Research advances and design specification codification of retrofitting techniques for steel structures

Retrofitting steel structures is not only beneficial for guaranteeing the safety of the structures in services, but also fits the idea of sustainable development. It is of positive significance to scientifically implement the ‘urban renewal’ and promote the achievement of the ‘double carbon’ targets. In terms of steel members, five retrofitting approaches by enlargement of section area, including the welding method, bolt connections or rivet connections, bonded steel plates, bonded fiber-reinforced polymers and composite retrofit, and prestress strengthening method, were summarized in this article. As for the connection and joints, the research advances of retrofitting combining connection with bolts and welds, beam-column joints, bolted spherical joints, welded spherical joints, and tubular joints were illustrated. Meanwhile, the research progress of retrofitting the steel structural system by indirect approaches and repairing techniques for local damage was outlined. On this basis, the representative technical points of GB 51367—2019 ‘Standard for design of strengthening steel structures’ were introduced. In the future, research efforts are suggested to make for developing quantitative design methods of traditional strengthening techniques, retrofitting technique and design theory of steel joints, theory of CFRP retrofitting, application of innovative materials and techniques, and reinforcement mechanism of structural system. © 2022 Science Press. All rights reserved.