Abstract
This paper presents a probabilistic approach for lateral buckling analysis based on a global FE model via a case study of a 5km long subsea flowline with sleeper mitigators on an undulating seabed. In the case study, axial/lateral pipe-soil interaction (PSI), pipe/sleeper friction factors, and horizontal out-of-straightness (OOS) of flowline at seabed and sleepers are defined as stochastic parameters, while other parameters, including flowline as-laid vertical OOS, pipe section and operating parameters, are defined as deterministic variables. First, the response surfaces for lateral buckling of the full-length flowline due to the stochastic parameters are created through FE analyses based on a load case matrix selected by the Design of Experiments approach. Then, Monte Carlo simulations based on the response surfaces are performed to obtain the distributions of lateral buckling responses, including parameters such as the limit-states for post-buckle, buckle amplitudes, walking speed or end pile loads, rogue and engineered buckle locations. Lastly, the probability distributions of the limit-state unity checks are compared with the target failure probabilities. This probabilistic approach will require more simulation time compared to the deterministic approach but can provide more detailed probability ranges for the lateral buckling responses and save the project on total cost. This approach can be used to assess the reliability of lateral buckling responses during the detailed design phase of subsea pipelines susceptible to lateral buckling.
