Analytical solution for upheaval buckling in buried pipeline

This work deals with the evaluation of the conditions that generate the local buckling in a buried pipeline due to a temperature gradient across its wall. The transport pipelines are often subjected to thermal gradients since the fluid temperature inside the pipe is greater than the external one. The minimal value of internal wall temperature depends on the physical properties of the inner fluid and thermal exchanges toward the surrounding environment. The present analysis has been performed for applications to submarine pipelines end supported by S.I.L.MAR. s.r.l. in a basic design study for pipelines in the North Sea. The problem here presented concerns the calculation of the limit elastic instability axial load in a rectilinear pipe whose ends are restrained and on which acts a constant frictional force exerted by the surrounding soil. The condition for the local buckling of the beam leads then to the comparison between the critical eulerian load for elastic instability with friction and the compressive forces acting at the extremities contrasting the axial deformation of the pipe. The mathematical model here presented allows the analytical evaluation of this critical load and then is particularly interesting in cases of rapidly varying axial load for high frictional forces where other methods (finite elements, finite differences) can give rise to significant errors due to discretization related to the modelling of the varying axial compressive force inside the elements. Finally, we hope that students and researches do not forget the objective of doing good to humanity by using human mind's conquests such as the analytical methods. (C) 2001 Elsevier Science B.V. All rights reserved.