A common finite element modeling approach for buried pipelines is the combined use of beam and spring elements. Typical loads are soil settlements, temperature variations, internal pressures, neutral topsoil weight load and traffic loads. The beam elements represent the pipeline; assemblies of spring elements represent the surrounding soil comprising an elastoplastic bedding with friction. The choice for such finite element models is a pragmatic one. The models are relatively easy to construct and the analyses can be performed within reasonable calculation time on an average PC. From a mechanical point of view the problem of a buried pipeline subjected to subsidence, or an offshore pipeline subjected to sand waves, is of a full 3D nature. Beam elements and spring elements only partly incorporate full 3D effects. In practice the common finite element models are therefore enhanced to take into account 3D effects that would be otherwise omitted. A major point is the distinction between beam action and cross sectional behavior of pipes in straight and curved sections and their mutual interaction. This paper discusses the pros and cons of two possible finite element approaches which deal with this full 3D problem. In the final example it is illustrated that the two approaches gives similar results for the relatively simple problem of a buried bended pipe subjected to a temperature load and internal pressure.

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