After submitting point loads, shop drawings etc we began our installation and ran into a problem with the Architect. They are claiming the building design allows for three inches of deflection in the floor slabs and beams. In turn they now want us to install deflection fittings where any horizontal runs turn vertical so as not to put downward pressure on termination points. We are using EMT conduit on trapeze hangers. Is there a standard amount of deflection EMT can withstand when rigidly braced? Any other solutions? This has noting to do with expansion joints etc. Seems to me the drop ceiling is going to be awfully wavy when the floor above gets loaded......
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We are using EMT conduit on trapeze hangers.
Maybe something like this though the travel isn't enough:
https://www.zoro.com/mason-vibration...45/i/G0327205/
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Originally posted by mak134 View PostThey are claiming the building design allows for three inches of deflection in the floor slabs and beams. In turn they now want us to install deflection fittings where any horizontal runs turn vertical so as not to put downward pressure on termination points......
https://www.topaz-usa.com/conduit-bo...ation-lb-type/
You would also preferably have a threaded fitting on the horizontal run to accomodate a slight rotation.
The principle is similar to that of "swing joints" used in plumbing, especially with steam, to accommodate the expansion.
The devil is in the details so it's hard to make any more specific recommendations.
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three inches of deflection in the floor slabs and beams
what type span are you talking about? Even at L/120, 3"= a 30 foot span, 30 ft of EMT length changes from about 360" to about 360-1/16". where is the problem?
Are the archys talking about floating end hangers? Hard to imagine 3" vertical 'deflection' at a wall unless suspended?
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3" of deflection seems excessive to me but I'm not the designer. With that said, why couldn't you just use an expansion coupling where the runs transition from horizontal to vertical? I would also assume that this maximum deflection is only at the center of the open slab. Anywhere around the perimeter you would never be able to have that much to deflection so couldn't you just make most of the conduit runs go vertical at the perimeter. If you had to make a vertical turn anywhere near the center, then use an expansion coupling.The world is round, you will get there no matter what path you take.
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Originally posted by rlundsrud View Post3" of deflection seems excessive to me but I'm not the designer. With that said, why couldn't you just use an expansion coupling where the runs transition from horizontal to vertical? I would also assume that this maximum deflection is only at the center of the open slab. Anywhere around the perimeter you would never be able to have that much to deflection so couldn't you just make most of the conduit runs go vertical at the perimeter. If you had to make a vertical turn anywhere near the center, then use an expansion coupling.
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Originally posted by rlundsrud View Post3" of deflection seems excessive to me but I'm not the designer. With that said, why couldn't you just use an expansion coupling where the runs transition from horizontal to vertical? I would also assume that this maximum deflection is only at the center of the open slab. Anywhere around the perimeter you would never be able to have that much to deflection so couldn't you just make most of the conduit runs go vertical at the perimeter. If you had to make a vertical turn anywhere near the center, then use an expansion coupling.
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Originally posted by junkhound View Postthree inches of deflection in the floor slabs and beams
what type span are you talking about? Even at L/120, 3"= a 30 foot span, 30 ft of EMT length changes from about 360" to about 360-1/16". where is the problem?
Are the archys talking about floating end hangers? Hard to imagine 3" vertical 'deflection' at a wall unless suspended?
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