Beam-Column Joints Strengthened with Steel FRP and Steel FRCM: Experimental Investigations

A new generation of composite material systems made of steel tapes in lieu of the more common carbon or glass fiber sheets has recently emerged for the seismic strengthening and repairing of reinforced concrete (RC) members. The steel tapes, whose first applications in Italy already date back to L’Aquila earthquake in 2009, consist of high tensile strength steel cords made by twisting steel wires within a micro-fine brass or galvanized coating; they can be applied in situ via wet lay-up by using polymeric or inorganic matrices, thus obtaining strengthening systems which can be gathered within the FRP (“Fiber Reinforced Polymers”) or FRCM (“Fabric Reinforced Cementitious Matrix”) families, respectively. This study investigates the feasibility of steel FRP and steel FRCM systems in improving the seismic performance of exterior RC beam-column joints. An experimental program was organized which includes fifteen specimens, most of which were strengthened by using different layouts while the remaining ones were used as benchmarks. The results of cyclic tests are examined through a comparison with the outcomes of the previous experimental program including companion specimens not provided with transverse beam stubs and strengthened by carbon FRP systems.