Ellipse / parabolic curve drawing

[Richard McDonald]

We are working on a 1930's vintage bridge that has a elliptical or parabolic main structural member.

The problem is we have accurate data measured on site of various point along its length and need to reproduce the arc. The data does not include were the centre of the arc or the X-axis end point. Is there a lisp routine around that can produce an ellipse with say 3 points of data.


Many thanks in advance for any info you may have.

Richard

[Mike.Perry]

Hi

Not an Ellipse, but see if anything from the following threads might help -

Generating Contours (http://forums.augi.com/showthread.php?t=9119)

Excel X,Y Coordinates -->AutoCad???? (http://forums.augi.com/showthread.php?t=10880)

Creating points from Excel Data sheets (http://forums.augi.com/showthread.php?t=13393)

Have a good one, Mike

[Chuckyd67]

Don't most of those structures have hyperbolic curves?

[Richard McDonald]

Mike,

Thanks for the info..but in this case we do not have any formula or total dimensions for the curve. I was hoping to find something like the 3 point curve tool for an ellipse. I think on reflection a tool to produce a part parabola would be impossible given the amount of variation there could be.

cgraham,

This is the 2nd bridge I have worked on that uses a parabolic curve as its main member. I thought is was a modern way of thinking with three bridges that a know of in the UK using the curved member to hang the deck from 2 just completed and one currently being fabricated. But the main member is under this bridge. I would say It is either an ellipse or a parabola due to the fact that it course will almost definitely touch the asymptotes.

I have made do for the moment with a curved fit polyline but would like to be more accurate than this if possible regards Richard

[jvicario]

Look at this web site: http://a-cad-emia.blogspot.com/2011/05/splines-2-parte.html