Wall Panel Dead Load

[twinnell]

Is the vertical dead load of metal wall panel supported by the girts or the foundation/slab/grade beam? We have 100 feet tall building and someone is telling me that the full weight of the wall panel is supported by the grade beam around the perimeter. Which means the wall panel has to support it's own cumulative weight. At the same time, I haven't seen girts designed for anything but wind load.

 

[JAE]

We don't ever put vertical dead load into girts (except self weight - and thus sag rods) so we assume it all goes to the grade beam.

 

[RareBugTX]

I think the girts transfer vertical dead load into the connections to cols and then that load plus any cumulative load is transfered to the column foundation. I do not assume the grade beam takes all the cumulative load from the panels above.

Regards,

Rarebug

 

[JAE]

So, twinnell....either way!

 

[civeng80]

What is a grade beam?

 

[msquared48]

In this case it would be a concrete beam at grade carrying vertical load (how much is left to the reader here) to the concrete footings beyond.

You could also design it as a strip footing, but maybe the dead load is needed at the footings for overturning...????

Mike McCann
McCann Engineering

 

[msquared48]

twinnell:

When you say "girts", I visualize horizontal steel members spanning between steel mainframes of a metal building.

Are these "girts" horizontal or vertical members? If they are vertical, I would term them studs.

Mike McCann
McCann Engineering

 

[twinnell]

horizontal girts.

 

[271828]

Cool situation. If the wall weighs 4 psf (2 psf panel + 2 psf other stuff), then that's 400 plf at the bottom. It would be interesting to check the wall panel itself for combined bending and column buckling for the length from the foundation to the first girt. I have no clue how that would work out because some of those are pretty darn skinny and the first girt might be 8-10' (guess) from the foundation. Might need to put the first few girts closer together to cut down the column buckling unbraced length.

 

[civeng80]

Thanks mssquare48

Last job I completed was girts spanning approx 9m and with 2 rows of sag struts. at the bottom of the bottom girt 2 short struts were put in propped from the panel and straightening the girt system as they are very weak in the vertical direction even under their own dead load.

 

[hokie66]

My normal practice is to support the cladding vertical load at the top, not the bottom. The girts are designed for horizontal load only. The cladding distributes the vertical loads by diaphragm action to the sag rods or other vertical supports which are in tension. But there are other ways of doing it, and it depends somewhat on the type of cladding. I would avoid relying on the cladding for much capacity in compression.

 

[csd72]

We have put 2 diagonal sag rods between the top two girts to take this weight out in truss action. This method has has worked on many buildings.

 

[civeng80]

Actually hokie66 from a practical point of view I find the sag rods and sag stuts for girts pretty useless for vertical load transfer, its mainly for lateral stability.
I find even a short bit of 90x45 timber sprayed with galvanised paint extremely effective at the bottom.

Cheers !

 

[civeng80]

Also csd72 in my opinion this may look good in drawings and theoretically may be ok but doesn't work well in practice.

Cheers !

 

[hokie66]

civeng,

Have used hangers many times to carry the dead load of the wall system. In a lot of cases in industrial buildings, the cladding stops well above the floor, so there is no choice but to hang it.

 

[civeng80]

If there nothing to support from below (e.g. concret panel on the inside of wall and girts on the outside wall) then hanging would be the only option. But In my opinion if propping can be done then go for it.

Cheers!

 

[JedClampett]

I checked in an old textbook I've got, "Design in Structural Steel", third edition, by Lothers. It sayeth on page 403, "Consisting usually of an angle, a small channel, or a zee section, it must be proportioned for a horizontal wind load and a vertical dead load, the latter being the weight of the siding. The only exception obtains when the weight of the siding is supported by sag rods, the latter being suspended by the eaves strut."
So it looks like unless you have sag rods, you need to carry the siding on the girts.

 

[hokie66]

Jed,

Lothers was one of my steel design textbooks, the 2nd Edition, 1965. The exact same wording you quoted was found on page 411. Maybe that is why I am partial to hanging the girts from the eaves strut.