Seismic Retrofit Schemes with FRP for Deficient RC Beam–Column Joints: State-of-the-Art Review

This paper aims to review and critically assess experimental research efforts on the seismic retrofit of existing reinforced concrete (RC) beam-column joints with fibre-reinforced polymer (FRP) sheets of the past 20 years. The review of the literature revealed several promising features of FRP strengthening schemes. FRP retrofits can be used to address a number of different deficiencies in non-seismically designed RC members framing into beam-column joints. A majority of studies concentrate on joint shear strengthening and strengthening in the axis of principle stress is found to be most effective. Other strategies include counter-acting the weak-column/strong-beam in non-seismically designed specimens by means of column flexural strengthening, as well as plastic hinge relocation within the beams, away from the joint. Only a limited number of studies look at combining several of these retrofit objectives into a more complete retrofit of the joint sub-assemblage. In most studies it is observed that simple FRP wrapping is used for anchorage, which is not always effective. Instead, it is shown that anchorage by means of FRP anchors or mechanical anchors is required to achieve adequate strengthening in most cases. Next to the detailed discussion of the literature, a database of all tested specimens is compiled and analysed. An assessment of shear strengthening design equations from major design guidelines is made based on the experimental results collected in this database, highlighting the need for their further improvement. Moreover, analysis of the database reveals a lack of tested specimens with realistic test set-ups, including scaled specimens, testing without axial load, as well lack of slab and transverse beams. It is found that these parameters heavily affect retrofit effectiveness and may lead to non-conservative results. Moreover, on average, the effectiveness of repairing pre-damaged specimens is found to be similar to that of retrofitting specimens without damage. ; JRC.A.5 - Scientific Development