Criteria Tab - Iterate On

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Criteria Tab - Iterate On

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Fixed Connection & Seabed Connection

When you select Fixed Connection or Seabed Connection as the iteration parameter, the Name drop-down list presents a list of all of the relevant connection points that you defined in your Model component. The Vector drop-down list facilitates the selection of either a user defined vector or a global axis. If a user defined vector is selected the User Vector drop-down list is enabled and presents a list of all Axis System components in the project file. You can use the Axis System component to define both axis systems and vectors. Note that PipeLay will move the connection in both the positive and negative directions of the vector or axis as required.

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Vessel Position

When you select Vessel Position as the iteration parameter, the Name drop-down list presents a list of all of the vessels in your model. The Vector and User Vector drop-down lists behave in the same way as if a connection point was selected.

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Component Length

When you select Component Length as the iteration parameter, the Name drop-down list presents a list of all of the Pipe Section components in your model. The Vector drop-down list is disabled in this case as previously noted.

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Water Depth

When you select Water Depth as the iteration parameter, the Name and Vector drop-down lists are disabled.

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Tolerance

The Tolerance dialog shown in the figure below allows you to vary the parameters that control how PipeLay iterates to satisfy criteria. The values you specify here are specific to the particular stage you are defining, so you can if you want define different values for different stages.

Tolerance Criteria Options

Tolerance Criteria Options

Max Iterations controls the number of attempts PipeLay makes to satisfy a criterion before deciding that it cannot be satisfied; you might want to increase this for a particular stage. Max Iterations defaults to 100. The subsequent two inputs are used to define “adjustment” values; “adjustment” in this context means how much PipeLay changes the value of whatever it is varying to satisfy a criterion in each iteration. You might want to reduce Min Adjustment to ensure convergence if you have specified a very narrow range of values for your criterion. You might likewise want to reduce the Max Adjustment to a small value for shallow water models. The minimum adjustment defaults to 0.1m or 0.328 ft, and the maximum adjustment defaults to 50m or 164.042 ft, depending on the unit system being used for the project. The iterations and adjustment options in this dialog are useful if satisfying criteria is proving difficult in a particular case, but it should not be necessary to invoke these options for the majority of analyses.

The final Multi-Pass option allows PipeLay to perform a two pass criteria analysis when set to Yes (the default). The first criteria analysis is performed with linear materials while the second is performed after non-linear material properties have been applied in a preceding analysis step. This multi-pass criteria analysis procedure offers a more robust solution as the majority of criteria adjustments are performed with the more stable linear materials prior to the inclusion of non-linear materials. If the Multi-Pass option is set to No then only the second criteria analysis (one after the inclusion of non-linear materials) is performed.