The Smithsonian`s new National Air and Space Museum

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The Smithsonian'snew National Air and Space Museum
Airportoffers valuabl6 le sons
at WashingtonDullesInternational
perforrnance-based
design
for outside-the-box,
BY ROCK SHI MENG, P.E., FireProtectionEngineer,Goge-Bobcock & Associotes, lnc., Chontilly, Vo,
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architect Eero Saarinen'slandmark terminal, one might not easily spot the
Smithsonian Institution'scontributionto
the airport,despiteits expansive760,000
sq. ft.That's becausethe museum'snew
facility,the Steven F. Udvar-HazyCenter,
very much r€sembles any other large airport hangar. And that was St. Louis-
Best performance
One of the principalfire-safetychallengeswas dealing
with egress distanceswithout compromisingthe unique
architecturaldesignthat supportsthe dramaticallysuspended aircraft.ln the facility'smain chamber, aircraft are displayedon threelevelsin an open500,000-sq.-ft.
atrium.Larger aircrattare at groundlevel,while smallerplanesare hung
from arches.These structuralelements
also support the roof via cables and
brackets on two separate levels. Lower-
based arhitect HOK's intent.The facility
i s e s s e n t i a l l ya c o l l e c t i o n o f a i r c r a f t
garages spanning the length of three
football fields. pn display are some of
levelaircraftare hung approximately25 ft.
above the floor, while upper-levelaircraft
hang roughly42ft. abovethe floor.
aviation'smost prized treasures,including the space shuttle Enterprise,an Air
FranceConcordeand the infamousSR71 Blackbirdspy plane,which, until now, hqs never been
In order for visitors to have the best
possibleview of the suspendedaircraft,
elevated walkways were constructed
along the sides of the main atrium/hangar.A gentle slope,
viewed by the public.This massiv€,multi-purposecomplex,which includesan IMAX theater,is expectedto host
3 millionvisitorsannually.And with so many people pres-
i n c o m p l i a n c e w i t h A m e r i c a n s w i t h D i s a b i l i t i e sA c t
requirements,was incorporatedinto the walkwaydesign.
ent, special fire-protectionand life-safetymeasures are
added to protect both buildingguests and the more than
300 rare aircraft on display.
However,this ADA-friendlyramp, along with the massive
size of the hangar created an immediate conflict with
applicablebuildingcodes for maximumexitingtraveldistance allowed. A means of safe egress had to be identi-
An upper and lower level aircraft suspension configuration of 25 and 42 ft., respedively, gives this Monocoupe 110
Special Little Butch and other aircraft a live, in-flight feel and takes advantage of the museum3 massive open volume.
Photography:
@
(Above)
Ghuck
Moorel
(Rlght)
Engineer . MAY, 2oo4
"or,"ulting-Specifying
Garolyn
Russo/NASM
fied to address the 650-ft.-plusdistance
from the most remote part of the walkwayto
the nearest exit, but in a way that did not
destroy the function of the walkways or
HOK's overallarchitecturaldesign.
Prescriptivebl,rildingcodes did not adequately address assembly occupancy in
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such a massive hangar-likestructure, so
the team had to take on a performancebased approach.The first step in that plan
involvedan exercisewith the Nationallnstitute of Standards and Technology'sFire
D y n a m i c S i m u l a t o r( F D S ) f i r e - m o d e l i n g
tool.The FDS model was chosen to create
a fire scenarioaddressingthe museum's
biggestconcern-ensuring that fire tenabili t y c o u l d b e m a i n t a i n e dw h i l e t h e p u b l i c
traveledto the distantexits.The FDS model
was also used to determine roof temperatures created by the design fires to help
analyzehow the light, unprotectedhangar
roofs might performduring a fire.
The designfire itself had to be reasonable
yet realisticto the kindsof hazardsthe museum might face. Therefore,proper input was
criticalto the model.Fortunately,
the Smithsonianhad alreadyidentifiedthe load of the
displaycontents,thus the hazardwas limited
to these materials.
Other worst-casescenarios were simulated,such as the sprinklersystemnot functioning, to maximizethe heat release and
the burn rate.The data was also compared
with resultsgeneratedby the egress models to ensure its accuracy.
In the end, the FDS modelclearlydemonstratedthat the worst-casescenariowould
not have a significantimpacton the levelof
life safety.The shear space in the main
hangarwould act as a smoke and heat sink
for any combustionproduct. In addition,
simulationsdemonstratedthat the design
fire fuelwould be completelyconsumedand
that the harmful upper smoke layer that
would be generatedby a fire within such a
space would have no effect on life safety.
The next major step was to identify the
appropriatemethod of fire suppression.A
sprinklersystemwas chosen.The minimum
sprinkler design criteria for the museum's
particular hazard classificationis Ordinary
Consufting-Specifying Engineer . MAY,
Cll
"ooo
It was not practical to install evacuation notification devices and related wiring in the
middle of the displayspace. Therefore, the building's intelligent public address system
was enlisted for double duty.
HazardGroup2, whichincludesadministrative time prediction models currently available
spaceas wellas exhibitareas.Thisclassifica- are not accurate for heights 100 tt. and
tion exceeds the requirementsof NFPA 13, greater.Once again, the FDS modeling proInstallation of Sprinkler Systems,and most of gram came to the rescue.Inthis case, mod-
To help people better exit
elinganalysiswasbasedon a
1O-ft.by 1O-ft.sprinklerspacresponsetime
ing.Appropriate
index (RTl) valuesand temperatureratingswereplugged
in along with borroweddata
and inputused in the initial
Attention on Deck
Atthough not required by applicabte
codes, a voice general
evacuation system was sefected for
the museum. This alternative has
building
many advantages over the horn or
bell-Ape general evacuation signals, for example, live voice instructfons and the capability to gen-
the fadllty, largeplasma-screen
Ws wereplacedthroughout.
erate selected rnessages in different
zones. But ltwas a code requitement
that the voice alarm system not only
had to provide an alarm message-
the buildingcodes.Smithsonianofficials,however, requested a more restrictivecriteria to
allow flexibilityfor future space utilizationwith-
egress analysis.
The results indicated that fewer sprinklers than expected were required in the
typtcally 15 dBA above the ambient
noise level-but it also had to deliver
a clear and understandable message
out havingto upgradethe sprinklersystem.
design areas and that the criteria set in
NFPA 13 was adequate.Furthermore,the
model proved that the response time and
throughout.
Quick response
As for the sprinklersthemselves,glassbulb,quick-responsesprinklerswere spec-
coverage were sufficient without compromisingany of NFPA 13's requirements.
(Gontinued on page 4Ol
ified, opposed to standard-responsemodels, as the former not only respondto heat
quicker, but also have less thermal lag.
Special consideration was also given to
sprinkler performance, given the museum's
elitreme volume and height-1O0 tt. at its
apex. Furthermore,museum otficials raised
concernsthat the cablessuspendingthe aircraft might melt during a fire. Sprinklers in
these areas, therefore, had to be able to
react within the appropriate response time
index and temperature criteria. This presented a minor dilemma in that responsef
Engineer
"or',"ulting-Specifying
o MAY,
The speakerc initially selected tor the
at their maximum settlng,
could ptoduce a sound level of 9O
dBA at lO tt. frcm the speaken As a
facilfu
rule of thumb, the output of an audlble notification appliance is rcduoed
by 6 dBA tt the distance befinrcen
the speaker and the listener is
doubled. At 2o.ft., the output is
rcdued to 84 dBA. lnstead, the
bui l dl ng' s i ntel l i gent public
address system was nepurpose4
as many features of a tire-alarm
system wene lnherent in lt. Noise
sensorls,however, wene installed
in the exhtbit aneasto adiust the
PA volume apprcpriately.
2oo4
I
( G o n t i n u e df r o m p a g e 3 8 )
On the spot
N a t u r a l l yn, o f i r e - p r o t e c t i o snc h e m e i s
c o m p l e t ew i t h o u ta f i r e - a l a r ms y s t e m .T o
meet buildingcode requirements,
a microprocessor-based,
analog-point
addressable
f i r e - a l a r ma n d d e t e c t i o ns y s t e m ,i n c l u d i n g
pull stations,smokedetectorsand notifica-
I
lr,
t i o n d e v i c e s ,w a s d e s i g n e da n d i n s t a l l e d .
However,designinga fire-alarmsystemfor
sucha uniquefacilitywith multipleoccupanEarly
cies requiredspecialconsiderations.
detection
and earlywarningare onlya few of
thathadto be achieved
the designobjectives
protectthe livesof the
in orderto adequately
'
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occupantsand the displays.
The mostdemandingof thesecriteriawas Fuelload from visiting aircraft is an issue. Therefore, no refueling is allowed near the site.
Photography: Mark Avino/OIPP
the selectionof the detectionsystem.First,
the entirefacilityhad to be protectedwith an
, h i c hh a st h e s h a p eo f
automatic
smokeor heat-detection
system,in follows:Smokeparticlesare drawnby a fan T h e r e f l e c t i npgr i s m w
a p y r a m i dw i t h l a t e r a lf a c e s f o r m e d b y
isoscelesorthogonaltriangles,enablesthe
beam enteringthe prism to reflectback to
h a n g a r ' s s t r u c t u r a l f r a m i n the
g transceiveralong the same path, thus
a c c o r d a n c ew i t h S m i t h s o n i a ns t a n d a r d s . intothe samplingpipe networkto the detecWhen consideringsmoke detectors,spot- t o r .T h i s w o u l da l l o wt h e s a m p l i n gp i p i n gt o
b e e x t e n d e da l o n g t h e
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or projected-beamdevices.
type detectorswere the initialchoice.The
m o s t c o m m o n t y p e o f d e t e c t i o n ,t h e s e
deviceshave the capabilityto adjust their
from the apex to detectors minimizingthe effectof vibrationand struc. u r t h e r m o r ew
, i r i n ga n d
mountedat an accessible t u r a l m o v e m e n t F
l e v e l . S u c h i n s t a l l a t i o n powercan be providedat one location.The
wourd
avoid
anyconlictsreflectorcan be mountedat the apex,and
w i t he x h i b i t a
s n d l i g h t i n gl t. onceaimed,doesnot needto be accessible.
wouldalsobe independent Additionally,
such devicescan blend aes. ulti-level
o f a i r s t r a t i ifc a t i o n ,a n d t h e t i c a l l yw i t h b u i l d i n gf i n i s h e s M
performed
ground
the
stratification
level.
detection
also
eliminates
servicecan be
at
includeda high effect, as service can be performedat an
This option'sdisadvantages
pipe network. accessiblelevel.Finally,the technologyis
limitation
of
the
cost and size
T h e p r o j e c t e db e a m d e t e c t o r o p t i o n
thus enablingthem to differentiate
sensitivity,
b e t w e e n r e a l f i r e a n d n u i s a n c ea l a r m s allowedfor the devicesto be mountedand
caused by dust.They also use state-of-the- aimedat variouslevelsand angles.The lat-
the leastexpensiveof the two.
Beam detectionwas chosen, but there
that had to
was stillone majordisadvantage
path
can wind up
art microprocessor
circuitrywitherrorcheck, est technologyalso enablesthe transceiver be resolved:The beam
d e t e c t o rs e l f - d i a g n o s t i casn d s u p e r v i s i o n and receiverto be a singleunit.The waythis b e i n g b l o c k e db y e x h i b i t so r l i g h t i n gT. h i s
the locationof
programsto reducenuisancealarms.
system works is that an invisibleinfrared was resolvedby coordinating
prism
pulse is beamedoff a
concavelens. the detectorsand the exhibitslayout.
More choices
One caveat,however,is that the sensitivity of the spot detectorsis limitedby mounti n g h e i g h ta n d c e i l i n gp r o f i l e .I n t h e m a i n
A replica of the 1903Wright Flyer soars
during opening-dayceremonies.
hangarwith a ceilingheightmore than 100
ft., smoke stratificationand accessfor service of spot detectorsessentiallywould have
m a d e t h e m u s e l e s s .C o n s e q u e n t l yt,w o
air-samwereconsidered:
otherapproaches
pling smoke sensorsand projectedbeam-
Havingalreadyhostedmore than half a
millionvisitorssinceits openingon Dec.15,
2003,the Udvar-HazyCenterwill likelysee
plentyof activityin the comingmonthsand
y e a r s . A p e r fo r m a n c e - b a s e d d e s i g n
approachyieldeda uniqueavenueto meet
whileprothe museum'sdesignchallenges,
type smoke detectors.
The air-sampling
systemoptionconsisted
of four components:an air-samplingpipe
viding a fire and life-safetysystem capable
of protectinglives and aviationtreasures
that also reduced constructioncosts. Furthermore,it provesthat designingvia the
network,a detectorassembly,a controlunit
and a power supply.lts operationworks as
designa safe building.
Engineer . MAY, 2oo4
4iI
Encore
".".ulting-Specifying
prescriptivecodes is not the only way to
l*sel