NON-LINEAR STRAIN ANALYSIS OF COUPLED SUB-MARINE PIPELINES DURING THE LAUNCH PHASE

It is shown the deformation analysis, in large displacements hypothesis, for two coupled sub-marine pipes rigidly connected and launched at the same time. Hydrodynamic forces on the pipes are referred only to drag component for which the semi-empirical Morison equation is used. For the hydrodynamic coefficients the results of experimental tests, reported in literature are used. The analysis of deformation of the structure under the effects of hydrodynamic loads and axial forces is carried out within the Bernoulli's hypothesis of the conservation of plane cross sections, without any torsional and Von Karman ovalization effect. The equations of the problem were expressed as a function of the slope of the cross section. In order to solve these equations an appropriate numerical model is presented. Finally, some examples are reported in which the use of this method in practical application is shown as well as the advantage of launch of coupled pipes in respect of single ones.