Deflection opinions sought

[connect2]

Hi all, have a roof truss that I'm designing in a Gymnasium. Truss spans 80' and supports 40'owsj each side and also supports a large folding wall accordian door divider. Thoughts on defelection limits and operability of the door. The dominate gravity load is snow. Thanks.

 

[steellion]

Do you know the manufacturer and model of the operable partition? You should be able to get deflection criteria from the mfr. Many door systems are designed to accommodate deflections up to 1" or so, but some require more strict deflection criteria. Make sure you add kickers or some mechanism for a nominal out-of-plane load to avoid out-of-plane movement of the partition.

 

[connect2]

Hi Steellion yes that seems to be the spec from the Manufacturer, 1". Just ends up with a 'bigger' truss than expected re in this case re 80' span, in the world of l'overs thats l/960. it's not our money but at the same time. Thanks.

 

[BAretired]

Check with the manufacturer again. That seems an unreasonable limit for such a long span.

BA

 

[connect2]

BAretired, have just emailed Architect to get this answer plus if there is an operating range.

 

[Timelord]

Wouldn't the door be installed with the dead load deflection already there and compensated for? The additional deflection would only be from the live load.

Timelord

 

[connect2]

That of course is the case. However we look at total deflection re roof drains and ponding and slopes as well as LL defl'n.

 

[OHIOMatt]

What would excess deflection do? What level of deflection loads / damages the partition? If it is simple a matter of usability, what is the likelihood of needing to open or close the wall at the design snow level?

 

[connect2]

By the way the door is a live load.
OHIOMatt, well it's a school so the door is used regularily through the winter and oddly we approached our design snow loads about a decade ago during an ice storm.....when schools were in use. Regardless, the full snowload is used and there is a requirement for operability at that design condition.

 

[ameyerrenke]

Hopefully the architect gives you a helpful response, if not...

Obviously I don't know all of the variables that you're dealing with, but it may be worth considering a truss which supports only the weight of the partition and is independent from the truss supporting the roof load. It may be more economical to design the extra truss taking the small load of the partition to the stringent deflection criteria, and allow the building's truss to adhere to less ridiculous deflection criteria. As Timelord hinted, (in this case anyway) this truss would already deflect under its own weight pre-install of the partitions track, so, if the track is installed level then the truss would only have to resist the additional deflection due to load from the partition.

Once again, I hope the architect gives you a helpful response!

 

[XR250]

I imagine the deflection limits are to keep the partition floating above the floor. What about cambering the truss to account for the roof dead and partition dead loads?

 

[dik]

The problem is the 20' of tributary width on each side. The last project I did with folding partitions was to use a separate structure for the partition. It's a matter of looking at the framing around the truss... in my case the partition supporting truss was lowered by 4".

Dik

 

[Ron]

Partitioning curtains in a gymnasium will not likely have a bottom track, so just shorten the curtain a bit to accommodate deflection. They are usually not soundproof and are there only to divide activities.

 

[Ron]

Partitioning curtains in a gymnasium will not likely have a bottom track, so just shorten the curtain a bit to accommodate deflection. They are usually not soundproof and are there only to divide activities.

 

[connect2]

Thanks all. Simpliest solution is to separate the partition from the roof with a seperate structure as per dik.

 

[Jerehmy]

Not designing anything like this, just curious -

If there's no bottom track, what stops the partition from sliding from a wind load if a gym door is open (which happens a lot, and gyms usually have a lot of doors).

Also, gym partitions are pretty large areas, do you design for 5psf wind load on the partition for out of plane load on the truss or take some smaller load?