Back to Back Curves
Updated October 19, 2017
This article applies to:
- Softree Optimal
This first example will look at the Curves [Fast] option (back to back curves with no tangents) used in the previous example, but with a well-defined curve length.
Open the Softree Optimal application.
File button | Open. Select Hart Rd optimal.dsnx. Press Open.
Maximize the Profile window, ensure the Alignment Properties panel is visible
Make a copy of Trial 1 and modify the Standards:
In the Alignments list, select Trial 1 then press the New button.
Change the Description to “K=30, L=50”.
Select the Standards tab and set the Minimum Curve Length to 50.
Figure 1: Options, Standards tab with Minimum Curve Length defined.
Press OK to close the modified options (nothing else should be changed).
If Minimum Curve Length is not checked (the default), a curve or tangent will be created between all sampled section points (defined in the Options dialog, General tab, Sections area). Adjacent curves with the same K factor will be combined so the actual number of curves is much smaller than the number of points.
If Minimum curve length is checked, you need to enter a curve length that is longer than the point spacing. In this case, most curve (or tangent) lengths will be greater than or equal to this value – the length of road is divided up into equal length segments. However, if Include Ctrl Pts/Ranges for curve definition is checked, then some curves may be shorter than the minimum because of the requirement to put a segment boundary on these special points. In this example, the control points are at the ends and the grade and curvature constraints are constant along the alignment so this check box will have no effect.
Note: You will be notified of a conflict, if base curve length is less than the point spacing defined in the General tab.
Do a feasibility check:
Right click on the new Trial 2 alignment and select Process | Feasibility Check.
The alignment is feasible. Press OK to close the Log message.
Note: You will avoid a lot of waiting around for Pre-Process and Optimization calculations on impossible designs if you get in the habit of checking feasibility first. Many of the examples do not include this step for brevity.
Optimize the Trial 2 alignment:
Press the Process button.
The Optimal Profile action should be selected (if it is disabled your Softree Optimal function group is not enabled).
Press Process (and wait for the calculations to conclude).
Press OK to close the Log report.
Compare Trial 2 and Trial 1:
Press the Set Current button (Trial 2 should still be selected).
Select Trial 1 and Re-Cost^ if necessary. (I
Set the Compare with current check box (at the bottom of the Alignment Panel).
These solutions are very similar; the total cost difference is just over 1% and the selected Trial 1 profile (solid line) is almost coincident with the current Trial 2 profile (dash dot).
Figure 2: Comparing the small difference between alignments generated with short back to back curves and 50m back to back curves.
The curves generated by Optimal are displayed in the Profile window (although we haven’t displayed all the applicable labels). Curve information can also be viewed in a data window.
View the Data:1 window, press the Data window shortcut from the bottom nav bar
We will need to configure the reporting columns.
Right-click, select Data Window Options.
Figure 3: Data Window Options
Press the for Point Types (Rows)
Deselect all Point Types Selected. Double click on BVC/EVC Points. It should now have a check mark next to it. Press OK to close.
Select Columns…, add:
L-Stn (L-Line folder)
Grade (L-Line folder)
K (Curves folder)
HD (L-Line folder)
Figure 4: Curves Generated Using Back to back curve with Minimum Length Set to 50m.
Notice that most of the curves are 50m in length (almost – a small tangent has been inserted between curves to accommodate the Location module’s data structure). Some curve lengths are multiples of the shortest (consecutive curves with the same K factor have been combined). The last tangent/curve length (0.294m in this case) is less than the minimum to deal with the fact that the total alignment length is not a multiple of 50m.
Select Trial 1 and push the Set Current button.
Notice that now you see many more curves in the Data window. Many are roughly 5.0m; this is the sample spacing we chose.
File | Close. Do not save changes.