Flexural response of underwater offshore structural members retrofitted with CFRP wraps and their performance after exposure to real marine conditions

Offshore structural members may require retrofitting due to various reasons as they age. This paper investigated strengthening and repairing of offshore steel tubular members of nominal diameter of 100 mm using Carbon Fibre Reinforced Polymers (CFRPs) subjected to four-point bending. Underwater retrofitting was compared with conventional in air retrofitting. The effect of the number of layers of retrofit was investigated parametrically for repairing and strengthening applications. Repairing corroded steel tubular members with CFRP was found to be very effective under bending. Strengthening of the steel tubular members also showed significant improvement in performance, but the improvement remained at the same level even when the number of CFRP layers increased. In the second part of the study, the durability of CFRP retrofitted tubular members was examined using 'Real Corrosion' test where the retrofitted members were fully submerged in a river (saline water) for a period of one year. While corrosion was observed in the non-retrofitted members, the CFRP layers prevented corrosion of retrofitted specimens. It was observed that the retrofit did not lose any structural integrity due to exposure to marine or underwater conditions for a prolonged period of one year. Lastly, a lower-bound interaction equation was developed for repaired steel tubular members under axial compression and bending.

Automated summary

This paper investigated the strengthening and repairing of offshore steel tubular members using CFRPs. The study found that CFRP was effective in repairing corroded steel tubular members and improving the performance of the members. Furthermore, the durability of CFRP retrofitted tubular members was found to be satisfactory even under underwater conditions.