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Snap behaviour in the upheaval buckling of subsea pipelines under topographic step imperfection
Abstract Pipelines exposed to high temperature and high pressure with a topographic step imperfection are susceptible to the phenomenon of upheaval buckling potentially leading to a hazard for the structural integrity of the pipeline. To analyse this problem we derive analytical upheaval buckling solutions and obtain the locations of maximum displacement and maximum axial compressive stress. We also analyse the typical post-buckling behaviour and its dependence on step height, axial soil resistance and wall thickness. The difference in behaviour between a pipeline with step imperfection and one with a symmetric prop imperfection is discussed. Our results show that a pipeline with a step imperfection is more prone to upheaval buckling than a perfect pipeline. For sufficiently small step heights the pipeline may suffer a snap-back instability under decreasing thermal loading, raising the possibility of hysteretic snap behaviour under cyclic thermal loading (for instance caused by periodic start-ups and shut-downs). The snap-back buckling disappears for large enough step height and the minimum critical temperature difference decreases with increasing step height and wall thickness or with decreasing axial soil resistance. The maximum compressive stress decreases with increasing step height and axial soil resistance or with decreasing wall thickness. A pipeline with step imperfection is safer than one with a symmetric prop imperfection.
Highlights We develop a mathematical model for upheaval thermal buckling of a subsea pipeline under a step imperfection. Analysis of the model reveals the possibility of hysteretic snap buckling under cyclic thermal loading. A parameter study shows that snap buckling back to the unbuckled state disappears for large enough steps. The maximum compressive stress decreases with increasing step and axial soil resistance and with decreasing wall thickness.
Snap behaviour in the upheaval buckling of subsea pipelines under topographic step imperfection
Abstract Pipelines exposed to high temperature and high pressure with a topographic step imperfection are susceptible to the phenomenon of upheaval buckling potentially leading to a hazard for the structural integrity of the pipeline. To analyse this problem we derive analytical upheaval buckling solutions and obtain the locations of maximum displacement and maximum axial compressive stress. We also analyse the typical post-buckling behaviour and its dependence on step height, axial soil resistance and wall thickness. The difference in behaviour between a pipeline with step imperfection and one with a symmetric prop imperfection is discussed. Our results show that a pipeline with a step imperfection is more prone to upheaval buckling than a perfect pipeline. For sufficiently small step heights the pipeline may suffer a snap-back instability under decreasing thermal loading, raising the possibility of hysteretic snap behaviour under cyclic thermal loading (for instance caused by periodic start-ups and shut-downs). The snap-back buckling disappears for large enough step height and the minimum critical temperature difference decreases with increasing step height and wall thickness or with decreasing axial soil resistance. The maximum compressive stress decreases with increasing step height and axial soil resistance or with decreasing wall thickness. A pipeline with step imperfection is safer than one with a symmetric prop imperfection.
Highlights We develop a mathematical model for upheaval thermal buckling of a subsea pipeline under a step imperfection. Analysis of the model reveals the possibility of hysteretic snap buckling under cyclic thermal loading. A parameter study shows that snap buckling back to the unbuckled state disappears for large enough steps. The maximum compressive stress decreases with increasing step and axial soil resistance and with decreasing wall thickness.
Snap behaviour in the upheaval buckling of subsea pipelines under topographic step imperfection
Wang, Zhenkui (author) / van der Heijden, G.H.M. (author)
Marine Structures ; 69
2019-08-31
Article (Journal)
Electronic Resource
English
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