dome strength

Lady Hawk · Post by **Lady Hawk** » Sun Jan 02, 2011 7:52 pm

i am trying to build my first dome, but i want it to be strong enough to hold up aerial fabric or a trapeze. i am planning on using EMT conduit, but how thick would the bars needs to be to support weight? would 1 1/4'' thick EMT tubes work? (the wall thickness is usually about .065'' on these, which is much better than the typical 3/4" bars).

i remember there was a "death dome" or something like that out on the playa that supported a huge number of people covering it as well as supporting two people in slings inside. anyone know what material they used?

FIGJAM · Post by **FIGJAM** » Sun Jan 02, 2011 8:05 pm

Check death guild thunderdome.

theCryptofishist · Post by **theCryptofishist** » Sun Jan 02, 2011 8:06 pm

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

http://eplaya.burningman.org/viewtopic. ... light=dome

I don't know if there's much discussion of Thunderdome's capabilities on here. But it's a possible search term. If I remember correctly, domes are pretty strong as an architectural form.

Bob · Post by **Bob** » Sun Jan 02, 2011 8:23 pm

The Death Guild dome was made by Pacific Domes. Try asking them.

See
http://www.pacificdomes.com/faq.html

Bob · Post by **Bob** » Sun Jan 02, 2011 8:33 pm

BTW, when you start an eplaya search, sort by 'posts', not 'topics'.

theCryptofishist · Post by **theCryptofishist** » Sun Jan 02, 2011 8:34 pm

Thank you.

Zhust · Post by **Zhust** » Mon Jan 03, 2011 5:56 am

Lady Hawk wrote:how thick would the bars needs to be to support weight?

First, there's not enough information to give an answer. Just to make a guess, you're going to have to tell us how big the whole dome is, what design was used, and how the vertices are attached. At that point the best you'll hear is "probably", "probably not", or "too close to call".

You'll need to start with understanding what the heck a dome is and how one is made. I googled around a while back and found Simply Different which documents different structures including domes. Linked from there is Desert Domes which is more of a how-to site.

I'd play with dome models (toothpicks, etc.) to see how strong things are. Do some destructive tests with weights and compare that to the strength of your strut material. Get hold of some EMT material and see how strong it is (use a big piece of pipe to see how it bends/breaks if it's not damaged) and how to make it fail (i.e. dent it and it'll bend right over). Take your best intuitive guess as to what would be good enough and design it. (It'd be good to pause here and figure out how much material you'd end up with and how much it would weigh ... one piece of EMT is pretty manageable, but 500' of it is very heavy). Build it at home and do some tests ... probably not destructive tests, but see how it behaves. Does it sway and bend with your target weights? How much weight can you put on one strut before it starts to bend (then replace that strut)?

Good luck ...

capjbadger · Post by **capjbadger** » Wed Jan 05, 2011 6:51 pm

I recall thunderdome either being 1 1/4" or 1 1/2" dia.

The dia really depends on if you want to climb it or not. The vertices are VERY strong, while the middle of a strut is the weakest point.

What frequency dome are you thinking of building? Thunderdome is a 6v dome (just loooked at a pic to double check).

1" EMT will take just about anything you throw at it if you keep the load at the verticies.

My dome is just a 3/4" EMT 2v dome, but is strong enough that I built a second story dome/deck on top of it.

-Badger

EDIT: Ahh... looks like TD is 1" EMT:
http://eplaya.burningman.org/viewtopic.php?p=310198

Bob · Post by **Bob** » Wed Jan 05, 2011 7:49 pm

The Thunderdome struts were nominal 1" EMT last I checked. Think they replace a lot of struts every year.

Consider that if you use an open performance dome, people are going to want to climb it, so it should probably be designed as such.

gyre · Post by **gyre** » Sun Jan 09, 2011 10:04 pm

Domes are strong as a stressed surface structure.

It sounds like you want to use specific points to suspend a high stress structure.
You need to engineer for that.

These guys might be some help.
http://www.shelter-systems.com/
http://www.shelter-systems.com/designs.html

falk · Post by **falk** » Thu Jan 20, 2011 3:16 pm

Lady Hawk wrote:i am trying to build my first dome, but i want it to be strong enough to hold up aerial fabric or a trapeze. i am planning on using EMT conduit, but how thick would the bars needs to be to support weight? would 1 1/4'' thick EMT tubes work?

If you connect your load from the vertices, this should be more than sufficient. If you want to hang your loads from the middle of the struts, it probably won't be so good.

capjbadger · Post by **capjbadger** » Thu Jan 20, 2011 6:18 pm

falk wrote:
Lady Hawk wrote:i am trying to build my first dome, but i want it to be strong enough to hold up aerial fabric or a trapeze. i am planning on using EMT conduit, but how thick would the bars needs to be to support weight? would 1 1/4'' thick EMT tubes work?
If you connect your load from the vertices, this should be more than sufficient. If you want to hang your loads from the middle of the struts, it probably won't be so good.

I think we covered that.

capjbadger wrote:The vertices are VERY strong, while the middle of a strut is the weakest point.

-Badger

ellorbito · Post by **ellorbito** » Thu Jan 27, 2011 11:16 am

I have built two 2 frequency domes out of EMT. The first one was 3/4 inch and supports weight only at the bolted areas...where all the pipes come together. The other I built out of 1 inch EMT and could support weight of about 160 lbs mid length a span of about 5 feet. I starts to sag with a little bouncing on it. I built the 1 inch emt dome as a climbing dome and was not as stable or strong as I would like it. We had about 5 people up there at times and would not recommend it for future climbing extravaganza.....just not strong enough. Go bigger diameter or a higher frequency like at least a four.

dome strength

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dome strength