AutoCAD Civil 3D General Discussion

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Posts: 96
Registered: ‎10-30-2009
Message 1 of 3 (230 Views)
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230 Views, 2 Replies
02-03-2014 12:37 AM



How can i add a "curve+curve+spiral" to the PI point "S1"?



- Umit Arslan -
Survey Engineer
Civil 3D 2014 x64
Windows 7 64-bit
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Posts: 331
Registered: ‎05-13-2010
Message 2 of 3 (191 Views)

Re: Curve+Curve+Spiral

02-03-2014 06:45 AM in reply to: Umit.Arslan

I would break up the alignment so I could use adding curves from end of entity (starting at S1) and go from there. Others might have better suggestions.

Eric Collins, P.Tech.(Eng.)

Win 7 Enterprise SP1 64 bit
Intel i7 3770 @ 3.40 GHz
Civil 3D 2012 SP2
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Registered: ‎11-08-2005
Message 3 of 3 (170 Views)

Re: Curve+Curve+Spiral

02-03-2014 08:58 PM in reply to: ericcollins6932

Start by breaking apart the PI, then you can add the pieces you need to connect the tangents.  It depends on what parts of the curve-curve-spiral are constrained and which are not.  I've attached a drawing with several possible combinations.


  • The first alignment has a floating curve with a specified radius attached to the incoming tangent, a second floating curve attached to that and a free spiral connecting to the outgoing tangent.
  • The second alignment has a floating curve-spiral with specified radius and spiral length attached to the outgoing tangent and then a free curve between that and the incoming tangent.
  • The third alignment has a curve with fixed centerpoint and radius in the middle, then a free curve connecting from the incoming tangent to it, and a free spiral connecting to the outgoing tangent.

There are probably more possibilities - choose the elements that work for your situation.


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