Furniture Loads? 1

[JStephen]

One of my co-workers asked a question that I have never had occasion to look into. At his church, they were going to make a free-standing steel cross about six feet high with a concrete or steel base. The question was, what size to make the base?

This will be inside, so there's no wind load, it's a non-seismic area, and the base will just be on top of the floor, not anchored to it. The only real loading is the possiblity that someone will lean against it or bump into it or pull it over on themselves (kids, you know!).

Now, it seems this would be exactly the same situation you'd have with a refrigerator or storage cabinet or vending machine or similar heavy but tippable items. Are there any requirements of any kind as to how stable stuff like this ought to be? Or can you just balance a beam on end and call it good?

 

[msquared48]

Seems to me to fall under ASCE7 Table 13.5-1 as a non-structural Architectural component.

Still need to design it seismically, at least.

Maybe three well-placed metal spikes to the floor structure would work.

Mike McCann
MMC Engineering

 

[msquared48]

Further, I would consider it to be a sign with R = 2.5.

After all, it does transmit a message.

Mike McCann
MMC Engineering

 

[SLTA]

Maybe also use concentrated loads like required for railings on a deck.

 

[BAretired]

If you make a concrete base, the weight will help resist overturning. If the base is high enough and wide enough, nobody will accidentally bump into the cross.

Vandals will be able to overturn it no matter what you do. They could easily overturn a refrigerator or vending machine.

BA

 

[MiketheEngineer]

Both solutions will work - I like three or four screws into the floor best of all.

 

[TXStructural]

As a minimum, apply handrail loads to it (IIRC, roughly 250 lbs at 42" high). The problem is that no matter how "right" the solution is, it isn't good enough if it falls over. A steel cross will be top heavy, unlike a refrigerator.

Do a free-body diagram of the entire assembly. I think you will find that a wider/longer base will be better than small and heavy. What kind of floor is supporting this assembly?

Also, the base needs to be strong enough, but you may be able to use a fairly thin plate at the floor for stability, and graduate to a thicker plate closer to the vertical, for bending resistance and attachment.

Also, since it will be about one-human tall, consider that the cross piece will be about eye height for many people, and a larger base may be ideal to keep from poking peoples eyes out as they walk by... most people are not looking straight ahead while walking (ask the bruise on my forehead right now about that.)

 

[MiketheEngineer]

Good point - my 16 month old grandson is just "learning" about things that are head height for a kid - LIKE most things.

He just crashes into them, shakes his head and keeps on going....