Full-field strain distribution and failure characteristics of CFRP-repaired steel structures

•Different repairs were designed to strengthen steel structures using CFRP.•Effects of repair method/configuration on strain distribution were investigated.•Damage evolution process was analyzed in comparison with strain distribution.•Hybrid repairs exhibited initial adhesive failure and final rivet shearing.•Various failure modes were characterized for different repair method/configuration. Mechanical behavior and fracture characteristics of adhesively bonded and hybrid bonded-riveted repairs with stepped single-side and double-side configurations were investigated. Digital image correlation (DIC) technique was used to systematically investigate the effects of repair configuration and repair method on full-field strain distribution and damage evolution process of CFRP-repaired steel structures under static loading. The strain distribution and evolution in the repairs were quantified to figure out failure process and fracture characteristics in details. The failure process of hybrid repairs displayed two stages including initial adhesive failure and final rivet shearing, and the behavior of rivets could prevent catastrophic failure of CFRP-repaired steel structures. Progressive failure process of different repairs indicated that crack initiated and propagated on the edge of repaired region between CFRP laminates and substrates, which was in good agreement with the findings from strain distribution. Mixed failure modes including adhesive failure, thin-layer cohesive failure, light-fiber-tear failure, stock-break/delamination and rivet shearing were identified for specific repairs.