Foundation for Rolling Aircraft Hangar Doors

[bjb]

In the preliminary stages for the design of a PEMB aircraft hangar. Hangar door will be of the rolling type supported by rails at the base. Door height is approximately 40 feet. Wind speed is 90 mph.

How is the bottom horizontal reaction from the door typically handled? Is it usually assumed that the slab-on-grade resists this force? I am uncomfortable with this approach.

Is the prefered approach to design a foundation wall under the slab supporting the hangar door for stability against overturning and sliding from the horizontal door reaction?

 

[dik]

Hangar doors are often vertical leaf type doors and not horizontal roll-up. There is a track both top and bottom.

Dik

 

[bjb]

I should have said sliding instead of rolling. The door is suported at the base where it slides on rails embeded in the concrete.

 

[MiketheEngineer]

Just take the wind load and apply it to the slab. I don't think it will be a problem. Even at about 90 mph and wind load of about 20 psf you are lookng at 200 plf top and bottom. The concrete should easily handle that. I have had problems with the "top" connection!!

 

[bjb]

My concerns with relying on the slab are that it will be placed on a vapor retarder which will eliminate friction with the subbase, and load transfer across slab joints. We do not typically run rebar thorugh control jonts.

 

[bjb]

For frost protection in my area bottom of foundation has to be a minimum of 48" below grade-therefore the perimeter foundations of my building has to be least 48" below grade.

Assuming 20 psf wind load with a 40' tall door, my bottom reaction is 400 plf. Assuming a 4'-6" distance from fin foor to bottom of footing, my overturning moment is 1800 lb-ft/per foot. A 4' wide strip footing with a minimum of 3' of soil on the footing would give me a resisting moment of 4200 lb-ft per foot of resisting moment for a FOS=2.33. If I sharpen my pencil I could probably get to a 3'-6 wide footing.

 

[bpstruct]

Not sure how the orthogonal walls tie into the wall with the hangar door, but we would normally have a perimeter grade beam supporting (all around the building). If your slab is tied into that perimeter grade beam (or strip footing), I would probably treat that slab as a floor diaphragm and allow the lateral load to be transferred into the orthogonal grade beams. You would get some help from friction between slab and subgrade, but probably not necessary.

 

[hawkaz]

Don't overthink this. Put in slab dowels and allow the horizontal load to be transfered directly into the slab. No overturning

 

[MiketheEngineer]

Sorry - thought it was 20' tall!!

 

[hokie66]

I have done these doors with a separate foundation as you described, bjb. But as I recall, this was with flexible pavements inside and out, so I didn't face the decision of whether to use the slab.

Surprised that rolling doors are still being used. These are good. Watch the video.

http://www.megadoor.com/

 

[msquared48]

It's not only the force into the building, but the suction you have to resist on these doors. Is the Tarmac concrete or asphalt?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bjb]

I believe that there will be an asphalt tarmac, but inside will be concrete. It's the suction force that I am most concerned about. I am ok with assuming that the concrete sog resists wind pushing on the door.

My door is actually only 30' tall now. If I assume a 12"x48"wide thickened slab to support the rails with a 12" foundation wall, I can make a 2'-6"x1'-0" footing work (preliminary calcs). This is with a guessed at 25 psf suction load. I am considering the building as partially enclosed.

I have to have a foundation at 48" below grade for frost protection anyway, so I might as well take advantage of the foundation wall and footing.

Wall footings for low buildings around here are typically 2'wide by 12" thick, so my estimated footing is only slightly larger than what we use as a minimum.

As the project moves forward I will coordinate with whatever door mfr that we are going to use as the basis of design for any specific requirements they might have.

Thanks everyone for your replies, and Merry Christmas.

 

[dhengr]

In your first example you were assuming the stem wall cantilevered from the footing to take the lateral loading. In your final example you thicken the interior slab and extend it for the door/track sill, over a more std. ftg. and stem wall. I’ve never done this exact detail, but give it some thought... Use your more std. ftg. and stem wall sized for the track at the top. Then fill the trench inside and outside with “flowable fill” and take advantage of the active pressure of the soil which hasn’t been disturbed. This eliminates soil recompaction issues and also provides a good solid shelf for your int. slab and the tarmac at the door sill, in terms of any differential settlement. The “flowable fill” is cement, water, fine aggregate, fly ash or slag, and the like, with a compressive strength of about 100 - 150psi, and not too expensive.

 

[msquared48]

If you run bent dowels from the foundation into the slab, there should be no issues.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com