Retrofit of RC joints with FRP composites

The exterior and corner beam-column joints are among the weakest members of RC (reinforced concrete) frames in terms of seismic resistance. Poor seismic performance of inadequately detailed exterior/corner joints can lead to total or partial collapse of reinforced concrete frame structures. Since most of the existing beam-column joints in relatively old structures have not been constructed properly in terms of reinforcement detailing, they are in urgent need of retrofitting, particularly in terms of shear strength. To address a solution for this problem, from beginning of 1990s up to now, many researchers spent efforts on retrofitting of beam column joints by making use of conventional and FRP (fibre reinforced polymer) materials. In this study, after the introduction of typical failure modes of RC beam-column joints, available results on the behaviour and retrofitting of exterior and corner beam-column joints are reviewed and discussed. Furthermore, the most common FRP retrofitting schemes and contribution of the FRP retrofitting to behaviour of exterior beam columns are examined. Additionally, the large-scale structural tests conducted at Istanbul Technical University (ITU) on retrofitting of beam column joints built with low strength concrete and plain bars by FRP sheets are summarised. Based on the available research, it seems possible to include the issue of seismic retrofit of RC joint using FRP materials in the future versions of seismic design/retrofit guidelines/codes.