Development For The Strength Analysis Program Of Submarine Pipeline Lifting

In the process of pipeline laying, the pipelines which were placed to the scheduled site need to be lifted from the seabed for welding. After that, they were put down and buried in the soil. One end of the pipeline was hung in the air when the pipeline was hoisted. The suspended span was long and bended severely. It was easily damaged under the complex environmental and lifting loads. It was necessary to do mechanical analysis for the pipeline lifting program in order to ensure the deformation of the pipeline within the elastic range.The suspended span was a large deflection problem of geometric nonlinearity in the process of lifting. At the same time, it was a moving boundary problem because the contact point with the seabed was unknown. Based on the large deflection theoretical of the pipeline and investigation on the specific steps of pipeline lifting construction, it developed a specific finite element analysis program for pipeline lifting which had with friendly interfaces to calculate the deformation and strength of the pipeline with the large displacement nonlinear analysis, using the APDL and UIDL secondary development language of ANSYS in the paper. The seabed was regarded as the rigid foundation model or the elastic foundation model in the caculation.The main function of this program was that it can automatically create finite element model for large displacement nonlinear analysis, got the pipeline deformation shape, axial forces of the cables, position of the contact point, stress and had strength check according to rules of DNV.Compared the calculation results with the specific pipeline laying software OFFPIPE, the accuracy and reliable of the program has been verified by the calculation of the actual project cases.