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

Abstract

This paper aims to review and critically assess experimental research efforts on the seismic retrofit of existing reinforced concrete (RC) beam-column joints with fiber-reinforced polymer (FRP) sheets of the past 20 years. A 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 nonseismically designed RC members framing into beam-column joints. A majority of studies concentrate on joint shear strengthening, and strengthening in the principal stress axis is found to be most effective. Other strategies include counteracting the weak-column/strong-beam in nonseismically 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 evaluate combining several of these retrofit objectives into a more complete retrofit of the joint subassemblage. In most studies, simple FRP wrapping is observed to be used for anchorage, which is not always effective. Instead, anchorage by means of FRP anchors or mechanical anchors is shown to be 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 analyzed. Shear strengthening design equations from major design guidelines are assessed based on the experimental results collected in this database, highlighting the need for their further improvement. Moreover, an analysis of the database reveals a lack of tested specimens with realistic test set-ups, including scaled specimens, testing without axial load, and lack of slab and transverse beams. These parameters are found to heavily affect retrofit effectiveness and may lead to nonconservative results. Moreover, on average, the effectiveness of repairing predamaged specimens is found to be similar to that of retrofitting specimens without damage.