Technical References#
SPT 2023: Lateral Buckling Design using the Friction Distributions at the Expected Buckles#
Operation at temperature and pressure of exposed subsea pipelines results in effective axial forces which may cause lateral buckling. To perform the lateral buckling design, the subsea pipeline industry typically uses a combination of Monte-Carlo simulations and finite element analysis.
The Monte-Carlo simulations are used to determine the longest VAS that can be reliably exceeded (characteristic VAS), and FEA is used to determine the longest VAS with acceptable mechanical conditions (tolerable VAS). The lateral buckling configuration then needs to ensure that the characteristic VAS is less than the tolerable VAS along the whole pipeline.
This paper presents a methodology that can be implemented through the introduction of minimal changes to the recommendations of DNV-RP-F110. The methodology is based on a Monte-Carlo algorithm which determines the soil friction distributions of the expected buckles, and then an approach in which the tolerable VAS is in turn determined using these soil friction distributions of the buckles. The paper presents the application of the proposed approach to a case study to illustrate the significant impact this can have on the overall lateral buckling design.
The Monte-Carlo algorithm used in this paper has been released under an open-source license to facilitate the implementation of this methodology by the industry.
SPT 2023: Lateral Buckling Design using the Friction Distributions at the Expected Buckles
ISOPE 2024: Retrospective Analysis of the Lateral OOS and Buckling Response of Operational Deep-Water Pipelines#
This paper examines the lateral buckling response of the pipelines in a deep-water field. This includes retrospective probabilistic analyses as per DNV-RP-F110, a review of the available survey data and a comparison of the predictions of the analyses with the actual observed responses.
From the reviews of the data and the results of the comparisons, aspects of the design code that could be improved are identified and recommendations are made. The paper also reviews the published pipeline out-of-straightness data and makes recommendations on how to improve it for use in probabilistic lateral buckling assessments.
SPT 2025: Analysis of Horizontal OOS Survey Data for use in Probabilistic Lateral Buckling Design#
The lateral buckling design of surface-laid, subsea pipelines can be optimised by using probabilistic design methods. In areas where the seabed has limited vertical unevenness, the key inputs used in these Monte Carlo simulations are the probability distributions for the pipe-soil interaction and for the lateral out-of-straightness (OOS).
For the pipe-soil interaction response, physical models have been developed based on experimental work and geotechnical principles and distributions can be predicted if adequate geotechnical data is available. For the OOS features however, it is not possible to make predictions based on engineering principles, since these features are the result of random deviations from the intended pipeline route during pipelay. Instead, for this parameter, the industry relies mostly on the empirical distributions that were developed by the Safebuck JIP, based on OOS data from pipelines installed before 2014. These distributions are currently presented in DNV-RP-F110 [Ref. 1].
The approach used in the Safebuck JIP to quantify OOS features consists in performing Finite Element analyses of sections of as-laid survey data to determine the axial force at which a buckle forms (with a certain lateral friction). The ratio of this force and the value predicted by a reference analytical equation (with the same lateral friction) represents the effect of the worst OOS feature in the section analysed. By repeating this process for many sections of survey data, distributions of OOS features can be developed.
This paper presents a modified version of the Safebuck approach to process OOS survey data and applies it to the data of pipelines installed as part of a TotalEnergies project. The approach proposed considers a different scale length than the DNV-RP-F110 distributions, which simplifies the treatment of route curves and allows generating significantly more data from the available survey data.
Sensitivity analyses are also performed to evaluate the robustness of the approach to quantify OOS features, including the effect of the breakout and residual lateral friction and the mobilisation displacements considered in the FE analyses and the appropriateness of the reference analytical equations used in the processing of the FE results.
Based on these results, the paper proposes a detailed methodology to produce a systematic quantification of the OOS features, based on mathematical post-processing and Finite Element modelling of the survey data. The paper also discusses the creation of an industry-wide database of OOS data, intended to gradually improve the OOS distributions available for the design of new pipelines.
SPT 2025: Analysis of Horizontal OOS Survey Data for use in Probabilistic Lateral Buckling Design