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外文翻译--振动台.doc

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外文翻译--振动台.doc

ShakeTableAshaketablecanbeusedtotesttheresistanceofstructurestoseismicshaking.Itcanalsobeusedtodemonstratethesensitivityofstructuresofdifferentheightstothefrequencyofthegroundmotion.Theshaketablepicturedbelow,whichwasdesignedandbuiltbyJohnLahrwithexpertadvicefromTomTompkins.Itisbasedonalightweightplatformthatisconstrainedtomoveinjustonedirection.Theplatformismadefroma10inchby10inchpieceoffoamcoreboard.Hollowmetaltubesareconnectedtotheleftandrightedgeswithhotglue.Metalrodsmadefromweldingrodsareslidthroughthetubesandtheendsoftherodsareheldfirmlybywoodenblocks.Theblocksarehotgluedtoaplywoodbase.ClickforlargerimageAtthispointintheconstruction,theshaketableplatformisabletoslideaboutaninchbackandforthontherods.Itshouldmovefreely,withoutbindingontherods.Iuseavariablespeeddrilltoshakethetable.Analternativetoavariablespeeddrillisasinglespeeddrillconnectedtoanelectronicspeedcontrol,suchastheonesoldbyMLCSLtd.Theirspeedcontrolunitisshownontheirwebsitehttp//www.mlcswoodworking.com/Pages/speedcon.html,ortheymaybecontactedat18005339298.WARNINGIwanttothankGregNowakgregorysroomyahoo.comforthemessagethathesenton2/22/2001fromconcerningleavingtheshaketablerunningforalongperiodoftime.Thetableshouldnotbeoperatedunattendedandthe110Vpowershouldalwaysbedisconnectedwhennotinuse.ParaphrasingGregThereshouldbeabigwarningonanyplansforanearthquakesimulationmechanismthatusesamotorofanysort,asitcouldbedangerousifnotdesignedandoperatedproperly.About10yearsagoataCalPolyStateUniversitySLOopenhousePolyRoyalanArchitectureorEngineeringstudentusedapowerdrillsetonlowspeedandlefthisearthquakemachinerunning.Itoverheatedandafireeruptedthatbasicallyburneddownafewclassrooms.ArodwithaUshapedbendismountedparalleltoonesideoftheplatformsothatitisfreetorotate.OneendofastiffwireisbentinalooparoundthebottomoftheUwhiletheotherendisshapedlikeahookandisattachedwithstrappingtapetotheedgeofthetable.Amoredurableandflexiblealternativetostrappingtapeistoattachasquarepieceofautomobileinnertubewithdimensionsofabout2x2inchestotheedgeofthetable.Therubberisfoldedoverandgluedtothetopandbottomofthetable.Hotgluehasworkedwellforme.Letabout3/4inchoftherubberstickoutbeyondtheedgeofthetableandpokeaholethroughthisflap.Thenthestiffwireisbentthroughtheholeintherubber.Thisarrangementwillcausetheplatformtomovebackandforthastherodisrotated.Thevariablespeeddrillisattachedtotherodbyitschuck.Thehandleofthedrillisalsofirmlyattachedtotheplywoodbase.Constructiondetailsarepostedfortwoshaketabledesigns.Todemonstratetheneedforadiagonalelementtogiveawallshearresistance,Iuse6inchlongpiecesofwoodorplasticwithmagnetsmountedateachend.IhaveattachedVelcrototheplatformandmatingVelcrotoabaseblock.Thebaseblockhasmagnetsmountedateachend.Abasicwall,consistingoftwoverticalsandahorizontalelement,canbebuiltonthebase.Thiswallwillfalldownduringanearthquake.If,however,adiagonalelementisaddedmadefromalongermagnetstick,whichisprovidedthenthewallwillresiststrongshaking.Iusuallyprovideonelongmagnetsticktobeusedasthediagonalandthreeshortmagnetsticksandchallengethestudentstobuildastrongwall.Eventuallytheydiscoverthatadiagonalelementiscrucial.Hereisaphotographoftheshaketable.Totheleftofthetableisapieceofplasticcutfromafluorescentlightdiffuserwithfourfingersofvaryinglength.Whenthisisvibratedontheshaketable,onecanexperimentwiththeeffectofshakingfrequencyontheamplitudeofmotionofbuildingsofvaryingheights.Belowarethreephotosoftheshaketableonewiththemagneticsticksandtwowithaflexiblebuilding.Clickhereforsomeadditionalinformationonuseandconstructionofmagneticsticks.AttheMay,2000,openhouseoftheUSGSinMenloPark,CA,BobPagedemonstratedsomeadditionalbuildingissuesusingtheshaketable.ClicktoenlargeHeaddedsomepoststoonesideofthebuildingsothatastringcouldbewrappedtoformxbracesforeachfloor.Belowarepicturesofthebuildingwithandwithoutthexbracing.ClicktoenlargeBobalsodemonstratedadesignfeatureofsomemodernbuildings,namelybaseisolation.Thefoundationofabuildingwithbaseisolationallowsthegroundtomoverapidlybackanforthwhilethebuildingstandsnearlystill.Toillustratethis,Bobusedtwojarspartlyfilledwithwater.Onewasattachedfirmlytotheshaketablewhiletheotherwasallowedtoslidebackandforthwithinaplastictray.ClicktoenlargeClickHEREforsomemoreinformationonbaseisolation.ClassroomExercisesthatuseaShakeTableLarryBraile,aPurdueUniversityseismologist,hasdevelopedafunclassroomcontestinwhichgroupsof4or5studentsdesign,build,andtestbuildings.Althougheachgroupstartswiththesameconstructionmaterials,itsamazinghowmanydifferentdesignsresultAlso,checkoutLarrysotherprojectsatPurdue.Instructionsforbuildingwatertowers.Simulatingwoodframe,masonry,andsteelframebuildingsideasfromMCEERMultidisciplinaryCenterforEarthquakeEngineeringResearch.ShakeTablesintheClassroomEachyearFrankDevereauxandDanArgentaruseashaketabletotestthebuildingskilloftheirstudentsduringtheirunitonplatetectonics.Herearesomephotosoftheshaketablebeingusedin2000and2001.Danhascreatedanextensivewebsitewithdetailedinformationonthisunittoaidanyotherteacherswhomaywanttoprovideasimilarunitofstudy.OtherShakeTablesCoralClarksuggests,Hereisalinktoashaketablethatuses4rubberballs,2rubberbands,and2stiffboardssuchascutapartbindersorthinplywoodscraps.Itisaboutassimpleasyoucangetforpreliminaryinvestigations.

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