Axial performance of locally corroded circular steel tubes strengthened with outer steel and sandwiched concrete jackets

• Applied axial compression to locally corroded steel tubular columns reinforced with STSJC. • Localized corrosion changed SCSHSTs' failure mode, causing concentrated deformation and larger bulges in corroded areas . • FE analysis showed corrosion caused stress concentration but improved concrete load support and interlayer contact stress. • Han's model effectively predicted the load-bearing capacity of corroded SCSHSTs. Hollow steel tubes (HSTs) are extensively utilized in bridge and building structures due to their excellent mechanical properties. However, prolonged service can result in localized corrosion, which compromises their load-bearing capacity. This study introduces a composite strengthening technique that employs outer steel tubes and concrete jackets (STSJC) and examines its reinforcement effect on locally corroded HST columns through experimental testing and finite element (FE) analysis. The findings indicate that this technique significantly enhances the load-bearing capacity and ductility of the specimens, with localized corrosion exerting a particularly pronounced effect on ductility. Furthermore, the FE analysis elucidates the stress concentration caused by localized corrosion, while also reinforcing the collaborative force mechanism between the inner and outer steel tubes and the concrete jackets, thereby augmenting the proportion of load supported by the concrete. Additionally, the study assesses existing load-bearing capacity calculation models, with Han's model exhibiting the highest applicability.