An innovative FRP confining system for repairing rectangular columns

This paper introduces the Sandwich Wrapping Confining System (SWCS) for strengthening rectangular columns. The SWCS replaces the conventional FRP sheet wrapping system with a sandwich wrapping confining system made up of two FRP faces separated by a light incompressible core. Unlike the thin FRP sheet system, which has only axial stiffness, the SWCS has both axial and flexural stiffness. The flexural stiffness contributes significantly to the confinement of the flat sides. Thirty rectangular columns of varying dimensions are upgraded and repaired using the SWCS and tested to failure. Nonlinear finite-element analysis is used to investigate the behavior of the strengthened columns. The results indicate that the SWCS can be used to improve the strength, stiffness, and ductility of rectangular columns.