Performance indices to assess the efficiency of external FRP retrofitting of reinforced concrete short columns for seismic strengthening

Structural reinforcement is an economical and ecological method of preventing damage caused by seismic loading. Indeed, it is estimated that two out of three buildings will become unsafe over the next 40 years if no policy of treatment for existing constructions is adopted. FRP strengthening appears to be an advantageous method of structural strengthening due to the mechanical properties of the composite and the ease of application in the damage area. Various reinforcement systems have been presented in the literature, characterized by several parameters (FRP materials, configuration, reinforcement ratio, anchored bars etc.). This paper proposes the use of a performance index, based on a damage index, to assess the efficiency of external FRP reinforcement retrofitting using three experimental investigations. The influence of (i) axial compressive loading, (ii) the shape of the reinforced short column, (iii) the presence of FRP bars and (iv) FRP reinforcement on the performance index of the columns is determined. A parameter ξ is also defined to evaluate the performance of the columns according to the geometrical configuration and mechanical properties of the FRP reinforcement.