Wave loading fatigue reliability and uncertainty analyses for geotechnical pipeline models

Abstract

The challenges involved with the fatigue damage assessment of a catenary pipeline in the touchdown zone (TDZ) are primarily because of the non-linear behaviour of pipe-seabed interaction and considerable uncertainty in geotechnical model parameters. The research undertaken in this study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. Furthermore, this paper presents the probability of failure associated with fatigue analysis of a catenary pipeline in the TDZ due to the uncertainty in seabed response model and geotechnical parameters. A first-order reliability method is used for predicting the fatigue safety index. The fatigue analysis results prove that the confounding results indicated by the previous research studies on the catenary pipeline in the TDZ are due to different geotechnical parameters imposed with the soil model. The main benefit of employing a reliability-based fatigue analysis framework is that it enhances the confidence in the steel catenary riser analysis with seabed interaction

Influences of pipe–soil interaction on dynamic behaviour of deepwater S-lay pipeline under random sea states

“…This model can sufficiently account for the effects of initial plastic penetration into the seabed, non-linear soil resistance, breakaway of the pipe from the seabed, finite soil suction, separation of the pipe from the seabed and repenetration of the pipe into the seabed. Meanwhile, the non-linear hysteretic seabed model proposed by Randolph and Quiggin (2009) was validated against laboratory and field-scale model experiments with reasonable accuracy, which has been implemented into the software OrcaFlex (Orcina 2014) for a riser or pipeline analysis due to valuable features and advantages (Westgate et al 2010;Elosta et al 2013Elosta et al , 2014Quéau et al 2013). Lately, Shiri (2014aShiri ( , 2014b applied the non-linear hysteretic seabed model proposed by Randolph and Quiggin (2009) to systematically investigate the influence of steel catenary riser dynamics and consequent stress changes on the fatigue life.…”

Two-phase flow induced vibrations in a marine riser conveying a fluid with rectangular pulse train mass

“…It is observed that the maximum fatigue damage per year caused by 2-FIV is in the order of 0.028, which could be higher than the one caused by waves. To have an idea, waves can cause fatigue damage per year of 0.001 in a SLWR (Felisita et al, 2017) and from 0.0013 to 0.004 at the TDP in a steel catenary riser (SCR) when considering a linear stiffness soil model (Elosta et al, 2014). On the other hand, slugging happens mostly at the end of the service life for hydrocarbon facilities, and therefore, the total cumulative fatigue damage can be kept under acceptable levels.…”

Report of Committee III.2: Fatigue and fracture

“…Adopting a non-linear model, the geotechnical parameter sensitivity has been investigated because of the considerable uncertainty. Fatigue reliability is not extensively investigated for riser design and a first-order reliability method has been adopted to estimate the fatigue safety index (Elosta et al, 2014).…”