Abstract Polypropylene (PP) plastic pipes have recently gained widespread application in non-pressurized gravity pipes used for seawater intake lines in the petrochemical industry. These pipes consist of a solid wall base pipe, on which an outer reinforcement called the omega-profile is spirally winded and hot fusion bonded. The omega-profile is usually filled with grout to provide on-bottom stability for subsea installation. It is of high importance that the bond between the omega-profile and the base pipe has sufficient strength to provide resistance against buckling of the pipeline system. The objective of this study is to investigate the collapse behaviour of such large-diameter PP pipes subjected to a negative internal pressure. The bond is modelled with cohesive zone modelling technique with the aim to determine the failure mode that governs the collapse behaviour of the pipe, e.g. buckling or delamination. Experiments where conducted on single cantilever beam (SCB) specimens cut from the pipe to determine the cohesive bond strength between the omega-profile and base pipe. The findings from the experiments are implemented in a full pipe model, where the surface between the omega-profile and base pipe is assigned bond strength characteristics in accordance with the experimental results. The FEA results of the non-linear collapse analysis of the full pipe model show that for the range of grout stiffness values considered (0 ≤ Eg ≤ 30 GPa), the governing failure mode of the pipe is initiated by buckling and proceeded by delamination. For delamination to govern the failure mode, a grout stiffness greater than 36 GPa in combination with a weaker bond strength than the experimentally measured would be required. The methodology presented in this study gives a rather accurate tool for the design and analysis of this type of structures, and can reliably assess the bond strength level required in view of the governing failure modes, e.g. buckling and delamination.

中文翻译：

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使用内聚区建模技术对大型塑料管进行坍塌分析

摘要 聚丙烯（PP）塑料管最近在石油化工行业海水取水管线的非承压重力管中得到了广泛应用。这些管道由实心壁基管组成，其上称为 omega 型材的外部加强件螺旋缠绕并热熔粘合。欧米茄型材通常填充水泥浆，为海底安装提供底部稳定性。欧米茄型材和基管之间的连接具有足够的强度以提供抵抗管道系统屈曲的能力是非常重要的。本研究的目的是研究这种大直径 PP 管在负内压下的坍塌行为。结合使用内聚区建模技术建模，目的是确定控制管道坍塌行为的失效模式，例如屈曲或分层。在从管道上切割的单悬臂梁 (SCB) 试样上进行的实验，以确定欧米茄型材和基管之间的内聚粘合强度。实验结果在全管模型中实施，其中欧米茄型材和基管之间的表面根据实验结果分配了结合强度特性。全管模型非线性坍塌分析的 FEA 结果表明，在考虑的灌浆刚度值范围 (0 ≤ Eg ≤ 30 GPa) 中，管道的主要失效模式是由屈曲引发，然后是分层。对于分层来控制破坏模式，需要大于 36 GPa 的灌浆刚度以及比实验测量值更弱的粘结强度。本研究中提出的方法为此类结构的设计和分析提供了相当准确的工具，并且可以根据控制失效模式（例如屈曲和分层）可靠地评估所需的粘合强度水平。