numerical investigation on structural behaviors of deficient steel chs long columns strengthened using cfrp

Structures often suffer damage due to various factors, including accidental loads, corrosion, and reduced strength, necessitating the need for repairs. the use of carbon fiber reinforced polymer (cfrp) to strengthen steel members has gained considerable attention in recent decades. however, most previous research has focused on studying the behavior of non-deficient steel structures. this study aims to investigate long steel circular columns with primary defects in vertical and horizontal notches, and examine the effects of cfrp retrofitting. a total of fifteen specimens of steel long circular hollow section (chs) columns, each with the same height but varying damage dimensions, were analyzed using abaqus 2016 software under compressive load. the main challenge with long columns is global buckling under compressive loads. to improve the accuracy of the analysis, a combined method was employed to study the post-buckling behavior of the plastic zone. specifically, the specimens underwent elastic buckling analysis followed by riks non-linear analysis considering both general and local imperfections. the results showed that defects in the steel columns reduced the load-bearing capacity by up to 52%. horizontal defects had a greater impact on reducing the ultimate load compared to vertical damage (up to 13%). additionally, deficiencies significantly affected the buckling of the defect area, resulting in axial deformation. cfrp retrofitting strengthened the columns, increasing the ultimate load capacity (up to 51%), delaying defect buckling, controlling fractures, and reducing stresses in the damaged zone.