Structure supported on ceiling 1

[slickstyles5]

I will need to perform calculations on a small structure that is supported on the ceiling with studs and nuts. The structure is 350 lbs. There is a bolt pattern circular to support this part to the ceiling. Would there be an example of calculation anywhere here? Any advice?

Thanks

 

[drawoh]

galeblanc,

This sounds like more of a civil engineering or structural engineering question.

How is the ceiling built?

JHG

 

[slickstyles5]

A concrete ceiling. There is a steel plate (probably anchored to the ceiling) with studs sticking out of it for me to attach my structure.

 

[MiketheEngineer]

350# is just one Fat Boy hanging by his fingers..

Surely this is a diminimus project??

 

[drawoh]

galeblanc,

I am thinking like a designer here, not a structural analyst. I have a bunch of questions, which ought to direct your analysis, and your decision making. An existing calculation might not be based on the same chain of reasoning, or the same answers.

[ol]
[li]How strong are the ceiling attachments? This may not be obvious, and you do not appear to be a civil engineer.[/li]
[li]How is your structure going to be loaded? Don't forget people with fork lifts. [/li]
[li]If it fails, how expensive is it, and what or who is it going to land on?[/li]
[li]How are you going to install it?[/li]
[li]At what point do you step aside and allow a more qualified person to do this?[/li]
[/ol]

JHG

 

[eromlignod]

Just don't build it like Kemper Arena in Kansas City, ca. 1979.

Don

 

[slickstyles5]

You're right I'm not a civil engineer. The only force I will have will be a tension force from the weight of the structure. It is held by a circular bolt pattern so it should be evenly distributed. I am thinking of verify if my plate on the wall will bend using the beam methods. Then I can determine the tension force of each bolt. The next step is to check if the anchors are strong enough to hold the plate and the structure. The structure only weighs 350 lbs and will be held with threaded studs + nuts.

Any other ideas? Thanks again.

 

[bvanhiel]

Keep in mind the safety factor is usually quite high (10x?) on overhead lift hardware.

-b

 

[drawoh]

galeblanc,

You want permission from whoever designed your ceiling, to hang stuff from it. If they were put there for that puropose, fine.

The load on your studs and nuts will be evenly distributed after they are all completely installed. The worst case scenario might be that the workers will get the first nut on, just as the coffee truck arrives.

I, personally, have smashed a door with a forklift. I was manoevering the forklift through the plant when a worker frantically signaled me to stop. I was halfway through a roll-up door that someone had not rolled up enough. You do not need a plant full of drunken cowboys to wreck equipment, although it helps.

How confident are you about the 350lb? What happens if some 200lb guy perceives this thing as a chin-up bar? Your safety factor is a factor of ignorance.

JHG

 

[eromlignod]

350 lbs is nothing. You guys are overthinking this.

Don
Kansas City

 

[bvanhiel]

Heavy enough to kill you when it falls.

 

[eromlignod]

...but not heavy enough to break a single 6-32 machine screw.

Spend the $10 and put half-inch bolts in it.

Don

 

[drawoh]

eromlignod,

Okay, now you have solved the bolt tensile strength problem. How about the anchoring in the ceiling, and the structure around the screws or bolts? 350lb may be nothing in your world, but it is a lot of weight in my world. If I hung 350lb from a ceiling, I would check my work carefully, and get a second opinion if possible, because I do not have a good gut feeling for this stuff.

People would not be asking questions about this thing if something was not marginal. Let us not forget the possible bruising, nose bleeds, blunt trauma and choking injuries that can occur shortly after someone notices a half million dollars worth of hardware accelerating towards the floor at 32.2ft/sec².

I don't think we are seeing all the information here.

JHG

 

[slickstyles5]

The studs are 1/2-13 UNC rods and there will be nuts + washers + lockwasher to fasten the structure to the plate. I did the beam calculations and the max stress was 2,000 psi assuming a simply supported beam at both ends. As for the bolts, the tensile strength of one bolt 1/2-13UNC is 120,000 psi so there's no worry there. As for anchors, they hold minimum 2,000 lb pullout force, so no problem there.

I know, this is over anlayzing, but our client wanted some calculations. I'll show him that one bolt will hold up the entire structure!!

 

[Zapster]

Where is this going to be installed?
Seismic loading?
Will a building permit be required?

 

[slickstyles5]

Anchored to a concrete ceiling with wedge anchors. It is only a tension load (constant). Lateral movement in minimal so shear can be neglected.

 

[Ussuri]

You have a object bolted to the underside of a concrete slab?

Firstly, make sure you know what loading you are designing for. Purely static, dynamic, lateral (can it swing for instance)

1) Check the attachment of the object, ie the flange you are bolting through to ensure it doesnt fail under weight.

2) Check the bolts you are setting into the concrete. This sounds like a post fix arrangment so I would contact a supplier such as Hilti or Liebig. There are usually restrictions on the thickness of the material you can fix into. You dont say how thick it is. If it is thin, you would have to drill all the way through and fix on the other side. This may be a problem.

3) If the bolts are sound, you then need to check the concrete you are bolting into. Are you likely to pull the bolts out of the concrete. You need to check concrete failure. This will depend on grade of concrete and reinforcement.

4) If this is all OK, then consider the slab/ceiling as a whole. Will the additional load affect the ceiling, increase servicibility deflection? Overstress members? Are there any other loads that need to be considered? On its own it may be insignificant but are there other loads present?

 

[slickstyles5]

The plate I am fixing my object to is 3/4" thick steel. I selected red head wedge anchors from Spaenaur for the correct plate thickness to fasten to the concrete ceiling. The loading is strictly tension (no later swinging).

Thanks for your advice!