Structure Best Practice
1.Remember that the Yoke attachment, as labelled in the PipeLay user interface, can be used to model any rotating arm about a pivot point on the structure body, which does not necessarily have to be an actual yoke. For example it can also be a piping frame or buoyancy apparatus etc.
2.The sign convention for the various offset terms/inputs (for COGs and connection points) on the Structure component is important and requires checking on a model by model basis. Note, that the various offset terms are depicted in the following figures for a sample elevation view of a 1st End PLET. An example of the sign convention is as follows, if the line start point has a smaller global Y coordinate than its end point then a positive vertical offset will place the COG node/pivot above the structure centreline - The opposite is true if the line start point has a larger Y coordinate. For full descriptions of all the sign conventions for the offset terms please refer to the other Structure component articles.
3.If there is still confusion over the sign conventions then you should verify offsets visually using the Cable Solution animation on the Analysis component as it shows the generated structure model before the FE analysis takes place.
4.For reference the International Offshore Pipeline Forum 2010 paper, “An Improved Approach to Modelling In-line Structure Installation”, outlines a case study which demonstrates the benefit of modelling an in-line structure in detail using suitable offset values for the various connection points and COGs.
Sample Animation of 1st End PLET Model
Offset Inputs for Sample 1st End PLET Model