Detailed Contact Analysis of the J-Tube Riser Pull-In Method
J-tube method of riser installation is a conventional method of connecting the subsea pipelines to fixed offshore platforms which are abundant in the Norwegian and international waters. The integrity of the J-tube, its supports, riser itself and the platform has to be maintained during pull-in of a riser into a J-tube. To ensure this, it is required that the pull-in and reaction forces, in addition to the riser plastic strain and J-tube stresses should be established either by detailed finite element contact analysis or by simplified methods available in literature. With the advances made in the finite element procedures and tools in the past decades and due to the higher degree of accuracy that they can capture, the contact analysis is often the preferred approach. Various parameters contribute to the riser pull-in operation which should be represented accurately in a finite element analysis to provide reliable results. Among others, they include the riser back tension (lay tension, seabed friction, etc.), riser J-tube friction, riser material’s yield stress and constitutive model, riser and J-tube fabrication tolerances, boundary conditions, clearances, etc. In addition, there are numerical modeling parameters such as the friction model (contact friction-clearance/overclosure relationship) and the details of the material’s constitutive model which can affect the accuracy and convergence of the analyses. In this paper, the general trends of response are presented with respect to physical variations of these parameters. Pull-in force, J-tube equivalent von-Mises stress and riser plastic strain are the response indicators which are studied. Analyses are performed using ABAQUS general-purpose finite element package [1]. The conclusions based on the observed trends can help to decide these input parameters as every individual project (i.e. study, detailed phase, etc.) and client requires.