ＪＯＵＲＮＡＬＯＦＴＨＥｌＮＴＥＲＮＡＴｌＯＮＡＬＡＳＳＯＣＩＡＴＩＯＮＦＯＲＳＨＥＬＬＡＮＤＳＰＡＴｌＡＬＳＴＲＵＣＴＵＲＥＳ：ＩＡＳＳ

ＳＵＭＩｉｆ４Ｒｙ

目IIEILDS~I~ＵＤＹＯＦＡ３０－ＭＳＰＡＮＩＣＥＤＯＭＥ

TｓｕｔｏｍｕＫｏｋａｗａ

DepartmentofArchitecture，ＳｃｈｏｏｌｏｆＡｒｔａｎｄＴｅｃｈｎｏＩｏｇｙ，HokkaidoTokaiUniversity

Chuwa22４，Kamuicho，ＡｓａｈｉｋａｗａＯ７０－８６０１,Japan

』た〃”‘のo〃６oz/z肋eco"s”c"o〃α"QIcregpjaytq/､α３０"zspα〃icedbme“"zj"6“e虚α'"aex,９．２"zj〃Ae妙rα”２５c籾j"αve7ag色jcerAjc肋“Sﾉｗａｓｃα〃”o"rarZbmα”‘加Ｈｂ碗域”加g油ｅｗ加”q/､2001.〃rooko"〃sな〔/bりＭﾌｧ坊eco”Jeがo"q/､fhe6jgdbme勿油eco"s”c"o""ze油oqIq/､6/owj"gs"owα””ﾉ叩"ｇｗｚｚ”o”oα〃αが”7α花ぬれｅｍ６ｍ"eａｓ./b'mwo'たＦｂ肋w加ｇ坊eco刀s”c"o",αcジセｇｐ彪鈍ｗａｓ“ecz"e“"“７ｔ〃ｅｗ”eγ"α”α/e"VかO”e"Z加jZbmα”/α”ｊｈｅＳ”c”α/6eAaVjOγ"""が"AeCO/”seWaSexα”"e‘Z4Sαγes"〃ﾒｶece""α/pα〃q/､avemgc伽pﾉace"ze"〃ａｒｅかOmF1e6γ"αryI7的わＭ‘z'℃ﾉｾ23城Wasa6oz"“加加/hkZy，α""ＷａＳＳﾙ0W"油α城edbmeA“αgひo‘e"O"帥s""c”α/轍Cie"qy.Ｂ”eJo"ﾒﾉzeres"lItq/､”s〃‘'ｳﾉ,tAeん”efzpp"cα"o"Q/､ａ３ａｍ‘sIpα"ice血沈a/bγα"αﾉ℃〃"eα"､!ノカcj肋ＣＯ"〃6e6asicaI〃possめ/ｅ

K2yw0J”３０－７〃助α"IbeDo碗e,Ｃｂ刀s”c"o〃219“ｃｅｅｐｍａ３ｆ

1．]mＶｒＲＯＤＵＣＴＩＯＮ

Snowandcoldenabletheapplicatioｎｏｆａｎｉｃｅｓｈｅｌｌ,whichprovidesanefficientsolutiontocertainproblemsinsnowyandcoldregions､Theiceshellisthin,anditsstructuralmateIialisice・Itisanew

typeoficestructurebasedonmodernstructuralengineeringanditcancoveralargerareacomparedtotheclassicalsnow-icestructuｒｅｓｓｕｃｈａｓ

"Kamakura，，ｏｒ‘‘Igloo，，､IthadbeensuggestedthattheiceshellcouldbeusedfbrcreatingaratheruniquebuiltenvlronmentasanewideaofarchitecturaltechniqUeinthesnowyandcoldregionsduringwinter［l],becauseithasaspecialshapeandahalfLtransparenttextureoftheice．

Anattemptneverexperiencedbefbretoconstruct

iceshellsfbranarchitecturalspace，hadbeendevelopedinTomamu,HoldKaidosincel997［２１Manyiceshellshavebeenusedasleisurespacefbrvisitorsabout3monthsineachwinterandthese

havecreatedafBntasticandbeautifUlspaceprovidingqUiteauniqUebuiltenvironmentinwinter，Takingitsarchitecturalsafetyintoconsi‐deration，ｔｈｅｓｉｚｅｏｆｔｈｅｓｅｓｈｅｌｌｓｉｓｌｉｍｉｔｅｄｕptol5mspanfbrthetimebeing､However,extensively

interpretingtheresultsinthepaststudy,alargeice

shellwithspansfi｡ｏｍ２０ｍｔｏ３０ｍｍｉｇｈｔｂｅｐｏｓｓｉｂｌｅｔｏｕｓｅａｓａｎａｒchitecturalstructure･Ａｎｄ

then，ｔｗｏｆｉｅｌｄｓｔｕｄｉｅｓｏｎａ２０－ｍｓｐａｎｉｃｅｄｏｍｅｗｉｔｈ６・sminheighthavebeencalriedoｕｔａｔｔｈｅｓａｍｅｓｉｔｅｏｆＴｏｍａｍｕｉｎｔｈｅｙｅarsl999and2000・Thesetest-domeshadshownahighstructuraleffi‐

ciency,anditconcludesthata20-mspanicedomeispossibletouseasanarchitecturalstructure[3]．

FollowingthesuccessfUlexperimeｎｔｏｆａ２０－ｍｓｐａｎ

ｉｃｅｄｏｍｅ,afieldstudyonboththeconstructionandcreeptestofa30-mspaniceｄｏｍｅ(２５minbasediameter,９．２minheightand25cminaverageicethickness)neverexistedbefbre,wascarriedoutat

TomamuinHokkaidｏｄｕｒｉｎｇｔｈｅｗｉｎｔｅｒｏｆ２００１，searchingthepossibilityoftherealizationfioomtheaspectofarchitecturalengineering・Basedonthe

resultofthisstudy,itconcludestheapplicationｏｆａ３０－ｍｓｐａｎｉｃｅｄｏｍｅｆｂｒａｎａｒｃｈｉｔｅcturalflacilitycouldbebasicallypossible．

2.ＣＯＮＳＴＲＵＣＴＩＯＮＴ]ESi]ｒ

2.1.Outli血eofConstructionalSequemlce

１．Constructingsnow-icefbundationｗｉｔｈａｂｏｕｔａ２５minnerdiameter、

2．Buildingupthe3-dimensionalfbrmworkbyinflatinga2-dimensionalmembranebagof30m

9３

ＶＯＬ､４３（２００２）ｎ．１３９

ノ

diameter，coveredwithropeswithareticularpattemdeterminedbythegeodesicdivisionanchoredtothesnow-icefbundation．

3．Coveringthemembranewiththinsnow-ice

sherbetbyblowingthemilledsnowwitha

rotarysnowplowandsprayingtapwaterwitha

high-pressureadjustablenozzleinthevicinityofthetop・Solidifyingthethinlayersnow-icesherbetduetocoolingbycoldoutsideair、

4．Repeatingtheapplicationofsnowandwateruptothe25cmshellthickness・Ｔｈｅｎremovingthebagandropesfbrreuse．

2．ＡｓｓｈｏｗｎｉｎＦｉｇｕｒｅ２，thegeometryofthenet

wasdeterminedbythegeodesicTriacondivision

８firequencies,Thenetwasmadeof●l4mmpolypropyleneropeanditslengthshowninFigure3betweenpointswascalculatedbySphericaltrigonometry，supposingthedesign

sectionshowninFigure4Supposingmaximum

waterｈｅａｄｏｆａｐｏｒｔａｂｌｅｂｌｏｗｅｒａｓ４６ｍｍａｑ.，thetensionfbrcebecomeaboutltonｏｎ

ｃｏｍｐutation，ｓｏｔｈｅｌ４ｍｍＰ・Ｐ、ｒｏｐｅｉｓｓｔｒｏｎｇ

enoughagainst3tonesofitsbreakingfbrce

2.2.Smow-iceFoIInlIationRing

TheconstructionwasdonefifomFebruary4thto6thin200１．Ｆollowingthemeasurementandread-

justmentofthesiteonFebruary4th，ａｈｅａｖｙｍａｃｈｉｎｅａｓｓｈｏｗｎｉｎＦｉｇｕｒｅｌｗasusedfbrtheconstructionoftheringwithabout25mininnerdiameter,４０rope-anchorswerelocatedequallyontheinnercircleandatthebase,preventingtheriseindomefromexcessiveheightcausedbythe5％elongationoftheP.Ｐ､rope．

F1ig2・Ｒｅ"αｲﾉα７．pα"eﾉ7１

F1ig3､RQpe/e"grAに”

.,卯

Rigも１.Ｃｂ"”･zJc"o〃Q/Wzow-ica/b””"o〃減"９

､●

apex

2.3.Air-In面atedF〔Drmwork

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FXg‘.Ｄas，jg"‘yec"o〃

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Thefbrmworkconsistsofmembranebagandcove‐●

rmgrope．

1．ThemembranebagisfBbricatedbywelding

alongthePeripheryafterwrappingintwopiecesofplanesheetswｉｔｈ３０ｍｉｎｄｉａｍｅｔｅｒ、ThespecificationsofthemembraneareasfbnowＳ．

Ｐ．Ｖ,Ｃ､,T-SFlOO％,weight:530~５７０９/ｍ2,Ten-silestrength：longitudmall50±２０ｋｇ/3ｃｍ，TransversellO±２０ｋｇ/3ｃｍ,Color:daIk-green．

ｸダ

“＆割

ＪＯＵＲＮＡＬＯＦＴＨＥｌＮＴＥＲＮＡＴｌＯＮＡＬＡＳＳＯＣｌＡＴｌＯＮＦＯＲＳＨＥＬＬＡＮＤＳＰＡＴｌＡＬＳＴＲＵＣＴＵＲＥＳ２ｌＡＳＳ

周『雨

2.4.Inflatiom

2 ／ 1 ２ ２ / 1 ３ ２ ／ 1 ４ ２ ／ 1 ５ ２ / 1 ６ ２ /1フ

ThefirstinflationtestwascarriedoutonFebruary

7th・Aportableblower，whichhasacapacityair-flowof44ｍ３/ｍin.，wasusedfbrtheinflation,sotheinflationtimeshouldbewithinaboutlhouron

thecomputation・However,becauseofsometrou‐blessuchasanadjustmentbetweenthemembraneandropes，ittookseveralhoursfbrtheinflationbeyondthetheory､Figure5showstheair-inflatedfbrmworkaftertheinflation､OnFebruaryl2th,justbefbretheapplicationofsnowandwater,about40

piecesofStyrofbamsticksfbrcheckingtheshellthicknessundertheconstructionwerepreparedｏｎｔｈemembrane・However,astheadhesiveagentwasnoteffectivebecauseofaverylowairtemperatureof-l3oCbelowatthatmoment,almostallofthemwerenotattachedonthemembrane､so,therationalmethodofattachmentshouldbedevisedinfUture

construction．

０５０５０５

－１１２２

『一一一

８W蝉

酉

outsideairtemp.(℃）

ＦＸｇｄＯ"航咋αj（e"lpeﾉ圏α”e"”eﾉ･ＣＯ"s"wc"o〃

＝ｒｌ

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上■

ドEＬ言

肥軸'､w紗－－－－‘瞥雷･－上…面

F1igス４pp"cα"o刀Q/s"ｏｗα"αｗａｚｅﾉ．

豚｡鰯溌I『

thanlcmduringoneoperation・Theonewiththe

capacityof22mmaximumthrowingdistanceswasusedfbrblowingthesnowexceptthevicinityoftheapex,Theotherwith30mthrowingdistanceswas

appliedincaseofthecentralpartsofthedome,Itis

assumedthatthethicknessofthecompleteddomewasapproximately25cminaverage・Ｉｔｔｏｏｋ２ｈｏｕｒｓｔｏｇｅｔｌｃｍｉｃｅｔｈｉｃｋｎｅssinthisexperimentbecauseitneeｄｅｄ５６ｈｏｕｒｓｉｎｔｏｔａｌｔｉｍｅｆｂｒｔｈｅ

ａｐｐlicationofsnowandwater．

Applicationofsnowandwaterwascarriedoutftom

Februaryl2theveninｇｔｏｌ６ｔｈｅａｒｌｙｍｏｍｉｎｇ、ＡｓｓｈｏｗｎｉｎＦｉｇｕｒｅ６，itwasveryniceweathertoconstructiceshellsatthatperiod、Figure7shows

thesituationunderconstructionA巾４０hoseand

sixウ２０hoseswereusedfbrsprayingwaterontothemilledsnowTotalamountofsprayingwater

was240-2901itter/min.､Itisassumedthatthe4)４０hosenormallysuppliedl50-2001ittelmin.(b20hoseswerecontinuouslyoperatedonfivehigh

stages，ａｎｄ（|)４０hosewasintermittentlyusedmovingaroundthedomeaccordingthesituation・

Ｏｎｔｈｅｏｔｈｅｒｈａｎｄ，blowingthemilledsnowontothemembranewaｓｃａｒｅｆＵｌｌｙｄｏｎｅｂｙｔｗｏｓｎｏｗｐｌｏｗｓｓｏａｓｔｏｋｅｅｐｔｈｅｓｎｏｗｔｈｉｃｋｎｅｓｓｌｅｓｓ

em5

Theairmembranebagbegantodeflatｅａｔ８ａｍ､on

Februaryl6th・Figure8showsaninsideviewunderdeflation､Ｉｔｔｏｏｋａｂｏｕｔ５ｈｏｕｒｓｔｏｒｅｍｏｖｅｔｈｅａｉｒ

ｏｕｔｏｆｔｈｅｂａｇ,andthenthemembranewasfbldedandｐｕｌｌｅｄｏｕｔｔｈｅｄｏｍｅ，Figure9showsthe

exteriorviewofthecompleted30mspangiganticicedoｍｅａｓｎｅｖｅｒｓｅｅnbefbre．

ＦＺｇ５．４i提jﾉﾘ7とz極加e"'6ノロ"e“んﾉ77zwo戒

2.5.ApplicationofS1mlwmdW証哩。

2.6.ｐＥｆ１胆箇o皿

■■■

１ １

－－．cessation

－appIicationofsnowandwater

｜’｜ハ’

ｒ、

０，

６馬０９０、

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ate(2001）

compIetio0ノ

f』ツ

ＶＯＬ、４３（２００２）ｎ．１３９

既五麺醇一万

４‘dQJ『僻

FZg68.Ｄe/7Zz"o〃

…-し

F1ig9・Ｃｏｍｐ/ereaice血沈ｅ

3.Ｃ]R１ｍＲＰＴＥＳＴ

ｂ■

Inordertoprovetheactualpossibilityofappli‐cationtoanarchitecturalstructuｒｅｉｎｃａｓｅｏｆｓｕｃｈａ

ｈｕｇｅｉｃｅｄｏｍｅ，ｔｈｅstructuralpropertyofthecompletｅｄｉｃｅｄｏｍｅｗａｓｅｘａｍｉｎｅｄｕｐｔｏｔｈｅｃｏ‐llapsewhichoccurredonAprillOth・Aftertheautomaticallymeasurement,thestructuralbehavior

wasobservedbyeyeuptothecollapse､Theresultsofthistestweremadeincomparlsonwiththestructuralbehａｖｉｏｒｓｏｆｔｈｅ２０ｍｓｐａｎｉｃｅｄｏｍｅｉｎ２０００[3]．

3.1.IcethickneSsandGeometry

Atthebeginningrofthedeflation,thepreparationof～〆

thepointfbrmeasuringdisplacementandthemeasurementoficethickness，asshowninFigurelO，ｗｅｒｅｄｏｎｅａｔｔｈｅｓａｍｅｔｉｍｅ、Asaresult,the

thicknessattheupperpartofthｅｄｏｍｅｗａｓ２２ｃｍｔｏ２６ｃｍ・Thethicknessatthemiddleandloweｒ

ｐａｒｔｓｏｆｔｈｅｄｏmeweremeasuredbycarefUlly

９６

Ｎ

4｡‘，

●verticaldiRnlucu皿8ｎt，（１～５）

Oinsidctomperaturo（６～７）

△iCetemp．（８～１０）◇oUtsidotGmp．（１ユ）

ＦＸｇｍ上ｅｊﾙiCk77“Sα"‘"1eaSZ"･加gpOi"/Ｍﾌﾉ・veﾉガcα/(油p/Zzce"ze"な&/e"Zpeﾉ．α血"･as，

ｒｅａｄｉｎｇｔｈｅｓｃａｌｅｏｆｌＯｐｉｅｃｅｓｏｆｔｈｅStyrofbamsticks．

Asaresult,thethicknessatthewestside(windwardside)wasdistributedfrom25cmto30cm,andthe

eastside（leewardside）wascomparativelythinfi･ｏｍ２２ｃｍｔｏ２７ｃｍ,Thetopheight921cmfhirly

correspondedto926cmcalculatedas５％ofropeelongation．

3.Z・Displa理ｍｅｌ１ｌａ皿。,１，唖叩erat皿睡

DisplacementsandtemperatureswereautomaticallymeasuredfiomFebruaryl7thtoMarch23rd・s

pointsfbrmeasurlngverticaldisplacementsand6

pointsfbrmeasuringtemperatures（Onepointof

outside,twoinside,andthreeicetemperatures)areshowninFigurelO・Figurellshowsthemethodofmeasuringaverticaldisplacement,Aprogrammabledataloggerrecordedthesedisplacementsautoma-ticallyat3-hourintervals､AselfLrecordedthermo-

metermeasuredthetemperaturesatl-hourinter‐vals、Figurel2showstemperature-timecurvesduringthewholeperiod[However,theoutsideairtemperatures(Tout)fiFomMarch4thtoMarchl3thwerenoｔｓｈｏｗｎｈｅｒｅ,becauseitwasnoticedlaterthattheoutsidethermometerwasembeddedinthe

snow1Tablelshowsaveragetemperatureateverypoint､ItrecognizesthatTout,theinsideairtempe‐ratures(Tin)andtheicetemperatures(Tice)ｗｅｒｅ

3/1４ 3/1９３/2４

ＪＯＵＲＮＡＬＯＦＴＨＥｌＮＴＥＲＮＡＴＩＯＮＡＬＡＳＳＯＣｌＡＴＩＯＮＦＯＲＳＨＥＬＬＡＮＤＳＰＡＴＩＡＬＳＴＲＵＣＴＵＲＥＳ：ｌＡＳＳ

FXgbI2､姥"zpeﾉ．α血ﾉ･e-""'ecz"-vaｓ

Zh6ﾉc１.Aveノロge/e"lpeﾉ．α加ﾉ℃(《'CＭ２〃7~3/2.3ノ

Hf=iii…

lowinorder,Tinwaslowinaverageanditschange

wasverylarge,becausethecoldoutsideairentered

easilyintotheinsidefiomtheopeninginstalledthewindwardside､Figurel3shows5pointsofdispla‐cements-timecurvesduringthesameperiodThebehaviorsofthesepointswerealmostsamequantitativelyandqualitatively・Asshowninsomeexamples，aboutl50mmdownwardsdisplacementfromMarch20thto21st，aboutl90mmupwardsfifomMarch21stto22nd,unbelievablelargechangeofdisplacementoccurredallovertherecorｄａｎｄｉｔｓｅｅｍｅｄｔｈａｔＦｉｇｕｒｅｌ３ｄｉｄｎｏｔshowtruedispla‐cementbehavior・Ａｎｄthen，inordertoseekthe

reason，varlousaspectssuchasthethermalexpansionoficeorchain,themovementofsnowlevelbyfreezingandtheinfluenceofthecracknear

theopeningwerecheckedbothquantitativelyandqualitatively、However,astheresult,theseftlctorsdidnotseemtogiverationalreasonfbrthe

phenomenon・Ａｔｌａｓｔ，theinfluenceofthetempe‐ratureonthedisplacementtransducerwasinvesti-gatedexperimentally・Figurel4showsthedisplace‐ment,temperature-timecurveundertheconditionthatthetransducerwasinstalledbetweentwoExed

points・Asaresult，ａｓｓｅｅｎｉｎｔｈｅｅｘａｍｐｌｅｔｈａｔ４５ｍｍｃｈａｎｇｅｄａgainstl3deg、intemperaturechange，thetemperaturechangeclearlyhadabiginfluenceonthedisplacementtransducer､Further‐more，ｉｎｔｈｅｓａｍｅｆｉｇｕｒｅ，ｔｈｅdisplacementcurvewasapproximatelyfittedtothestraightlinebythemethodofleastsquaremeanandtheslopeofthelinebecameOwhichmeansnomovementbetween

－－－Tice<point8）

←cablelengthL=1.5～2.0ｍ

displacementtransducerDTP-5１，sＣｆl▽snoWleV９１

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2/1７２/2２２/2７３/４３/９

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(pointll）

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００００００００００

４３２１１２３４５

－一一】一

帥1０

一一一disp,(ｍ、）

画再一・Iinearapproximation(disp.）Ｌ

《

ｑ

5/2２５/2４５/2６５/2８５/3０６/１６/３６/５６/７

ＦＺｇＩ‘.ＣｿhecﾉﾋQ/､伽p/ace"ze"r”"sめ/Ｃｅﾉ‘

6average(ｍ、）

EｍＵ

、

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riment，asalargedefbrmationwasnotobservedbefbrethecollapse、Itindicatesthatthecollapsedoesoccurabruptly，andthepredictionofthecollapseisdifficultbyeyeobservation,Therefbre，brittlecollapseisnotsuitablefbrthearchitecturalstructurewhichneedsenoughtimetopredictthedangerofthecollapse、Futureexperimentsofa30-mspanicedomeshouldbeconfilmedwhethersuchalargeshellbringsthebrittlebehaviorofcollapseornot・Thebrokenpiecesoficeplatesatthｅｓｏｕｔｈｓｉｄｅｗｅｒｅｖｅｒｙｐｏｏｒｄｕｅｔｏｔｈｅdamagebysolarradiation・Itissuggestedtospraywaterandbloｗｓｎowontothedomeseveraltimesduringits

application，astheeasymethodfbrkeepingthequalityoficewhichmeansimprovementofthestructuralsafetyoftheiceｄｏｍｅ､Figurel6showsthetemperaturesduringuntilthecollapse・After

twofixedpoints・Basedupontheconsideration,asshowninFigurel5,themethodwasappliedtotheaveragedisplacementof5curvesshowninFigurel3anditsaveragedisplacemeｎｔｗａｓｃｏｍｐｕｔｅｄａｓ６､５ｍｍ/day・Thisvaluecoincidesverywellwiththevalue５．４ｔｏ７．２ｍｍ/daycalculatedfromthemembraneshelltheory，Maxwell，linearviscosematerialandthe3to４ｍｍ/dayintheexperimentalstudyof20mspanicedome[3]．

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Accordingtothemembraneshelltheory，thecompressionstressattheapexofthisdomecoveredunifbrmlywith50cmsnowdepth(colrespondingtolOOkg/m2verticalload）ｉｓｃｏｍｐｕｔｅｄａｓａｂｏｕｔｌｋｇ/ｃｍ２ｗｈｉｃｈｉｓａｂｏｕｔｌ/40thoftheuniaxialcompressivestreｎｇｔｈｏｆａｎｉｃｅ・Ｔｈｉｓｉｓｔｈｅｓｉｍｐｌｅｒｅａｓｏｎｗｈｙｔｈｅ３０-mspanicedomehasenoughstrengthtoexiststructurally・Therefbre，anactualprooftestof30-mspanicedomeconcemingtotheconstructiontechniqUeandthestructuralsafetywaschallengedatTomamu，Hokkaidoinwinterof2001‐

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April2nd，theoutsideairtemperatureoftenexceededOoCandthesunshinebecamestrong、Accordingtoanon-siteobserver，theweatherconditionpromotedrapidly,ｔｈｅｍｅｌｔｉｎｇｉｃｅｏｆｔｈｅｄｏｍｅａｎｄｔｈｅｓｏundofthemeltingechoedinside，Figurel7showsthesequentialordeｒｏｆｔｈｅｃｏ‐llapse・Ｔｈｅｆｉｒｓｔｃｏllapseoccurredatthemiddleofthesouthsidewherethesunshinewasthestrongestoverthedome・Furthelmore,thecrackbesidestheopeningwasnoｔｓｏｓｐｒｅａｄａｎｄｄｉｄｎｏｔａｆｆｅｃｔｔｈｅｓｔｒucturalbehavior・Figurel8showstheexteriorviewafterthesecondcollapse．

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Asaresult,itisconcludedthattheapplicatioｎｏｆａ３０－ｍｓｐａｎｉｃｅｄｏｍｅｆｂｒａｎａｒｃｈｉｔecturalfIacilitycouldbebasicallypossible､Thisconstructionme‐thodofblowingsnowandsprayingwaterontoanai趣nflatedmembraneasfbrmwork,isveryrationalfbralargeiceshellbecauseitneededonlysixdaysfbrthecompletionofthe30-mspanicedome､Ａｎｄ

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then,itisconfirmedthecompleteddomehadahighstructuralefficiency，becauseitsaveragedispla-cementｒａｔｅａｔｔｈｅｃｅntralpartofthedomewasestimated６．５ｍｍ/dayduringthewinterperiodandthecollapseoccurredonAprillO1haftertheoutsideairtemperatureoftenexceededOoCandthreedaysoverOoCinaverageairtemperaturelasted．

Takingtheactualconstructionequipmentssuchasthesnowplowfbrblowingsnowandtheadjustablenozzlefbrsprayingwaterintoconsideration，ｔｈｅｓｉｚｅｏｆｔｈｅｉｃｅｄｏｍｅｍａｙｂｅｌｉｍｉｔｅｄｕｐｔｏ３０－ｍ

ｓｐａｎｓｏｆａｒ、However，itwouldbepossibletoconstruｃｔａ４０－ｍｓｐａｎｉｃｅｄｏｍｅｉｆｔｈｅｅｑｕｉｐｍｅntswereprepared，ＰantheoninRomeconstructedinabouｔｌ２０Ａ.Ｃ､ｉｓｗｅｌｌｋｎｏｗｎａｓｏｎｅｏｆｔｈｅｂｉｇｇｅｓｔｃｌassicalstonedomeanditssizehasabout40min

basediameter,Theicematel･ialiseasiertomanu-

flElcturethanstoneanditsstrength/densityisbetter

thanstoneinshorttermloading，soitcouldbe

possibletorealizestructurallysuchasizeoficedomeinsteadofastonedome,Ｏｎｔｈｅｏｔｈｅｒｈａｎｄ，

theiceisahalftranslucentmaterial,sotheiceshell

createsafmtastic,beautifillspaceprovidingquitea

uniquebuiltenvironmentinwinter､Particularly,incaseofalargespan,itwillbemoreexcitingartis-ticallyandgettingmoreusefhltoapplytovanouskindsofarchitecturalfをicilitiesfbrwinterevents．

Ａ３０－ｍｓｐａｎｉｃｅｄｏｍｅｉｓｑｕｉｔｅａｈｕｇｅｉｃeshellneverexperiencedbefbre,soitsstructuralbehaviorsarenotｋｎｏｗｎａｓｗｅｌｌ,Therefbre,theconfidenceof

itsstructuralreliabilityisnotenoughatall，eventhoughthisfirstexperimentwassuccessfill・Towardtherealizationofthe30-ｍｓｐａｎｉｃｅｄｏｍｅｆｂｒarchi‐tecturalstructure,theuntiringfieldstudiesconcer‐

ningtothereliabilityofitsstructuralsafetyandtheimprovementoftheconstructiontechniquewillbeneededmuchmoreintheftlture．

ＡＣＫＮＯＷＬＥＤＧＥＭＥＮＴＳ

ThisworkwasmadepoSsiblebythefinancial

supportsfromKEIRYOSEIKAＴＳＵＫＡＩＫＡＮＧｒａｎｔｉｎ２０００ａｎｄｂｙｔｈｅｍｅmbranematerialsupplyfi･ｏｍＴＯ－ＲＡＹＬｔｄ､Company．

Theauthorwishestothankthestudentsof

HokkaidoTokaiUniversityandthemembersofResortManagementCompanywhoworkedfbrtheconstructionofthetestdomeandthepreparatiOnofthecreeptest．

1００

ＲＥＦＥＲＥＮＣＥＳ

[l]ＫｂﾙαｿﾂａＺＸα”唾'･ａｓαﾌﾂαＺ，1982/1983：“Onthebehavioroficedomesundershort声telmloading''(ｉｎ

Japanese)，Bull，HokkaidoTokaiUniv.，vol、３/４，ｐｐ､77-85.

[2]ＫｂﾉｔａｗａＺ:,〃0ﾉｉＯ.α"‘恥”ｚａ６ｅＫ,2000:“IceShell-Reviewandrecentapplication，'，ＪｏｕｍａｌｏｆｌＡＳＳＶｏ1.41(2000)、.',Apriln､132,pp､23-29.

[3]ＫｂｋａｗｊＥ，lifoAO．α"‘恥”ｚａ６ｅＺ，2001：‘‘Rechallengeto20-mspanicedome，，，ＣＤ－ＲＯＭｏｆIASSinNAGOYA(editedbyKunieda),TPl87‘