Long Span Metal Roof Deck (+30'-0" spans)

[Charred]

Have any of you used long span metal roof deck for +30'-0" spans before? I have a few projects coming up that I would like to utilize this and wanted to reach out and see what experiences anybody has had. Issues with bounciness, erection, etc.? I know Vulcraft, New Millenium, etc. have several options for doing this in their catalogs/design tools so I am not questioning if it will work or not - just looking for feedback from anyone who has experience with it.

Projects are in the southeast: no RTU's, standard roof live load (20 psf), high seismic, wind velocity is 115 mph (ASCE7-16), risk category III. Lateral system will be SMF and/or light-gauge bearing walls.

 

[dik]

3" for 10 or 12'... but we have snow... for 30' it's almost a caterary... You might be able to do 15', but talk to a roofer to see what they would like to climb on.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

Wasn't this one of the issues identified in the Hard Rock collapse? Crazy long deck spans and/or inadequate shoring. It may "work" but probably needs a while lot of attention to detail.

 

[Charred]

The Hard Rock collapse was concrete though. This is plain metal deck so there will not need to be any shoring since the construction load is the design roof live load.

 

[phamENG]

Concrete filled deck at the upper floors, but still not quite your situation.

That does seem really long, though. What depth? I'd use a hard limit on deflection, not just L/240 or whatever you're using. Certainly no more than 1"... tighter if needed depending on what's attaching to it. Pay attention to ponding, too. Even if you don't have parapets, at that span you could easily see some localized impoundment that could lead to an instability.

 

[Charred]

Ponding - good point. There will be 4' parapets on all sides.

I'm currently looking at New Millennium's Deep-Dek. Seems like more of an individual beam rather than metal deck though as it is only (1)flute with a 12" coverage on a ~20,000 ft² roof.

 

[Roukkia]

Check out the epic metals catalog, I know this is a thing they have been focusing on in their product line.

 

[Charred]

Roukkia

Appreciate it - I’ve never heard of this group before but they appear to be worthwhile. Are they regional or nationwide?

 

[jayrod12]

What's the likelihood that roof top mechanical is added in the future? What's the usage of the buildings? If there's any sort of tenant spaces, then I'd be avoiding this as most tenants end up needing some form of additional heating/cooling/ventilation for their processes.

 

[dik]

I used to concern myself with questions like that... not so much now. The addition of a new mechanical unit, in the future, is a different problem. You should point that out to the EOR/ARCH or Owner... that's it.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Brad805]

I see gravity load calcs for the New Millenium deep dek, but no diaphragm charts. I see you mentioned high seismic. Have you done any prelim checks if you require the deck to be a diaphragm? I would get some budget prices from a supplier and do some estimates. We have used the long span deck products for slabs, and they are not always cost effective. I have my doubts it will be cost effective. If it were, the Pre-eng building suppliers would have jumped on this. They are the most cost effective bunch you will find, and it would take nothing for them to add this to their rolling lines. This would be an ideal product for their typical 25'-0" bays.

I see now the SMF note. My mistake.

 

[jayrod12]

Dik,

Although I agree with you that in the end it's the owner's call, it would be prudent to have those conversations. With 30 feet between girders, any additional mechanical added after the fact on the roof will likely result in substantial costs. Maybe all that means is it informs the owners for their tenant fit-up contracts. Needed to be said nonetheless in my opinion.

 

[dold]

I second Roukkia with Epic Metals Wideck. They claim spans up to 58ft with deck profiles up to 18" deep. I've never spec'd it but we had a rep come to our office once. It does make for a really clean looking roof system from the inside. And apparently good acoustic performance. I'd be interested in what sort of diaph shear capacity you can get out of that.

 

[Brad805]

dold, did you see what the epic metal 58ft span deck weighs? The deep deck is 4-8lb/sqft and seems to be single span only for long spans.

 

[dik]

Yup Jay... I'd just make sure I had a copy of the eMail I sent, cautioning them... that would be it. If nothing more than, "This confirms our conversation of 'such and such' where I outlined..."

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dold]

@Brad805

The max span deck is even heavier - ~12psf.

Their IAPMO report (IAPMO 0226) doesn't give diaph shear values directly. Looks like they want you to calculate it yourself based on connector strength but doesn't seem to address the actual capacity of the deck spanning 58ft to your LFRS (panel buckling, etc)... Not sure I like that too much.

 

[Roukkia]

dold - they have a diaphragm design manual but you may need to contact them for it, not sure how to post that here either