A Fourier Series Solution to Bottom Roughness Induced Stresses During Pipe Laying

by Naum Kershenbaum, Gulf Interstate Engineering Co, Houston, United States,
J. T. Powers, Gulf Interstate Engineering Co, Houston, United States,
Donald Chang, Gulf Interstate Engineering Co, Houston, United States,

Document Type: Proceeding Paper

Part of: Civil Engineering in the Oceans V


Often during installation, a subsea pipeline must be laid along seabed portions with rough profiles. The pipeline is forced by the bottom irregularities to bridge across consecutive protuberances. In many instances, the pipeline is simply supported at a single point following a double curvature pattern. These irregularities in the conditions of support cause the pipeline to be subjected to large bending stresses. These stresses, combined with the action of hydrostatic pressure, can initiate catastrophic buckling causing damage to long lengths of pipe. Also, depending on the span between supported points, it is possible that the pipe will have concurrent vibrations due to vortex shedding caused by sea current velocities. This paper presents an incremental Fourier series approximation for the solution of the beam deflection equation for a prescribed set of support conditions due to a determined bottom profile. It also provides valuable information on deflections, pipe slopes, and stresses at any point of the pipeline section under analysis. The analysis procedure is set in a spread sheet program environment. An example of the use of the analysis procedure is also presented.

Subject Headings: Offshore pipelines | Fourier analysis | Stress analysis | Pressure pipes | Underwater pipelines | Pipes | Displacement (mechanics) | Computer models

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