Low and medium strength concrete members confined by fiber reinforced polymer jackets

The objective of this study is to evaluate the effects of unconfined concrete compressive strength and the thickness of the external jacket on the stress-strain behavior of fiber reinforced polymer (FRP) jacketed concrete specimens, particularly on the strength, ductility and energy dissipation characteristics. In this experimental study, totally 16 concrete cylinder specimens are tested under axial compression. The unconfined concrete compressive strength for 8 specimens is around 30 MPa, while the remaining 8 specimens have the concrete compressive strength around 6 MPa. In each set, two unconfined specimens are tested without any strengthening, and other specimens are tested after they are externally confined by 1, 3 and 5 plies of FRP jackets in sets of two. Test results indicate a significant enhancement in compressive strength, ductility and energy dissipation for the externally confined specimens for both low and medium strength concrete, with a more pronounced effect on low strength concrete. Consequently, the investigated strengthening technique may be more preferable when dealing with structural members that have the problems of low compressive strength and ductility.