Concrete or FRP Jacketing of Columns with Lap Splices for Seismic Rehabilitation

Seismic rehabilitation of rectangular columns with corner deformed bars lap-spliced at floor level through RC jacketing or CFRP wrapping, is experimentally studied. In three unretrofitted columns, deformation capacity and energy dissipation drop fast with lap length below 45-bar diameter. Three columns were cyclically tested after concrete jacketing of their full length and another nine after CFRP wrapping of the lap splice and plastic hinge region. Five CFRP layers were found to be more effective than two, but the improvement was not major. The positive effect of FRP wrapping on flexural resistance, ultimate deformation and energy dissipation declined with decreasing lap length. There is a limit to the improvement that can be obtained through FRP wrapping: if lapping is as short as 15-bar diameter, its adverse effects on force capacity and energy dissipation cannot be sufficiently removed by FRP wrapping. Overall, RC jacketing is more effective than FRP wrapping for the improvement of the deformation capacity of columns with 15-bar diameter lapping.