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Author Topic: Hanging fixture from uni-strut  (Read 27409 times)

Tim McCulloch

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Re: Hanging fixture from uni-strut
« Reply #10 on: April 09, 2011, 09:42:16 pm »

We had a multi-level skywalk between buildings collapse in Kansas City a number of years ago because an onsite change was made due to scheduling and parts arrival.  Long lengths of threaded rod were not available, short lengths were used instead and applied in a manner that caused structural failure years later.

The Hyatt-Regency Skywalkers, performing their *smash hit* 'Bridge Over Troubled Waiters."    One show only...  ::)
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

waldo [Casey Williams]

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Re: Hanging fixture from uni-strut
« Reply #11 on: April 11, 2011, 12:09:58 am »

Was I trying to say, don't use Unistrut for the proposed little project, no.  Just pointing out an engineering truth.

Now you are beginning to 'refute yourself' a bit. What you actually seem to be saying in this thread is, "don't use unistrut (or anything else) unless you get a structural engineer to sign off on the final design".

Hopefully, what is being argued about here is liability more than actual mechanical failure. Knowing a few structural engineers (including my brother-in-law), I have been told more than once that their methodology is, 'am I going to get sued if I sign off on this? and will my professional practice insurance cover it?' That, and 'guesstimate a reasonable weight limit for this system, and divide by 5'.

Have *some* structural engineers signed off on systems that included unistrut, even though it is not *explicitly* rated for overhead lifting? Yes. So there you are, proof of concept.

waldo
(no unistrut in my building, actually.)
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Lee Buckalew

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Re: Hanging fixture from uni-strut
« Reply #12 on: April 11, 2011, 07:26:27 am »

Now you are beginning to 'refute yourself' a bit. What you actually seem to be saying in this thread is, "don't use unistrut (or anything else) unless you get a structural engineer to sign off on the final design".

Hopefully, what is being argued about here is liability more than actual mechanical failure. Knowing a few structural engineers (including my brother-in-law), I have been told more than once that their methodology is, 'am I going to get sued if I sign off on this? and will my professional practice insurance cover it?' That, and 'guesstimate a reasonable weight limit for this system, and divide by 5'.

Have *some* structural engineers signed off on systems that included unistrut, even though it is not *explicitly* rated for overhead lifting? Yes. So there you are, proof of concept.

waldo
(no unistrut in my building, actually.)

Yes, The issue comes down to liability, especially in a church atmosphere when much is done on a volunteer basis.  When a question is asked about suspending lighting, speakers or other items and the manner in which the question is asked seems to lead one to believe that the person asking has no professional expertise/experience in the specific area being asked about, I want to remind them of the potential for problems.
When it comes to rigging/suspension, on the job training without an experienced mentor to guide you is asking for trouble.
When it comes to concert speaker rigging, most international companies meet or exceed the German standards since they are the highest published standards.  If these are followed then their systems should be acceptable anywhere in the world.  Now, when I go to attach that system to the building... ;)

Lee Buckalew
Pro Sound Advice, Inc.
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Lee Buckalew
Pro Sound Advice, Inc.

Chris Jensen

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Re: Hanging fixture from uni-strut
« Reply #13 on: April 14, 2011, 09:25:46 pm »

Not to say rigging and safety should be taken lightly but what keeps the engineer in check.  There is a point where things need to be reasonable.  Many engineers pride themselves on being able to do something bare bones and super cheap.  Many pride themselves on overbuilding and extending budgets and time till the points of just being silly.  The fact is unistrut is unisturt.  The manufacture says that every piece will be the same as the next.  Someone's "engineer friend"(it's never I in these arguments only my friend) can not sign off on a hang that is 100:1 because they don't feel that it is safe, but another can say 3:1 is perfect.  This country was built on honest work and design, now it is being ruined by liability.  People won't do what they know is safe because it isn't safe enough.  Is the threshold safe, safe + 10%, or safe + 1000%.  This is an argument of the amp going to 11 instead of making 10 louder.  Don't say it's safe unless it's safe period.

I understand people don't know what they are doing.  That is a different story.  I feel the same way, that the question was asked means the OP most likely is in over their head.  But I also don't feel it is necessary to start conflict over what an engineer friend says.  If the real root of the problem is implantation then keep it there.  It seems silly to make the argument over unisturt when you admit what it is used for.  I always find it funny how much someones Degree can get in the way of common sense. 

If you want to see a good argument some time listen to an architect, an engineer and framer argue about beam distribution.  One will want no beams to support because they are ugly.  One will want beams evenly spaced because thats what the snap tool did in the software and someone didn't want to do the math to see if you could kill an inch to subtract a beam in the middle of a living room, and one will argue that it will be fine just to cut out a beam or two based on experience.  Guess who is who and which one is right.  Usually it's the lowest on the pole framer.

I try not to discredit what is done in this field but I do find it funny that things are way over done because there is no way to break them to test them.  If you could find a breaking point then dial back I assume rigging might be taken a little more lightly.  Unistut was tested in this manner so that is why there is a rating on it.  It's not as if they put it up there with only calculated breaking points and then beefed it up as an educated guess. 

Unistrut will hold a 20lbs Source 4, now will the clamping system be used correctly?  There was no engineer to spec that out even though that is the real weakpoint.

Chris
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duane massey

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Re: Hanging fixture from uni-strut
« Reply #14 on: April 15, 2011, 12:58:05 am »

We all work in different realities. Virtually none of my clients would hire me if I insisted they hire a structural engineer to specify the proper method for hanging a light fixture or speaker. Some of them are in areas with no building codes or inspectors. If you want to do business down here you have to be confident in your own judgment. And, yes, I do use unistrut for some installs, as does virtually every other trade that installs gear in ceilings.
If you want to feel nervous, look over your head in most bars, restaurants, and churches around here; rope, "jack" chain, 1/8" cable tied in a knot, Trackspots held up with drywall screws, and even worse if you look above the lift-out ceiling.
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Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

Jeff Bankston

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Re: Hanging fixture from uni-strut
« Reply #15 on: April 15, 2011, 05:12:16 am »

We had a multi-level skywalk between buildings collapse in Kansas City a number of years ago because an onsite change was made due to scheduling and parts arrival.  Long lengths of threaded rod were not available, short lengths were used instead and applied in a manner that caused structural failure years later.

The Hyatt-Regency Skywalkers, performing their *smash hit* 'Bridge Over Troubled Waiters."    One show only...  ::)
yep and the contractor didnt follow the blueprints and spliced the support rods and used an unapproved and fatal design. the rods pulled through the steel tubing tht was not designed to carry the load. the example was 2 mountain climbers on "one" rope vs one mountain climber on the rope and the other climber hanging from the climber on the rope who could not support the weight of them both an fell. a lot of people died when those catwalks fell on them.
« Last Edit: April 15, 2011, 05:13:50 am by Jeff Harrell »
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John Livings

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Re: Hanging fixture from uni-strut
« Reply #16 on: April 19, 2011, 12:37:29 am »

We all work in different realities. Virtually none of my clients would hire me if I insisted they hire a structural engineer to specify the proper method for hanging a light fixture or speaker. Some of them are in areas with no building codes or inspectors. If you want to do business down here you have to be confident in your own judgment. And, yes, I do use unistrut for some installs, as does virtually every other trade that installs gear in ceilings.
If you want to feel nervous, look over your head in most bars, restaurants, and churches around here; rope, "jack" chain, 1/8" cable tied in a knot, Trackspots held up with drywall screws, and even worse if you look above the lift-out ceiling.

+1-Sometimes Common Sense must rule the day.

Someone told me a long time ago;  " The Titanic was designed and built by Professionals, The Arc was designed and built by Amateurs, Which one would You and your Family have preferred to have been passengers on?

Regards,  John
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Re: Hanging fixture from uni-strut
« Reply #16 on: April 19, 2011, 12:37:29 am »


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