Selective upgrade of underdesigned RC beam-column joints using CFRP

Seismic regions are characterized by reinforced concrete (RC) structures that have been designed without seismic provisions. As the structural upgrade of such structures becomes necessary, one of the approaches that recent design guidelines suggest is that of the hierarchy of strenght. By increasing the strenght and ductility of critical components, their brittle and catastrophic failure is prevented and the occurrence of more desiderable mechanisms is promoted. This approach allows improving the global behavior of the structure. The key issue of strengthening design od RC frames is represented by the beam-column connection. This paper presents a technique based on fiber-reinforced polymer (FRP) composites for the seismic upgrade of RC beam-column connections that was validated with tests on 11 initially underdesigned specimens. The results of the experimental investigation are presented, and a discussion on how different parameters influenced the behavior of the samples in terms of strength or ductility, or both, is offered.