Wave-induced fatigue of multi-span pipelines

Free spanning of the multi-span pipeline is an important subject for design of pipeline in uneven seabed. The seabed intervention costs are largely influenced by pipeline spanning design, which includes assessment of trawl pullover response, vortex-induced vibrations and wave-induced fatigue. The objective of this paper is to develop a rational design methodology for the determination of the free span lengths based on the multi-span pipeline in-line fatigue assessment. Following the summary of the procedure, a detailed mathematical model for the free span movement and its analytical closed form solution are developed. The fatigue damage models are detailed both in time domain and frequency domain approaches. A numerical example is presented to illustrate the technical models.