Table Design 8

[dik]

I’m looking at designing a steel table… four legs and a frame on the top fabricated from small HSS to support 1-1/4" of granite. I’ve not done this before, but shouldn’t be difficult.

Does anyone have any suggestions about the lateral load on the 3D frame? like 25% of the vertical load? and a means of attaching the granite table top… use is fancy industrial… either pins or adhesive? any sort of buffer between the frame and the stone?

Any thoughts about the thickness to span ratio for the depth of the stone?

Dik

 

[EngineeringEric]

I think you should look at kitchen cabinets for reference. they attach the granite and they seem to limit all spans to 22" or less. You may even want to put steel joists in and maybe some sheathing, then glue the granite to it all. this will help take up irregularities at the welds.

I'm thinking place small tabs some 1" below top of steel, then install 1-1/8" plywood, screw the plywood from below into tabs with slotted holes (wood shrinks). then the granite can be glued to the plywood and nobody will see it ever, the granite can cantilever over the edge of plywood and edge of steel and hide more... or something different if the granite sits flush inside the steel frame. jsut an idea

Regardless, id look wood cabinets for guidance.

Sounds like a fun project! you have actual loads or is this just for decoration?

 

[r13]

I think a 300# neighbor lean/butt on the table will produce a hell lot of lateral load

 

[EdStainless]

Fairly thin piece, how large?
Steel cross braces and layer of plywood for a mounting surface makes sense.
Very thick pieces (4" and up) are usually not fastened down, gravity works for them.
You may want to think about the bracing at the tops of the legs. You don't want this 'wobbly'.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[dik]

No plywood... but thinking of adding some knee braces... also 300# butt load seems reasonable. As far as design live load 20 psf seem reasonable?


Dik

 

[EngineeringEric]

Guardrail load of 200#, add in some p-delta, and boom 400# minimum per frame!

I would think you'd want a buffer, at least to help eliminate stress concentrations due to uneven surface. something softer than granite that can locally crush

 

[rb1957]

the weight of the stone is something to consider.

I'd use a point load, 300 lbs, rather than a load distributed over the table area.

any simple steel frame should be fine … angles to hold the table top, angles for legs, angles for bracing.
joints … weld, braze, or rivet.

another day in paradise, or is paradise one day closer ?

 

[r13]

I think 20 psf is more than adequate, you can pile a lot of dishes on it. But seriously, you do need substrate to hold the granite, and utilize it to tie the metal frame.

 

[jayrod12]

The local granite suppliers might be a good phone call. I find they're extremely helpful.

I am of the opinion that a substrate, like plywood, would be beneficial.

Also, if using HSS members as per your OP, I'd bet you're looking at fully welded joints, I don't think knee braces, or cross bracing is necessary. Considering what I'm used to seeing for table construction when it's wood (i.e. 2 bolts moment connections) and their performance (seems adequate in most cases), I feel that a welded HSS frame will have more than enough lateral capacity. Depending on sizes obviously.

 

[dik]

EngineeringEric... would do a P-delta... and will use your loading.
rb1957... point load is good...
retired13... you would use plywood?
jayrod12... I already have a call into a local stone top supplier... OK will look into no knee braces, just thinking they were more rigid.



Dik

 

[r13]

If your concern is looking, how about plywood with laminate bottom, so not so obvious from view. I couldn't think something else fancier at this moment.

 

[IRstuff]

The metalwork around our granite tables at work are VERY beefy; looks more like heavy-duty angle iron

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[dik]

IRS: Thanks...


Dik

 

[rb1957]

look at kitchen cabinets and islands … boxes out of "manufactured" wood.

Aesthetically, you can hide a substrate under the rock surface, maybe cover with Steel edging angle?; but a wood panel base seems "ugly".
you could have a lower shelf … rock surface 3' to 42" above floor; shelf 12" above floor ...
you could have the shelf functional and structural, or hide structure (diagonal bracing) under it.

another day in paradise, or is paradise one day closer ?

 

[dik]

Heard back from two stone topping suppliers and both recommend plywood substrate... passed this on to the client.


Dik

 

[AaronMcD]

We have a tall kitchen table that came with our apartment similar to this. The top is maybe 5/8 or 3/4 marble. The frame is ~1 1/4" square tubes welded. There are intermittent angle brackets on the inside of the top tubes screwed from below into a flat piece of wood. Not sure what the wood is. Maybe ply but it's super smooth compared to structural stuff. There is a horizontal "H" frame about a third of the way up the legs. The marble top just sits on the wood, no connection. It doesn't move easily. The whole table is on these heavy duty spherical caster things sim to this

https://www.vxb.com/2-inch-Shepherd...JKeVEGqLY4-G9GH3mGH8DNWRk1Bc_BxoCmwQQAvD_BwE.

2 of them have a locking mechanism.

http://www.hellodwell.design

 

[dik]

Thanks...


Dik

 

[JStephen]

At the least, you should be able to tilt it up on two legs and lean it over on its side without tearing up the legs. With a granite slab, that may be more than the "buttlean" factor. Speaking of which, a 300 lb person leaning on it wouldn't exert 300 lbs of force.
If the legs are angled, then the vertical load also produces a lateral load at the base.

 

[dik]

Thanks... JS have to put a note about moving it... didn't think of that... I've used 250 for both lateral and vertical...

Guys were a lot of help.


Dik