Effect of Non-homogeneity of Seabed Soil on Natural Frequency of Offshore Free Spanning Pipeline

Sarkar, Goutam; Roy, Pronab

doi:10.1007/978-981-16-5673-6_11

Cited by 2 publications

(1 citation statement)

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“…Nevertheless, Sarkar and Roy [36] performed parametric studies for computing the frequencies with various magnitudes of parameters (i.e., thickness, diameter, span length, and homogeneous soil stiffness) up to a maximum free span of 100 m using the finite element method and the DNVGL-RP-F105 [24] guidelines. Additionally to these, Sarkar and Roy [37] also determined the frequency by considering the nonhomogeneous soil stiffness using Abaqus. Last but not least, DNVGL-RP-F105 [24], which is the design guideline for free-spanning offshore pipelines used by the most dominant oil and gas industries, developed an empirical equation for computing the frequency by including the effects of the static deformation of the pipe, axial forces, and the stiffness of the supporting soil.…”

Section: Introductionmentioning

confidence: 99%

An Analytical Expression for the Fundamental Frequency of a Long Free-Spanning Submarine Pipeline

Phuor,

Trapper,

Ganz

2023

Mathematics

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The DNVGL-RP-F105 guidelines provide essential techniques for the preliminary design of undersea pipelines. However, its approximations for static displacement and the natural frequency of the pipe are restricted to cases where the ratio of the pipe’s diameter to its length (L/D) is less than 140. This limitation poses challenges for longer spans, which, although rare, can sometimes be unavoidable. This study introduces a novel analytical method, rooted in the energy method and cable theory, for computing the static deformation and natural frequency of long free-span underwater pipelines. We conducted a comprehensive verification of our proposed method by comparing its outcomes with those of 212 finite element analysis simulations. The results reveal excellent predictions for long spans. However, for shorter spans, traditional methods remain more accurate. Additionally, we explored the influence of pipeline’s diameter, thickness, and boundary conditions on both static displacement and frequency, providing valuable insights for design considerations. We found that the boundary conditions’ impact on the fundamental frequency becomes negligible for long spans, with up to a 10% difference between pinned–pinned and fixed–fixed conditions. In essence, this research offers a vital enhancement to the existing DNV guidelines, becoming particularly beneficial during the preliminary design phases of pipelines with L/D ratios exceeding 140.

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Section: Introductionmentioning

confidence: 99%