Deflection Criterias for Folding Partition

[rscassar]

Hi guys

When designing the supporting structure for a folding partition, I have been told to limit the deflection to span/1000 or 1/4" (whichever is less). Does this deflection criteria only apply for the partition load (20psf).

For the example I have, I have provided a W16 beam which also supports wood roof trusses. The dead load from the roof trusses causes the steel beam deflect 1".

This 1" deflection will be present when the track for the folding partition is installed. Is the curvature of the track the reason for the stringent deflection criteria or is it the fact the folding partition may catch on the ground if the deflections are too great.

Anyways, some feedback would be appreciated.

 

[dcarr82775]

The partition manufacturer normally will provide the deflection requirements. My understanding it that their deflection limits are total deflection

 

[RHTPE]

Think about what you have ... a movable load on your support structure. Depending upon the use(s) intended for the spaces on either side of the partition, there will be requirements to limit the gap between the bottom of the partition and the floor (sound transmission, etc.). As the gap is held to a small amount, the operability of the partition becomes a concern. If the gap is adjusted during installation to a small dimension (say in the Summer), and then Winter arrives with a substantial snowfall, will the partition still be able to operate? I believe that the deflection due to all in-place elements can be accomodated (except for the partition itself) during installation. Live load + partition load deflection will impact operability.

Just another opinion.


Ralph
Structures Consulting
Northeast USA

 

[rscassar]

Luckily snow loads are not a consideration in my region.

I was able to get a manufacturer's specification today which said it is the owners responsility to ensure a square framework for the track with tolerance of +/-1/4" or a total toletance of 1/2". I guess that answers my question that the steelwork deflects too far. I am going to need to either stiffen up the steelwork or precamber the deadload.

 

[csd72]

I check it for the deflection under the door weight only and taken as a point load at mid span. For this case I would check for l/500 or 10mm (I will let you work out the fraction).

If you think about it, you are mainly trying to stop the bottom jambing against the floor, so whatever installed gap there is is the maximum deflection it can take.

Just remember that for tdeflection it is the order things are done that counts. The floor will already be in and taking its dead load before the tracks are installed and levelled to tolerance.

 

[rscassar]

I didn't think the floor would be taking any load for folding partition walls and that all the load is supported from the track above.

 

[paddingtongreen]

Cambering is not necessary, and not that accurate either, look at your code mill tolerances. No, you need adjustments/standoffs to take care of dead load "shape" and design to limit the live load deflection.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[MiketheEngineer]

Don't forget to check when the door is all folded up - practically all the wall weight in one small area - and what if you can fold the door up in the middle of the opening. Some partition systems allow for this.

 

[csd72]

kikflip, yes that is the point! when it comes in contact with the floor below then it will jam.

Cambering is meaningless in this situation, a cambered beam will deflect just as much as an uncambered one, it will just be straighter afterwards.

Mike,

Agreed, thats why i recommended taking the door self weight as a point load.

 

[structuresguy]

I agree with paddington and Mike above. Design your structure to limit live load deflections to their specified tolerance, checking the wall fully closed (retracted) in one location (both mid span and end of track). Consider the wall weight as live load, along with any live loads in the space above (for you it is roof).

The wall tracks typically hang by threaded rods from the structure, so that the track be be installed level, regardless of the dead load deflection. also, the partitions will frequently have an adjustable bottom seal, which allows +/- movement while still touching the ground to make a better acoustic seal.

One final note, be sure to provide lateral restraint at the top of the track, to keep the wall from swinging when pushed on.

The detail we typically use is a steel channel (8-12" wide) laid flat 6-12" above the ceiling elevation. The channel is supported by angles from the roof (or floor) framing above, which could be some distance up. We then brace off the channel with kickers up to the structure. The track is then bolted to the channel with threaded rods at whatever spacing is needed by the manufacturer. The gap from the channel to the track is kept as low as possible, preferably less than 6".