Behavior of square and circular columns strengthened with aramidic or carbon fibers

The confinement of reinforced concrete (RC) columns with transverse reinforcement has been extensively studied and it is known that the response of concrete cylinders subjected to equivalent levels of pressure depends on how that lateral pressure is transmitted, and not on its magnitude alone. When confinement is, additionally to that given by steel stirrups, provided by external jackets of fiber reinforced polymers (FRP) the complexity and the scarcity of experimental data increase and tests to gain insight into the structural behavior and consequent design procedures are still required. The present study reports tests performed on axially loaded RC columns, with and without jackets. The FRP tested were made either of carbon fibers reinforced polymers (CFRP) or aramidic (AFRP) wraps and the geometry of the specimens included square and circular cross-sections. Comparison of gains of axial strength and ductility are presented and aspects of the variation of the lateral pressure and rupture of FRP jackets are examined.

► Gain of axial load capacity of RC columns from FRP jacket confinement.
► Estimate of efficiency of confinement on prismatic columns by geometry factor.
► Maximum confinement stresses at the corners of square sections.
► Aramidic versus carbon fiber confinement on improvement of column ductility.
► Sharp corners prevent improvement of capacity and ductility from CFRP confinement.