Strengthening of corroded steel CHS columns under axial compressive loads using CFRP

Abstract

Stemming from unfavorable environmental conditions, corrosion can adversely affect the behavior of steel structures and damage them. To investigate this phenomenon and study the failure mode and load bearing capacity of corroded slender steel columns to retrofit them by Carbon Fiber Reinforced Polymer (CFRP), 8 equal-height slender Circular Hollow Section (CHS) column specimens were subjected to corrosive conditions at mid-height and near to bottom supports for 12, 18 and 24 hours, retrofitted by CFRP sheets and then all corroded and retrofitted columns were experimentally tested under axial compressive loading; damage dimensions were different. These specimens and two more were also studied numerically based on the Finite Element (FE) analyses of imperfected models using ABAQUS software. The specimens were first analyzed elastically to find their local and global buckling modes and then inelastically (with nonlinear geometry and material). Experimental and numerical results showed that the main problem with slender columns was their global buckling under compressive loading and corrosion reduced their load bearing capacity and ductility. According to these results, corrosion highly affected the buckling of the corroded area and deformed it axially. Regarding corroded columns retrofitted with CFRP, fibers increased the ultimate load capacity and ductility, delayed buckling of the corroded area, controlled fractures and reduced stresses in the damaged zone.