Diaphragm Question - urgent.. 1

[jsu0512]

Hi,

I'm desperately looking for some help with calculation of vertical deflection of cold formed stud wall as shown in the attached drawing.

The stud wall is sheathed with 1mm thickness of steel sheet attached to the vertical stud members.

The approximate self weight of the stud wall is 3.5kN/m. The span between the dead load support is 5783mm.

The stud wall has two large opening as shown in the drawing.

I attempted to calculate the vertical deflection as per the B5.4 from AISI S240, but there is no guidance there for stud wall sheathed with steel panel.

Can someone please me with this? I desperately need someone's help on this. I would greatly appreciate for your help.

Thank you

 

[CELinOttawa]

I want to state that I am a big fan of hand methods before I say the rest of this.

What? Why would this be spanning so far, and clad only in 1mm steel? Is this a shipping container, or some other normally industrial application?

In any case, I think this needs to be modelled. There are very distinct regions and behaviours going on here; this isn't going to analyze well as a simple beam. You have very significant differences in stiffness, and re-entrant corners, to worry about.

Shear deflection is going to be significant for this structure as well.

If you *must* get an approximation, then I would treat it as a series of beams that are fix-connected to one another. Again, easier as a model with a computer, but possible by hand.

I don't see this working at all without some detailing help: Continuous bottom plate track, etc.

 

[jsu0512]

This is prefabricated wall. I'm trying to have a wall span between concrete columns and trying to avoid dead load support (shim) at the mid span because the concrete floor slab deflect most at that location.

Do you mean segmenting a single beam (5763mm length) into five beams in proportion with the each sheet panel's width?

I was thinking to solve this by a diaphragm for vertical loads (self weight), treating it as a deep beam where top and bottom chord can be considered as a flange of deep beam.

The top and bottom beam (HSS 6"x3"x1/8"thk) is continuous by the way.

 

[jayrod12]

You have a concrete slab below this? Does the slab have the capacity to support the dead load?

If the answer to both of those questions is yes, then you are spending way too much time on this. Sit the wall directly on the slab and move on with your life. If they have to shim it at a couple locations, so what? The simpler you keep your load paths and thought processes, the more likely it is to get built correctly and perform adequately.

 

[XR250]

I can't imagine this working. Do what Jayrod said or put a 6" I-beam or something in the base that can span the distance.

 

[MIStructE_IRE]

I agree with Jayrod. Why is the slab below this wall not considered to be supporting it? We don’t design every partition to span from column to column.

 

[jsu0512]

Yes, the wall will be supported by the slab below. And yes, the slab has capacity to support the dead load of pre-fab wall.

I was trying to avoid any damage to the wall due to the slab deflection during it's service life time by putting dead load shim as close to the concrete column where the slab deflection is much less.

 

[jayrod12]

Assuming your slab is designed appropriately, and there's no significantly brittle finishes on the wall, there shouldn't be any issues from slab deflection on the wall. In fact, I would expect to see more issues if you tried some fancy calculation that suspended the wall slightly off of the slab. Just fasten it down and move on. Save your time for designing teh actually complicated stuff.

 

[MIStructE_IRE]

Its just a normal stud supported on a normal slab. This is an everyday occurrence.

Don’t worry about it. In fact, don’t think about it ever again!

 

[Tomfh]

You don’t have to design walls like this to span column to column. What you typically do is design the slab and limit the deflections so it won’t harm the wall (easier said than done!).

Check deflections above the wall too. Stud walls often have deflection tracks above, so prevent them being loaded by structure above.