﻿ PipeLay > Technical Notes > Technical Note 8 - Calculation of Support Fine Tune Offsets > User Interface Calculation

# User Interface Calculation

When the user specifies their support locations on the Vessel or Stinger components there will be a column entitled Fine Tune Offset in the respective input dialog. When this is set to [CALCULATED] the user interface calculates the value for the Fine Tune Offset based on the data specified in the Radii of Curvature dialog on the Vessel component. If no Radii of Curvature data is defined then the calculated offsets are to be given a zero value.

In the Radii of Curvature dialog the user can specify the radii of pipe curvature they want the user interface to achieve at various points along the vessel and stinger. The sizes of the radii are input under the Radius of Curvature column; all entries here must be positive and non-zero. The transition points between two areas of different pipe curvature are defined in the Y Coordinate column; this entry is local to the Vessel axis system and is mandatory for all Radius of Curvature entries specified. For multiple Radii of Curvature the coordinates are to be in descending order. The final column allows you to instruct the analysis engine to maintain the curvatures achieved by the user interface during the static analysis procedure by running a Support Elevation Optimisation step; this is explained in the Analysis Engine Calculation section later.

All specified Radius of Curvature values are to apply to supports on the stern side of the associated Y Coordinate until a new lower Y Coordinate is encountered after which the new Radius of Curvature is to be applied. If the Y Coordinate for the first Radius of Curvature input is greater than the Y Coordinate for the most forward support on the Vessel then the first transition point is to switch back to the most forward support and the first Radius of Curvature is to take effect on the stern side of this support. Any supports on the forward side of the first transition point are to be assumed fixed and so the [CALCULATED] Fine Tune Offset for these supports is a zero value.

Please note that the Radii of Curvature are also to be applied to supports on any associated S-Lay type Stinger component where the Fine Tune Offset is set to [CALCULATED].

When all the Radii of Curvature data is specified, the user interface attempts to map an arc profile across the vessel and stinger. The creation of this profile is started by plotting the arc of curvature associated with the most forward transition point first. This first arc starts at the intersection between the projected tangent line of the supports on the forward side of the first coordinate and a vertical line at the first coordinate itself. As per the paragraph above, if no such forward supports exist then the transition point is moved to coincide with the most forward support. The end point for the initial arc is assumed to be where it intersects the vertical line at the next transition point. Once the end point is found a new arc of desired curvature is started on the stern side of new transition point and in a direction tangential to the original arc. The same procedure is repeated over all remaining Radius of Curvature entries.

Once the arc profile matches the desired Radii of Curvature inputs, the supports are moved from their original position onto the profile by following a vector defined by the Fine Tune Direction in the relevant Support Locations dialog. The Fine Tune Direction, which defaults to a right angle, is relative to the support Angle and the support itself can be moved in both directions along the corresponding vector. If a support moving along its associated vector cannot intercept the arc profile defined by the Radii of Curvature data then the support will not be moved at all and will remain in its original position in which case a warning will be issued in the Status area to inform the user of this. Note that for the case of an Explicitly Defined – Rigid S-Lay stinger, the support Angle referred to above can either be a user input on the Support Locations dialog or alternatively the user interface can calculate it so as to ensure the support is tangential to its surrounding supports. Angle inputs on the Stinger component are measured positive from the positive stinger-Y axis to the negative stinger-X axis which is consistent with the right hand rule positive rotation about the stinger-Z axis. In the case of Rigid S-Lay – Hinged or Articulated S-Lay type stingers the Support Angle can be found on the Stinger Section – Supports component. The support Angle is relative to the stinger section in question and is measured using the convention above. When default values are used for the support Angle and the support Fine Tune Direction then the corresponding support is moved in a radial direction towards/away from the centre of curvature for the radius in question.

The new support positions can be reviewed in the Model Viewer of the Model component and the Installations tab of the Analysis component. In the Model Viewer you also see the centres of curvature (labelled Rad1, Rad2, etc.) and the associated transition/tangent points (labelled TP1, TP2, etc.) for the different areas of curvature. The Show Radius of Curvature checkbox will display colour coded radii of curvature in the Model Viewer to enable additional visual assessment of how supports are mapped onto the curvatures. There is a Support Data button below the Model Viewer as well; this is used to create a CSV file containing a summary of the support data as calculated/applied by the user interface for all supports. This CSV file contains 10 columns of data per support, namely: Support Name, Initial X Coordinate, Initial Y Coordinate, Radius of Curvature, X Movement, Y Movement, Fine Tune Offset, Max Offset, Min Offset, and Analysis Optimisation.

The Support Name column contains the names of all the supports in the model, and the Initial X Coordinate and Initial Y Coordinate columns contain their initial position in global coordinates. The Radius of Curvature column shows the radius of curvature the user interface is trying to achieve at that particular support, if requested. The X Movement and Y Movement correspond to the vector components of the Fine Tune Offset. The Fine Tune Offset is the magnitude of the offset applied to the support along the Fine Tune Direction in order to achieve its new position. If the support cannot be moved along the Fine Tune Direction in order to achieve its’ specified radius of curvature then ‘n/a’ is output for the Radius of Curvature and the X Movement, Y Movement, and Fine Tune Offset are calculated as zero. The Max Offset and Min Offset correspond to the max and min values that the user wishes to apply to the supports Fine Tune Offset, as specified in the relevant Support Locations dialog. Note that the user interface does not use these values as limiting thresholds when moving supports and so they are provided for comparison purposes only. Finally the Analysis Optimisation column is set to either Yes or No depending on whether or not the user has requested a analysis step for a given support.