Cyclic behavior of RC columns strengthened by FRP and steel devices

This paper presents several results of a wide experimental program undertaken to evaluate the seismic performance of RC columns, externally confined with fiber-reinforced polymers (FRPs). Specimens consisted of full scale square columns, 300 mm on each side, reinforced by using both smooth and deformed steel rebars and subjected to a constant axial load and monotonic or cyclic flexure; in particular, two levels of the axial load were considered. Tests were conducted, in displacement control, on both FRP confined and unconfined RC columns: the confinement system was obtained by partially wrapping two or four unidirectional carbon (CFRP) or glass (GFRP) fiber layers around the member; additionally, some tests were performed on members strengthened by using both the external CFRP wrapping and longitudinal steel angles. Experimental results allowed evaluating depending on the level of applied axial load and on the type of steel rebars adopted for reinforcing each column-the benefits introduced by the considered strengthening systems in terms of strength, ductility, and energy dissipation capacity.