Abstract
With the exploitation of offshore oil and gas gradually moving to deep water, higher temperature differences and pressure differences are applied to the pipeline system, making the global buckling of the pipeline more serious. For unburied deep-water pipelines, the lateral buckling is the major buckling form. The initial imperfections widely exist in the pipeline system due to manufacture defects or the influence of uneven seabed, and the distribution and geometry features of initial imperfections are random. They can be divided into two kinds based on shape: single-arch imperfections and double-arch imperfections. This paper analyzed the global buckling process of a pipeline with 2 initial imperfections by using a numerical simulation method and revealed how the ratio of the initial imperfection’s space length to the imperfection’s wavelength and the combination of imperfections affects the buckling process. The results show that a pipeline with 2 initial imperfections may suffer the superposition of global buckling. The growth ratios of buckling displacement, axial force and bending moment in the superposition zone are several times larger than no buckling superposition pipeline. The ratio of the initial imperfection’s space length to the imperfection’s wavelength decides whether a pipeline suffers buckling superposition. The potential failure point of pipeline exhibiting buckling superposition is as same as the no buckling superposition pipeline, but the failure risk of pipeline exhibiting buckling superposition is much higher. The shape and direction of two nearby imperfections also affects the failure risk of pipeline exhibiting global buckling superposition. The failure risk of pipeline with two double-arch imperfections is higher than pipeline with two single-arch imperfections.
Highlights
Pipeline global buckling is one of the major issues in pipeline design [1], especially for deepwater pipelines
The comparisons displayed above shows that the pipeline with 2 initial imperfections may suffer from the superposition of lateral global buckling, making the lateral displacement, axial force and bending moment increase much faster, and harming the stability of pipeline systems
The ABAQUS/Explicit numerical simulation method is used to calculate the lateral deformation of pipelines with 2 imperfections
Summary
Pipeline global buckling is one of the major issues in pipeline design [1], especially for deepwater pipelines. A global buckling simulation method called the Buckle-Explicit united algorithm is proposed for finite element analysis with the software ABAQUS This method first calculates the most likely geometry feature of an initial imperfection based on the modal analysis results, and outputs the geometry of the imperfection through the “Nodefile” keyword. The comparisons displayed above shows that the pipeline with 2 initial imperfections may suffer from the superposition of lateral global buckling, making the lateral displacement, axial force and bending moment increase much faster, and harming the stability of pipeline systems.
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