Imema1ionalJoumalofOfYShorenndPolarEngineering

醗雌1Wもty聴暁柵M灘i鵬洲｡rc過ndPol麺Enginccr，

FieldExperimentoflceDomeSpanning20～３０Meters

TsutomuKokawa

DepartmentofArchitecture，SchoolofArtandTbchnologyHokkaidoTbkaiUniversity,Asahikawa,Hokkaido,Japan

ＡＢＳＴＲＡＣＴ

Ａｉｍｉｎｇａｔｔｈｅ１℃alizati0nofalargeiceshelltobｅｕｓｅｄＩｂｒａｖａｒｉｅｔｙｏｆａ1℃hitectural紺cilitiesinwinte喝experimental

studies⑪ｆｉｃｅｄｏｍｅｓｓｐａｍｉｎｇ２０～３０ｍｈａｖｅｂｅｅｎｃａｒｒｉｅｄｏｕｔａｔＴｂｍａｍｕsince1999．ＴＷ⑪neldstudiesofa20-m-span

icedome（17-ｍｂａｓｅｄｉａｍｅｔｅｒａｍｄ６､5-mheight)ｗｅ唾deveIopedinl999-00,Thesetestdomessh0wedahighstructural

e価cienC恥ｓｏｉｎｔｈｅｗｉｎｔｅｒｏｆ２００１ｔｈｅｅｘｐｅｒｉｍｅntationwastakenastepfmrtherbycarryingoutafieldstudyfbcusing⑪n

boththeconstructionandcreeptest⑪fａ30.ｍ､spaniced0m母(25-mbasediameteｒａｎｄ９､z-mheight).Based0nthefindings

fmmthesestudies,ｉｔcanbeconcludedthattheapplicati⑪ｎ０ｆａｎｉｃｅｄｏｍｅｓｐｆｍｎｉｎｇ２０～３０ｍｓｈ⑪ｕＩｄｂｅ従asibIe．

IＮＴＲＯＤＵＣＴＩＯＮ

Snowandfrigidconditionsenabletheapplicationofanice

shell，whichwouldprovideanefncientsolutiontocertainprob‐

lｅｍｓｃｏｍｍｏｎｉｎｃｏｌｄａｎｄｓｎｏｗｙｒｅｇｉｏｎｓ・Ｔｈｅｓｈｅｌｌｉｓｔｈｉｎ，and

itsstructuralmaterialisice、Ａｎｅｗｔｙｐｅｏｆｉｃｅｓｔｒｕｃｔｕｒｅｂａｓｅｄ

ｏｎｍodemstructuralengineering,ｉｔｃａｎｃｏｖｅｒａｎａｒｅａlargerthan

theclaSsicsnow-icestructurcssuchastheJapaneseAα"】αAl”

ｏｒｔｈｅｉｇｌｏｏ・Itwassuggestedthatlheiceshell，asaconcept

inarChitecturaltechniqueincoldandsnowyregionsduringwin‐

ter,couldbeusedtocreateauniquebuiltenvironment(Kokawa，

1985).Sinceexperimentationintheconstructionoficeshellsfbr

architecturalspacebeganinTbmamu,Hokkaidoinl997(Kokawa

eta1.,2000),manyiceshellshavebeenmadefbractualuse,pro‐

vidingauniquebuiltenvironmentforvisitorsfbrabout3months

eachwinte砿Takingarchitecturalsafetyimoconsideration,thesize

ofthesesheIIshadbeenlimｉｔｅｄｔｏｎｏｍｏｒｅｔｈａｎａｌ５－ｍｓｐａｎ、

Howeve鴎extensivelyinterpretingtheresultsofthepastStudies,a

la屯ｅｉｃｅｓｈｅｌｌｗｉｔｈａｓｐａｎｂｅｔｗｅｅｎ２０ｍａｎｄ３０ｍｗｏｕｌｄａｌｓｏｂｅ

ｐｏｓｓｉｂｌｅｔｏｕｓｅasanarchitecturalstructure・Ａｎｄthen，twofield

studiesona20-m-spaniceｄｏｍｅ（l7-mbasediameterand6､5-m

height)werccarriedoutatthesamesiteinTbmamuinl999-00、

ＴｈｅｓｅｔｅｓｔｄｏｍｅｓｓｈｏｗｅｄａｈｉｇｈｓｔＩ･ucturalefYiciency・Follow‐

inglheexperimentswith20-m-spaｎｉｃｅｄｏｍｅｓ，afieldstudyoI1

boththeconstructｉｏｎａｎｄｃにｅＰｔｅｓｔｏｆａ３０－ｍ－ｓｐａｎｉｃｅｄｏｍｅ

(2S-mbasediameterand9､2-mheighI）wascalTiedoutaIIhe

sameplacedurｉｎｇｔｈｅｗｉｍｅｒｏｆ２００１，ａ爵sessingthepossibili【yof

itsrealizationfromtheaspectofarchitecturalengineering,Based

ontheresultsofthesestudies,itisconcludedthattheapplicatiｏｎ

ｏｆａ２０～３０m-spanicedomefbranarchitccturalfacilitywould

bepracticabIe．

､ISOPEMembeに

RCCeivcdAugust9，2002；revisedmanuscriplreceivedbytheedik〕rs

September30,2002.TheoriginalverSionwassubmitteddirecIlyloIheJoumal、

ＫＥＹＷＯＲＤＳ：２０～30-m-Spanicedome･ハcldcxperlment，consIruclionIes【.ｃ唾eptest,wimerarchitecture．Ｎ､Ｂ､:“30-mspan，，ｒｅ肥rｓＩｏｌｈｃｄｉａｍｅＩｃｒｏｆｌｈｅｍｅｍｂｒａｎｅｂａｇｕＳｃｄｉｎｔｈeibrmworkbefbreinfMIion．

ＳＩＭＰＬＥＣＯＮＳＩＤＥＲＡｍＯＮ

Ａｃｃｏｒｄｉｎｇｔｏｔhemembraneshelltheory,thecompressionstressattheapexofasphericalshell(witha30-mbasediameterand

l30oopenangle）underthedeadtypeofloading（icedensity

O､８５９/cm3）ｉｓｃｏｍｐｕｔｅｄａｓ７・ＯＮ/cm2，whichcon℃spondstoaboutl/60thoftheuniaxiaIcomp雁ssivestrengthofice、Thus，

the30-m-spanicedomehasenoughst雁ngthtostand，lheoret‐

ically，ThisistherEasoningbehindthefieldexpenmentofthe

20～30-ｍ-spanicedomeconcemingtheconstructiontechnique-

andthestructumlsafety,whichwassubsequentlyconducted．

ＯＵＴＬＩＮＥＯＦＣＯＮＳＴＲＵＣＴＩＯＮＭＥＴＨＯＤ

Ｔｈｅ“"IaAⅨmandiglooareclassicsnow-icestructures,butil

seemsthatthesestmcturehaveneitherconstructionrationalitynor

structurale価ciencyinthecaseofalaIgespan，Ａｊｈｚｍａ紬misa

lraditionalJapanesesnowhutwherechildrenplayhouseduring

thｅＮｅｗＹｅａｒｈolidays；ｉｔｉｓｆｂｒｍｅｄｂｙｓｃｏｏｐｉｎｇｏｕｔｓｎｏｗｆｉ｢ｏｍ

ａｓｍａｌｌｍｏｕｎｄｏｆｓｎｏｗ､ＡｎｉｇｌｏｏｉｓａｓｎｏｗｈｕｔｂｕｉｌｔｂｙａＩＴａｎｇ‐

ingsnowblockshemispherically・Incontrast,theiceshelliscon‐

sIructedbylbllowingasimple,quickandeconomicalmethod：

１．buildingupthe3-dimensionalfbrmworkbyinHatinga

2-dimensionalmembranebagcoveredwithropesanchoredtothesnow-icefbundation．

２．coveringthemembranewithathinsnow-icesherbetlayer

(１ｃｍ）byblowingthemilledsnowwitharotarysnowblowe属

sprayingwaterwithahigh-pressureadjustablenozzle,thenletting

itfreezenaturallywheretemperaturesｒｅｍａｉｎａｔ－ｌＯｏＣ

３．repeatingtheapplicationofsnowandwateruntilthedesi肥d

shellthickness（l/IOO1hofIhespan）isreached,then肥moving

thebagandropesfbrreuse・

Theicequalityofthecompleteddomecanbejudgedsatisfactory

ifthe雁issufficientoutwardtransmissionoflightfromthelightedinterior．

ＦＩＥＬＤＴＥＳＴＯＦ２０－Ｍ－ＳＰＡＮＩＣＥＤＯＭＥ

Ｔｈｅｏにtically,ｔｈｅｕｓｅｏｆａｎｉｃｅｄｏｍｅｗｉｔｈａｓｐａｎｂｅｔｗeen20

and30misfeasible・However,lheactualprooftestofanicedome

Ihislargehadnotbeendonebefbre，exceptfbrlheiieldexperi‐

mentofa20-m-spanicedomeinI985(KokawaandMurakami，

1986);moreworkwasnecesSarytodemonstrateitsstructuralreli‐

abililyfbruseasanarchi〔ecturalstructure・Thus、ｗｉｔｈａｎｅｙｅ

ソ

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middlcparland2()cmatthebotLom,ｂｕｔlheactualthicknesswas

foundtobe１２．５ｃｍ，１７．９ｃｍａｎｄ１８．４cmonaverage，Ｉ･esI)cc-

tively・Thciccwascomparativelythinalthebottombecauscof

Ihcsteepslopc・Ｉ１ｔｏｏｋ２ｈｔｏＩ･eachathickncssoflcminthis

construclion，takingａｔｏｔａｌｏｆ３６ｈｔｏａｔｔａｉｎｔｈｅａｖｅｌ｡agcthick-

nesso1.17.9ｃｍ・Displacementsandtcml〕el･atuI･esweremeasurcd

au[oma[icallybelweenFebruaryl2andMarch27・Ｆｉｇ．６shows

fi､omwhichpointsthesemeasurementsweI･etaken､Thehanging

method(Kokawa,1985)wascmployedillmcasuI･ingthedisplace‐

ｍｅｎｔａｔ２１１ｏｃａｔｉｏｎｓｏｎｔｈｃｉｎｓｉｄｃｓｕｒｆａｃｃｏｆｔｈｅｄｏｍｅ，Apro-

grammablcdfltaloggerl･ecordedthcchangcsautomaticallyat3-h

intcl･vals､Ｔｂｍｐｃｌ･alul．ｅ１℃adingswerelakenatl-hintervals,using

aselfrecordinglhermometerin51ocations：lforexteriorail･tem-

peratu1℃,２ibI･interiorairtemperature,and2foricetemperaIurc・

Ｆｉｇ．７showstcmperature-timecurvesfortheentirepel･iod，

Figs，８and9showthedisplacemenl-1imecurves,Mostnotewor-

thyintheseIigul･esisthedramaticincreascindefbrmationh･ｏｍ

Ｍａｒｃｈ４ｔｏ６，whenicetemperatul･ｅｓｓｔａｙｅｄｃｌｏｓｅｔｏＯｏＣｄｕｒｉｎｇ

ａｐeriodol､warmerweatherandstl･()ngc１．ｓunlightatthebegin‐

ningofspl･ing・Duringtheothel･pcl･iods，ｌｈｅｓｔＩ･uctul･albehavior

wasslalionary，ａｎｄｌｈｅａｖｅＩ･agccI･cepdisplaccmcntof605was2､5～3.0ｍｍ/day,ａｓｓｈｏｗｎｉｎＦｉｇ、８．

Thelhil･dcolumnofTablelaandbqualilativelyshowsthc1cm‐

pcraturesanddisplacementsduringthisperiｏｄ(3/4~3/7),ａｎｄｉｌ

ｃａｎｂｅｓｅｅｎ(hatthenearlyOoCicetemperaturecausestheincrcasc

ofdefbl･Imti()n．Exceptfbrthispcriod，ａｓｓｈｏｗｎｉｎ'mablelbol・Fig.９，thcslructuralbehaviorofthedomeisstable､although68and8I3atthcsouthsideａｒｅｌａｌ･gcl･thanthcother8､Concel･ningthcI･csulls（)flheperiodsbefbreandanc１．３/4-3/７，aspreseI1ted

inTablcIb，displacementsduringthccaI･licl･pcriod，２/１４～2/29、

ｉｎｓｐｉｌｅｏＩ、itscoldertempcI･atul･ｅｓａｓｓｈｏｗｎｉｎ'ｎａｂｌｅｌａ，wcI･c

largerthanduI･ingthelaterperiod,３/１１～3/26,cxceptfbr8s・Ｆｉｇ．１０ｓｈｏｗsthe2000domeqshighstructuralcfficiencycomparedlo

tha1ofthe、８５ｄｏｍｅ､whichhadgeomelI･icalandmaterialimpe限

fections(Kokawaeta1.,1986).Aflel･theautomaticmeasurements

ended,theslructuralbehaviorwasvisually()bserveduntilthecol‐

lapse，whichoccurloedonApril4fbllowingtheappearancc（)falal･gcde(bl･malion(Fig.１１)．

Fig.１ｌｃｅｓｈｅｌｌｓｉｎＴｏｍａｍｕ（1999-00）

lowardthereliabililyofitsstI･ucIuralsafetyandimpl･ovementof

thcconstructiontechnique，ｔｗｏｉｉｅldstudiesona20-m-spanice

dome６．５ｍｈｉｇｈｗｅｒｅｃａｒｒｉｃｄｏｕｔａｔｔｈｃｓａｍｅｓｉｔｅｉｎＴｏｍａｍｕ

ｉｎｌ９９９ａｎｄ２０００・These1cstd()messhowedahighslructul･al

c｢iiciencycomparedwilh（hcIirsltestdomeconstructcdinl９８５，

whichhadgeometl･icalandmalcl･ialimperfeclionsbecauseof

inexperienceinsnow-bl()ｗｉｎｇｏＩ〕Cl･ations・ThefollowiI1gdescribesIhcconstructionandcrecplcsloi､thcyear2000，ｓｔｅ馴一dome，ａｎｄ

concludesthata20-m-spanicedome,ａｓａｎａ1℃hitecturalstructuI･e

duringwinterinHokkaido，ｉｓ他asiblc・

Theconstructionpl･ocessisbl･ieHydescribedasfollows、Aner

Ihecompletionofthesn()w-icclWoundationring，ｗｉｌｈａｎｉｎｎｅｒ

ｄｉａｍｅｔｅｒｏｆａｂｏｕｌｌ７ｍ，９(）ｃｍｄｅｐｔｈａｎｄｌｍｗｉｄｌｈ，ａＰＶＣ

ｍｅｍｂｒａｎｅｂａｇｃｏｖｅｌ･edwilhanetwasinHatedasshownillFig.２．

Fig.３ｓｈｏｗｓｔｈｃｌ･eticulaI･patlcmoflhecoveredl･opcsbascdona

geodcsicdivision・Ｔｈｅｐｏｌｙｐｒｏｐｙｌｅｎｅｒｏｐｅｗａｓｌ４ｍｍｉｎｄiam-

e1eI．，ｗｉｔｈａｎｅｑｕａｌｌｅｎｇＩｈｏｆｌ､Smbetweennodes・TheccnU･al

hcightoftheinHatedformwol･ｋｗａｓａｂｏｕ１６．５ｍ・Milledsnow

wascal･ｅＭｌｙｂｌｏｗｎｏｎ[ｏｌｈｃｍｅｍｂＩ･anebyarolarysnow-bloweI・

wiIhamaximumblowingdistanceof2２ｍ，ａｎｄｗａｌｃＩ･ｗａｓｃｏｎ‐

tinuouslysprayedontothcsnowusing6adjuslablenozzleswilhamaximumsprayingdistanccofl5mandatotalsprayingamount(){､６０１ilers/ｍin・Ｆｉｇ．４showstheoutsideaiI･tcmpcI･atul･cdur-

iI1gthcapplicationo{・ｓｎｏｗａｎｄｗａｌｅｌ３Ｔｈｅｃｏmpletedd(〕ｍｅｗａｓａｓｓｕｍｅｄｔｏｈａｖｅａｌ()40-cmradiusofcurvatuI･ｅａｎｄａｌ７２()-cm

basediameter､baseduponthcmcasurementofthcccntralheightandthcilmerdiameteratthcbasc・Ｆｉｇ．５showsthcshclllhick-ncssatthelocations・Theiccthickncssreadil狸wasunavailable

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ibl･ｔｈｅｐａｒｔｏｆｔｈｅｓｈｅｌｌｗｈｅI･ctheStyrofoammeasuI･illgstickswerecoatedwithsnowandwatel･sprayduringconstruction､Theintcndedshellthicknesswasl5ｃｍａｔｔｈｅｔｏｐ，１７．５ｃｍａｔｔｈｃ

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RiejdExPer""e"！(ＷｂｅＤｏﾉ"ｅSpa""加９２０~３０雌花応

Ｎ 2ﾉ1０２ﾉ2０ 劃１ 別1１３ﾉ2１刃3１

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ＦＩＥＬＤＥＸＰＥＲＩＭＥＮＴＯＦ３０－Ｍ－ＳＰＡＮＩＣＥＤOME

Afieldstudyinvolvingtheconstructionandcreeptestofa30-m-spanicedome(25-mbasediameteE9､2-mheightand25-cm

averageicethickness）wascaITiedoutatthesamesiteduringthewinterof2001・Ｉｔｔｏｏｋ６ｄａｙｓｔｏｃｏｍｐｌｅｔｅｔｈｅｃｏｎｓｔｒuction・

Fbllowingtheconstruction，acreeptestwasperfbrmedandthe

structuralbehaviorexamined・Ｉｔｗａｓｆｂｕndthattheaveragedis-

placementrateinthecentralpartsofthedomefromFebruaryl7toMarch23wasabout６．５ｍｍ/day,ａｎｄｉｔｗａｓｓｈｏｗｎＩｈａｔｔｈｅ

ｄｏｍｅｈａｄａsufficientstructuralefficiency・

TheconstructionprocessisbrieHydescribedasfbllows・Afierthecompletionofthesnow-icefbundationthathadabouta25-m

innerdiameterandl80-cmdepth，ｔｈｅ２－ＤＰＶＣｍｅｍｂｒａｎｅｂａｇ，３０mindiameterandcovercdwithropeswithareticularpattem，wasinHated・Fig・l2showsthereticularpattemofthecovenngropesbasedonageodesicT1riacondivision8frequencies・Ｔｈｅ

ｰ､

ｅ

……

266

poIypropyleneropesweにｌ４ｍｍｉｎｄｉａｍｅｔｅ喝andtheirlengths

weredeterminedbysphericaltrigonometry・Ｆｉｇ．’３showsthe

inHatedfbrmworkwithacentralheightofabout９．２ｍ・Snow

andwaterwereappIiedfiFomthｅｅｖｅｎｉｎｇｏｆＦｅｂｒｕａｒｙｌ２ｔｏｔｈｅ

ｍｏｍｉｎgofFebruaryl6th(Fig.14).Using2snow-blowers,each

applicationwaskeptwithinathicknessoflcmFig，l5showstheapplicationofsnowandwater・Ｏｎｅ①４０ｈｏｓｅａｎｄ６①２０

hoseswereusedfbrsprayingwaterontothemilledsnow・The

totalamountofwatersprayedwas240-2901iters/ｍin､Usingthesmallerhoses，waterwassprayedcontinuouslyfrom5scaffblds

placedaroundthedome､Additionalwaterwassprayedinvarious

pIacesasneeded,usingthelaIgerhose・

ＴｈｅｄｅＨａｔｉｏｎｏｆｔｈｅｍｅｍｂｒａｎｅｂａｇｗａｓｂｅｇｕｎａｔ８ａｍ、ｏｎ

ＦｅｂｒｕａＩｙｌ６､Ｆｉｇ．１６showsaninsideviewduringthedenation,Ittookabout5h,afterwhichthemembranewasfbldedandremoved

iTomthedome・Fig・ｌ７ｓｈｏｗｓｔｈｅｅｘｔｅｒｉｏｒｖｉｅｗｏｆｔｈｅｃｏｍpletedicedome

lnordertoprove〔heactualpossibilityofapplica〔iontoan

architecturalstructureiｎｔｈｅｃａｓｅｏｆｓｕｃｈａｌａＩｇｅｉｃｅｄｏｍｅ，thestructuralpropertyofthecompletedicedomewasexamineduntil

itscollapse，whichocculTedonApｒｉｌｌＯ、AftertheautomaticmeasurementsweuEfinished,thestructuralbehaviorwasvisually

observeduntilthecollapse､Thentheresultsofthistestanｄｔｈｅ

２０－ｍ－ｓｐａｎｉｃｅｄｏｍｅｉｎ２０００ｗｅにcompar℃｡、AtthebeginningofthedeHation,themeasulcmentoficethick-

nessｗａｓｔａｋｅｎａｔｔｈｅ５１ｏｃａｔｉｏｎｓｉｎｔｈｅupperpartofthedome、

Asarcsult,ｔｈｅｒａｎｇｅｗａｓｆｒｏｍ２２ｃｍｔｏ２６ｃｍ・ReadingsweretakenfiromlOStyrofbamice-thicknessindicatorsinthemiddle

andlowerpartsofthedome，Itwasfbundthatthethicknesson

thｅｗｉｎｄｗａｒｄｓｉｄｅｗａｓｆｒｏｍ２５ｔｏ３０ｃｍ,whiletheleewardside

wascomparativelythin，rangingfirｏｍ２２ｔｏ２７ｃｍ,TheaveragelhicknessofthecompleteddomewastheninferTedtobeapprｏｘ－ｉｍａｔｅｌｙ２５ｃｍｌｔｔｏｏｋ２ｈｔｏａｃｈｉｅｖel-cmicethicknessinthiS

experiment,takingatotalof56htocomplete・Displacementsandtemperatureswe肥automaticallymeasu1℃d

fromFebruaryl71oMa1℃ｈ２３．Ｆｉｇ．１８ｓｈｏｗｓ５ｐｏｉntsfbrmea-surmgverticaldisplacementsand6pointsfbrmeasurmgtemper-atures(loutside,２inside,and3icetemperatuIcs).'nlble2showstheaveragetemperaturesduringtheperiod・

Figl9showsthemethodofmeasuringaverticaldisplacement、Althoughthismethodisbasicallythesameasthatofearlierexper迄iments(Kokawa,1985:Kokawaeta1.,1986),thedisplacementtransducers,DTP-5MDS(built-inrEeltype,measurablerangeupto5m)inthisfigure,areadiffercnttypefromthestrain-gaugetypeoftransducersusedintheexperimentsonsmallerdomes

raｎｇｉｎｇｆｒｏｍ５ｔｏ２０ｍ，ｂｅcausealalgerdefbrmationwaspre‐dictedinthecreepexperlmentofthis30-m-spanicedome､Fig.２０showstheaveragedisplacement-timecurveofthe5points,whosedisplacementswercverysimilardurmgtherEcoIdingperiod，Accordingtothiscurve,aroughlyl50-mmdownwaIddisplaｃｅ－ｍｅｎｔｆｒｏｍＭａｒｃｈ２０ｔｏ２１，aroughlyl90-mmupwaIddisplace‐ｍｅｎｔｆｒｏｍＭａｒｃｈ２１ｔｏ２２,andotherunexpectedlylalgechanges

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ofdisplacememoccuITedthroughouttherecordingperiod､Ｈｏｗ‐

ever,itisdoubtfUlthattheserEadings1℃Hectthetruedisplacement

behavio眼PossiblefactorsofinfluenceweIcinvestigated,suchas

thethermalexpansionoficeｏｒｔｈｅｃｈａｉｎ，temperature-induced

heightfluctuationsinthesnowfloorandthecrackneartheopen‐

ingofthedome,butthesefactorsdidnotseemtogiveanyrational

reasonfbrthePhenomenon、Inaddition，thedisplacementtrans‐

ducersweIctestedfbrtemperaturEinHuence・Itwasstillnotclear

whythechangeｓｗｅｒｅｓｏｌａＩｇｅ・Ｆｉｇ．２０showstheaveragedaily

creepdisplacementderivedfromtheactualdatausingtheleast

squaIcmethodtofitthedisplacementcurvetoastraightline,Ｔｈｅ

slopeofthestraightlinerEprEsentingtheaveragecreepdisplace‐

ｍｅｎｔｗａｓｃｏｍｐｕｔｅｄａｓ６､５ｍｍ/day・Thisvaluecoincidesvery

wellwithｔｈｅvalue５．４ｔｏ７．２ｍｍ/daycalculatedfTomthemｅｍ‐

branesheIltheoryinconnectionwithMaxwell，slinearviscose

material,ａｎｄｔｈｅ３ｔｏ４ｍｍ/dayintheexperlmentalstudyofthe

20-m-spanicedomedescribedabove、

AfterにmovingthedisplacementtransduceｒｓｏｎＭａｍｈ２３，

thestructuralbehaviorwasvisuallyobserveduntilthedome，s

collapse・Fig．２１showsthetemperature-timecurvesduringthe

period・Ａｓｓｅｅｎｉｎｔｈｉｓｆｉｇｕｒｅ，theoutsideairtemperatu１℃often

exceededOoCafterApri１２.Accordingtoanon-siteobservemthe

weatherconditionspromotedtherapidmeltingoftheice,andthe

rushingsoundechoedinsideｔｈｅｄｏｍｅ・Then，fbllowing3co､‐

secutivedayswithanaverageairtemperatuIcofoverOoC，the

collapseoccurTcdonAprillO,ａｔaboutｌｐ．ｍ．Theicequalityof

thebrokenplatesｏｎｔｈｅｓｏｕｔｈｓｉｄｅｗａｓｖｅｒｙｐｏｏｒｄｕｅｔｏsolar

damage､Althoughthebehaviorwas“brittla，，asalaIgedefbrma‐

tiondidnotappearbefbrethecollapse，ｔｈｅｄｏｍｅｈｅｌｄｉｔｓｓｔｍｃ‐

turalstability，consideringthewarmcondition・Clearlyうitwas

thesprmgweatherthatloweIeｄｔｈｅｑｕａｌｉｔｙｏｆｔｈｅｉｃｅｐｌａｔｅａｎｄ

4 / ６ ４ 州

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Fig.２１Tbmperature-timecurvebefbrEcollapse

２

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1halalliccｄｏｍｃｓＩ〕anning20～３０ｍｃｏｕｌｄｂｃｕｓｅｄａｓａｎａｌ･chi‐

IccUlI･ａｌＳｌＩ･ucIure､Thiscollstructionme[hodoi・blowiI1gsnowand

slprayingwaleroｎｔｏａｎａｉｌ=inHatedmembraneasIbI･ｍｗｏＩ･kisvcry

praclicalfol･ａｌａｒｇｅｉｃｅShell，becauseitneeded（)nly6daysIo

complelc、despitetheconsiderablesize・

ConsideI･inglheactualconstructionequipmeｎｌｓｕｃｈａｓ（hc

snow-blowerandthea(ljustablenozzleft)rspl･ayingwaLeI．,thesizc

oI､ｌｈｃｉｃｃｄｏｍｃｍａｙｂｅｌｉｍｉｔｅｄ，ｆｏｒｎｏｗ,ｔｏａ３０－ｍｓｐａｎ，How-

evcI．，ilwouldbepossibletoconslrucｌａ４０－ｍ－ｓｐａｎｉｃｃｄｏｍｃｉｆｔｈｃｃｑｕｉｐｍcnlwel･eavailable・ThePantheoI1inRomc,ｃ〔)nsLI･uclcd

iI1abou（１２０Ａ.Ｄ、ａｎｄｗｅｌｌｋｎｏｗｎａｓｏｎｅｏｆｔｈｅｂｉｇｇｅｓｌ,classi-calsl()llcdomcs,ｈａｓａｂａｓｃｄｉａｍｃｔｃｒｏｆａｂｏｕ(４(）ｍ・lcciscasicr

l()manuIacturelhanslolle,andiIsstrength/densityiSgI･catcrthan

sloncinshol･t-tcl･mloading，soilshouldbeslructuI･allypossiblcl()l･cａｌｉｚｃａｄｏｍｅｏｆｔｈｉｓｓｉｚｅｉｎｉｃｅａｓwellasslonc､Ｏｎｔｈｃ()1hcr

hand，iccisa1ranslucenlmalerial，ｓｏｌｈｅｉｃｅｓｈｅｌｌｃＩ･catcsafan‐

las｛ic，bcauIji,ulspaceprovidingquiteauniquebuilIcnvironmcnl

inwintcr､PaI･ticularlyinthecaseofalargespan,ilwillbcmore

impressiveaestheticallyandmoreusefilllbI･applicaIjontovari‐ouskindsofarchitecturalfacilities・

AI1iccdomespanning20～３０misalargeiceshellol､unprece‐

dcnlcd馴zc､ｓｏｉｔｓｓｔｌ･uctul･albehavioI･ｓａｌｌｄｌ･cliabililyarcnotfully

known、ｅｖｅｎthoughthisexperimentwassuccessハlldul･ingthe

periodol,intendeduse．'Ibwardtherealizationofthc20～30ｍ－

ｓｐａｎｉｃｅｄｏｍｅｆｂＩ･ａｉ･chitecturalstructuI．c，muchmorcconlinued

l･cscaI･chcoI1cemingthereliabilityofitSSU･uctul･alsametyandthe

iml)rovement()I､thcconstI･uctiontechniqucwillbencededtocon‐(ｉｎｕｃｉｎｌｈｅ「unlre．

ＲＥＦＥＲＥＮＣＥＳ

４

Fig.２２BehavioI･()rcoⅡapsc

ＩｅｄｔｏｔｈｅｂＩ･ittlefailul･cofthestructureinthiscase・Itisadvis-

abletospraywateraｎｄｂｌｏｗｓｎｏｗｏｎｔｏｔｈｅｄｏｍｅｓｃｖｅｒａｌｔｉmcs

evenafIerilscompletion，asaneasymeansofmaintaining［he

icequality,thusimprovingthcstructul･ａｌｓａｆｅｔｙｏｆｔｈｅｉｃｅｄｏｍｃ、

Itcanbeconcludedthatthissizeoｆｉｃｅｄｏｍewillbeapplicablcasanal･chitecLul･alsll･uctureduringthewinterseasoninTbmamu・

AveryimpormnlqucsUoniswhethel･a30-m-spaniccdomcwilh

good-qualiｌｙｉｃｅｒｅｓｕｌｌｓｉｌｌthcbl･ittlebehaviorofcollapseorllol・

Fig.２２showsthcscquentialoI･derofthecollapse､Ｔｈｅ６１．slcol‐

lapseoccurrcdinthcmiddleofthcsouthsidc，whcrcthcsun

shoncstI･ongcstovcI･ｔｈｅｄｏｍｅ､ThecrackbesidetheopeningoI

thcdomedidllo（spreadenoughloa雌ｃｔｔｈｅｓｔｌ･uctul･albehavi()１．．

Fig.２３showslhccxlcriorviewafierthesecondcollapse．

ＡＣＫＮＯＷＬＥＤＧＥＭＥＮＴＳ

Ｔｈｉｓｗ()１．ｋｗａｓmadcpossiblcbytheIinancialsupI)or（n・ｏｎｌ

ＫＥＩＲＹＯＳＥＩＫＡＴＳＵＫＡＩＫＡＮＧＩ･ａｎｔｉｎ２０００ａＩ１ｄｂｙｌｈｃｍｃｍ‐

brancmalcl･ｉａｌｓｕｐｐｌｙｆｒｏｍＴＯ－ＲＡＹＬＩｄ･Company・ThcaulhoI・wishcstothankthestudenlsol､Hokkaido'I1okai

Univel･ＲｉｌｙａｎｄｌｈｅｍｅｍｂｅｒｓｏｆＲｅｓｏｒ【ManagemenlCompany，ｗｈｏｗｏｌ･kedtowardtheconstruclionorlhetestdomcaI1dlhc

prcpaI･atiollofthecreeptest．

ﾛ

Kokawa，Ｔ（1985)．“ExperimentalStudiesonIceShellin

Asahikawa,'，ＣＯ〃Re8io"ｓＳｃｉα"ｄ姥c/】，ＶｂＩｌｌ，ｐｐｌ５５－１７０、

Kokawa､'EandMurakami,Ｋ(1986).‘‘Challengeto2()-MSpan

lccDomc-Shclls，MembraneandSpaceFramcs､｡，Ｐﾉりｃ〃〃

Ａ“(）(､/bﾉ．Ｓ/Ie/／α"ＪＳＰα"α/Ｓ"･"Ｃ／Ｓ)'ﾉ"ﾉﾌ゙，Ｏ”kα，Ｖｂｌｌ，Ｐｐ297-304．

Kokawa,'ｎＷａ(anabe,Ｋ,andltoh,Ｏ(2000).“IccShcll-Rcccnt

Applica(ionloWinlerArchitecture.，，Ｐｊりc/0ﾉﾉ1/"/CWjiﾉﾉoノゼα"(／”/〔"･励ＩｇＣ(ﾉ"jfSeaUle,ＩＳＯＰＥＶｂｌｌ，I〕ｐ716-721.

27り

Fig.２３Exteriol･viewrightancrcollapse

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