How the length of the vertical curve is calculated in the C3D?

[JamaL9722060]

How the length of the vertical curve is calculated in the C3D?

I’m wondering regarding the equation used to calculate the length of the vertical curve.

Thank you

Best

Jamal

[Joe-Bouza]

I'm not in front of a work station right now, but you could try using the sub-entity editor in the profile floating tool bar. I think you wilb be able to change the curve restriction where you can adjust the length

http://docs.autodesk.com/CIV3D/2013/ENU/index.html?url=filesCUG/GUID-AA560246-C38F-4939-9242-6586281...

If not it should not  hurt to delete the curve and add one of the length you desire

[Jay_B]

---

@JamaL9722060 wrote:

How the length of the vertical curve is calculated in the C3D?

I’m wondering regarding the equation used to calculate the length of the vertical curve.

---

A desired Length can be entered as Joe mentioned, did you the use Criteria based Design?

The defaults in Civil 3D for Criteria Based Design are based on AASHTO design guidelines AFAIK.

AASHTO stands for "American Association of State Highway and Transportation Officials"

[Joe-Bouza]

I should read these post before I answer <G>

[Joe-Bouza]

Civil3d uses http://docs.autodesk.com/CIV3D/2013/ENU/index.html?url=filesCUG/GUID-31B9D1DF-1AFC-4836-A750-04DB413...

Is there another way to compute a parabolic curve?

[JamaL9722060]

In the attached example, the vertical curve is assumed and then it is checked to ensure if it is sufficient to provide the visibility.

But couldn’t find any formula from which the vertical curve is calculated.

Best

Jamal

[Jay_B]

Jamal,

Does This link help to answer your question re: how the length of the curve is calculated?

Joe had posted it in his previous post.

[Joe-Bouza]

L=KA
and if you enter L K is computed. How do you compute it?

[sboon · Accepted solution]

It looks like the OP is trying to calculate the required length for a crest curve from first principles, based on Stopping Sight Distance.  I don't typically use the AASHTO standards, but I believe that page 200-5 of this link has what you're looking for.

It should be noted that a parabolic crest curve with a consant rate of grade change along its length has the same sight distance throughout.  This means that if you know the design speed then you also know the required sight distance, and you can find the required rate of grade change for all crest curves (also known as the k value.)  For this reason many designers just work from a table, design speed vs. k value.

Civil 3d allows the user to build a table of Design Speeds and k values in a Design Criteria file, and use that while creating and editing layout profiles.

Steve
Please use the Accept as Solution or Kudo buttons when appropriate

*** It looks like Joe's link has the same equations as mine, but with fewer pictures and details. *** 

[JamaL9722060]

Many thanks guys for the help. Now it is much clearer.

Best

Jamal