Flexural behavior of external beam-column reinforced concrete assemblages externally strengthened with steel cages

In this paper, an experimental study referring to the flexural behavior of full-scale external beam-column joints externally strengthened with steel angles and strips and subjected to cyclic reversal loading is presented. One control specimen and five other specimens having the same characteristics as the control specimen but strengthened with steel angles and strips along beams and columns, and characterized by different configurations of strengthening in the critical regions, were tested. The control specimen was designed with a weak column and strong beam to reproduce the most common cases of old frame structures in the Mediterranean area, which were designed only for gravity loads and are in need of retrofitting to seismic standards. A detailed discussion of the strengthening technique used and of the mechanical properties of the specimens studied under cyclic loading is presented. It is highlighted that, referring to the case of external beam-column assemblages that are not yet extensively studied in the literature, the steel cage is an effective reinforcing technique to increase the flexural and shear strength of beams and columns, also increasing the energy capacity dissipation and reducing the stiffness degradation.