Distinguished Contributor
Posts: 142
Registered: ‎10-19-2011
Message 1 of 5 (2,031 Views)

Superelevation Transition Length Formula

2031 Views, 4 Replies
11-20-2011 02:02 PM

Hello There,

I would like to ask if i can apply Superelevation Transition Length Formula for length of runoff and runout from AASHTO

{Lr=(w*ed*n*bw)/maximum relative gradient}, {Lt=(enc/ed)*Lr} in XML file (in Civil 3D).

Beacause i tried many times to apply this formula but it didn't success with me.

I will be very appreciate for help and advice.

Thank you.

Please do not forget approve as solutions and Points
Valued Mentor
Posts: 322
Registered: ‎06-21-2011
Message 2 of 5 (2,022 Views)

Re: Superelevation Transition Length Formula

I have not tried defining the formulas for superelevation.  But based on the following two resources I found, it seems that you need to define the superelevation using the variables as defined by Autodesk for AutoCAD Civil 3D.

See Superelevation Variables and Formulas

Also it appears that while you can change the formulas in the XML file or perferably a copy of the XML file, that it probably makes more sense editing them through the Design Criteria Editor.

Not sure if you had already looked at those resources, but if not, maybe that helps.

Distinguished Contributor
Posts: 142
Registered: ‎10-19-2011
Message 3 of 5 (2,003 Views)

Re: Superelevation Transition Length Formula

So, i got it we can modify this formula from

tLength="{v}^3/(46.656*{q}*{r})"

to the following formula

tLength="({w}*{e})/{q}"

Please do not forget approve as solutions and Points
Distinguished Contributor
Posts: 142
Registered: ‎10-19-2011
Message 4 of 5 (1,998 Views)

Re: Superelevation Transition Length Formula

But one more thing,

I want to calculate the superelevation rate from this equation eRate="({v}^2/(127*{r}))-0.12" instead of this one

eRate="{v}^2/(2.82528*{r})"

But actually it didn't success with me and return me the minimum eRate

So, is there any advice for this issue.

Thank you.

Please do not forget approve as solutions and Points
Valued Mentor
Posts: 322
Registered: ‎06-21-2011
Message 5 of 5 (1,979 Views)

Re: Superelevation Transition Length Formula

Are you changing the eRate formula in the Design Criteria Editor?  See attached Editor image.  Note make sure Make File Read Only box is unchecked.

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