Doors and partially enclosed wind 1

[haynewp]

I had a question today that is exactly like this, whether doors should be considered openings in deciding if partially enclosed should apply. thread507-375034.

I found this from an old FEMA document.

Has anyone received an opinion from ASCE about this?

 

[EDub24]

I've always considered doors as openings when determining the enclosure classification of a building. Even if doors are designed to withstand wind forces (storm doors etc) there's no guarantee they'll actually be closed during an event. Better to be conservative than make assumptions.

 

[dik]

From my project notes...

THE STRUCTURE HAS SIGNIFICANT LARGE OPENINGS THAT CAN BE RELIED ON TO BE CLOSED AND SHALL BE DESIGNED FOR INTERNAL PRESSURES STIPULATED IN THE WIND LOADING COMMENTARY ON PART 4 OF THE CURRENT NATIONAL BUILDING CODE OF CANADA CORRESPONDING TO CATEGORY 2 (-0.9 <= CgCpi <= 0.6)


Dik

 

[phamENG]

I'd say the bare bones requirements of the code would be to assume the doors are shut. I think there are two things that support this:

1) Doors are typically shut, especially when a storm is coming. I get EDub24's concerns, but I think there has to be some acknowledgment of a survival instinct if not general intelligence. If you're in a building with a design wind event outside, you'd have to be pretty dumb to look at the open door and feel the gale+ winds in your face and not think "hmm...I should shut that." And if you are that dumb, incapacitated, or otherwise incapable of closing the door, you probably aren't the only person in the building. If somebody did leave you alone in that condition with a door standing open, you hurt yourself and you're all alone, or some other scenario like that, you're probably a statistical outlier that the code doesn't consider.

2) Most doors only open in one direction. Commercial buildings with outward swinging doors may be more susceptible to this as there are more faces with negative pressure than positive, but for residential and other inward swinging doors, the odds of having a closed but unlocked door swing open are low - the wind or debris has to hit the door just right. This is less code interpretation and more just thinking through it - if an inward swinging door is open, the negative pressure would likely slam it shut before the internal pressures reached a significant and contributing level.

It should probably be a conversation with the owner. Lay it out: the code lets us assume the doors will be shut. Is that how your business will operate? Yes? Great. Maybe or No? Ok - this is the cost of strengthening the proposed structure to account for partially enclosed wind loads. Want to revise your operating procedures? Yes? I thought so. No? Ok - we'll make it stronger.

 

[haynewp]

I was thinking more of the positive pressure since that is part of the partially enclosed criteria. And in that case, outward swinging doors would be shut by the positive pressure. Unless they swung open all the way under suction first and remained all the way open under the next positive pressure cycle as well.

If doors are supposed to be considered openings, then all the hurricane debris impact requirements of the Florida code must be focused only on stopping missiles and glass shrapnel and not about maintaining the building envelope.

 

[phamENG]

Fair point about receiving positive pressure. The procedure is sufficiently ingrained that I calculate it correctly - I just forgot that piece of the definition while thinking through the event.

I don't think the swinging open during suction and being pinned by positive pressure would be all that likely. Most doors in commercial buildings have auto closers on the doors.

The code specifically says that "apertures or holes" designed to be opened during a storm should be considered openings. That would imply that those that aren't (read: doors) are not openings.

Some possible exceptions: overhead doors at a medic or fire station that needs to leave during a storm to render aid, an unusually large door in a region where design wind loads aren't driven by large, "easily" predicted storms or hurricanes that could be bound up and unable to close on short notice (I'm imagining a really big hangar door), or an industrial facility with a lot of normally open doors in a similar region with limited warning before major winds hit.

 

[EDub24]

While I agree with has been said so far I'll add a caveat that I'm in seismic country (CA) so wind almost never governs my designs whether or not I include the doors and windows as openings