Experimental and numerical investigation of FRP-based post-seismic repair for damaged RC columns

This study explores the post-seismic retrofit of reinforced concrete (RC) columns with fibre-reinforced polymer (FRP) systems. Known for their high strength-to-weight ratio, corrosion resistance, and ease of application, FRP materials are widely used in seismic retrofitting, though their use in repairing damaged elements remains less explored. In this study, RC columns initially subjected to combined static and cyclic lateral loading, with a resulting 20% strength loss, were retrofitted and re-tested. A constant axial load equal to 10% of the concrete’s compressive strength and lateral push–pull forces were applied during the test. Damaged regions were restored using repair mortar, followed by external bonding of carbon FRP (CFRP) fabrics in tension zones, confinement wrapping, and base anchorage reinforcement. The repair strategy adhered to Eurocode 8 – Part 3 and Eurocode 2 – Annex J. Re-tested columns exhibited notable gains in strength, ductility, and energy dissipation. Finite element (FE) models of the undamaged reference and retrofitted specimens were developed in ABAQUS, validated against experimental results, and used in a parametric analysis to assess the contribution of each strengthening component to the yield and ultimate strength. The test results confirm the effectiveness of CFRP systems in restoring and enhancing the seismic performance of previously damaged RC columns. The proposed numerical model reasonably predicts the behaviour of the retrofitted specimen and highlights the significant contribution of CFRP spike anchors in preserving the integrity of the retrofitted specimen.