Seismic Retrofitting of Realistic Beam-Column Joints with Shear Failure Using FRP Sheets and FRP Anchors

One of the common deficiencies of pre-70s reinforced concrete (RC) moment frames is the shear failure of beam-column (BC) joints. In addition to that, joints with high tension demand have limited shear capacity to resist seismic actions, according to the New Zealand (NZ) seismic assessment guidelines. Fiber-reinforced polymers (FRP) have been widely used in research and practice for seismic retrofitting of BC joints prone to shear failure. However, in many cases, the tests were conducted on two-dimensional BC joints, which does not necessarily represent the limitations structural engineers face in practice, such as the presence of the diaphragm slab, transverse beams, and access limitations to the joint panel. The American Concrete Institute guidelines for FRP strengthening only mention that strengthening joints is possible but do not provide design guidance. The European fib Bulletin 90 provides design guidance but assumes that the joint panel is always available to install FRP, which is rarely the case in real structures. We have proposed a design method for shear strengthening of beam-column joints using FRP sheets and FRP anchors based on the adaptation of aforementioned design documents, published research, and first principles of engineering. The intention is for this case study to inspire other engineers who face the same issue and to encourage further research in this area.