procedure of the bracing-friction damper system is formulated. The design procedure is applied to a case study frame considering different combinations of the design parameters. The analysis of the seismic response of the bare and rehabilitated frames provides information on the effectiveness of the upgrading technique and proper setting of the design parameters.