Mechanical Response and Failure Mechanism of AFRP-repaired Corroded CHS Tubes Under Axial Compression

Corrosion-induced defects, extensive and unavoidable in marine structures, pose significant threats to structural integrity and safety. This study aims to assess mechanical response and investigate the failure mechanism of composite-repaired circular hollow section (CHS) steel tubes. A feasibility analysis is conducted through verifying the axial compression performance of a uniformly corroded tube and an Aramid fiber-reinforced polymer (AFRP) strengthened perfect tube. Subsequently, mechanical responses of the corroded and AFRP-repaired tubes are studied, accompanied by parametric studies to comprehensively evaluate the influence of corrosion region, and the depths and densities of corrosion pits. Consequently, critical damage modes of the AFRP patches are explored using a user-defined material subroutine developed based on Hashin failure and Yeh delamination damage criteria. Numerical predictions indicate that composite patches improve the structural residual strength, but not necessarily enhance the structural ductility under diverse failure patterns. In addition, AFRP patches contribute to improving the overall structural load-bearing capacity by alleviating local buckling or regional collapse. Moreover, fiber compression damage emerges as the dominant mode. Premature failure of putty agent initiates stress concentration, intensifies subcritical damage, aggravates critical damage, and expedites final failure.