Non-Invasive retrofit of existing RC frames designed for gravity loads only

Abstract

Recent experimental and analytical investigations on the seismic performance of existing reinforced concrete frame buildings, designed for gravity loads only, as typically found in Italy before the introduction of seismic-oriented design codes in the 1970s, confirmed the expected inherent weaknesses of these systems [1,2]. Because of the poor detailing of reinforcement, the absence of capacity design philosophy and the use of plain round reinforcing bars, peculiar brittle failure mechanisms were observed. At the local level, most of the damage occurred in the beam-column joint panel zones, through particularly brittle failure mechanisms. At the global level, the formation of undesirable soft-stories, resulting from a combination of column hinging and exterior joint damage, greatly impaired the overall structural performance of these RC frames.