Abstract An analytical model of expansion movements at the ends of pipelines is developed. A comparison with measurements on two North Sea pipelines shows that the analysis is consistent with observed behaviour, and can be used to assess the results of corrective action. An alternative mechanism, that of creep deformation in corrosion coating, is analysed briefly. Introduction Expansion due to changes in temperature and internal pressure can produce substantial movements at the ends of submarine pipelinesl. At platforms, these movements are important because they can overstress risers and elbows, and bring the pipe into contact with the platform itself. The paper begins by describing the mechanisms that give rise to expansion movements, and goes on to an analysis that predicts how much movement is to be expected. The results are compared with measurements on two North Sea pipelines. In a few instances, another mechanism may occur, and the movement may be due to creep deformation in the corrosion coating : this will be analysed briefly. Movements At The End Ofa Pipeline Consider a straight submarine pipeline connected to a platform riser (Fig.la). The riser passes through clamps on the platform, and then has a 90° elbow. At a short distance from the platform, the pipeline reaches the bottom, and from then on is continuously in contact with it. It is helpful to begin by considering why the pipeline should tend to move. The operating temperature and pressure are higher than the temperature and pressure when the pipe was tied in. Because the temperature is higher, the pipeline tends to expand. Far from the platform, the expansion is constrained by friction between the pipeline and the sea bottom, am longitudinal expansion stresses are set up. At the platform, however, the pipeline is only slightly constrained (by the vertical leg of the riser, which is relatively flexible), and there it can expand freely and move towards the platform. Alterations of pressure also cause movements. Close to the elbow, in the horizontal leg, the longitudinal stress is tensile, am the combination of circumferential and longitudinal stress induces a longitudinal tensile strain, and therefore a longitudinal movement. Far from the platform, on the other hand, longitudinal movement is prevented by friction on the bottom: there the strain is zero and the longitudinal stress is not the same as it is close to the elbow. It follows that both temperature and pressure changes induce movements. At a distance from the platform, friction prevents these movements, but it does not do so close to the platform. The movements occur within a transition region whose length depends on the limiting frictional force between the bottom and the pipeline: if friction is large, the transition region is short and the movements are small, but if friction is small the movements are larger. If the operating temperature and pressure are reduced, the movement towards the platform is reversed.