Ultimate strength of hybrid repaired offshore pipelines with various slenderness ratio subjected to through-thickness pitting corrosion under axial compressive loading

Offshore pipelines are susceptible to various types of corrosions where pitting corrosion is generally considered the most severe. This study aims to study the effect of ratio of Carbon Fiber Reinforced Polymer to Glass Fiber Reinforced Polymer and wrapping patterns on the repair performance of composite repair system for offshore pipelines subjected to pitting corrosion. Four sets of samples with different slenderness ratios are subjected to axial compression, where the peak loads are recorded as the performance indicator of different repair schemes. Based on the experimental results, the average repair index, which is the ratio of repaired strength to intact strength, increases from 1.06 to 1.40 as the ratio of CFRP to GFRP increases. However, 1G3C repair schemes experience brittle failure while other repair schemes show different extents of ductility upon failure. Longitudinal wrapping pattern achieves the average repair index of 1.19 while Alternate and Horizontal yields the average repair index of 1.18 and 1.15 respectively. Furthermore, Longitudinal wrapping pattern exhibits the highest rigidity followed by Alternate and Horizontal. A higher slenderness ratio can contribute to a lower repair index where the cross-sectional properties have a more prominent effect compared to sample length. The theoretical results calculated based on equations provided in ASME PCC-2 show good agreement with the experimental results as there is only a percentage difference of 5.5% between them.