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Americas
ShowcaseHangarSteven F. Udvar-Hazy CenterBy Satish Shah, David
Oleynik and James Whynot
The Smithsonians new National Air andSpace Museum Steven F.
Udvar-Hazy Centerlocated at Dulles Airport in Chantilly,
Virgin-
ia, houses a collection of hundreds of aircraftand related
artifacts. Some of the exhibitsin this larger than life facility,
affectionatelydubbed Americas Hangar by the museumstaff, include
the Space Shuttle Enterprise, theSR-71 Black Bird, an Air France
Concorde,the B-29 Superfortress Enola Gay, a BoeingS-307
Stratoliner and many others.
During the pre-schematic planning ses-sions the tremendous scope
of this projectimmediately became evident, with at least sixor more
major interconnected structures. Themain hangar and its side
galleries are the cen-
terpiece of the facility, enclosing an enormousexhibit hall of
more than six acres (about 2.4ha for those fluent in metric).
Other components include another largeadjoining hall called the
space hangar, dedicat-ed to space exploration, adding an
additionalacre of exhibit space, a 47.5m (150-foot) tallair traffic
control tower (exhibit), a 450 seatIMAX theater with rooftop
restaurant andconference center, entry and administrationwings with
offices, classrooms, food court,museum shop, etc., and the central
utilityplant building.
Designed, but not yet built, are a largerestoration hangar and
an archive facility.Together they will add another 235,000
square-foot (about 2.2 ha) of space to thecurrent facility.
The cost of construction was funded entirelyfrom donations. The
tension between theneeded flexibility of the program
requirementsand the budget constraints required everyoneinvolved,
including Smithsonians exhibitplanners and the design consultants,
to thinkcreatively. During the master planning phasevarious forms,
shapes and materials wereconsidered to arrive at suitable
solutions.
Spiegel Zamecnik & Shah Inc. studied
various structural systems and the estimatedunit costs of
various building shapes andmaterials to create column free spaces
withspans ranging from 50m to 120m (160 to400 feet). Also included
in the study wereproprietary systems. The architect added costsfor
roofing and perimeter enclosure for eachsystem that together
resulted in a comparisonof total unit costs for the range of spans
andsystems under consideration.
Based on various factors, including cost, thefinished space and
use, a design featuring threedimensional arch trusses with an
overall widthof 74m (243 feet) and a crown height of 31m
Vertical shoring posts temporarilyprop up the lower, side
portionsof the arches
The truss base subframes have a 500 mm(20 in.) diameter vertical
pipe column beloweach arch chord member. They are adjustedto final
position and placement of capreinforcement begins.
The completed foundation block standsready for erection of the
arch truss. Thearchitecturally exposed upper portions ofthese
concrete bases are a visual feature inthe main hangar.
(102 feet) was selected for the main hWith a truss spacing of
15m (50 feet) thlength of the main hangars roof is over
(1,000 feet).
The site assembled center portions arecraned into position
completing the arch.
Additional assembled lower, side portions
which have not yet been raised are visible the foreground on
either side of the crane.
The trusses are triangular in cross sehaving a pair of top
chords 5m (17apart and a single bottom chord 4m (1radially below
the top chords. Chords nominal 300mm (12-inch) diameterpipe with
varying wall thickness. Thdiagonals are 125mm and 150mm (5- ainch)
pipe. Each truss is designed for vcombinations of roof dead loads,
balancunbalanced snow and wind loads, haartifacts of up to 9000 kg
(20 kips) perand hanging walkway mezzanines 3mfeet) wide. There
were over two hundrecombinations, with a few dozen combinbeing
critical.
All three chords of each truss contithe base and connect to the
concrete fotion block. This type of base conn(which is different
from that of a thinged arch) provides additional stiffnthe roof to
control deformations under vloads. It was critical to minimize
thmovements, as planes and other artifactfrom the trusses.
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Arch truss web-to-chord connections wereoriginally designed as
fitted, gap K typewelded connections as an architectural
feature. The Canadian Institute of SteelConstruction (CISG)
recommendationswere used as a design guideline since it was
prior to the publication of the AISC HollowStructural Sections
manual. A fabricatorinitiated value-engineering proposal resultedin
a change to the transverse gusset platesshown here. The re-design,
took placeduring the shop drawing phase. It requiredaddressing each
of the many web-to-chordmember size/wall thickness combinations,in
a timely fashion, to arrive at the properconnection geometry for
each variation.
Between the trusses, openweb steel joists support anacoustic
roof deck. Acousticdeck was chosen to minimizethe effects of sounds
echoingback to the hangar floor andcreating a noisy
environment.
The arch bases consist of(3) 1070mm (42-inch) diam-
eter caissons socketed 1.2m to2.4m (4 to 8 feet) into
decom-posed or solid rock. Reinforcedcaissons are tied to a large
rein-forced cap, creating a momentframe resisting the lateral
andvertical reactions from the steelarches. A structural steel
sub-
frame was encased in each cap to allow precisefield adjustment
of the arch truss to founda-tion connection.
At each end of the main hangar is a largetwo leaf canopy door
with an opening of 45m
(150 feet) by 12m (40 feet) to allow for trans-portation of the
artifacts into the hangar.The structure for the end wall over the
doorsis a vertical steel truss spanning betweenbuttressed column
frames flanking the door.The curved top chord is independent of
theendmost arch truss for in-plane movements.It is detailed to
receive support and bracingfrom the arch to resist out-of-plane
loads.Lateral forces collected at the top of door open-ing are
resisted by a horizontal truss spanningbetween the buttressed
columns, which arecantilevered from their caisson foundations.
The space hangar is a 45m (150 feet)wide and 80m (260 feet) long
exhibit spaceadjoining the west side of the main hangar
at the north end. Its superstructure is a threedimensional
proprietary design space frame.It houses the space shuttle
Enterprise, alongwith other smaller rocket and space
explorationexhibits. The frame is designed to support upto 2,300 kg
(5 kips) of hanging load from anyof its bottom nodes.
At the west end of this hangar there isa large six leaf
parting/sliding door witha maximum opening of 30m (100 feet)wide
and 12m (40 feet) tall. The openingwidth is suf ficient to all ow
pas sage of theshuttle, except for its tail. The structure atthe
end wall is designed so that the centerportion can be removed when
the doors arefully open to allow the shuttle with its tailto pass
through.
The floor of the main hangar is designedto support up to
21,200kg (46 kips) ofconcentrated load, the wheel load of
theheaviest anticipated artifacts. The concrete slabthickness
varies from 250mm to 325mm (10to 13 inches), and is reinforced with
steel fibersand a two directional mat of reinforcing
bars to minimize cracking and to distconcentrated loads.
Similarly the 3(15 inch) thick floor of the Space Han
designed to support a concentrated lo45,000 kg (100 kips). Light
reflective dryhardener was used for uniform appearanto resist
surface deterioration under foand other equipment that deliver,
suand set the artifacts. Embedded in that 8m (25 foot) intervals
are utility dufuture communication and power conneas needed for the
exhibits.
The Smithsonian needed a buildishowcase the many aircraft and
other arin their collection. The museums main haccomplishes this
from a functional aspealso architecturally, with its
three-dimen
arch structure which is reminiscent dirigible hangars of times
past.
The segmented top chord of the vertical truss, spanning
acrossthe canopy door opening, follows the curving bottom
chordmember of the endmost arch truss. The x-braced,
buttressedcolumns flanking the opening, support the vertical truss
and thedoor and house the doors counterweights.
The museum entrance, mimicking thecurbside feel of an airport,
features a
glass roofed porte-cochere, an extensive,cantilevering bus
canopy, and monumentalatrium and the control tower.
The 47.5m (150 ftall control tower,which contains a lobservation
deck aas the air traffic coexhibit, has a slensteel frame
encasedconcrete shear walto control drift anvibration. The
upplevels, egg shaped i
plan, cantilever frthe core.
This article was prepared by three memof the Spiegel Zamecnik
& Shah Inc de
team: James Whynot, senior engineer, DOleynik, P.E. principal,
and Satish Sh
P.E. senior principal. Spiegel ZamecniShah Inc, has offices in
Washington, DC
New Haven, CT. They can be [email protected]
All photos courtesy of James Whynot/S
STRUCTURE magazine September 2005
