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KootK (Structural) (OP)
5 Jun 09 18:03
I'm investigating a movable partition wall for an art galley.  It needs to be 3m high x 3.7m long x 610mm thick.  It's got a layer of gyp and plywood all around and rests on a light angle frame supported by casters.

I was asked to investigate this thing for stability when art work is hung from it and/or when it's moved by gallery personell.  The real trouble, however, is that it isn't anywhere near stable enough to resist the code mandated 5 psf wind load for interior partitions.  The wall is not supported at the top in any way.

I wonder: is this a misapplication of the 5 psf code provision?  Would there be any reasonable justification for ignoring or relaxing it?  Pressure differentials would presumably be equalized on either side of the wall.

Thanks all.
 
RCinVA (Structural)
5 Jun 09 18:40
Is this a pure cantilever that is not fixed at the bottom? I'm confused on the base connections.....

RC
All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke

 

KootK (Structural) (OP)
5 Jun 09 18:47
The wall is cantilevered.  The only thing keeping the wall from tipping over is its own self weight acting as ballast.
JAE (Structural)
5 Jun 09 18:58
If you didn't use 5 psf, what would you use?  5 psf is pretty minimal.  I agree that unbalanced internal pressures probably wouldn't be a realistic explanation for why you would use a lateral force on this partition.

Perhaps these would be reasons to use a lateral force:

1.  Seismic event (unless the partition is on wheels and just rolls with the seismic event.
2.  Unbalanced weight placed on the partition.
3.  Lateral force from accellerating the partition sideways (a gang of workers moving it too quickly)
4.  Lawyers

 
Lutfi (Structural)
6 Jun 09 7:38
JAE, I love your forth reason!

Art can be expensive. We do not want the wall to tip over and damage expensive art work. Go conservative. JAE gave solid rational. I wonder if code 5 psf lateral load applied to moveable walls though? i need to read my code.

You will have overturning due to the way they hang the art work. It usually few inches from the face of the wall which added to the eccentricity.
 

Regards,
Lutfi
 

MikeHalloran (Mechanical)
6 Jun 09 9:48
Note that if you keep the casters within the device's footprint, the effective thickness of the wall, for righting moment calculation purposes, is defined by the caster wheel centers, which in the case of swiveling casters, should be considered inboard of the caster swivel centers, i.e., with the casters swiveled into the worst position.

If you put the casters under outriggers to increase the righting moment, you have to make sure that the outriggers don't become tripping hazards, e.g. by making them as pilasters.

Arbitrary wind load may be irrelevant.  The other tipping moment that you have to consider is your typical high school football team, once they discover they can have fun by rocking the wall into resonance and over.  Hell, they do it to >automobiles<.

I think that's why movable walls in schools and other public buildings are typically suspended from a track in the ceiling.

 

Mike Halloran
Pembroke Pines, FL, USA

BAretired (Structural)
6 Jun 09 16:18
It sounds as though this movable partition is a potential hazard to the occupants.  When used in a public space, it should be tied down to the floor to prevent overturning.  It should certainly be capable of resisting at least 5 psf lateral pressure.

BA

msquared48 (Structural)
6 Jun 09 21:55
Is the floor on which it is moved concrete or wood?

You should consider embeds or holes in the floor where special connections (temporary) can be utilized to stabalize the panel when in use, or storage.  It can be designed and detailed.  You just need to use your imagination.  

Mike McCann
MMC Engineering

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