ErectingtheStaggered-trussSystem:AViewfromtheFieldARTHURE.HASSLERThestaggered-steeltrusssystemhasbeenusedasthemajorsupportingelementformanyyears.Projectsusingthistrusssystemareeconomical,easytofabricateanderect.andasaresultbeatoutallotherframingsystems.Thispaperdealswithabuildingrecentlycompletedwhichusedthestaggeredsteeltrusssystem.TheprojectistheResortsInternationalHotelinAtlanticCity,N.J.FABRICATIONFabricationofthistypeofstructurecanreadilybeaccomplishedbyanyshopengagedinstructuralsteelfabrication,providedtheypossesscertifiedweldersandarewelding-oriented.Inaddition,thebuildingmustcontainoverheadcranescapableoflifting10to15-tontrussesandcolumnsforprojectsupto20stories.Fabricationinvolvesthefollowingcomponents:(1)Columns,(2)SpandrelBeams,(3)Trusses,(4)SecondaryColumnsandBeamsand(5)FloorSystem.1—ColumnsColumnfabricationisnotcomplicatedforbuildingsupto20-storieshigh.Theywillberolledwide-flangesectionsuptoW14×720withthelongestbeingapproximately25ftinlengthandwithatotalweightof9to10tonseach(baseplatesareshippedloose).Columnscontainedinbuildingsfrom20to30storieswillprobablybereinforcedwithflangeplatesasinFig.1.Above30storieswillbebuilt-uptypecolumnsconsistingofthreeplatesofvaryingthickness.OntheResortsInternationalHotelproject,wehadtofabricate(Fig.2)columnswith8-in.thickflangeplatesand6-in.thickwebplates.Thistypeofcolumnrequiresmoresophisticatedfabricationequipmentsuchaspreheatdevices,submergedarcweldingequipmentandheavyliftingcapacityof25to40tons.Inotherwords,Figure1Figure2shopshavingthecapacitytohandleheavyplatesandplatefabrication.AsinFig.3,thesecolumnscanalsocontainheavybracingconnectionsinthebottomtierwhichtransfersthewindloadtotheconcretefoundation.Asanalternatefortransferofthiswindstress,abracingtruss(Fig.4)canbeusedatthebottomifarchitecturalfeaturesarenotobstructed.2—SpandrelBeamsSpandrelbeamsaredesignedtoresistthewindmomentimposedontheendwallsinthelongitudinaldirection(Figs.5,6).Toresistthisforce,theycanbesteelbeamsmomentconnected(Fig.7)eitherbyendplateconnectionsorflangeplatestopandbottomwithaweb-shearplate.Fabricationofthistypeofbeampresentsnoproblem.However,duetorollingtolerances,thematchingholesonthecolumnflangeplatesortheflangewidthdimensionwhenusingendplateswillhavetobecheckedandmatchedwiththebeamtoinsurecorrectcenter-to-centerofcolumns.Thisbeamcontrolsthetotallengthofthebuilding.Inabuildingwith9or10baysadeviationof+?in.perbay(withintherollingtolerance)increasestheoveralllengthby2to2?in.Thebeamwillalsorequirea2-hourfirerating(sprayon)inaccordancewithmostbuildingcodes.Figure3Figure4Figure5Figure6Figure7Figure8Asaresultofthis,andwiththeinputofthearchitectontheprojectswehavecompleted,aconcretespandrelbeamwasdeveloped(Fig.8)tonotonlyprovideanincreasedleverarmtoresisttheappliedmoment,butalsotoeliminatefireproofingandatthesametimeserveaspartoftheexteriorfacade.Thisdistancebetweenconnectionsonthecolumnproducedaconsiderabledecreaseinthequantityoffieldbolts.Inaddition,byusingconcrete,thebeamcanalsofunctionaspartoftheexteriorfacade.FortheResortsHotelthisbeamwasastructuralcomponentonlyandcontainedinsertstosecurethewindowwallfacade.However,itdideliminatefield-appliedfireproofing.Shopworkwasnoteliminatedbythissubstitutionofconcreteforsteel.Toinsuretheaccuratefit,aspreviouslydiscussed,itwasdecidedtodevelopaspandrelrebarcagetobefabricatedintheshopandshippedtoaprecastcontractor,whowouldsettheminasteelformcontainingashopsuppliedsteeljigdesignedtomaintaintolerancesonlyasteelfabricatorcouldprovide.3—TrussesTheweightofatrussisdeterminedbygravityloads,windloads,penetrationsduetocorridor,doors,pipesand/orwindowopenings(Fig.9).Thetrussweightwillvaryfrom10,000lbs.ina4-storybuildingto36tonsina43-storybuildingontheResortproject.Trussfabricationisnotdifficult.Theyshouldbesetuponjugstomaintaincorrectoveralldimensions.However,qualifiedweldersarerequiredtofollowaqualityassuranceprogram(Fig.10).4—SecondarySupportingStructuresSecondarysupportingstructuresarethosenecessarytosupportstairopenings,elevatorshaftsandotherframedopeningsrequiredbythearchitecturaldesign.Thisisimportanttooverallcosts.Ifthearchitectrecognizesthistypeofstructuralsolutionwillbeused,hecandesignwithinitsconstraintsandavoidunnecessaryadditionalframing.(Figs.11and12).TheResortsprojectandtheTowersontheParkproject(Figs.13and14)requireadditionalsupportsteelduetoarchitecturalconfigurations.Theaddedsteelframingcanbedesignedasconventional(i.e.,simpleshear-connected)ortoresistappliedwindmomentsrequiringpartialmomentconnections.Thistypeofframingisfamiliartomostfabricationshops.5—FloorSystemsFloorsystemscanbethefollowingtypes,howeverallmustbedesignedtodeliverthewindloadasadiaphram(shearload)tothesupportingtrusses.Forthesteelfabricatortheyposenoproblems.Architecturally,depthofconstructionandmechanicalrequirementscanandwilldictatethetypeofsystemtobeused.Asanexample,the8-in,hollowcorefloordeckprovidesafloor-to-floorheightequaltoaflat-plateconcretesystem.Therefore,totalheightofthebuildingwillnotbeaffected.Figure9Figure10Figure11Figure12Figure13FIELDERECTIONThistypeofstructurehastobeerectedonafloor-by-floorsequencebecauseoftheinstabilitycausedbyafloorsystemnotinplace.Also,dependingontheheightofthebuilding,atowercranehastobeusedtoreachoverthespandrelbeams.Therefore,acranemusthavetherange(reach)andcapacity(pickingload)tocovertheentirefloorareaifthebuildingistoremainstable.Usingguycablesortemporarybracinginterfereswiththeerectionprocess.Guyderricks(thoseattachedtoandclimbinguponcolumns)andinternalclimbingcranes(supportedonthefloorstructure)cannotbeused,unlessthedesignprovidessupportareas—suchasanelevatorcorewhichcanbereinforcedtosupporttheadditionalloads.Forbuildingsuptoabout20storieswithafloorheightof8ft-9in.(atotalheightofabout190ft,atowercrane,selfsupported,truckorcat-mounted(similartoaManitowoc4100W),canbeused.Above20stories,useanexternalclimbingcrane(similartoLinkBeltTG-1900)supportedonsteeltowerunitsandconnectedtothestructureatintervalsof75ft,withtheinitialtie-inat160ft.Figures15,16,17and18showcranelocation,rangeetc.forerectionofHillsdaleSeniorCitizensBuilding,HackettstownSeniorCitizensBuildingandTowersontheParkrespectively.Theerectionsequenceisimportantbecauseofthepreviouslymentionedstabilityofthestructure.Itshouldproceedasfollows:1.Setcolumns2.Setspandrelbeamstotiecolumnsalongstrongaxis3.SettrussesFigure14Note:Connectionofthebottomchordshouldbeboltedtightafterthedeadloadisimposedfromthefloorsystem.Thebottomchordshouldbeshortenedapproximately3/16in.toallowforcamberreductionandsubsequentchordlengthening)4.Boltupandtorquehigh-tensionbolts5.The8-in.hollow-coreplanksarebolted(inlieuofweldplates)tothetruss(Fig.19).Thisprovidesanimmediatebracingsystem,workingplatformetc.betweentrusses.However,groutingthekeyjointsmustproceedtoprovidethesheardistributionpreviouslymentioned.Note:Duetotheinherentstiffnessofthetrusses,concretespandrelbeamsandhollow-corefloorplanks,thesestructurescansafelybeerectedforabout8–10floorsbeforegroutinghastobeinplace.Duringextremeweatherconditions—cold,rainetc.—erectioncanproceedeventhoughconcretecannotbepoured.Figure15Figure16Figure17Figure18Figure19BUILDINGCOSTSUsingabuildingcontaining13supportedlevels,9bays@25ftc.toc.longand56ft-1in.c.toc.mainbuildingcolumnscontainingabout170,000sqftofsupportedareausing6-in,thickconcretespandrelbeamsactingalsoastheexteriorfacadeand4-in.thickprecastendwallsasanexample,thefollowingisthebuildingcost:BuildingCostBreakdown1.Structuralsteel2.Precastconcreteelements3.Miscellaneousitems4.Erection5.UnitpricepersqftItem1—StructuralsteelMaterialcostsWeight(lbs.)1.Anchorbolts5002.Columns&loosebaseplates600,0003.Trusses580,0004.MiscellaneousbeamsA.ElevatordividerbeamsB.EndspandrelbeamsC.RoofbeamsD.Penthouse&elevatormach.roombeams167,5005.Fieldbolts12,0006.Paint(ifrequired)7.ShippingTotalcost:1,360,000@$.30/lb.average1,360,000lbs.(8lb./sqft)=$408,000.Note:NomaterialdiscountshavebeenappliedShopdrafting—1,360hrs.@=27,2$20/hr.00.Shoplabor—Shoplaboraveraged15hrs./ton680tons×15H/T=10,200hrs.@$15/hr.=153,000.Totalitem1—steelfurnished&delivered$588,200.Item2Precastconcretecomponents1.Spandrelbeams(a)Rebarcages234pcs.@$400=$93,600(b)Casting22,340sqft@$9.50=212,230Totaldeliveredprice$305,830=$350,830.2.4-in.precastendwalls,12,826sqft@$6.50/sqft=83,369.3.8-in.hollow-coreplank,165,000sqft@$3.50/sqft=577,500.4.Connectionangles,plank&spandrelties,fieldbolts=10,000.$976,699.5.Groutprecastplanks(a)Plankjoints(b)Plankends,165,000sqft@$.50/sqft=82,500.6.CaulkingExteriorjointsInteriorplankjoints=25,000.TotalItem2—precastconcrete$1,084,199.Item3Miscellaneousitems(a)Fieldexpenses(b)Shop&fieldtesting=25.000.Item4Fieldlabor—EquipmentcraneManitowoc4100W(a)1.Cranesetup&removal2.Shippingto&fromsite3.70-tontruckcrane&crewtoassemble=40,000.Hoisting(b)Forthissizebuilding—shouldcompleteabout13,000sqft/floorinfourdays,includesa10%downfactorforweatherandmaintenance.Crane—3monthsrentalCranecrew—2men×60days=120man-daysHoist"—6men×60days=360""Bolt"—6men×60days=360""Stone"—4men×60days=240""Surveys—1man×60days=60""Super—1man×60days=60""Total1,200""@$315/day=378,000.TotalItem4—Fieldlabor418,000.TotalItems1,2,3,4Totalcost$2,115,399.×O&P15%317,310.Total$2,432,709.+SalestaxifrequiredItem5Unitpricepersquarefoot(a)Structuralframeconsistingof:1.Structuralsteel2.Conccreteespaandreelbeeams3.8-inn.hoolloww-correpllank,,inccludiingggroutting(b)Archhiteccturaalcoomponnent(c)4-inn.Prrecasstenndwaalls,,inccludiingccaulkking1.Totaalcoostoofthhesuupporrtedframme=$2,2284,3343==$133.44sqfft2.""""eexterriorfacaade==1488,2666=..87Total$$2,4332,6009=$14..31ssqfttErectioonalllowaance—apprrox.$31,,760COSTFOORFRRAMINNGTHHEREESORTTSINNTERNNATIOONALHOTEELBuildinngDeescriiptioonAsprevviousslysshownn,thhisbbuilddingconttaineed433suppporttedllevellsappproxx.1,,116,,000sqfft;4420ffthiigh.Center(eleev.ccore))—35fft×114ftTTwoaadjaccentwinggs—68fft×157ft-66in..Totalssteellweiight—13,,700tonss,244.6llbs.//sqfft0Totalccostoftthisprojject,,bassedoonaconttracttpriiceoof$222,1000,0000(iincluudinggperrformmanceebonndanndsaalestax)),ammounttedtto$119.800/sqft.Notes:1.FiellderrectiionccommeenceddonMarcch188,19985,withhtheefinnallliftonMMarchh31,,19886.PProjeectwwasestimattedttotaakeooneyyearusinngtwwocrraness,anndinncluddingholiidayss,weeatheerannddoownttime..2.Thestruucturreisspluumbwwithiin5//8inn.frromttopffloorrtogrouundllevell—quitteannachhieveementt(Fiig.220).SUMMARYYIthasbeennshoownttheuuseoofthhisssysteemfoorappartmmentssanddhottelsisffastandeconnomiccal.Asttructturallfraame,inclludinngthheexxteriiorffacadde,ccanbbecoompleetedassshownnintwomontthsfforaacossteqqualtowwhatwoulldprroviddeonnlyaastrructuuralsuppportframme,ssuchasfflat--plattecooncreete.Mateeriallcosstsaarebbasiccallyytheesammethhrougghoutttheecouuntryy.Hooweveer,ttheycanvaryydueetomillldisscounnts,freiightetc..Thecosstoffshoopprroducctionnanddfieeldllaborrcannvarrycoonsidderabblydduettofaactorrssuuchaasunnionvs.non--unioon,ffringgebeenefiits,insuurancceettc.TToannalyzzethheimmpacttofthisssysstemlocaally,,carreshhoulddbeexerrciseedinnconnverttingtollocallwagges.ResortssIntternaationnalAAtlannticCityy,NeewJeerseyyFigure20172ENGGINEEERINGGJOUURNALL/AAMERIICANINSTTITUTTEOFFSTEEELCCONSTTRUCTTION關于鋼結(jié)構(gòu)交錯錯桁架體系系的一個觀觀點鋼結(jié)構(gòu)交錯桁架架體系成為為主要的支支撐體系已已經(jīng)很多年年了，工程程中使用這這種桁架體體系是經(jīng)濟濟的，易于于制造和安安裝，因此此優(yōu)于所有有其他的支支撐體系。這這篇論文研研究了一棟棟近期建造造的完全使使用了交錯錯桁架建筑筑體系，該該工程是新新澤西州,大西洋城城的一家國國際度假酒酒店。制造任何從事結(jié)構(gòu)鋼鋼生產(chǎn)的企企業(yè),只要他們們擁有合格格的焊工及及焊接方面面的技術,特們就能能輕而易舉舉地制造出出這種結(jié)構(gòu)構(gòu).此外,建筑還必必須具備架架空吊車,能夠?qū)?0至15噸重的桁桁架及柱吊吊至20層高處.該結(jié)構(gòu)的制造包包括下列構(gòu)構(gòu)件(1)柱(2)拱側(cè)梁(3)桁架(4)次柱及次次梁(5)樓蓋1-柱高達20層的建筑物,其其柱子的制制造并不復復雜.它們被軋軋制成寬翼翼緣截面大大可達W14××720,,最長近25英尺,總重量達9至10噸每塊(底版分散散安裝).30層以上建建筑物的柱柱子是組合合式柱,由3塊厚度不不一的板組組成.我們所建建的國際度度假酒店,其翼緣板板厚8英寸,腹板厚6英寸.這種柱需需要精密的的制造設備備,如,預熱裝置,水下焊接接設備以及及具備25-440噸的攜重重能力.換句話說,企業(yè)必須須具有處理理重板及板板面制造的的能力.如圖3,這些柱子子底層具有有重型支撐撐連接,此連接可可將風荷轉(zhuǎn)轉(zhuǎn)移到混泥泥土基座上上.支撐桁架(如圖4)作為一種種轉(zhuǎn)移風壓壓的方法,如果對建建筑特色不不造成影響響,可以用于于底部.2-拱側(cè)梁拱側(cè)梁是是用于抵抗抗衡附壓在在縱向尾墻墻上的風矩矩(見圖5\6)).為抵抗這這股力量拱拱側(cè)梁可以以是鋼板梁梁矩,由尾板的的連接部分分來連接的的,或者帶有有焊剪板的的翼緣板頂頂和底連接接起來的.這種梁的的制造不會會出現(xiàn)任何何問題.但是,由于輾軋軋耐度不同同,在使用尾尾板時,柱上的匹匹配孔,翼緣板,或者是翼翼緣寬圍必必須經(jīng)過校校對,與梁相匹匹配,以確保柱柱心與柱心心之間無誤誤.這種梁控控制著整個個建筑物的的長度.一棟建筑筑物有九個個或十個壁壁洞(偏差為±1\4英寸),每個壁洞洞將使總長長度從2英尺增加加到2.5英尺.根據(jù)大多多數(shù)建筑物物的規(guī)則,梁也要求求有2小時的耐耐火定額度度。因此，再再加上建筑筑設計師的的努力，一一根混泥土土拱側(cè)梁就就不僅是提提供了一根根杠桿來抗抗拒應用矩矩，并能根根除防火裝裝置的使用用，同時還還可作為外外用面的一一部分。柱柱上的這種種連接距離離促使域螺螺栓的使用用大大減少少。此外，通通過使用混混泥土，此此梁還可以以作為外正正面的一部部分。拱側(cè)側(cè)梁只是度度假酒店的的一個構(gòu)件件，它包含含了一些插插入件以確確保窗墻的的正面。但但是，它確確實消除了了防火裝置置的使用。用用混泥土代代替鋼板并并不能消除除車間工作作。為確保保能夠精確確匹配，如如前所述，決決定在車間間內(nèi)研制一一個拱側(cè)箱箱，并將它它運送給預預制承包商商。承包商商會將它安安入一個鋼鋼板格7，此鋼板板格具有工工廠提供的的用來保持持韌性的鉆鉆模（只有有鋼板生產(chǎn)產(chǎn)商才能提提供）。3—桁架桁架的重重量是由物物荷、風荷荷以及由于于走廊、門門、管道及及窗戶的敞敞開而引起起的穿透率率所決定的的（如圖9）。其大大小變化可可以從4層樓建筑筑的10，000IIbs變到43層的度假假酒店工程程的36噸。桁架架制造并不不困難。桁桁架應該是是豎立在壺狀物上上以保持準準確的總面面積大小。但但是，合格格的焊接工工必須遵循循質(zhì)量保證證程序，（如如圖10）4—次支撐結(jié)構(gòu)次支撐結(jié)結(jié)構(gòu)就是那那些在建筑筑設計上要要求用來支支撐樓梯接接隙、電梯梯軸、以及及其它框架架物的附屬屬物。次支支撐結(jié)構(gòu)對對總成本至至關重要。如如果設計師師意識到這這種結(jié)構(gòu)方方法會被使使用到，他他的設計就就能保持在在限度范圍圍之內(nèi)，從從而避免不不必要的附附加設計。度度假酒店工工程及公園園工程中的的塔（如圖圖13、14），由于于建筑設計計構(gòu)造都要要求附加支支撐鋼板。附附加支撐鋼鋼板結(jié)構(gòu)可可以設計成成傳統(tǒng)式的的或者設計計成抗風矩矩的。這種種框架與大大多數(shù)生產(chǎn)產(chǎn)廠里的是是相似的。5—樓蓋樓蓋可以以是如下幾幾種類型，但但是設計上上都必須能能作為一種種隔板傳遞遞風荷帶支支撐桁架上上。這對鋼鋼板制造者者并不會產(chǎn)產(chǎn)生任何影影響，從建建筑上說，建建設的深度度及機械要要求能夠也也會決定所所使用的樓樓蓋種類。例例如，那塊塊8英寸的空空心樓板就就能提供一一種樓層與與樓層間的的高度（等等同于混泥泥土樓蓋）。因因此，建筑筑物的總體體高度不會會受到影響響。領域建筑物這種類型的結(jié)構(gòu)構(gòu)必須按照照一層接一一層的順序序建筑，因因為不適合合的樓蓋會會造成不穩(wěn)穩(wěn)定所以必必須這么做做。也取決決于建筑物物的高度。一一因為高樓樓起重機的的使用，所所以會超過過拱側(cè)梁。因因此，如果果想保持建建筑物的穩(wěn)穩(wěn)定，一臺臺起重機必必須要有覆覆蓋整個摟摟層面積的的范圍和能能力。使用用鋼索電纜纜成臨時的的支撐裝置置介入建筑筑物進程。鋼鋼索起重機機（那些附附屬的和向向上的柱狀狀物）以及及內(nèi)部上升升起重機（支支撐摟層結(jié)結(jié)構(gòu)）不能能使用，除除非設計提提供支撐區(qū)區(qū)域---比方說電電梯中心，它它能支撐額額外的負荷荷。對于高達20層層，每層高高度為8fft-9iin的建筑筑物來說（總總高度大約約為1900ft）高高樓起重機機、自我支支撐物、卡卡車或貓形形拖架（類類似于一個個mainntowooc41000w）可以被被使用。20層以上，可可使用一個個外部上升升起重機（類類似于LinkkBelltTGG19000），它由由鋼筋塔單單元支撐，在在間隔為775ft原原始拉結(jié)為為160伏特ft的地方與與結(jié)構(gòu)連接接。圖15、16、17和18顯示了起起重機的份份量和范圍圍等等。對對于Hilllsdalle老年人樓樓，Hackkettsstownn老年人以以及公圓的的塔來說，建建筑物的順順序是十分分重要的。因因為先前就就提到過結(jié)結(jié)構(gòu)的穩(wěn)定定性問題。它它可以按照照下面的程程序進行：：1）建柱2）建立拱側(cè)梁用用來沿著強強軸系柱狀狀物3）建立構(gòu)架注意：在冷負荷荷從樓層體體系中被加加附以后，底底部弦應該該用螺栓緊緊緊連接?？伎紤]到木材材，底部弦弦應縮短到到大約3\16iin。建筑成本建筑一個包含113支撐程度度，9堤@25fftcttoc長和56fft-1in.ctooc.的建筑物物。其主要要的建筑柱柱狀物包括括用6-in厚的混泥泥土拱側(cè)梁梁作成的大大約170，000ssqftt的支撐區(qū)區(qū)域，同時時也擔當外外表的角色色?？梢杂糜?-in厚的預制制端面墻作作為例子。下下面是建筑筑物的成本本。建筑成本的分解解1鋼材2預制混泥土成分分3各種條款4建筑物5每個sqft的單價價條款1—鋼材材料花費重量（1bs）1貓形螺栓50002柱及松木板6000，0003構(gòu)架580，00004各種梁A電梯隔離梁BB端面拱側(cè)側(cè)梁C屋梁D電梯機器器房＆電梯梯機器房梁梁167，5005領域螺栓12，0006油漆（如果有要要求）7運輸總成本：1，3360，000＠＄.3001lbb平均1,3660,0000lbbs(8lbb./sqqft))=$$4088,0000.注意：沒有任何何材料折扣扣可供應用用工廠制圖-----1,3360hhrs.@=227,2$20//hr.00.工廠勞力-----工廠勞力力平均155hrss./toon680tonns×15HH/T=10,220