SPECIFICATIONS OF THE CIRCULAR AIRCRAFT HANGERS AT GRIMBERGEN AIRFIELD

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP83-00423R000700190002-2
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 3
• Document Creation Date: November 9, 2016
• Document Release Date: February 8, 1999
• Sequence Number: 2
• Publication Date: May 25, 1953
• Content Type: REPORT

~,,rpp-ved For Release 1999/09/10 : CIA-RDP83-00423R0
Country - Belgium
25X1A2g
Subject - Specifications of the Circular Aircraft Hangars at Grimbergen Airfield
Place Acquired - 25X1A6a
Date Acquired -
25X1X6
1. Grimbergen Airfield near Brussels is intended generally for the use of light
and training aircraft. It is the site of Belgium's civilian flying school.
2. There are two circular hangars at Grimbergen. One feature of a training
field is that the planes do not leave on any planned schedule. When the
hangars are rectangular, the machine needed first may be the one at the
very back of the hangar. Circular hangar construction overcomes this
difficulty. The aircraft are housed with their tails toward the center.
The double-tracked sliding door system can be opened at any point so that
any plane can be brought out at a moment's notice. An element of runway
must be maintained, of course, around each hangar.
3. The hangars at Grimbergen are 50 meters in diameter. Designed expressly
for small aircraft, they can house up to 35 Piper Cubs and twin-engine
Percivais. They were built by Messrs. Blaton-Aubert, Brussels, on detailed
designs by M. Chas, from patents owned by M. Hardy of Quievrain, Belgium.
4. Apart from their aluminum and glass sliding doors, each hangar looks like
a large concrete mushroom on a squat, hollow stalk. The top of the mush-
room is hollowed by the down-slope of the roof from the circumference
rather more than half-way to the center, inside which it rises in a low
dome crowned by a glazed lantern top.
5. The base of the dose is a circle, 11 meters in radius, from which the edge
of the mushroom slopes upwards a8d outwards for another 14 meters. The
slope of the mushroom edge is 14 to the horizontal, rising to a maximum
height of seven meters at the circumference. The dome is a segment of a
sphere, 22 meters in radius, the tangent in the vertical plane at the
point of intersection, with the mushroom edge being inclined 300 to the
horizontal. The intersection forms, on the under side of the roof, a cir-
cular girdle 60 cm thick - the hollow stalk of the mushroom. This is
hollowed into four low arches. The. girdle is 1.20 meters deep at the top
of the arches and 1.75 meters deep at the thickest points, at which it
rests on the four support pillars. These pillars are the only support
of the roof; the mushroom edge has no other pillars to support it and no
struts or girders. Thus, there is plenty of headroom and no obstruction
of access to any point in the 1,584 sq .m. of main hangar space under the
mushroom edge. The additional area, the space under the dome, is 380 sq. .m.
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6. Apart from the glazed lantern, the entire structure is built of reinforced
concrete, none of which is pre-cast. The super-structure is in one piece,
laid on an arrangement of radial and circumferential (annular) reinforcement
bars.
7. There is no deflection in the mushroom edge. The radial and hoop reinforce-
ments are complementary in absorbing the moments of deflection and torsion.
The thickness of the concrete in the dome is 8 cm, in the mushroom edge
10 cm, thickening to 12 cm in the portion approaching the girdle.
8. The annular reinforcement bars are laid in groups roughly calculated to
absorb strain moments at the points in question. In the mushroom edge,
in the thicker concrete near the girdle, there are 18 bars of 16 mm in
the first meter and 14 bars of 16 mm. in the second meter. Outward from
that point, the bars are of 20 mm caliber, at a frequency of six to the
meter for two meters, seven to the meter for four meters, and thereafter
eight to the meter. The last half-meter, at the circumference, presents
a special problem since the concrete must be thickened to bear the additional
weight of the runway for the sliding doors. The weight of concrete in this
section is 370 kg per meter-run so that, with the door-runway and allowance
for surcharge weight, 470 kg must be allowed for, at a mean radius of 24 3/4
-meters. The circumferential tension is thus given:
an oc
470 x 24.75
tanl14
46.2 tons
Allowing for a tension of 1.2 tons per cm2 of bar-section, this calls for
a total section of 38.5 cm2, which is approximately satisfied by 13X 20 mm.
The outermost half-meter is therefore reinforced with no less than 13 annular
bars 20 mm in diameter.
9. The stability of the roof thus assured, the next point is the stability of
the structure. At the junction of the dome and the mushroom-edge there is,
of course, an offsetting of the lateral cmpression stresses. Unfortuna-k-Ly,
the difference between the tangents of 30u (at which the dome comes in) and
14? (the slope of the mushroom edge) results in minimizing the extent of the
compensation. The horizontal in-thrust from the mushroom edge is 38.4 tons
per meter-run, while the out-thrust from the dome is only 2.95 tons per meter-
run. The result is therefore an inward thrust of 35.45 tons per meter-run.
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10. The total weight of the structure is 800 tons. The roof is drained of
rain water by four drainage pipes which run down the inward side of the
support columns. Thehollowed-out roof could, if necessary, be used as
a water reservoir or as a store for sand. Allowance has been made for
a surcharge weight of 100 kg per square meter, brix4ng the total weight
above ground to a thousand tons. Allowing for the below-ground weight,
the total weight at the foundation is 303 tons for each of the four
support columns.
11. These columns are essentially rectangular posts 4.26 meters lopg and 25 cm
thick, each end thickening to 75 cm, the end-faces being trim to the line
of the.'.radius of the hangar circle. Below ground each column rests on e
75 cm section continuation pillar which continues to a depth of 40 cm,
after which it is broadened out to a base 65 c9n below. This base is 2.50
in broad and seven m long, at a tangent to the curve of the girdle. This
17 1/2 sq m of foundation-foot results in pressure at the foundation of
about 1 1/2 kg per sq chi.
12. The support columns stand above floor-level to a height of 2.30 meters.
The low arches in the girdle are such that the highest point is 2.85 m
above floor-level, but a foot inside or outside the archway there is a
full four m of headroom. The central space under the dome, though avail-
able for hangar space as necessary, lacks the immediate accessibility which
is the main advantaged the outer periphery. It is considered mainly as
workshop space. It gets much of its light from the lantern top in the dome,
where there is also a ventilation opening.
13. The application of the design of the Grimbergen hangars to accommodate
the large wing span of modern commercial aircraft might result in hangars
that were cumbrously large. At Grimbergen they have been a complete
success.
Approved For Release 1999/09/10 : CIA-RDP83-00423R000700190002-2