New Folding Wall and Existing Floor Trusses

[DaveAtkins]

I am working on a project where a folding wall is being suspended from existing wood floor trusses. Fortunately, when the wall is open, or in the stacked position, the wall will bear on the slab-on-grade. So the worst case scenario is a single, 4' wide X 8' tall panel (weight = 192#) hanging from the floor trusses as it is being moved.
I calculated the moment and reaction at a single truss, without the panel concentrated load, and then with the concentrated load. The concentrated load adds 13 percent to the bending moment (when at midspan) or the reaction (when near the support).
I think if I suspend the wall panel track from two trusses, I can live with a 6.5 percent increase in bending moment and reaction.
But what have you done in such a situation?

DaveAtkins

 

[structuralaggie]

With such a small increase, the plates would likely be the only ones that are undersized. If you can't track down the plate properties, adding plywood gussets would work. Also, just adding nails to the plates will help with the griping part, but not the tensile strenth of the plate. If possible, track down the cut sheet for the trusses from the truss company.

 

[csd72]

Check with your architect/manufacturer, Most of these types of walls are designed to hang and therefore will drag along the slab if they are sitting on it (not desirable).

I would usually limit deflection to about1/2" with all the door in the middle to avoid this. I would imagine that this deflection would be more of a concern than strength.

Spreading it between two trusses is a good idea.

In reality many of these doors dont even get designed for.

 

[miecz]

I work under IBC 2003, so I would try to get the increase under 5% to meet 3403.2. Can you spread the load to 3 trusses?

 

[DaveAtkins]

csd72,

I am being told by my Architect that these wall panels only hang when they are being moved--otherwise they bear on the slab.

DaveAtkins

 

[DaveAtkins]

I just discussed this with my supervisor. We brainstormed some other possibilities:
1. Can this suspended wall panel be considered part of the 20 psf partition allowance for the floor above?
2. Can the 70 psf live load on the floor above, and the weight of this panel, be reduced by 25%, assuming we have two transient loads?

DaveAtkins

 

[lkjh345]

DaveViking:

Just my opinion:

1). Yes, I think you logically could consider this moveable partition as part of the partion loading. Its is a partition with 'location subject to change' after all.

2) In my opinion, I do not think you could reduce the live load and partition load by 25% (IBC 2000 1605.3.1.1) as the floor live load above is not a transient load. My intepretation of this section of the code is for two transient loads, in the thinking that it is unlikely they would both have their maximum occurance at any one time. In my opinion, one 'permanent' load and and one transient load do not qualify.

I agree with jmiec suggestion to try and spread it out to 3 trusses to get under the 5% added stress 'rule'.

Vulcraft has a method to size the 'spreader' beam to distribute the load to mutiple steel joists. I would assume this analysis would work for wood trusses. See 'Designing with Steel Joists, Joist Girders and Steel Deck' by Fisher, Wrest and Vand De Pas.