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Pitting corrosion poses a threat to plated steel structures serving in aggressive corrosion environments. This paper involves numerical studies on the structural behaviour and ultimate strength reduction of plated steel structures due to random pitting damage. Stochastic simulations were used to model the random nature of the pitting corrosion varying pitting shape, depth and distribution. A series of nonlinear analyses were performed on unstiffened plates and stiffened panels to understand the mechanisms of structural collapse due to random pitting damage. Empirical formulae were derived respectively for the prediction of ultimate strength reductions of unstiffened plates and stiffened panels in terms of regression analysis from the numerical results. Random pitting corrosion induces a variation and reduction in ultimate strength, and can lead to a transition in failure mode. The collapse of pitted structures under uniaxial compression has a feature that the onset of plasticity initiates in the areas close to the unloaded edge of the structure, and propagates into a continuous plasticity region linking the pits with highly concentrated stress. The pitted area with intensively stress-concentrated pits undergoes a locally amplified deformation that determines the failure mode, leading to structural failure.

Exploration of deeper oceans for oil and gas requires increasingly lightweight solutions. A key enabler in this aspect is the use of fiber-reinforced composite materials to replace metals in risers. However, design synthesis and analyses of composite risers are more challenging than for conventional metals due to the complex behavior and damage mechanisms which composite materials exhibit. Composite risers are predicted to be a high-impact technology that will be mainstream in the medium term but there is still relatively little literature pertaining directly to the behavior of these materials under the complex loading scenarios arising from their use in deep water structures. Therefore there is a need to perform a review and assessment of the available technologies and methodologies in the literature to gain a good understanding of their predictive capabilities, efficiency and drawbacks. This article provides a comprehensive review of published research on manufacture, experimental investigations and numerical analyses of composite risers in deepwater conditions determining the gaps and key challenges for the future to increase their application.

Due to environmental challenges it is important to investigate potentially more sustainable new materials, including natural fibre reinforced composites. Whilst a number of natural reinforcements show promise there is a concern that laminate properties are too difficult to predict due to the lack of uniformity in natural fibres. The paper quantitatively evaluates the high variability observed at yarn scale, at cloth scale, which shows significant decreases, and at laminate scale, showing comparable variability to synthetic based composites. This demonstrates that natural fibre reinforced composites have reproducible properties at the macroscale level and provides a pathway to application in industry.