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Clearing corridor bowties in Civil 3D is an essential step when working with corridors that involve sharp turns or intersections. Bowties occur when the corridor regions overlap at vertices where the alignment has tight curves or loops, leading to overlapping and incorrect surfaces. Here's how you can fix and clear bowties effectively:
1. Identify Bowties in the Corridor
Bowties are typically visible in areas where the corridor surfaces overlap, creating crisscrossing lines in plan view or jagged surfaces in 3D view.
Use the Object Viewer or zoom into the problematic area for closer inspection.
2. Check Corridor Targets
Select the corridor and go to Corridor Properties.
In the Parameters tab, review the Targets for width and offset:
Ensure that the target objects (e.g., alignments or feature lines) are correctly defined and correspond to the design intent.
Remove any conflicting or incorrect targets causing the overlap.
3. Adjust the Alignment Geometry
Tight curves or loops in the alignment often cause bowties. To resolve this:
Open the Alignment Editor by selecting the alignment, then right-click and choose Edit Alignment Geometry.
Smooth out tight curves by increasing the radius or adding transition curves.
Check PI Angles:
Sharp angles at points of intersection (PIs) can cause bowties.
Add fillets or curves at these points to smooth the transition.
4. Revise Assembly or Subassemblies
Simplify Subassemblies:
Open the assembly used in the problematic corridor region.
Replace complex subassemblies with simpler ones to minimize overlaps.
Adjust Widths and Slopes:
If the subassemblies target excessively wide regions, reduce their widths to prevent overlaps.
5. Adjust Corridor Frequency
Select the corridor and go to Corridor Properties.
In the Frequency tab:
Reduce the frequency of sampling along curves.
A lower frequency may reduce the overlap in tight curve regions.
6. Use the "Clear Corridor Bowties" Option
Select the corridor in the drawing.
Right-click and choose Edit Corridor Sections.
In the ribbon, click Clear Corridor Bowties. Civil 3D will automatically try to resolve overlapping regions.
7. Manual Cleanup Using Targets or Grip Edits
Select the corridor and use grip editing to manually adjust regions where bowties occur.
Modify the targets or baseline properties in Corridor Properties for more control.
8. Rebuild the Corridor
After making adjustments, ensure that the corridor is rebuilt to reflect the changes.
Right-click on the corridor and choose Rebuild Corridor.
9. Validate the Fix
Inspect the corridor in 3D view or Section Editor to confirm that the bowties are cleared.
Check the corridor surface for smooth transitions and proper grading.
Tips to Prevent Bowties:
Use appropriate curve radii for alignments.
Avoid sharp PI angles or overlaps in the baseline geometry.
Keep assembly targets and width
