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Truss for a stage.


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Just starting to try and understand truss a little more than I do (minimal to zero knowledge).

Not looking to put it into practice as a designer etc just to learn a little for when I am rigging under other's supervision/designs etc I can understand what I see a little more.


So I´m gonna take the example of a job I´m going to be rigging in the summer (I'm doing sound and led screens.. truss will be done by another company before I arrive, the job is just in my mind so picked it as the example).


So imagine a standard outdoor concert with 52cm truss, floor standing (yeah I might not have the technical terms...)

Lets say (for example) 8x4mtr stage at 2mtrs high under the truss.. expecting to hang a decent sized (but not massive) line array from the sides too.

Minimal lighting (eg 10x 2k fresnels to highlight) and 900kg of LED screen at the rear of the stage.


Now I once heard that a guideline is that truss built from the floor up shouldnt be higher than its length or width ( true/false?)´


So with this lets say I go to a 9mtr width (3x3mtr sections). I´d be able to get the truss to 8mtrs safely?

So in the end would I be able to create a 9 mtr across by 5.5 mtr deep and 8 mtr high truss (obviously the legs/ supports raised higher for the rollers etc).?

I say 5.5 as I was thinking for depth I could, from the cube/roller go to a 3mtr section, add another cube and another span crossing the stage (more for adding lights there than anything else), then a 2mtr section.. then the rear span with its led screen.


Would I want to add legs/supports to the centre cubes/rollers as well or would one in each corner work?


I have also looked at some photos of truss staging online. I see some add other legs/ supports between the main truss and the outer side of each line array...

To work out if I needed this, would I just take the max supported weight of a 1mtr section and relate it to the weight of line array... or is it more complicated?

Eg if the array weighed 500 and the 1mtr section could take 550, its fine, but if the section only took 400 I´d need another leg?




Again.. this is hypothetical.. just looking to start understanding the principals of truss design... not to put into practice.


Thanks in advance.

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http://shop.istructe.org/temporary-demountable-structures.html is the last piece of industry guidance following


I am not personally confident about advising on structural safety on an open forum or that even good books like Dunc's suggestion are up to date enough to be beneficial. There are too many variables for bullet point answers when soil constituency, wind strength/variability and even crowd control are merely a few of the factors under consideration. (Backdrops, side-walls, guying, etc.etc.)


OK, I am being ultra-careful, but when I consider what I used to think nowt of 15+ years ago with a motorised trussing roof the size you speak of, I blanch. It would raise howls of alarm today, yet not one person at the PLASA show said a word except in praise.

We all learn and some of us live to tell the tale!

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Read the books. They are a great resource, and answer many questions, and will let you go back to them again and again.


However a note to Forum - reading them doesn't make you a Rigger (as in someone hanging Tons of kit from a roof). It makes you a person who's read a book about rigging design and implementation. That's where on the job experience and training along with the theory will start you on the process of being a Rigger. But then we all know that don't we...

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The book arrived.

Also got




Now to hope the 1yr old son wants to have a sleep this afternoon and I can get an hour or two on the sofa with the nose in the books!

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