Large Multi-Slide / Bi-folding Door Deflection Criteria 1

[jdgengineer]

On high-end residential projects it's fairly common to have large multi-slide (usually bottom supported) or bi-folding doors (usually top hung). Typical manufacturer's would be Nanawall, La Cantina, Fleetwood, etc.

They all have slightly different design requirements, but generally speaking limit the deflection to 1/8" live load and the lesser of 1/4" total load or L/720. Once the span over these doors exceeds ~15' the headers are usually steel.

Where there is only roof above the header, and no snow loading, do you think it is too conservative to include the roof live load in the deflection limits? The manufacturer's are not typically sophisticated enough to know the subtle differences between floor and roof live loads. Below is Fleetwood's requirement for a multi-slide door.

 

[NorthCivil]

I work with these doors in a former life.

the doors are generally designed to still function/operate with 6mm of vertical deflection. Getting this communicated properly to the structural engineer, and having him care, was a heroic feat.

key questions:

how much deflection is your door opening really going to see vs what do your calcs show you
is there going to be full snow load, full wind load, full live load all at the same time, and will people be opening the doors when this happens? my bet is the doors stay shut when its snowing, the doors stay open in a crazy house party with people on the roof
opening the door is a serviceability issue, ie SLS not ULS

 

[dik]

and I've done a few 747 hangars and the doors are even more interesting...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[jdgengineer]

Thanks guys and yes we check these with serviceability limit states. D + L, D + Lr or D +.75L +.75 Lr. We don't have snow loads where we are.

In this specific instance we have a single story structure. We are specifying a deep steel beam largely due to the roof live load which seems unlikely to be present often. I think we'll keep it in there but the architect isn't stoked with the beam size we came up with to meet the 0.25" deflection with D + Lr.

 

[Harbringer]

I think we'll keep it in there but the architect isn't stoked with the beam size we came up with to meet the 0.25" deflection with D + Lr.

I guess the architect is free to select another type of door then.

I've done a few "Nanawall" doors of pretty long spans (I used pretty deep GLB's) and I used D+Lr for deflection.

I mean do you expect that a contractor is going to remove this door when they pile materials on the roof for a re-roof...
You don't want live load deflection shattering some super expensive doors.

 

[dik]

I've also supporfted folding partitions on a separate structure that accommodates load from the folding partition only. separate from the floor or roof load.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[NorthCivil]

"I guess the architect is free to select another type of door then."

Very true

I'm pretty familiar with the operation of these doors, the deflection values the door manufacturer has provided has ventured beyond practical and into unreasonable "arse-covering", IMO.

But hey, not your role to approve the violation of their specs. Maybe if enough architects give them grief, they can revisit their specs and publish something reasonable/alter their system to accommodate

 

[jayrod12]

has ventured beyond practical and into unreasonable

I feel the same way about elevator suppliers.

"We need a full width opening at the top and bottom floors, we don't care that this is a 6 storey building, we need that 15 foot wide opening. No you can't have a column at the middle. Oh and the opening needs to be 8 feet clear even though your floor to floor height is only 10 feet. You're an engineer, figure it out."

 

[LuK13]

Tell the architect he can put the big fancy door in a non-load-bearing gable end wall.

Of course then the whole gable will turn into expensive custom shaped windows (read dead load of multi-pane glass) and you'll be back offending them with the size of the header you want to stick in the middle of their residential curtain wall.

 

[XR250]

Residential ones that I typically work on require 1/16" deflection!
Kind of ridiculous, I know - especially for wood construction where shrinkage will occur.
I generally keep it at 1/8" total load if I can fit the beam in there without too many gymnastics.

 

[JLNJ]

This is typically what I see on commercial projects. L/2160. Pretty tight tolerances, but you can level the door after the structure DL is already in, so that doesn't necessarily count toward the deflection limit. It can still be problematic when the door is tall and therefore heavy. We did tall and long partition in a school cafeteria/multipurpose room recently where we used an absurdly deep roof truss to keep the deflection within limits.

http://www.panelfold.com/resources/Instructions/Pd DEFLECTION -pdf.pdf

One of the problems we always wrestle with is the point load when the whole partition is folded up and hanging in the middle. The deflection isn't as important in this case, but you can easily overload a member if the partition weight isn't spread out nice and even over the whole span.

 

[phamENG]

My problem is that I rarely receive the specs for these things. The architect shows a door, and the contractor picks it out after I'm 'gone'. Has anyone ever tried adding a note on their drawings like this: "Beam has been designed for code minimum deflection requirements. If installed doors or windows require tighter tolerance, contractor shall adjust bearing elevations to accommodate beam deflection and door shimming or contact EOR for redesign of beam." How horribly did it go?

 

[NorthCivil]

@phameng

I would not worry at all. Worst comes to worst, a few chippies have to rip out the header and replace. That's what you get for being an ambiguous architect.

A good project team, whether that be architect, builder, or even door installer will know the beam is undersized when they see it.

Unfortunately they don't issue crystal balls with our stamps, and it would be a severe waste of materials to design everything for 0 deflection

 

[Agent666]

Medical pendant suppliers also come to mind with unrealistic deflection expectations....
Me - "What deflection limit do we have to comply with?".....
Supplier - "we would like it to be infinitely stiff, thanks"....
Me - ".....ooookkkkkaaaayy........ so span/600?"....
Supplier - "I don't know, is that stiff?"

Just give them what they want, as someone who has a couple of bifold doors in my house don't skim on the deflection criteria as they do bind up a little otherwise and get harder to open over time if the deflection of the top and bottom frame is too much or vastly different.

Where they meet in my house at the middle for example there is a definite wider gap at the bottom than the top for example, and they run quite rough when opening them.

EDIT - FYI that opening is probably only 2400mm wide with two folding panels wither side.

https://engineervsheep.com

 

[NorthCivil]

Agent666

i wouldnt blame the header over your door. Knowing what i know about NZ alum windows, your bifolds are probably buckling under their own weight.

NZ residential construction is generally complete garbage compared to the rest of the developed world, and one of the poorest parts of NZ homes are the atrocious windows. look how badly those windows are sweating in your photo!

Most garden sheds in the US/Canada are built to a better standard than New Zealand single family homes.

 

[dik]

Does this include construction tolerances? Let's see that built into a spec... and see what the costs would be...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JLNJ]

dik

The commercial partitions to which I'm referring generally have a track which hangs off the structure from a series of threaded rods. Any erection tolerances or dead load deflections can be corrected for when the track is hung from those threaded rods.

 

[dik]

For that tolerance you cannot have it connected to structure that takes load. IMHOANHS (and not humble, sometimes).

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik