Strengthening rectangular concrete columns using FRP: A new technique

The objective of this paper is to introduce an innovative sandwich wrapping confining system (SWCS) for upgrading and repairing rectangular columns. The system described here replaces the conventional fiber reinforced polymer (FRP) wrapping, which has only axial stiffness, by a sandwich wrapping confining system that has both axial and flexural stiffness. The new system is made up of two FRP faces separated by a light incompressible core. Experimental and numerical analyses are performed on rectangular columns upgraded and repaired using the SWCS. Thirty rectangular columns with different dimensions are upgraded and repaired using the SWCS and tested to failure. A numerical study based on nonlinear finite-element analysis (material nonlinearity) is used to investigate the behavior of the columns repaired using the SWCS and to predict the experimental failure loads. Finally, the experimental and the analytical results are compared. Unlike conventional FRP jackets, the SWCS can be used to improve the strength, stiffness, and ductility of rectangular columns.