Although it is not strictly necessary that a laybarge have a stinger, PLDYNA offers a multi-section stinger set modelling capability to enable proper articulated stinger modelling. Fixed stinger can also be modelled as an extension of the barge by attaching the rollers to the barge if a stinger definition is not provided.
A fixed stinger analysis is simpler than analysis with an articulated stinger as stinger dynamics is no longer involved in the analysis. Roller locations are simply calculated using rigid body translations and rotations which are derived from the laybarge motions by the program.
PLDYNA offers an alternative overband profile based on a curve discovered more than 200 years ago. The curve is the Euler spiral. Euler spiral has two desirable properties for this application. First property which makes this curve ideal for overband is that it has zero curvature at the start. Second property is that its curvature is proportional to the distance from the start which would have maintained a constant shear force if the pipe was supported continuously. Unfortunately, in adopting Euler curve some compromises has to be made. Firstly, because pipe is supported at discrete points at the rollers rather than on a continuous support, the pipe shear force distribution and therefore roller loads are not actually constant. The second compromise results from the fact that Euler spiral cannot satisfy the overband length, departure angle, and the allowable maximum curvature or the allowable pipe moment requirements at the same time. PLDYNA uses a proprietary algorithm to find the best Euler curve for a given combination.
optimal profile offers much more uniform load distribution on the overband and lower bending moments. It also reduces the dynamics stresses pipeline experiences.