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Structural response of a compliant pipe-in-pipe under frictionless and frictional conditions of the seabed.

Mohammed, Auwalu I.; Bartzas, Konstantinos; Johnson, Callum; Spence, Stuart; Skyes, Paul; Kidd, George; McConnachie, Jennifer; Njuguna, James


Konstantinos Bartzas

Callum Johnson

Stuart Spence

Paul Skyes

George Kidd

Jennifer McConnachie


Pipe-in-Pipe (PIP) technology has been studied significantly owing to its superior performance in deep-water and high-pressure high temperature fields than conventional single pipe. The PIP system has excellent track record of mitigating flow assurance problems from subsea wells through maintenance of the fluid's temperature in the pipe. It has also been applied in marine environment where conventional single pipe cannot perform. However, owing to complex interaction and contact within the PIP system and seabed, the mechanism of load transfer and the stresses that developed due to pressure, temperature and combined loading has not been fully understood and quantified. Therefore, this study examined the effect of pressure, temperature and the combined loading on PIP systems for flat seabed subsea pipeline. Simulations are performed to examined frictional and frictionless conditions of the flat seabed on PIP system and individual results of inner pipe, insulation material and outer pipe are presented for each analysis. The analytical calculations are carried-out for determining the operating stresses in each component of the PIP system in view of its significance for the overall structural behaviour of the system and validation of the numerical model. The impact response of the inner pipe, insulation and the outer pipe based on pressure, temperature and the combination of both (pressure and temperature) and the resulting stress on each component of the PIP system are investigated and the result presented. Furthermore, results of axial, radial and hoop stresses for the individual loading condition and with coupled analysis corresponding to each simulation (Frictional and Frictionless seabed conditions) are found to be closely similar with percentage difference less than 5 except for the von Mises stress which give 5.3%. This interesting finding revealed that the friction force does not affect structural integrity of the PIP system compared to conventional - single pipeline assuming all other parameters remains constant. Moreover, the presence of the outer pipe and the insulation material enhanced the performance of the inner pipe. The numerical simulation predicts closely the impact response for pipe-in-pipe composite specimens under individual and combined loading conditions. Therefore, the results obtained will serve as a reference guide for designing, construction and operating PIP system in the future to develop unconventional challenging energy resources like High Pressure High Temperature fields.


MOHAMMED, A.I., BARTZAS, K., JOHNSON, C., SPENCE, S., SYKES, P., KIDD, G., MCCONNACHIE, J. and NJUGUNA, J. 2023. Structural response of a compliant pipe-in-pipe under frictionless and frictional conditions of the seabed. Ocean engineering [online], 276, article 114020. Available from:

Journal Article Type Article
Acceptance Date Feb 17, 2023
Online Publication Date Mar 21, 2023
Publication Date May 15, 2023
Deposit Date Mar 27, 2023
Publicly Available Date Mar 27, 2023
Journal Ocean engineering
Print ISSN 0029-8018
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 276
Article Number 114020
Keywords PIP; Pipeline stress; FEA; Seabed; Pressure; Temperature
Public URL


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