This paper presents the results of finite element (FE) analysis of axially loaded square hollow
structural steel (HSS) columns, strengthened with polymer-mortar materials. Three-dimensional
nonlinear FE model of HSS slender columns were developed using thin-shell element, considering
geometric and material nonlinearity. The polymer-mortar strengthening layer was incorporated
using additional layers of the shell element. The FE model has been performed and then verified
against experimental results obtained by the authors [1]. Good agreement was observed between
FE analysis and experimental results. The model was then used in an extended parametric study to
examine selected AISC square HSS columns with different cross-sectional geometries,
slenderness ratios, thicknesses of mortar strengthening layer, overall geometric imperfections, and
level of residual stresses. The effectiveness of polymer-mortar in increasing the column’s axial
strength is observed. The study also demonstrated that polymer-mortar strengthening materials is
more effective for higher slenderness ratios. An equivalent steel thickness is also accounted for the
mortar strengthened HSS columns to discuss the effectiveness of polymer-mortar strengthening
system. The polymer-mortar strengthening system is more effective for HSS columns with higher
levels of out-of-straightness. Level of residual stress has a slight effect on the gain in the column’s
axial strength strengthened with polymer-mortar.