On modelling of lateral buckling failure in flexible pipe tensile armour layers

In the present paper, a mathematical model which is capable of representing the physics of lateral buckling failure in the tensile armour layers of flexible pipes is introduced. Flexible pipes are unbounded composite steel–polymer structures, which are known to be prone to lateral wire buckling when exposed to repeated bending cycles and longitudinal compression, which mainly occurs during pipe laying in ultra-deep waters. On the basis of multiple single wire analyses, the mechanical behaviour of both layers of tensile armour wires can be determined. Since failure in one layer destabilises the torsional equilibrium which is usually maintained between the layers, lateral wire buckling is often associated with a severe pipe twist. This behaviour is discussed and modelled. Results are compared to a pipe model, in which failure is assumed not to cause twist. The buckling modes of the tensile armour wires can be obtained by the presented method. ► Lateral buckling of armouring layers in flexible pipes is addressed. ► The wires are modelled as curved beams on a frictionless toroid. ► On the basis of multiple single wire analyses a flexible pipe is modelled. ► As instability occurs in the inner layer, a global pipe twist occurs. ► The torsional equilibrium is established on the basis of Newton–Raphson iterations.