土木工程专业毕业设计外文翻译.docx

土木工程专业毕业设计外文翻译.docx

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土木工程专业毕业设计外文翻译

High-RiseBuildings

Introduction

Itisdifficulttodefineahigh-risebuilding.Onemaysaythata

low-risebuildingrangesfrom1to2stories.Amedium-risebuilding

probablyrangesbetween3or4storiesupto10or20storiesormore.

Althoughthebasicprinciplesofverticalandhorizontalsubsystem

designremainthesameforlow-,medium-,orhigh-risebuildings,whenabuildinggetshightheverticalsubsystemsbecomeacontrollingproblemfortworeasons.Higherverticalloadswillrequirelargercolumns,

walls,andshafts.But,moresignificantly,theoverturningmoment

andthesheardeflectionsproducedbylateralforcesaremuchlargerand

mustbecarefullyprovidedfor.

Theverticalsubsystemsinahigh-risebuildingtransmitaccumulated

gravityloadfromstorytostory,thusrequiringlargercolumnorwall

sectionstosupportsuchloading.Inadditionthesesamevertical

subsystemsmusttransmitlateralloads,suchaswindorseismicloads,tothefoundations.However,incontrasttoverticalload,lateralloadeffectsonbuildingsarenotlinearandincreaserapidlywithincreaseinheight.Forexampleunderwindload,theoverturningmomentatthebaseofbuildingsvariesapproximatelyasthesquareofabuildingsmayvaryasthefourthpowerofbuildingsheight,otherthingsbeingequal.Earthquakeproducesanevenmorepronouncedeffect.

Whenthestructureforalow-ormedium-risebuildingisdesignedfordeadandliveload,itisalmostaninherentpropertythatthecolumns,walls,andstairorelevatorshaftscancarrymostofthehorizontalforces.Theproblemisprimarilyoneofshearresistanee.Moderateadditionbracingforrigidframesin“short”buildingscaneasilybe

providedbyfillingcertainpanels（orevenallpanels）withoutincreasingthesizesofthecolumnsandgirdersotherwiserequiredforverticalloads.

Unfortunately,thisisnotisforhigh-risebuildingsbecausetheproblemisprimarilyresistaneetomomentanddeflectionratherthanshear

alone.Specialstructuralarrangementswilloftenhavetobemadeandadditionalstructuralmaterialisalwaysrequiredforthecolumns,

girders,walls,andslabsinordertomadeahigh-risebuildingssufficientlyresistanttomuchhigherlateraldeformations.

Aspreviouslymentioned,thequantityofstructuralmaterialrequiredpersquarefootoffloorofahigh-risebuildingsisinexcessofthatrequiredforlow-risebuildings.Theverticalcomponentscarryingthegravityload,suchaswalls,columns,andshafts,willneedtobestrengthenedoverthefullheightofthebuildings.Butquantityofmaterialrequiredforresistinglateralforcesisevenmoresignificant

Withreinforcedconcrete,thequantityofmaterialalsoincreasesas

thenumberofstoriesincreases.Buthereitshouldbenotedthattheincreaseintheweightofmaterialaddedforgravityloadismuchmoresizablethansteel,whereasforwindloadtheincreaseforlateralforce

resistaneeisnotthatmuchmoresincetheweightofaconcretebuildingshelpstoresistoverturn.Ontheotherhand,theproblemofdesignforearthquakeforces.Additionalmassintheupperfloorswillgiverisetoagreateroveralllateralforceundertheofseismiceffects.

Inthecaseofeitherconcreteorsteeldesign,therearecertainbasicprinciplesforprovidingadditionalresistancetolateraltolateralforcesanddeflectionsinhigh-risebuildingswithouttoomuchsacrifire

ineconomy.

1.Increasetheeffectivewidthofthemoment-resistingsubsystems.

Thisisveryusefulbecauseincreasingthewidthwillcutdowntheoverturnforcedirectlyandwillreducedeflectionbythethirdpowerofthewidthincrease,otherthingsremainingcinstant.However,thisdoesrequirethatverticalcomponents

ofthewidenedsubsystembesuitablyconnectedtoactuallygainthisbenefit.

2.Designsubsystemssuchthatthecomponentsaremadetointeract

inthemostefficientmanner.Forexample,usetrusssystems

withchordsanddiagonalsefficientlystressed,placereinforcingforwallsatcriticallocations,andoptimizestiffnessratiosforrigidframes.

3.Increasethematerialinthemosteffectiveresisting

components.Forexample,materialsaddedinthelowerfloors

totheflangesofcolumnsandconnectinggirderswilldirectlydecreasetheoveralldeflectionandincreasethemoment

resistaneewithoutcontributingmassintheupperfloorswheretheearthquakeproblemisaggravated.

4.Arrangetohavethegreaterpartofverticalloadsbecarried

directlyontheprimarymoment-resistingcomponents.Thiswillhelpstabilizethebuildingsagainsttensileoverturningforcesbyprecompressingthemajoroverturn-resistingcomponents.

5.Thelocalshearineachstorycanbebestresistedbystrategicplacementifsolidwallsortheuseofdiagonalmembersinaverticalsubsystem.Resistingtheseshearssolelybyverticalmembersinbendingisusuallylesseconomical,sinceachievingsufficientbendingresistaneeinthecolumnsandconnecting

girderswillrequiremorematerialandconstructionenergythan

usingwallsordiagonalmembers.

6.Sufficienthorizontaldiaphragmactionshouldbeprovidedfloor.

Thiswillhelptobringthevariousresistingelementstowork

togetherinsteadofseparately.

7.Createmega-framesbyjoininglargeverticalandhorizontaicomponentssuchastwoormoreelevatorshaftsatmultistoryintervalswithaheavyfloorsubsystems,orbyuseofverydeep

girdertrusses.

Rememberthatallhigh-risebuildingsareessentiallyverticalcantileverswhicharesupportedattheground.Whentheaboveprinciplesarejudiciouslyapplied,structurallydesirableschemescanbeobtainedbywalls,cores,rigidframes,tubularconstruction,andotherverticalsubsystemstoachievehorizontalstrengthandrigidity.Someoftheseapplicationswillnowbedescribedinsubsequentsectionsinthe

following.

Shear-WallSystems

Whenshearwallsarecompatiblewithotherfunctionalrequirements,theycanbeeconomicallyutilizedtoresistlateralforcesinhigh-risebuildings.Forexample,apartmentbuildingsnaturallyrequiremanyseparationwalls.Whensomeofthesearedesignedtobesolid,theycanactasshearwallstoresistlateralforcesandtocarrytheverticalloadaswell.Forbuildingsuptosome20storise,theuseofshearwallsiscommon.Ifgivensufficientlength,suchwallscaneconomicallyresistlateralforcesupto30to40storiesormore.

However,shearwallscanresistlateralloadonlytheplaneofthe

walls（i.e.notinadiretionperpendiculartothem）.Therefore,it

isalwaysnecessarytoprovideshearwallsintwoperpendiculardirectionscanbeatleastinsufficientorientationsothatlateralforceinanydirectioncanberesisted.Inaddition,thatwalllayoutshouldreflect

considerationofanytorsionaleffect.

Indesignprogress,twoormoreshearwallscanbeconnectedtofromL-shapedorchannel-shapedsubsystems.Indeed,internalshearwallscanbeconnectedtofromarectangularshaftthatwillresistlateralforcesveryefficiently.Ifallexternalshearwallsarecontinuouslyconnectedthenthewholebuildingsactsastube,andconnected,thenthewholebuildingsactsasatube,andisexcellentShear-WallSeystemsresistinglateralloadsandtorsion.

Whereasconcreteshearwallsaregenerallyofsolidtypewithopeningswhennecessary,steelshearwallsareusuallymadeoftrusses.Thesetrussescanhavesinglediagonals,“Xdiagonals,or“K'arrangementsAtrussedwallwillhaveitsmembersactessentiallyindirecttensionorcompressionundertheactionofview,andtheyoffersomeopportunityanddeflection-limitationpointofview,andtheyoffersomeopportunity

forpenetrationbetweenmembers.Ofcourse,theinclinedmembersoftrussesmustbesuitableplacedsoasnottointerferewithrequirementsforwiondowsandforcirculationservicepenetrationsthoughthesewalls.

Asstatedabove,thewallsofelevator,staircase,andutilityshafts

formnaturaltubesandarecommonlyemployedtoresistbothverticalandlateralforces.Sincetheseshaftsarenormallyrectangularorcircularincross-section,theycanofferanefficientmeansforresistingmomentsandshearinalldirectionsduetotubestructuralaction.Butaprobleminthedesignoftheseshaftsisprovidedsufficientstrengtharounddoor

openingsandotherpenetrationsthroughtheseelements.Forreinforcedconcreteconstruction,specialsteelreinforcementsareplacedaroundsuchopening」nsteelconstruction,heavierandmorerigidconnectionsarerequiredtoresistrackingattheopenings.

Inmanyhigh-risebuildings,acombinationofwallsandshaftscan

offerexcellentresistaneetolateralforceswhentheyaresuitably

locatedantconnectedtooneanother.Itisalsodesirablethatthestiffnessofferedthesesubsystemsbemore-or-lesssymmertricalinalldirections.

Rigid-FrameSystems

Inthedesignofarchitecturalbuildings,rigid-framesystemsfor

resistingverticalandlateralloadshavelongbeenacceptedasan

importantandstandardmeansfordesigningbuilding.Theyareemployedforlow-andmediummeansfordesigningbuildings.Theyareemployedfor

low-andmediumuptohigh-risebuildingperhaps70or100storieshigh.

Whencomparedtoshear-wallsystems,theserigidframesbothwithinandattheoutsideofabuildings.Theyalsomakeuseofthestiffnessinbeamsandcolumnsthatarerequiredforthebuildingsinanycase,butthecolumnsaremadestrongerwhenrigidlyconn