This study investigates the axial compression behavior of hollow steel columns (HSCs) with and without defects, specifically horizontal and vertical slits, and strengthened using Glass Fiber Reinforced Polymer (GFRP) wrapping. Twelve specimens were tested for failure under axial compression. The parameter varied in the study are circular and square sections and type of slit. Experimental and finite element analyses (FEA) were performed to evaluate the structural performance of intact and defective columns. The load-carrying capacity HSC with a horizontal slit was increased by 20 % when compared to the control specimen without a slit. GFRP wrapping was applied in three plies to enhance load-bearing capacity by 50 % and mitigate the effects of structural deficiencies. The results demonstrated that GFRP significantly improved the axial load capacity and ductility of the columns, particularly in defective specimens, by reducing stress concentrations around the slits. Failure modes were analyzed, showing delayed local buckling, reduced plastic hinge formation, and controlled rupture or delamination of GFRP layers. FEA simulations in ANSYS replicated the experimental behavior accurately with a minimal error of less than 5%, providing insights into stress distribution, load–axial deflection characteristics, and failure mechanisms. This study underscores the effectiveness of GFRP wrapping as a strengthening technique for improving the performance and reliability of deficient CHSCs.
