Fabric Covered Structure

[SteveMort]

I have a client who wants me to design a 60' x 75' open sided canopy structure that will be covered with fabric. The fabric is to be removed in the fall and therefore he does not want us to include snow loads in the design. is this allowed? Does anyone have any experience with that kind of request?

 

[JAE]

Never been in that situation - I think you have a valid concern that someone, somewhere, sometime, will forget that you qualified your design to not include snow and leave the dang think up there over the winter.

However, it is valid to qualify a design and require the removal - full disclosure to the owner, documented, etc.

 

[lexim]

I agree with JAE that the design be qualified an full disclosure regarding the necessity for removal of the cover during the times agreed.

Good luck

 

[MikeHalloran]

Yeah, they're going to roll up that tent and reinstall it just about once.

Be sure the tent itself includes visible and prominent warning tags.



Mike Halloran
Pembroke Pines, FL, USA

 

[JStephen]

I've noticed on some similar posts in the past that people recommended designing the structure for the breaking strength of the fabric plus some margin- this might be a place to try that approach.

We lived up in Colorado for a while, and you could get fairly early heavy snows there- it would be easy to get taken by surprise.

 

[dik]

JAE... in some jurisdictions, it's possible to put a caveat on the property that identifies the 'temporary' structure.

Dik

 

[BAretired]

Not a good idea. For one thing, they will forget to remove the fabric in the winter. For another, spring snow can be very heavy, and can arrive when least expected.

BA

 

[DaveAtkins]

Hi, Steve,

The structure must be designed for minimum live load anyway (20 psf, I believe), so I don't think there is much to gain here.

And I don't thing a code official will allow it. For example, a few years ago I went to a code official with a proposed floor plan for an existing second floor room, to be used for storage. I showed him how the owner would only store boxes in a certain way, so as not to overload the floor. He wouldn't approve this.

DaveAtkins

 

[MiketheEngineer]

I do it ---- but also include all the warnings.

Usually check it for at least a 12 psf load - in the hopes that wind, slope etc. will allow this....

And people do take them down!! esp restaurants, nurseries, etc.

 

[RacingAZ]

Actually per IBC, you can design it for a 5 psf live load for fabric roof. There's no way around the snow load though unless you classify the structure as temporary.

I'm not a fan of using the temporary structure designation as I've seen a number of them being used year round. You can put all sorts of disclaimer and warnings but you don't really have control if they take it down or not. When that thing collapses, that's the only time you'll ever hear from them again. The fee on these types of structures is typically a small dollar amount that I normally walks away than be painted in a corner. You're taking increased liability for peanuts if you're going the temporary structure route.

 

[Inlander]

What if you designed it with a known weak link (grommets & stitching) that wouldn't allow much snow to build up. It would tear apart in the middle or something and dump the snow. Just don't stand under it when it's snowing.

 

[BAretired]

Perhaps it would be better to avoid the problem altogether by simply not getting involved in the first place. Consider the merits of accepting or rejecting the assignment and choose wisely.

BA

 

[HereTwoLearn]

If you aren't a "fabric structure" expert, recognize that you "don't know what you don't know" and steer clear of large fabric structures. I say that with no disrespect intended.

Personally, if this was a "two day event" type structure that was legitimately taken down, I'd probably design it for now snow. However, if it was supposed to be a "only in the spring/summer/fall", I wouldn't trust maintenance guys timing the weather. I'd inform the client I would only design a permanent structure for all loads including snow. They may need to find another engineer to do this structure in that case.

 

[Inlander]

You might consider talking the client into using a steel or wood framed roof with steel roofing. You could lighten the roof snow load based on the ability of the roof to shed the load.

 

[flash3780]

I assume that you are signing off on this thing? I wouldn't feel comfortable signing off on something like that - people could be hurt or killed in the event of the structure collapsing from the snow load because someone forgot to roll up the roof. Who's liable?

I suppose that you could design the fabric to tear before the structure collapsed... but that might not work for ice buildup.

 

[csd72]

I dont see what the issue is, there will be a visible warning tag when it is loaded with snow - its called sagging! Lay people are much more paranoid about these things than we are and I guarantee no-one will go under it if it is that overloaded.

Also, a fabric structure is much less likely to accumulate snow because it moves in the wind.

 

[BAretired]

Let's not forget the Dallas Cowboys Training Facility collapse.

BA

 

[csd72]

BA, that is a very different scenario to this one.

It was a framed structure with an air supported roof and it was brought down by a sudden storm. What is being described in this thread is basically an oversized tent an any impending overload from snow will be clearly visible from the start.

 

[DaveAtkins]

The Dallas Cowboys facility was not air supported. But I agree that this is a different scenario.

DaveAtkins

 

[BAretired]

Different in what respect? They are both framed structures covered with fabric.

BA