Abstract Subsea pipelines with a free suspended span segment may be subject to upheaval buckling under high temperature, which may lead to a failure mode such as local buckling, fracture and fatigue. Mathematical models are established to study the upheaval buckling behaviour of subsea pipelines with a free span segment. Then, the accurate locations of the maxima of displacement and stress are obtained. The buckled configuration and the typical post-buckling behaviour and their dependence on free span length are analysed. Furthermore, a detailed analysis is presented for critical temperature difference, displacement amplitude and maximum axial compressive stress. Finally, the influence of touchdown on post-buckling behaviour during the process of upheaval buckling is discussed. The results show that the pipeline is prone to upheaval buckling when the free span length is large enough and the critical temperature difference decreases with increasing free span length. The displacement amplitude and the maximum stress within the span increase with the increase of the free span length before touchdown. However, after the pipeline touches the bottom of the free span, the maximum stress within the span decreases significantly compared to the case without touchdown, which becomes further smaller for smaller depth of the free span.

中文翻译：

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自由跨越管道热剧屈曲分析研究

摘要 具有自由悬跨段的海底管道在高温下可能会发生剧变屈曲，从而导致局部屈曲、断裂和疲劳等失效模式。建立了数学模型来研究具有自由跨度段的海底管道的剧变屈曲行为。然后，获得位移和应力最大值的准确位置。分析了屈曲配置和典型的屈曲后行为及其对自由跨度长度的依赖性。此外，还对临界温差、位移幅度和最大轴向压应力进行了详细分析。最后，讨论了在隆起屈曲过程中触地对屈曲后行为的影响。结果表明，当自由跨长度足够大时，管道容易发生隆起屈曲，临界温差随着自由跨长度的增加而减小。随着接地前自由跨距长度的增加，位移幅值和跨距内的最大应力也随之增加。然而，管道接触自由跨底后，跨内最大应力与未接触情况相比显着降低，自由跨深度越小，该应力进一步越小。