Gateway to the West Arch

[Anonymous]

I am creating an arch similar to the Gateway to the West Arch in St. Louis, Missouri, only not quite on the grand scale the gateway is.
How would I do this in archicad?
I have tried a few features only to stopped at dead ends so far.

Thanks

Timothy Green
Instructor
Howard College
Big Spring, TX

[Erika Epstein]

For those not familiar with the Arch it was designed by Eero Saarinen.

Arch website

Do you have any of his drawings to know the geometry? Or are you 'eyeballing' the model of it?

And is some data on the Catenary Arch. Scroll down and it talks about the St. Louis Arch.here

[Anonymous]

I am planning on just eyeballing it. It doesn't really have to be to exact mathematical calculations.
I was hoping to plug in some sizes or radii or etc. and see what it looks like - sort of a 'trial and error' until I get the right look.

[David Collins]

A variable triangular section following an elliptical path....?
I would build it flat on the ground and lift it up. Isn't that what Saarinen did?
(Just joking: I got my M.ARCH at Wash U. in St Louis.)

1) Paste in a photo of the St. Louis arch and trace the elevation outline in plan with a polyline.
2) Create a mesh using the magic wand on the polyline. Use "Linear Segments" Tracing method to create nodes at regular intervals. (The actual arch is segmented, too.)
3) Keep the inside nodes at 0. Raise each outside node to 1/2 the trianglar section height at that location. Ask Pythagoras for help. That should give you the top half of the arch.
4) Save as 3d object, with view in 3d window from top of the arch.
5) Place the object. Mirror a copy to complete the arch.
6) Viola! (joke, old, ArchiTalk)

For extra credit, drag and drop the mesh into GDL, mirror the mesh using MULz -1, use CUTPOLYA to eliminate the unsightly line at join, rotate up into place. Create 2d symbol, with museum entry shown.

[Ralph Wessel]

tgreen wrote:
I am creating an arch similar to the Gateway to the West Arch in St. Louis, Missouri, only not quite on the grand scale the gateway is.
How would I do this in archicad?
I have tried a few features only to stopped at dead ends so far

Try modelling this with OBJECTiVE. I've modelled a quick example - although it's bent to a regular arc rather than an inverted catenary, you could achieve a similar effect by placing 3 or more segments rather than one. It all depends on the effect your after. With OBJECTiVE you could:

• 1. Draw the shape of the arch in plan (as if you were looking down on it) with the fill tools, and use the menu OBJECTiVE > Component > New Profile to construct a profiled object from it. Set the type to 'Elevation'
  
  2. Elevation profiles have a bending hotspot at the midpoint. If you grab this, you can loft the arch to the required height.
  
  3. The finished arch.

[Erika Epstein]

Tim,
I noted that you are on the faculty, Objective is free for educational licenses, correct Ralph?

[Ralph Wessel]

Erika wrote:
Tim,
I noted that you are on the faculty, Objective is free for educational licenses, correct Ralph?

Yes, correct. Just download from http://www.encina.co.uk/sw-download.html and install - no registration is required for educational users.

[Anonymous]

Hello Ralph,
I notice that your arch has a rectangular cross section.
Can Objective make a tapering equilateral triangle cross section
like the gateway arch ?
Thanks,
Peter Devlin

[Erika Epstein]

Just to see what I could do in archicad,
I. drew in floor plan window with lines and arch an eyeballed Catenary arch.

2. Magic wanded a Polygonal wall into the area of the arch. I used the wall tool as thin slabs are not easily trimmed using the trim to roof function. I did not want to SEO as cumbersome for this exercise.

3. placed a roof on the top of the wall. in 3D window I adjusted the slope and trimmed with top of wall.
4. Dragged a copy of the roof down and put a minus sign in front of its angle to reverse the slope and then trimmed bottom of wall.

5. Saved trimmed wall as a library object and stood it up.
Crude result; If I had made a true Catenary arch in plan it would have been much better.
Time: ~10 minutes

[Anonymous]

Here's my quick and dirty arch. It's made with one profiled wall sandwiched between two slanted walls. No SEO necessary. They clean up automatically.

This was very easy. Just a couple of minutes depending on how much you want to tweak the curves. The triangular section of the original would be much more difficult.