Violation? 314.23 F or Luminiare hung by conduit (with "reinforcement")

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ADub said:
Almost every piece of strut that you see outside has a least one field cut edge. We put a galvanized coating on these edges but I doubt the rest of the world does. It probably depends where you're at it concerning how fast it would rust. I've seen installations many years old without any evidence of rusting.

I agree the pipe the doesn't need that bracket but I wouldn't for one second try to say it's hindering in any way.
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It's more common that not to spray the cut surfaces on the jobs I have been on.

This is good stuff

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speak2jenni said:
The strut is absolutely structurally compromised. It is cut and would only require time and vibration and weather to cause it to fail, all of which are in plenty in outside conditions. If this installation had been made using 45° strut angle 3 or 5 hole straps, i would agree, but this installation is using the strut inappropriately. Yes, it will hold... For a while. But i wouldn't use that for any type of permanent installation.


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I agree. Even if the strut was made with aluminum that is self-resistant to excessive corrosion, it still is modified in a way that would ruin the structural integrity. The folded shape gives it its resistance to bending. Cut through the sidewalls, and now it is just an 1/8" thick piece of metal, with a stress point nearby.
 
jap said:
I'm still trying to figure out how they got the strut straps to work that way.

jap>
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JDB3 said:
I'm thinking that may be a spring nut and a separate conduit hanger.

I believe that we use-to call them pain-hangers. But they would do the trick!
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texie said:
I'm thinking that may be a spring nut and a separate conduit hanger.
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I don't think it's either.
I think he bent the tabs of the strut strap so it will grab.
 
ADub said:
Everything we put outside has the potential to rust. Stress fracture? Have you worked with strut before or do you just spec it?
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Yes but we don't cut it and bend it backwards like that at the cut point since that is not its intended use. We usually have our shop manufacture a bracket with proper welded seams and paint it as well.

I also get to see what wind does to hardware when causing oscillations. Adding a rusty cut and bent-backwards piece of metal is a potential point of failure.
 
mivey said:
What is the length of that pipe? Would that fixture be whipping excessively in a storm or on a windy day?
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Well how much wind are we designing for?

An F5?

If that is RMC or IMC I would have no problem hanging that fixture without that extra brace.
 
K8MHZ said:
Actually, the brace increases the wind load. It also increases the weight on the RMC without adding any benefit. It looks like the RMC is supporting the brace, not the other way around.
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It may be adding rigidity to the right angle runs it triangulated, but it is not clear whether it does anything for the bending moment at the point where the vertical conduit leaves the strut structure.
 
GoldDigger said:
It may be adding rigidity to the right angle runs it triangulated, but it is not clear whether it does anything for the bending moment at the point where the vertical conduit leaves the strut structure.
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As added offset weight, it is a force vector not directed through the attachment point so it is clear that it adds to the bending moment. It does add rigidity (until it slips or fails) to the right angle, much like a shelving bracket.

add: forgot to look at picture first. I forgot the strut was attached below the last clamp so it will transfer some of the vertical load below the clamp. If I was at my desk, a force diagram with some approximate calcs would be interesting but I'm mobile.
 
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mivey said:
As added offset weight, it is a force vector not directed through the attachment point so it is clear that it adds to the bending moment. It does add rigidity (until it slips or fails) to the right angle, much like a shelving bracket.

add: forgot to look at picture first. I forgot the strut was attached below the last clamp so it will transfer some of the vertical load below the clamp. If I was at my desk, a force diagram with some approximate calcs would be interesting but I'm mobile.
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Looking at the strut clamps and the way they were hacked to fit, won't they be the weak link?

If there is enough force to bend the RMC, do you think the cheesy bent strut strap is going to make a hill of beans worth of difference?

Like I said before, it looks like the conduit is supporting the brace, not the other way around.
 
The force on the strut is all in compression except for a very short portion at the ends, while most of the load on the RMC is bending moment.
The axial compression strength of the piece if strut is more than adequate.
 
K8MHZ said:
Looking at the strut clamps and the way they were hacked to fit, won't they be the weak link?

If there is enough force to bend the RMC, do you think the cheesy bent strut strap is going to make a hill of beans worth of difference?

Like I said before, it looks like the conduit is supporting the brace, not the other way around.
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A calc with some general assumptions would be revealing but it would have to be later. My phone calculator and a napkin just won't do it for me.:D


Add: Not real sure what they did with the clamps. They may wind up slipping.
 
I doubt the strut bracket was installed for anything else but to be a stiffener.

I don't need an engineering degree to know that if I jumped up with all 225 lb's of me and grabbed onto the fixture that most likely the top strut strap on the horizontal run would slip, that is until the strut slid horizontally until it hit the 90 degree bend above the fixture, then the lower verticle strut strap would slip until the bracket ran into other lower strut strap on the strut rack. At this point I would have bent the upper 90d elbow furthest from the fixtures but would probably still be able to support all my weight off of it as long as the threads didn't pull out of the fixture hub.

The same scenario above without the bracket in play would have a little different outcome. I'd jump up and grab onto the fixture and the 90d elbow furthest from the fixture would immediately bend in half althought it would still probably support my weight,,,,, the biggest problem is that when that happens the conduit would have cut into the wires and if I hung there until the photocell called for the lights to come on,,, it would short out at the bend,,,,,burn the 1/2" rigid in half and I'd go crashing to the ground in a firey decent.

Just saying..

JAP>
 
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