Force transfer between existing concrete columns with reinforced concrete jackets subjected to axial loading

The study presents the results of an experimental program concerning the force transfer between reinforced concrete (RC) jackets and existing columns. It includes 16 columns (core) of low concrete strength (fc= 24,37 MPa) with square section (150 mm side, 500 mm height, and scale 1:2). Fourteen columns have full jacketing at all four faces with 80 mm thickness and contain longitudinal bars and closed stirrups spaced at 25 mm, 50 mm or 100 mm. Twelve specimens contain dowels between the interface of old and new concrete. Ten columns have initial (construction) damages. All columns are subjected to repeated (pseudo-seismic) axial compression with increasing deformation cycles up to failure. The effects of the initial damages, of the reinforcement of the interface (dowels) and of the confinement generated by the stirrups are investigated through their axial forcedeformation (slip) diagrams