combined deflections criteria - metal wall framing

[asixth]

Hi

How is combined deflections considered for a metal stud wall system where the top track is fixed to a structural system that allows movement (i.e. a hot rolled channel spanning 8000mm / 27' opposed to a rigid system such as a ceiling diaphram).

For example, the wall manufacturer recommends a H/250 deflection criteria for wall studs. This means that the deflection of the wall studs is limited to 16mm (5/8"). Does this mean I need to limit the deflection of the wall stud in additional to the deflection of the channel to 16mm?

And secondly, what is the maximum limit to wall stud deflections that people normally use? I use H/100 for wood walls studs that normally span 9' (2700mm). Using this criteria the deflection is limited to approximately 1" (27mm).

Is the 1" the total maximum deflection people are willing to accept for wall framing. The governing deflections load case is wind.

 

[msquared48]

If there is sheetrock on the wall and it is an expensive home, then I always use L/360 or greater.

The L/100 value seems very liberal, even for office partition situations. And I assume that the studs are not vertically load bearing, only seeing psf wind.

Regarding the top channel deflection, depending on the useage, I would look for some way to limit the lateral dedflection.

If you are the design engineer for the only studs (as in TI work), I would limit the lateral of the studs to the manufacturer's recommendations or greater depending on the useage. I would recommend that the top channel be stiffened as the system was seeing deflections of XXX at the top. This is L/XXX, beyond the recommendations of the code (?).

Remember that the code recommendations are the Minimum. If the situation warrants, you can, and should, go higher.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[hokie66]

I think the H/250 limit recommended by the manufacturer refers to the bending deflection of the stud, not the relative displacement of the supports. The head deflection is a different consideration.

Stud deflection criteria differ markedly, and usually depend on the cladding materials. H/100 sounds too flexible for most situations.