Influence of the key parameters of suspended structures on the inherent frequency of oil and gas pipelines

• Hetenyi model was adopted to analyze the inherent frequency of oil and gas pipelines.
• The influence of the 3 factors (G, T and K) are examined to achieve better stability.
• Flexural stiffness of the continuous layer (G) should be firstly increased.
• The pipe-axial precompression force (T) should be secondly considered to increase.
• The spring stiffness (K) should be improved at last.

Inherent frequency is an important parameter that reflects the dynamic stability of fluid-conveying pipelines. In engineering applications, the inherent frequency of pipelines is usually increased to improve their dynamic stability. The flow velocity and pressure of oil and gas pipelines cannot be altered freely. Among all of the parameters that affect the inherent frequency of suspended pipelines, the flexural stiffness of the stiffening girder, the tensile force of the cable system, and the pipe-axial precompression force are the most important. Revealing the influence laws of these three parameters could provide theoretical support for engineering designs. In this paper, a suspended crossing pipeline project was simplified as a Hetenyi׳s elastic foundation model. The flexural stiffness of the stiffening girder and the tensile force of the cable system were simplified as the foundation parameters G and K, respectively. The influence regularities of G, K, and the pipe-axial precompression force T on the pipeline inherent frequency were analyzed. According to the numerical simulation results, the ranks of these three parameters in descending order of importance were G, T, and K. During construction, G should be increased as much as possible. If the inherent frequency needs to be improved while pipelines have already been built up, it should be firstly considered to increase T, to values higher than zero if possible. On this basis, the further improvement of K could achieve a better result.