CFRP strengthening and rehabilitation of corroded steel pipelines under direct indentation

摘要

udud - CFRP strengthened and repaired corroded pipes were subjected to 3-point bending.udud - Three phases of deformation were observed, namely, denting, bending and denting, and structural collapse.udud - CFRP significantly increase the strength of corroded pipes.udud - The gain in strength depends on the section slenderness.udud - Two lower bounds were developed to predict the combined strength of pipes.ududududA recent paper by the authors showed that the innovative technique of CFRP repair of severely corroded steeludcircular pipes is promising. This paper presents further experimental results for two series of CFRP strengthenedudand rehabilitated pipes under quasi-static large deformation 3-point bending and direct indentation. The mainudparameters examined in this paper were the corrosion penetration in the wall thickness, its extent along the pipe,udthe type and number of the CFRP sheets. The corrosion in the wall thickness was artificially induced 360° aroundudthe circumference and in the wall thickness by machining where four different severity of corrosion were examinedudof 20% (mild), 40% (moderate), 60% (severe), and 80% (very severe). The first series was for rehabilitationudof 12 artificially degraded pipes with limited corrosion repaired using externally wrapped sheetsudwhere the extent of corrosion along the pipeline was in the range of L/D = 1.0–3.0, where L = length ofudcorrosion and D is the nominal diameter of the pipe. The second series represents strengthening of 4 degradedudpipes with corrosion that extended along the full length of the pipe. The extent of corrosion along the pipeline inudthis series was L/D = 8.0. The external diameter-to-thickness ratios examined in this paper was in the range ofudD/t = 20.32–93.6. The results show that the combined flexural and bearing strength of the pipe can be significantlyudincreased by adhesively bonding CFRP. The maximum gain in strength was 434% which was obtainedudfor the most severe 80% corrosion which extended along the full length of the pipe where L/D = 8.0. Theudaverage increase in the load carrying capacity was 97% and 169% for the rehabilitation and strengthening series,udrespectively.