design vertical curves using either parabola or circular curves

RE: design vertical curves using either parabola or circular curves

Oleg Makarov — Fri, 18 Aug 2023 09:17:14 GMT

Ok, let me try again

RE: design vertical curves using either parabola or circular curves

Mark Shamoun — Fri, 18 Aug 2023 09:16:00 GMT

If you zoom in closely, you will see there is a difference between them. Drawing a Microstation Arc I can see the circular curve graphics are correct. When the incoming and outgoing grades are the same and the crest is the same between the curves, you will only see very minor level differences between them.

RE: design vertical curves using either parabola or circular curves

Oleg Makarov — Fri, 18 Aug 2023 09:06:22 GMT

Thanks for reply Mark - I use vertical alignment design tools in ORD, i set up approach and departing gradients and experiment with circular and parabolic curves (not asymmetrical)

RE: design vertical curves using either parabola or circular curves

Mark Shamoun — Fri, 18 Aug 2023 09:01:43 GMT

Same with the Curve from Element tool

RE: design vertical curves using either parabola or circular curves

Mark Shamoun — Fri, 18 Aug 2023 08:58:17 GMT

Which tool are you using to test? Profile Between Points shows a clear difference between the 2 curve types.

RE: design vertical curves using either parabola or circular curves

Oleg Makarov — Fri, 18 Aug 2023 08:34:29 GMT

Took me a bit of time to confirm it but I think your assumption is not correct and differences between the two curves are significant, which I believe has a far reaching consequences... You can see image of comparison below. Happy to be corrected.

RE: design vertical curves using either parabola or circular curves

Jan Blaasse — Wed, 09 Aug 2023 06:36:34 GMT

Oleg,

I never claimed there are no differences, it's just that they aren't visible for the small section of the parabola that is displayed.

Jan

RE: design vertical curves using either parabola or circular curves

Oleg Makarov — Tue, 08 Aug 2023 14:20:31 GMT

Thanks Jan, even if both the circular and parabolic curves are symmetrical, there are fundamental differences between the two. But to make sure I have made a consultation with both online academia and Chat GPT Wolfram engine - they both concur with my premise of a small difference that should be obvious in vertical alignment design.

Oleg

RE: design vertical curves using either parabola or circular curves

Jan Blaasse — Tue, 08 Aug 2023 07:46:25 GMT

Oleg,

It's mostly true that there are no visual differences. One of the differences isn't in what you can see, but in how they behave in combination with other elements.
In theory you can design a vertical loop using a circular curve, but when you use a parabolic curve that will never happen.

I suggest you do an internet search for the differences and why a parabola is the preferred curve type.

Jan