BIM in Bridge DesignJrund JohansenMaster of Science in Engineering and ICTSupervisor: Tor Guttorm Syvertsen, KTDepartment of Structural EngineeringSubmission date: June 2013Norwegian University of Science and Technology BIM in Bridge DesignJrundJohansenJune6,20131AbstractBuilding Information Modeling (BIM) is a relatively new technology and workprocess. Themainideaistomodel3Dobjectsandstoretheinformationinadatabasesuchthatthisinformationcaneasilybeextractedandviewedfromtheseobjects. Theconstructionsectorhasmoreorlessemployedfull BIM,however,the infrastructure sector has not incorporated the new technology inthesamefashion. Inthisthesis,modelingofaspecicbridgestructureusingthe BIM tool AutodeskRRevitTM2013, and the current bridge design processusedat Norconsult were analyzedinorder toevaluate the advantages andchallengesofusingBIMinbridgedesign. InorderforRevittobeapplicableithastobeabletoaccuratelydesignthestructureandprovidethenecessarydocumentation, aswell asincorporatethestepsleadingupto, andfollowingthebridgedesign,satisfactory. Themainconclusionsare:ThereisafutureforBIMinbridgedesign.AdvantagesbyutilizingBIMinbridgedesignhavebeenshownthroughpilotprojects.The collaboration of the Revit model with road and underlay models (2Dmodelsdisplayingtheprojectionofastructureonthehorizontalplane,usedas aidfor themodelingof theactual 3Dmodel) for referenceissatisfactory, howevertheroadgeometryhastobeappropriateforBIMpurposes.Theuseof Robot wasnot studiedextensivelyinthisthesis; however,non-standardgeometrymakestheincorporationofRobotdicult.Although this thesis does not explicitly investigate the representation ofthe model created in Revit with other disciplines, there is documentationshowingsuccessfulinterplayinthisregard.The reinforcement tool included in Revit works well when modeling stan-dardobjects, butneedsimprovementsintermsofmodelingcurvedob-jects.In terms of being able to eectively utilize BIM, the skill level of the useris of major importance; in the most extreme cases it can dictate whetherornotataskcanbedone.2SammendragBygningsinformasjonsmodellering(BIM)erenrelativtnyteknologi ogarbei-dsprosess. Hovedideeneramodellere3D-objekter oglagreinformasjoneniendatabaseslikatdenneinformasjonenenkeltkanhentesutogvises. Bygn-ingssektorenbenyttermerellermindreBIMi helearbeidsprosessen. Infras-truktursektorenhar derimot ikke inkorporert dennye teknologieni sammegrad. I denne rapportenhar modelleringenavenbrukonstruksjoni BIM-verktyetAutodeskR RevitTM2013, i tilleggtil dennavrendebruprosjek-teringsprosesseni Norconsult, blittanalysertfor aevaluerefordeleneogut-fordringeneBIMstarovenformedtankepabruprosjektering. DersomRevitskalkunnebenyttessometverktyibruprosjektering, maprogrammetvreistandtil anyaktigrepresenterebrukonstruksjonenogproduserendvendigdokumentasjon, i tilleggtil ainkorporerebadelmaterialesomfungerersomen basis for modelleringen, og lmateriale som skal eksporteres til videre brukettermodelleringen. Hovedkonklusjoneneer:DeterenframtidforBIMibruprosjektering.Fordeler ved benyttelse av BIM i bruprosjektering har blitt vist gjennompilotprosjekter.Samhandlingen mellom Revit og vei- og underlagsmodeller (2D-modellersom viser projeksjonen av en konstruksjon pa horisontalplanet) for refer-ansetil modelleringenertilstrekkelig, salengegeometrieni referanse-modelleneerpassendeforbrukiRevit.BrukavRobotbleikkestudertnye. Allikevel bledeterfartatikke-standardgeometri skaperproblemervedoverfringavmodell fraRevittilRobot.DennerapportenunderskerikkerepresentasjonenavmodellenlagetiRevit sammen med andre disipliner,men det nnes dokumentasjon somviseratdennefunksjonalitetenfungerertilfredsstillende.Armeringsverktyet i Revit fungerer godt for standardobjekter, menbehverforbedringermedhensynpabuedeobjekter.Ferdighetsnivaettil brukerenerenekstremtviktigfaktori sprsmaletom BIM kan benyttes eektivt; i ekstreme tilfeller kan det diktere om enoppgavekanutfresellerikke.3ContentsAbstract 2Sammendrag 3TableofContents 4Acronyms,AbbreviationsandTerms 6Preface 71 Introduction 81.1 Motivation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.2 Theidea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.3 Thethesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Background 92.1 BuildingInformationModeling(BIM) . . . . . . . . . . . . . . . 92.2 Bridgedesigntoday. . . . . . . . . . . . . . . . . . . . . . . . . 102.3 TheroleofBIMinbridgedesign . . . . . . . . . . . . . . . . . 122.4 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.4.1 Revit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.4.2 Robot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.4.3 Microstation. . . . . . . . . . . . . . . . . . . . . . . . . 172.4.4 Civil3D. . . . . . . . . . . . . . . . . . . . . . . . . . . 182.5 Summaryoftheprojectassignment . . . . . . . . . . . . . . . . 192.5.1 Therstmodel . . . . . . . . . . . . . . . . . . . . . . . 192.5.2 Thesecondmodel . . . . . . . . . . . . . . . . . . . . . . 203 ReviewofpilotBIMprojects 223.1 E.Pihl&Sn . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.2 SundtConstruction. . . . . . . . . . . . . . . . . . . . . . . . . 234 ModelinginRevit 264.1 RevitUserInterface . . . . . . . . . . . . . . . . . . . . . . . . 264.2 ModelingBasics. . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2.1 ObjectTypes . . . . . . . . . . . . . . . . . . . . . . . . 274.2.2 Views . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294.2.3 Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304.2.4 ReferencePlanes . . . . . . . . . . . . . . . . . . . . . . 314.3 TheBridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.4 ImportingthecenterlinefromCivil3DintoRevit . . . . . . . . 354.5 Modelingthebridge . . . . . . . . . . . . . . . . . . . . . . . . 394.5.1 Bridgedeckandabutmentbackwalls . . . . . . . . . . . 404.5.2 ColumnsandFoundations . . . . . . . . . . . . . . . . . 4144.5.3 Abutmentwingwalls . . . . . . . . . . . . . . . . . . . . 424.5.4 TransitionPlate. . . . . . . . . . . . . . . . . . . . . . . 434.6 ImportingthemodeltoRobot . . . . . . . . . . . . . . . . . . . 445 DesignChanges 475.1 Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495.2 Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525.3 Slope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555.4 Radius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585.5 Depthofthepiers . . . . . . . . . . . . . . . . . . . . . . . . . . 585.6 Orientationofthepiers. . . . . . . . . . . . . . . . . . . . . . . 605.7 Summaryofdesignchanges . . . . . . . . . . . . . . . . . . . . 616 Reinforcementofthebridge 616.1 Theareareinforcementtool . . . . . . . . . . . . . . . . . . . . 626.2 Revitreinforcementextension . . . . . . . . . . . . . . . . . . . 646.3 Therebartool. . . . . . . . . . . . . . . . . . . . . . . . . . . . 656.4 Reinforcementofthesubstructure. . . . . . . . . . . . . . . . . 666.4.1 CoverDistance . . . . . . . . . . . . . . . . . . . . . . . 716.5 RebarDrawings . . . . . . . . . . . . . . . . . . . . . . . . . . . 746.6 Rebardocumentation. . . . . . . . . . . . . . . . . . . . . . . . 786.7 Reinforcementofthebridgedeck . . . . . . . . . . . . . . . . . 816.8 Post-tensioningreinforcement . . . . . . . . . . . . . . . . . . . 847 Discussionandconclusion 897.1 BIM,RevitandRobotinbridgedesign. . . . . . . . . . . . . . 897.2 DierencesbetweentraditionalmethodsandBIM. . . . . . . . 907.3 SkillLevel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927.4 Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . 928 References 945Acronyms,AbbreviationsandTermsTerm ExplanationCivil 3DAutoCADR Civil3DTM2013Revit AutodeskR RevitTM2013Microstation BentleyR MicrostationTMRobot AutodeskR RobotStructuralAnalysisTMTekla TeklaR StructuresTMRobustness The objects resilience towards unexpectedandunwantedchangewhenmodelingotherobjectsFlexibility The objects ability to be changed accordingtouserpreferenceStandardgeometry Geometry already dened through the exist-ing objects in the Revit library. This includesslopesandcurvatureinoneplaneNon-standardgeometry Curvedand/or irregular geometry(lackinguniformityor symmetry; uneveninshape,position,arrangement,etc.) notalreadyde-nedintheRevitlibraryPT Post-tensioningPTR Post-tensioningreinforcementRebar Reinforcementbar6PrefaceThroughsummer internships at Focus Software andproject assignment, IlearnedaboutBIM(BuildingInformationModeling)andtoolsusedtoper-formBIM.Indtheeldinteresting,andamintriguedbythepotentialBIMhas to increase the eectiveness of construction projects. The objective of thisthesis is to gain an understanding of the possibilities and challenges connectedtorepresentingbridgedesignwithBIM, especiallyfocusingonthereinforce-mentdesign. Thisreportisbasedon:TheworkprocessinNorconsultandMicrostationasanexampleofhowinfrastructureprojects, andinthiscasebridgedesign, ispresentlyap-proached.Civil3DasanaidforBIMmodeling.RevitasaBIMmodelingtool.Othercompaniesmayusealternativeprograms, andhaveadierentap-proachtotheirwork.I would like to thank my advisor Tor Guttorm Syvertsen for valuable assistancethroughoutthethesiswork. I wouldalsoliketothankFocusSoftwareandNorconsultfortheircooperation, andinparticularDaniel AaseandChristerWolden,mycontactpersonsinFocusSoftwareandNorconsult,respectively.71 Introduction1.1 MotivationSinceitsorigininthe1980s, BuildingInformationModeling(BIM)hasbeenusedmorefrequentlyastheprocessitselfandthetoolsusedtoperformBIMhavematuredandalsoasaresultofincreasedcomputingpower. Wherepurecomputer performance previously was the threshold, software and informationtransferbetweendierentplatformsandexpertsinvariousdomainshavenowtakenitsplaceasthemainconcerns.Focus Software uses Revit and Robot for generating BIM-models and struc-turalanalysismodels,respectively. Therearestillproblemsrelatedtodesign-ing bridges when BIM is concerned, and in this case Revit. Revit has a bridgeconstructionextension; yetitdoesnotincorporatesucientfunctionalityforcast-in-placeconcretebridgeswithcurvaturesandslopes. Thereisaneedtoassesstheapplicabilityof Revitforbridgedesignwherethegeometryof thebridgeisnon-standard.ReinforcementofbridgesinNorwaytodayisdonemostlyusing2Ddraw-ings, which means that in order to get an overview of the full reinforcement ofa bridge one has to combine several separate drawings. With a 3D representa-tionitwillbeeasierandquickertogainthatoverview,especiallyintermsofinterferenceofreinforcementbars. ThereisaneedtoevaluateRevitsabilitytorepresentthereinforcementofbridges.1.2 TheideaPresently, thebridgedesignprocessisnotwell denedintermsoffull BIM,andtraditional methodsarestill preferred. Thus, itisappropriatetoassesshowBIM-toolslackingabilitytodesigncomplicatedbridgescanberemediedandhowBIMtoagreaterextentcanbeusedasaresourceinbridgedesign.Byevaluatingtheprocess as it is donetodayandcomparingit toamoreBIMdominatedprocess, onecangainknowledgeaboutthepossibilitiesandlimitationsconcerningachangeinthebridgedesignprocess.1.3 ThethesisThis thesis evaluates Revit as a BIM tool, and what advantages, disadvantagesandcomplicationsboththeprogramandBIMingeneral holdscomparedtotraditional methods. Acentral questioniswhetherornotthewholebridgedesigncanbedoneusingBIMtools. Emphasiswillbeprimarilyonmodelingdonewiththeuseof Revit, whilealsoconsideringtheentiremodelingpro-cessandtheinterplaywithothersoftware. Bypersonallydesigningabridge8includingthereinforcement of thebridgeI will beabletogainamorede-tailedunderstandingoftheissuesrelatedtoBIMinbridgedesign,forfurtherevaluation.2 Background2.1 BuildingInformationModeling(BIM)BIMisanacronymforBuildingInformationModelingorBuildingInforma-tionModel. The meaningof the acronymineachcase has tobe derivedfromthecontext. ThetermBIMhasbeendeneddierentlybyvariouspeo-ple/organizations. However, TheNationalBuildingInformationModelStan-dardProjectCommitteegraspsthecoreofthetermintheirdenition:BuildingInformationModeling(BIM)isadigitalrepresentationofphys-ical andfunctional characteristicsof afacility. Assuchitservesasasharedknowledgeresourceforinformationaboutafacilityformingareliablebasisfordecisionsduringitslifecyclefrominceptiononward[1].Onecandiscusswhetherornotthetermsharedknowledgeresource isacorrect description, as a BIM contains information from which people can gainknowledge. OnemayarguethereisnoknowledgecontainedintheBIMperse;howeveritisaresourceforpotentialknowledge. Thetwomostimportantletters in BIM are I and M; a model is made where the information is availablefor all the people working on the project. By using BIM, architects, engineers,contractors and owners can create digital information and documentation (e.g.cross sections, elevations and material lists). It is a powerful tool which enablesall the actors related to the project to extract the same information and connecttothesameplatform.Bycreating3D-models andaddinginformationrelatedtoall thedier-entdisciplinesinvolved(Plumbing,Electricaletc.),alltheinformationwhichpreviouslyhadtobecoordinatedaftertheyweremade(sheetsdescribingthebridgeusedintheconstructionphase)canbeincorporatedinthemodel im-mediately. Thisway, oneobtainsanoverviewof theprojectearly, whichinturnmeansthatproblemsorimprovementscanbeidentiedearlyinthede-signprocess. Incontrast totraditional drawingandtheuseof CAD-tools,wherethedrawings areindependent of eachother, theBIMis a3D-modelwith3D-objectsandelementswithparameterizedpropertiesandrelationstoeach other. Parameterized properties means that the objects are assigned withcertain parameters (e.g. dimensions, oset from original placement, slope etc.)easily altered through a property palette. Once an object is altered, the objectwill bealteredeverywhereintheBIM, whichrenderstediouschangesinthe9documentationobsolete.2.2 BridgedesigntodayThedescriptionof howbridgedesignis presentlyapproachedis formedonbasisof theworkprocessinNorconsultandtheprogramMicrostation. Theknowledge acquired was gained through correspondence with Christer WoldenatNorconsult,andalsoavisittoNorconsultsheadquarterinOslo,Sandvika[2].Therearenumerousconsiderationsneededtobemadethroughoutthede-sign. Thedecisionsanddesignsaremadebasedonpreviousexperiencesandexpertise, as well as manuals with specications that every bridge must follow(e.g. theNorwegianmanualforbridgedesign[3]andEurocodes[4]). Aspectsneededtobeconsideredinclude,butarenotlimitedto:Istheprojectfeasibleandcost-eective?Dierentspecications: elevationsif thebridgespansoverariveroraroad,roadspecications,detailingetc.Zoning: theareaassignedfortheprojectdescribingstructuresalreadysituatedinthearea.Basicdata: dataof theareainuencingtheproject(heightof existingterrain,vegetation,existingtechnicalinfrastructureetc.).3D-model,drawingsofproles,sectionsanddetails,plans,reinforcementandmaterial lists etc. have to be established. These documents are generally madeseparately,andmostcalculationsaremademanually.In CAD programs such as Microstation, the user can model the bridge withageographicallycorrectposition. Theengineerusuallystartsbyreferencingtheterrainandroadgeometry, whichinturnaremadeaccordingtozoningandbasicdata. Moreaccurately, theprocedureoftenstartswitharoadandterrain model in which an underlay including the centerline of the bridge in thehorizontal plane is identied,along with road width, slopes,terrain elevationsetc. Theouter boundaries of thebridgearelaidparallel tothecenterline.Thecenterlineis, inthisthesis, referredtoasthelinethatrunsparallel tothebridges spananddivides thebridgeintwoequal halves. Thereis noexactprocedurewhendesigningthebridge, andtheengineermightalterthesequencingof theoperationsfromoneprojecttoanother. Figure1showsagenericworkowofthebridgedesignprocess.10Figure1: BridgedesignworkowOften, the engineer starts by creating the cross section which in most casesfollows the centerline. Then, either the bridge geometryinthe horizontalplaneor a3Dmodel is established. Basedonthat decision, either the3Dmodel or the bridges projection on the horizontal plane from the 3D model isdrawn, beforeelevations, foundationandpierdetailsetc. arecreated. Thesedrawingsaresocalledlayersofinformation,andinMicrostation,CADlayersaredisplayedbasedonthewantedrepresentation. Thiswaytheuserisableto, for instance, create an elevation showing only the bridge itself, and anotherlayer showing the terrain surrounding the bridge, and choose whether to showthebridgewithorwithouttheterrain,ortheterrainonitsown.The required dimensions of the bridge and the reinforcement need are spec-ied by structural analysis, where reaction forces, stresses and strains are eval-uatedbasedonpertinentloadcombinations, boththroughhandcalculationsand with the aid of softwares such as NovaFrame and NovaDesign. NovaFrameis used for global analysis of the bridge, while NovaDesign focuses on the forcesatgivensectionsofthebridge,whichinturndictatesthereinforcementneedandthedimensioningofreinforcedconcretecrosssections. 2Dreinforcementdrawingsaremadebasedonthestructuralanalysis.Designingabridgeisaniterativeprocess,wherechangesinthebasicdataand data received from other disciplines results in a need to update the bridgedesign. The better the basic data, the fewer changes need to be made through-11outthedesignprocess.2.3 TheroleofBIMinbridgedesignToevaluatethepotential roleof BIMininfrastructureprojects, andinthiscase in bridge design, one has to address the shortcomings of the present workprocess. At thesametimeonehas toassess thepotential of anewdigitalprocess. This includes, amongother things, toevaluatetheprograms used(in this case Revit) and how they can be integrated in infrastructure projects.TheconstructionsectorhascometoastagewheretheymoreorlessemployBIM. The infrastructure sector has, until now, approximated BIM by creatingdierentlayersofinformation(describedinBridgedesigntoday??),whichincomparisonisrelativelystaticandcumbersome. AsimpleoverviewofthedierentstagesofBIMisshowningure2, whereLevel0isthelowestlevelof interoperabilityandLevel 3is thehighest. Theinfrastructuresector inNorway is at Level 1, with combined 2D and 3D representations of the structurewithouttrulyanyinterconnectivity, meaningtherearenorelationsbetweenthedierentrepresentations. TheconstructionsectorismoreorlessatLevel2, utilizingBIMmodelswithobjectrelations. Theaimforthisthesisistodetermine whether or not Level 2 is applicable for infrastructure projects, andspecically bridge design. The ultimate goal is to reach Level 3 with completeintegratedinteroperabilitywithacommonleformat (IFC) andintegratedwebservices, suchthatall theinformationstoredinaBIMisretainedwhentransferredbetweenprograms,andeasilyviewedthroughwebapplications.12Figure2: ChartoftheBIMstages[5]Thereareseveral reasons whyBIMis not utilizedintheinfrastructuresector:NouseforBIM;existingCAD-toolsareconsideredsucient.BIMisnotdemandedbythecustomers.New technology takes time to employ in companies and are often utilizedreluctantly. Known and ingrained work processes are hard to change, andgainingcompetenceinnewprocessesaretimeconsuming.The BIM-technology still has problems, especially concerning non-standardgeometry. Theproblemwithbridgesconstructedwithconcretecastinplace is an example of this. Curvatures are often needed in two planes aswell asvariablecrosssection. ProgramsthatarenotcreatedforuseinBIM, suchasforexampleAutoCADandMicrostation, deal withthesechallenges in a superior manner as they only create the correct geometrywithoutregardtotherelationsbetweenobjectsinthemodel. Howevertheylacktheobjectrelations.Benets of utilizing BIM have been proved by pilot projects using programslike TeklaandRevit. Inthese projects accurate 3D-models were created,showingthatitispossibletomodelmoredicultgeometrywithBIM.Laserscanning of existing structures have also been incorporated where additions totheexistingstructuresweretobecreated.132.4 SoftwareThe modeling reported here was done in Revit. Revit and Robot are two of theprograms Focus Software has specialized in. Microstation is the program usedbyNorconsultforbridgedesign. Civil 3DwasusedtoextractthecenterlineofthebridgefromaroadmodelandimportthiscenterlineintoRevit.2.4.1 RevitFigure3: AbridgemodelinRevitRevitisaBIMtoolwhichfocusesonthedesignpartoftheconstructionpro-cess. It has an intuitive and clean user interface, and enables the user to modeleverything from basic structures to specically dened geometries. PreviouslyRevit was divided into an Architecture application, an MEP (Mechanical, Elec-trical andPlumbing)applicationandaStructureapplication. InRevit2013these applications are combined in one application. Revits le format is .RVT,butitcanalsoexporttoandimportfromtheleformatIFC, whichisthestandardformatforBIM.142.4.2 RobotFigure4: AstructureanalyzedinRobotRobotisAutodesksFEMstructural analysisprogram. Thereareanumberofprogramsthathandlesimplestaticsystems,butRobotismadetoanalyzelargeandcomplicatedstructures. This,andthefactthatRobotisconnectedtoRevitinthesensethatitcantransfermodelstoandfromRevit, makesitanimportanttool. ModelsmadeinRevitcanbetransferredtoRobotforstructuralanalysis,andchangesmadeinRobotcanbeupdatedinthemodelinRevit. Atypical exampleis theuseof Robot tocalculatetheneedforreinforcement bars, which in turn is updated in Revit to show the reinforcementbarsinthemodel. InRevit,thechangesproposedinRobotareavailableforreviewbytheuser,whocanchoosewhethertoexecuteallthechanges,someof them, orproposeentirelynewsolutions. Thisfunctionalityisimportant,especially in practice, where dierent people often work with the two dierentprograms. This allows for the Revit specialist to send the model to the Robotspecialistwithouthavingtocreatetheanalyticalmodeloveragain.152.4.3 MicrostationFigure5: Dierentviews(layers)ofabridgestructureinMicrostation[6]AtBentleyswebpageMicrostationisdescribedasfollows:MicroStation is the worlds leading information modeling environment ex-plicitly for the architecture, engineering, construction, andoperationof allinfrastructure types including utility systems, roads and rail, bridges, buildings,communications networks, water and wastewater networks, process plants, min-ing,andmore[7]Microstationenablestheusertocreatethegeometryof theconstructionandthedocumentationneededfortheconstructionphase. Theprogramis,however, notaBIMtool; itdoesnotincludeobjectswithrelationstoeachother.162.4.4 Civil3DFigure6: AroadmodelinCivil3DCivil 3Dis aBIMsolutionfor civil engineeringdesignanddocumentation.Civil 3D is often used for the creation of bridge deck geometry in bridge designprojects. InCivil 3D, theuserisabletorepresentgeometrythatcurvesinthreeplanes.2.5 SummaryoftheprojectassignmentThe aim of the project was to learn about Revit as a modeling tool and also in-vestigate its applicability for bridge design. This was approached by modelinga simple bridge structure in Revit and assessing the problems, advantages andchallenges related to the modeling. Focus was primarily on the modeling itself,buttheinterplaywithothersoftwarealsohadtobeinvestigatedinordertoevaluatetheusefulnessofthe program. Inparticular,beingableto eectivelyincludearoadmodel andattaintheroadgeometrywiththecorrectcoordi-nates was important. This was relatively easily done with the incorporation ofCivil3DbylinkingthecenterlineoftheroadmodelintoRevit. However,thecenterlineoftheroadmodel wasnotapplicableforuseinRevit. Thereasonbehindthiswasthatthecenterlineconsistednotofonecontinuousline, butseveral straightlinesegmentsattachedtoeachother, creatingslightpertur-bationsintheRevitmodel. Theprocessof importingthecenterlineworkedperfectly, whichmeansthattheissuewiththecenterlinewascausedbytheroadmodelitself.172.5.1 TherstmodelThe rst bridge model was made withthe objective of quicklygaininganoverview of the complications one would encounter during the modeling of thebridge. As an eect, it consisted of poorly dened objects and solutions, mak-ingtheBIMlackrobustnessandexibilityintermsof adaptingtochangesmadelateron. Itbecameapparentalreadyintheearlystagesthatthechoiceof objects intheBIMandmodelingprocedurewereimportant, andshouldbecarefullyconsidered. The3Dmodelofthebridgelookedcorrect, howeverwhenscrutinizingthemodelthereweremultipleerrorsofunacceptablemag-nitude (several millimeters). Because of the lackingrobustness, remedyingerrors in one place of the BIM often caused errors elsewhere,making the BIMunpredictable. An example is shown in gure 7, where the vertical dimensionsarecorrectwhereasthehorizontalarenot. Ifthehorizontaldimensionswerechanged to their appropriate values (200mm and 300mm), the vertical dimen-sionswouldalsochangeasaneectof howtheobjectwasmodeled, leavingthegeometryincorrect.Figure7: Detail showingerrors(dimensionsintheredcircle)causedbylackofrobustness2.5.2 ThesecondmodelWiththeknowledgegainedthroughmodelingtherstmodel,itwasrealizedthatbeforestartingtheactual modelingof thebridgeinthesecondmodel,preparations hadtobe made. Newobject families were createdtoattainrobustnessinthemoredicultobjectsintheBIM.Objectswereattachedtoreferenceplanesandlevelsratherthantoeachotherinordertoavoidhaving18objects dimensionsandattributessuddenlychangewhenchangingthoseofanotherobject,whichwasanissueintherstmodel.Figure8: ThedetailinthesecondmodelWithamoderateamount of skill onewas abletocreateabasicbridgemodel and accompanying drawings, with the exception of the following issues:When creating the bridge deck and barriers, there was no convenient wayof specifying that they should have a slope while at the same time retainvertical ends. Theresultwasaslightangleattheendswhichhadtobemanuallycut,leavingthedimensionsofthedeckattheendsslightlywrong because of the slope. This problem needed to be circumvented bychoosingwhichsectionstoannotate;whenannotatingtheabutmentsina vertical section one had to leave out the annotation of the bridge deckbecauseofthewrongdimensions.Inorder toviewthecross sectionof theslopedbridgedeckandalsobeabletoaddannotationstothiscrosssection, thesectionswhichcutthebridgedeckhadtobeperfectlynormal tothebridgedecksx-axis(theaxisrunningalongthedeckslength). Thiswasexperiencedasasometimesfrustratingtask. FocusSoftwarehas, aftertheprojectwasconcluded, madeatool forRevitusedtoautomaticallycreateacrosssectional view of an object regardless of orientation. This tool has madetheoperationaloteasier.Railings can only be attached to stairs and ramps, or placed in the hori-zontal plane. The intention was to attach railings to the barriers,but in19ordertodothat,newspecializedfamiliesneededtobecreated. There-sult was that attention was placed elsewhere, leaving the issue unsolved.It should be noted that the level of detail was not the highest in neither ofthe bridge models, and reinforcement was not studied extensively, because themaingoalwastogetanoverviewofthebigpicture,andalsobecausetrivial,yettediousoperationswereneglected. However, thebridgeasawholewasrelatively accurately represented. Slightly inaccurate dimensions in the secondmodel arosemostlyduetoroundingerrorsor minor modelinginaccuracies,andwereintherangeof afewmillimeters at most. Whenoperatingwithmillimeter precision, this is also unacceptable. However, the errors were easiertoxthanintherstmodelduetosuperiorrobustness.Animportantthingtomentionisthefactthatthewaysof representingthe model have tobe reconsideredwhenoperatingwithBIMcomparedtotraditional2Ddrawings. TheBIMconsistsofactualobjects,andonecannotsimply alter the representation of the objects in a 2D view without altering thewhole model. In traditional design using multiple 2D drawings one sometimeschangethepositionoraltitudeofcertainelementsinthedrawingtomakeitlook cleaner and more legible. Also, for the same reason and also for dimensionpurposes, crosssectionsaresometimesshownasvertical inadrawingwhentheyareinfactsloped. Thisisnotpossible,norisitdesirable,whenworkingwithBIM.Thus,therepresentationofthemodelinthedrawingsneedstobereviewedandthemethods usedhavetobechanged. This is apart of thetransferfromtraditionalmethodstoBIM.3 ReviewofpilotBIMprojectsTwopilotprojectsdonebytwodierentcompanieshavebeenreviewed. Athirdcompany, WSPFinland, wasalsocontactedbutdidnotrespond. ThiscompanyusedTeklaintheirBIMmodelingwork[8].3.1 E.Pihl&SnE. Pihl & Sn (Pihl) is a Danish contractor that performs projects in numerousareas,includinglargeinfrastructureprojects,constructionsandpowerplants.Theylistastheworlds133rdlargestinternational contractor[9]. Pihl hassuccessfullyutilizedBIMinpilotprojectsinScandinavia. WiththeusageofBIM they have provided eye-opening experiences for the people involved in theprojects, making them understand the benets of the new technology. Duringone of their projects, the constructionof arailroadbridge inthe heart ofGothenburg, Sweden, Pihl used Tekla as a tool in the reinforcement work [10].Thebridge,aconcretestructuredesignedtowithstandheavyloads,required20vast amounts of reinforcement bars, making the reinforcement bars placementdicult.Theprojectwassplitintotwostages; therststageincludedanewspanof 450meters, andinthesecondstageanexistingspanof 550meters wasbroughtdowninordertocreateanewone. Therststagewasdesignedandreinforcedentirelybytraditional methods, alongwiththerst bridgedeck(thedistancebetweentwopiers) of thesecondspan. Theresult was 20-25out of 100reinforcement bars that hadtobereshapedat theconstructionsiteforeachdeck, asaconsequenceofthedicultiesarisingfromusingandinterpreting2Ddrawings. TherestofthebridgewasmodeledinTeklaasanadditiontothe2Ddrawings,andtheerrorinreinforcementbarswasreducedto 0-2 per 100 on each deck. In addition, on the rst bridge deck Pihl spent 23daysonthereinforcementbarsworkalone,incomparisontoapproximately8ontheseconddeck. Eventhoughsomeoftheincreaseinproductivitycanbeexplainedbytheseasoninwhichthetwobridgedeckswerereinforced. Therst deckwas createdduringthewinter, andthus naturallybecomes morecumbersome. Nonetheless, Pihl states in their report, most of the explanationlieswithintheincorporationofBIM.Amongtheadvantages of usingBIMinthereinforcement of thebridgedeck,thereisthepossibilityofprintingoutthereinforcementbarschematicsandhangthemupontheconstructionsiteforthepeopleworkingwiththereinforcementbarstosee. Thisletsthemgetamuchbetterunderstandingofthe greater picture, the 3D picture, instead of having to visualize the reinforce-mentbarsplacementbasedon2Ddrawings. Lesstimeisspentdiscussingtheplacementof thebars, andmoretimecanbespentactuallyinsertingthem.AnotherveryusefultoolTekladevelopedforthisproject,basedonspecica-tions from Pihl, was a function which enabled reinforcement bars to be orderedtotheconstructionsitebyselectingandorderingthemthroughtheBIM.Allthe specications of the reinforcement bars were sent to the manufacturer. Be-causeof this, andbyhavinganimprovedoverviewof thereinforcementbarschematics,Pihlcouldveryecientlyplantheorderingofreinforcementbarsinawaythatleftfewerexcessreinforcementbarsontheconstructionsite.3.2 SundtConstructionSundt Constructionis anAmericanfull-servicegeneral contractor withex-pertise that spans the entire lifecycle of construction. Withinthe civil &transportationsector,Sundthasbeeninvolvedindesigningandconstructingroadsandhighways, bridgesandinterchanges, airports, hangars, andwatertreatmentplants. SundthasusedBIMinbridgedesignprojectssince2010,and use Civil 3D and Revit extensively in both the design of the geometry andthe reinforcement work. Sundt also used AutodeskRNavisworksRManage tocreate a 4D model of one of the arches, exploring the construction sequencing.21NavisworksManageisaprojectreviewsolutionthatsupportscoordination,analysis, and communication of design intent and constructability. InformationaboutSundtConstructionandtheuseofBIMintheirbridgedesignprojectswas gained through a skype conversation with one of their modeling engineers,EricCylwik[11],andfromtheirwebpages[12].Inoneof theirdesignprojects, therenovationof the7thstreetbridgeinTexas [13], Sundt Construction used Civil 3D and Revit to model the existingbridgewithits 12newprecast post-tensionedconcretearches that runthelengthof thebridge. Thearches includedcomplexpost-tensioningtendonsandlightingelements whichneededcareful planning. Beingabletomodelthese elements in3DhelpedSundt visualize howall these components ttogether. Thepost-tensioningtendons,whichcurvedinallthreedimensions,were modeled in Civil 3D before imported to Revit, where the rest of the bridge,includingreinforcementbars,wasmodeled. AccordingtoEricCylwik,Sundtusuallymodel thebridgesuperstructure(i.e. thebridgedeck) inCivil 3D,which holds superior functionality compared to Revit in terms of the creation ofnon-standardgeometry. ThebridgesuperstructureisthenimportedtoRevit,wherethesubstructure(i.e. columns, foundationsetc.) isincluded. ThereisnotmuchinterplaybetweentheobjectsimportedfromCivil 3DtoRevitand the objects created in Revit. The user can neither attach to the importedobjectsnordimensiontotheminRevit. However,curvatureingeneralposesproblems inRevit, andCylwikdidnot consider the lackof interplayas amajorconcern. Hementionedthat,asofCivil3Dverison2014,solidobjectscan be shown in Civil 3D when imported from Revit to Civil 3D. This way, oneisabletobringasectionfromRevitintoCivil3D,obtainasolidobjectanddocument it there. According to Cylwik, Civil 3D is superior to Revit in termsof dimensioning objects with curved geometry. He stressed that both Civil 3Dand Revit should be utilized in bridge modeling to eectively represent a bridgestructurecorrectlyandincludetheinformationneeded.Eric Cylwik was not thrilled with how Revit worked in terms of rebar mod-eling. Itwasnotveryexibleorecientingeneral, andinparticular, Revithad a dicult time with reinforcing objects that were curved, which caused is-sues when modeling the concrete arches. Another reinforcement problem withRevitexperiencedbyCylwik,wasthefactthatRevithasaconceptwherere-bar can only be created within a concrete object, resulting in an error messagewhen attempting to add rebar outside of an object. However they found an adhocsolution; iftheusergroupstherebarsinRevit, theruleRevitgeneratesfortherebarsisremoved,allowingforrebarsoutsideofconcreteobjects.Thebiggest advantagewithBIM, accordingtoEric, is thebetter com-municationbetweenall parties. Duringplanningsessionstheycouldvisuallycommunicatewiththeirsubcontractorstodevelopamorerealisticconstruc-tionschedule, andeveryonebetterunderstoodboththeirowntask, andthetasksofothers.22AnothergreatadvantagewithusingBIMisthemoreecientsharingofinformation. Asanexample,iftheelevationsofspecicpointsonthebridgewhicharenotincludedintheconstructiondocumentsneedtobedetermined,previously one would have to gure out the elevations and include them on newspreadsheets. Thus, new spreadsheets would need to be created when updatesandchangesweremade. Now,theseelevationscanbeenteredintothemodeland automatically be included in drawings extracted from the model, reducingtheamountofspreadsheets.4 ModelinginRevit4.1 RevitUserInterfaceFigure9: Revit2013UserInterfaceToolsaresortedindierentRibbonsandfurthercategorizedinPanels.ThetoolsenabletheusertoperformdierenttasksinordertocreateamodelwhichwillbevisualizedintheModelWindow.TheQuickAccessToolbarallowsforpromptaccesstofrequentlyusedtools, andthetoolsdisplayedintheQuickAccessToolbarcanbeper-sonalizedbasedonuserpreferences.TheTypeSelectordisplaystheobjectcurrentlyselectedorchosenforcreation with customizable properties displayed in the Properties Palette.23TheProjectBrowsercontainsall theobjectscreatedaswell asall thedierentviewscontainedinthemodel.TheViewControl barincludestoolsforcustomizinghowthemodel isdisplayedintheModelWindow,includinghidingorisolatingelements,andadjustingthelevelofdetailoftheobjects.4.2 ModelingBasicsThroughout themodelinganalysis of this thesis, therearecertainelementswhichwill bereferredtofrequently. Otherelementswill beexplainedwhenneeded. Four important elements whichareincludedinanymodel arethefollowing:ObjectTypesViewsLevelsReferencePlanes4.2.1 ObjectTypesWhendescribingthemodelingprocess, Iwilldistinguishbetweenthreewaysofdeningtheobjectsusedinthemodel:Standard objects: These are the built-in objects that are already denedintheRevitlibrary,accessiblethroughtheRevittools. Theobjectsarecategorizedinfamilies(e.g. anIPE220beamisamemberofthebeamfamily). In object modeling terms, a family is a generic class/superclass,andanobjectisaclass/subclass.User denedobjects: These are objects denedthroughthe familiesalreadyinRevit. Asanexample,theuserisabletocreateanewbeamfamily with a dierent prole than the ones already in the Revit library.Thenewbeamwill havebeamproperties andwill beavailablewhenselecting the beamtool. The user denedfamily canbe loadedinto andusedinanyproject.In-Place Mass objects: These are objects dened in the model windowandarespecictothecurrentmodel. TheIn-PlaceMassesarealsocategorized in families, but they lack some of the properties and modelingoperations otherwise attainable usingobjects alreadyavailable intheRevitlibrary.24Revitworksverywellwhenusingthestandardobjects; thesearetheobjectsRevitismainlyprogrammedtodeal with, andtheframeworkof operationsavailable for the standard objects makes for a robust model if created smartly.Howwell theincorporationofuserdenedobjectsinthemodel works, com-paredtostandardobjects,dependsgreatlyonhowwellthefamiliesaremod-eled. Auserdenedfamilywithoutawsisjustasgoodasastandardfamilywith the exception of the non-standard geometry it may comprise. However, apoorlydesignedfamilymaycauseunexpectedbehaviorintheobjectsplacedinthemodel, especiallywhenmakingchanges(alteringdimensions, aligningitwithotherobjectsetc.) totheobject.When modeling user dened geometry, it is very useful to create well func-tioningfamilies. Notonlydoesthisensurerobustandcustomizableobjects,thecreatedfamiliescanbesavedandusedinotherprojectsaswell. Theim-portanceofreuseoffamiliescannotbeemphasizedenough, andisespeciallyvalidwhencreatingobjectsthatareusedoftenandacrossmultipleprojects.Thefamiliesarethensimplyloadedintothedesiredproject,wheretheymaybecustomizedaccordingtotheneedsofthatproject.TheIn-PlaceMassesaretheleastrobustobjects; however,theycanbeuseful when objects do not need to be included in a family, and the user wantstocreatethemquickly. Infact, sometimes anIn-PlaceMassis theonlyobject suitable. An example is a void form used to cut another object in orderfor that object to attain the desired shape when other built-in methods fail toprovidetheresultstheuserwants. Ingure10, oneofthevoidformsattheabutmentwingwallsisshown.25Figure10: Voidformcuttinganabutmentwingwall4.2.2 ViewsAs mentioned in 4.1, Revit consists of dierent views in which the user is abletoworkonthemodel. Thedefaultviewsare3D-view, elevations, andplanviews. Theplanviewsarealignedtothedefaultlevelsinthemodel,allowingthe user to evaluate the model either looking upwards or downwards from thoselevels. Theusercandenemultiple3D-viewsdisplayingthemodeldierentlyorcreatemorelevelsfromwhichplanviewsareautomaticallyincluded. Inadditiontothese views, other views canbe created, displayingthe modeldierentlyorfocusingondierentpartsofthemodel. Therearetwotypesofviewsusedinthisregard:Sections: Sectionsarecreatedfromwithina2D-viewtocreateanother2D-view. Theuser is abletospecifytheviewareaof thesectionbydeningthedirectionandtheviewrangeof thesection. Sectionsaregreat when the user needs to evaluate objects from a certain angle (oftenperpendicularly),andcancut througha modelinorder to view objectscrosssections. Sectionviewsdisplayassectionrepresentationsininter-sectingviews.Callouts: Callouts isolate a specic portion of the model to show a greaterlevel of detail. The usage of callouts prevents the model itself displaying26toomuchdetail,makingithardandcumbersometoworkwith.4.2.3 LevelsBefore startingthe modelingitself, it is useful toanalyze the constructiondocuments and identify important elevations at which levels should be placed.Levels are reference planes visible in the elevation views as well as sections andcallouts created parallel to the vertical plane. Objects are often required to beattached to specied base and/or top levels. It is possible to include osets toobjects base and/or top levels, and sometimes there is a need to have anotherobject as a base or top. However, creating levels as references is a good idea, asit makes keeping track of where the objects are supposed to be situated easier.Furthermore, havingstablereferencesincreasesthemodelsrobustness, andreducestheprobabilityofunexpectederrorsduetoalteringofobjects.Figure11: Elevationviewincludinglevelsandthreecolumnsattachedtothedierentlevels4.2.4 ReferencePlanesReferenceplanesare, asthenameindicates, aplaneusedasareferenceforobjects. Theycanonlybeplacedin2D-viewsasplanesparallel totheviewdirectionofthat2D-view,however,aslongastheyareparallel,thereferenceplanesmaybeattributedanyorientation. Furthermore, iftheviewdirectionisdenedasthex-directionof theplane, andthenormal vectordenesthez-directionoftheplane,theusercanalsoaltertheorientationoftheplaneinaviewwithaviewdirectioninthey-direction. Thus, areferenceplanecaninpracticebegivenanyorientationin3D. Ingure12tworeferenceplanesincludingdimensionsareplacedinthesameelevationsviewasingure11.27Figure12: Referenceplanes4.3 TheBridgeThe bridge modeled as a framework for the evaluation of BIM in bridge designisathreespanrailroadbridgewithaslightslope(1%)andcurvatureinthehorizontal plane(r=600m). Themiddlespanruns over aroadandpiers 2and3arethusskewedcomparedtopiers1and4. Thefollowingdrawingsarereceived from Norconsult as a part of the basis for the modeling. They are notmadeinRevit.Figure13: Elevationviewofthebridge28Figure14: PlanviewofthebridgeFigure15: Crosssectionofthebridge4.4 ImportingthecenterlinefromCivil3DintoRevitTheoriginofthebridgemodelisoftentheroadcenterlinefromaroadmodelina.dwgleformat. Acorrectlygeometricallyandtopographicallyplacedcenterlineprovides arobust basis for thebridgemodel, whichis extremelyimportant as it sets thetonefor theentiredesign. Civil 3Dis atool wellequippedfordealingwithroadmodels, whichareimportedtoRevitforfur-ther use. The road model received as a basis for the modeling of the bridge in29this thesis consisted of multiple layers which comprised the whole road model.Oneof theselayerscontainedthecenterline. Thetaskof isolatingthislayerforimporttoRevitisfairlysimpleaslongastheusermakessuretheunitsarespeciedtobethesameinCivil3DandRevit. Whenextractingthecen-terlinefromtheroadmodel onehastoeitheraltertheunitswithintheroadmodel inCivil 3D, orspecifytherightunitsduringtheprocessofimportingthecenterlineintoRevit. Thecenterlineincludedintheroadmodelreceivedwas, incontrasttotheonereceivedintheproject2.5, acontinuouslineseg-ment. However, Revitdidnotrespondwell totheverylargecoordinatesoftheroadmodel. NorconsultusesthemapprojectionEUREF89NTM[14],whichensuresthattheroadmodel iscorrectlysituatedgeographically. ThisresultedinanX-value(NorthpositionintheRevitgrid)of 6679346005mm.RevittruncatesimportedcoordinatevalueshigherthanE9,whichresultedinanX-valueof about 1000kmwhenacquiringthecenterlines coordinates inRevit.Furthermore, thelargecoordinatescreatedinaccuraciesinthecenterlineobject inRevit. Whenmovingthe line tothe origininRevit, it behavedunpredictably, not lettingitself attachcompletelytotheoriginbut insteadshiftingfromeither sideof theoriginwhenzoominginandout about theorigin.Figure16: Perturbationatrstposition30Figure17: PerturbationwhenzoomedinSpecifyingthecorrectlargecoordinatesatapointinthemodel afterim-porting the centerline worked properly, yet it is desirable to be able to acquirelarge coordinates directly from the imported model without manually alteringthemafterimport. However, theproblemwiththecenterlinesbehaviorre-mained. After some troubleshooting, it was realized that the problem could becircumventedbyalteringthecoordinatesintheroadmodelinCivil3Dto0,0beforeimportingthecenterlinetoRevitandspecifyingthecoordinatesthere.Thisoperationremovedtheperturbationproblemof thecenterlineinRevit.Thus,thecenterlinecouldbecorrectlyplacedwiththerightgeographicalpo-sition.31Figure18: CorrectpositionThe rst modeling step included creating the bridge deck prole and usingthisproleasthefoundationforabeamcrosssectionwhichinturnwasusedto create a new beam family. The beam family was then used to insert a beamobject of that familyalongthecenterline, simplybyclickingthecenterlinewhilehavingthebeamselected. ThecenterlineimportedfromCivil 3Dwassomewhat longer than the bridge itself, and known elevations along the center-linewereusedtoidentifythecorrectstartandendpointofthebridgeinthemodel. A 2D .dwg le containing the outlining of the bridge including founda-tions, columns, coordinatesetc. wasthenimportedtothemodel andmovedtothecorrectspotforfurtherdetailingofthebridge. Thecoordinatesofthisledidnotmatchthecenterlinescoordinates. Thiswascausedbyslightin-accuracies attheends ofthecenterlinewhencreatingthebridge beam,whichresultedinthebeamstartingwithanoset of approximately15mmintheX-directionand70mmintheY-direction(seegure19)fromthestartofthecenterline. Thereasonfor this was probablyaslightlywrongshapeof thecenterline.32Figure19: Wrongcoordinates,N=X,=YAlthough this eect is not desirable, the problem was easily xed by simplyalteringthecoordinatesof aknownpointinthemodel totheonesspeciedinthe2D-le. Intheenditwasconcludedthattheprocessofimportingthebridge centerline was successful, despite the hiccups encounteredalongtheway.4.5 ModelingthebridgeFigure20showstheterminologyofbridgecomponentsusedinthisthesis.Figure20: BridgeTerminology334.5.1 BridgedeckandabutmentbackwallsAsmentionedin4.4, thebridgedeckwascreatedasabeamalongthecen-terline. Aftersomeconsideration, theabutmentbackwallswerecreatedthesameway. Toseparatethebridgedeckfromtheabutmentbackwalls, refer-enceplaneswereusedatthelocationswherethebridgedeckendedandthebackwallsstartedandended. Thesereferenceplanesdenedthepositionsofverticalcutssuchthattheextentsofthevisibilityobjectswerecontainedbythe reference planes. The objects themselves still had the original extents, butwiththeexceptionof somebehavior issues (e.g. 5.3), theyrespondedas ifthey had the correct extents. By creating reference planes one obtained a waytocontroltheextentsoftheobjectswithoutalteringthemdirectly,andtheycouldbeusedasreferencesforotherobjectstoattachtoorbedimensionedwithrespect to. Another reasonto modelthe bridge deck andabutment backwallsinthiswaywasthattheendsweresupposedtobevertical. If verticalreferenceplaneswerenotused, theobjectswouldhaveaslightslopeattheendsrelativetotheverticalplane.Figure21: Referenceplanescuttingthebridgedeckandabutmentbackwall4.5.2 ColumnsandFoundationsMostlystandardobjectswereusedinthemodelingofthecolumnsandfoun-dations. Anewcolumnfamilywasmadetomodelthecolumnsatpiers1and4(i.e. thepiersateachendofthebridge), however, thisfamilywasquickly34establishable. Whatposedthemostproblemsweretheconnectionsbetweenthe columns and the bridge deck. One had the option of creating a new columnfamilywiththeconnectionattached,anewfamilyincludingonlytheconnec-tion, ortocreatetheconnectionsthroughobjectsalreadyavailable. Inthisbridge model, the connections were simply modeled as a new family consistingoftwosquarecubes,seeingasacorrectrepresentationwasnotimportantforthe model as a whole. If the connections were to be modeled properly, a moredetailedfamilywouldbeneededtodisplaytheconnection. Thequestionofwhetherornottoincludetheconnectioninacolumnfamilywouldremain.The connection family in this bridge model was not included in a column fam-ily. Ifitwasincluded, onewouldhavetocustomizethefamilysuchthatthetop elevation of the column could be specied while at the same time leave theconnection free to be attached to the bridge deck. This is possible; however bylettingtheconnectionoutofthecolumnfamily, theextraworkwasavoided.Additionally, by modeling the connection separately, it could be added to newcolumnsinaquickerfashionifneeded.Figure22: Connectionbetweenthebridgedeckandacolumn4.5.3 AbutmentwingwallsTherearefour wingwalls at eachendof thebridge, reachingout about 2meters from the abutment back walls. They were all created as individual wallobjectswithoutadirectconnectiontothecenterline,butinsteadattachedtothereferenceplanedeningtheendof theabutment backwall. BasedonthedrawingsreceivedfromNorconsult, thewingwallscurvealongwiththecenterlineofthebridgeandaresupposedtocreateasmoothtransitionfromthebackwall. Thiscausedsomemodelingissues:If awall objectcurves, onecannotmakeuseof theeditproletool,which lets the user customize the contour of the wall object as seen from35an elevation view (e.g. 21). The shape then needs to be created throughthe use of void forms. Void forms are separate geometrical objects hiddenintheviewunless selected. Bylettingavoidformintersect anotherobject, onecanchoosetocuttheareaof intersectionfromtheobject.Thisprocessismorecumbersomethantheeditproleapproach,anditishardertocreateexactgeometry.Thecurvedwall objects didnot always attachtothereferenceplaneproperly,resultinginagapbetweenthebackwallandthewingwall.Usingstraight wall segments solvedthese problems, andalsomade themodelmoreexible. Thequestioniswhetherthisisanacceptablesimplica-tion. Theeectof thecurvatureof anobjectwithalengthof 2metersandaradiusofabout600metersisverysmall. However, formworkforthewingwallsisusuallycreatedasanextensionofthebridgedeck,suchthatitisac-tuallyeasiertocontinuethecurvature. Also, theaestheticsofthebridgeareimprovedbykeepingthewingwallscurved. Theuserhastheoptionofcreat-ingacommentdescribingthatthewallsaresupposedtocurve, butitisnotpreferable to resort to that solution as the model should be as visually correctaspossible. Thecreationofthecorrectgeometryatthetopofthewingwallsinorder toobtainasmoothtransitionfromthebackwall was particularlydicult. Aswellashavingaslopealongthelengthofthebridge, thebridgedeckandabutmentbackwallshaveaslopeatthetopinthecrosssectionaldirection. Regardlessofhowthewallsweremodeled,voidformswereneededto display this correctly. These void forms were not attached to the wing wallsorthebridge,renderingtheminexible.4.5.4 TransitionPlateThe transitionplate was perhaps the easiest component tomodel. It wascreated by adding a wall object with a width of 3200mm, which was the widthof the transition plate, to the basic wall family. The wall object could then beplacedatthecorrectposition,andwiththeuseoftheeditproletool(see4.5.3), onewasabletoprovidethecorrectgeometryof thetransitionplate.The ledge on which the transition plate was to be placed was modeled using anIn-PlaceMasscreatedbythesweeptool. Thesweeptoolletstheuserpickordenea3Dpathfora2Dproletofollow, thuscreatinga3Dshape. Bydening the bottom edge of the transition plate situated next to the abutmentbackwall asthepath, andcreatingtheappropriateprole, onewasabletoeasilymodeltheledgeobject.36Figure23: Transitionplateandledge4.6 ImportingthemodeltoRobotInitially, structural analysis was meant to be done in Robot based on the Revitmodel. Based on the structural analysis, where appropriate load combinationsare included, cross section dimensions and reinforcement need should be deter-mined. StandardobjectsinRevitcausednorealtroublewhentransferringtoRobotforstructural analysis. However, whenattemptingtotransfermodelswith geometries and cross sections not specied as standard objects in the Re-vitlibrary,dicultiesarose. GeometrieswerentdisplayedcorrectlyinRobotandanalyticallinesusedtoperformcalculationshadtobedenedmanually.Whenimportingthebridgemodel toRobot, awindowappearedwheresec-tionswhichwerenotdenedshouldbespecied(gure24). Onlystandardsectionswereavailableforselection, thusthesectionscreatedfortheobjectsusedinRevitcouldnotbeused.37Figure24: ProleselectionwhentransferringthemodeltoRobotTheconsequenceof this was that themodel inRobot was left withoutsectionsfortheuserdenedobjects(gure25), whichinturnrenderedthemodeluselessforstructuralanalysis(gure26).Figure25: ThemodelinRobot38Figure26: SectionnotdenederrorwhenattemptingtoanalyzethemodelAfterattemptingdierentapproachesandconsultationwithFocusSoft-ware, theconclusionwasthatfocusingonmakingamodel compatiblewithRobot would be too demanding. Especially taking into consideration the workneededtoassess modelinganddocumentationinRevit wouldalsobetimeconsuming. Thus, thedimensionsof thebridgeaswell asthereinforcementincludedinthebridgemodel werenotanalyzedinRobot, andthereinforce-mentwasplacedsolelyaccordingto2DdrawingsmadebyNorconsultduringtheirdesignprocess(see2.2).5 DesignChangesAnimportant aspect of BIMis the relations betweenobjects; bydeningconnections andconstraints, objects behaveinacertainwaywhenalteringobjects they are related to. Which objects are related and how the relationshipsare dened inuences the model greatly when modifying the model. In a bridgeprojecttherewillbechangesthroughoutthedesign,andthusaneedtomakechangesinthemodel. Ecientchangemanagementisahighlyappreciatedfeatureinengineeringprojects. Acentral questionishowwell Revitisableto deal with changes. Are the objects related to the change exible enough tobehave appropriately, do they behave incorrectly, do they need to be adjustedordotheyneedtoberecreatedaltogether?Is Revit exible enough, and how does dierent modeling approaches aecttheobjects responsetothechanges? Theideal situationwouldbehavingamodel where all the objects behaved perfectly to every change according to theuserspreferences. Thisisnotpossible, bothbecauseoflackingconstrainingpossibilitiesandthefactthatwhileconstrainingtheobjectstobehavecor-rectlyforonechange,theverysameconstraintmaypreventtheobjectsfrombehavingcorrectlyforanotherchange.Furthermore, there are almost always several ways to perform a task/createthegeometryofamodel,andhowthemodelbehaveswhenchangesaremade39mayvarydependingonmodelingchoicesmadebeforethestageinwhichtheuser performs the changes. Thus, in order to achieve a exible model, the userneedstokeepinmindthemostprobablechangeswhilemodeling. InRevit,this is usually approached by attaching objects to either levels, reference planesor to each other. If done correctly, the result is exible objects that respond tosome of the foreseen changes appropriately. This becomes increasingly dicultwhendealingwithnon-standardgeometry, especiallycurvedgeometry. Inorder to align objects lines or faces to each other, those objects need to be abletoaligncompletely. Whenoperatingwithcurvedlines/faces, thereareveryoften slight dierences in the orientation of the lines/faces, rendering alignmentimpossibleorcausingunwantedresults. Sometimesonehastosacricesomeof theauthenticityof themodel inorder toattainexibility, whichis notdesirable. Thequestionneededtobeaskedinthisregardishowmuchthemodelcandeviatefromthecorrectgeometrywhilestillbeingvalidasabasisfortheactualconstruction.Revit mayparameterizeobjects andcreatesmart interplaybetweenob-jects, but this does not meanadjustments canalways be made easilyandautomatically. Onealsohastoconsiderwhetherornotitisappropriatetomodel for automaticity in each case, since it often requires a lot of time. How-ever, once the changes have been made, the model is updated in all the views inthe project, removing the cumbersome process of redesigning the model wher-everthechangehaveaneect. Combinedwiththefactthatmaterial usageandotherusefulinformationareautomaticallyupdatedandcanbeextractedfrom the model, this provides a great advantage compared to traditional designmethodsinwhich3Dand2Dviewsarecreatedseparately.Thisthesisincludesthetestingofthefollowingdesignchanges:1. Length2. Position3. Slope4. Radius5. Depthofthepiers6. OrientationofthepiersFor eachof thedesignchanges onehas thepossibilityof reworkingthecenterlineinCivil3DbeforeimportingitintoRevityetagainandcreatethebridgedeckbeamalongthis line. Thesurroundingobjects will needtobereattached, butinsomecasesthisprovideslessworkthancustomizingthemtoanalteredbridgedeckwithinRevit.405.1 LengthA change in the bridge length means a change in the bridge deck and abutmentbackwallsobjects(1), apositional androtational changeof thepiers(2)andtheabutmentwingwalls(3).1. As mentionedin4.5.1, boththe bridge deckandthe abutment backwallswerecreatedasbeamswiththebridgecenterlineasareference,and cut at the endpoints using reference planes, removing the extents ofthebridgebeyondthereferenceplanes. Thesereferenceplanescanbemovedandrotated,resultinginalonger/shorterbridgedeck.2. The piers can be locked in a position relative to a reference plane, makingtheuser abletoonlychangethepositionof thereferenceplanewhenmoving the piers and foundations. However, rotating this reference planedidnot givetheintendedresults, andsimplyselectingall theobjectsconnectedtothepierandrotatingthemmightbeabetteridea.3. Howtheabutmentwingwallsbehavedasaresultofachangeinbridgelengthdependedonhowtheyweremodeled. Eachwingwallwasabout2000mmlong, andwas supposedtocurvealongwiththebridgecen-terline. Theywereabletobealignedwithandlockedtothereferenceplanecuttingthebridgedeck. However, whenmovingorrotatingthatreference plane, the constraints turned invalid because of the slight anglecreatedbetweenthewallsandthereferenceplane.Ingure27thetopandthebottomwingwall werecreatedwithoutcur-vaturewhereasthemiddletwowere. All of thewingwallsarealignedwiththereference planeintherststate. Boththetopandthebottomwingwallsweresettohavealengthof2000mm,andthetopwingwallwasconstrainedangularly to always remain perpendicular to the reference plane. The referenceplanewasrstmovedinordertoelongatethebridgebeforerotated.41Figure27: WingwallsandreferenceplaneatthelowendofthebridgeWhenmovingthereferenceplanethetopandbottomwingwall behavedappropriately,whiletheconstraintsofthecurvedmiddlewingwallswerevio-lated.42Figure28: MovingthereferenceplaneIf the wing walls were created without curvature, aligned with the referenceplaneandconstrainedangularly, theywereabletofollowthereferenceplaneappropriatelybothwhenmovedandrotated. Thiscanbeseeningure29;aftertherotation, onlythetopwingwall, whichwasconstrainedangularly,followedtherotationof thereferenceplane. Therotationisexaggeratedinordertodisplaytheeects. Aninterestingfeaturediscoveredinthisregardwas the fact that if only the top wing wall was constrained angularly, the centerofrotationforthereferenceplaneusedbyRevitwasnottheonespeciedbythe user. The reason for this remains unclear, but it is not a desirable feature.However, if both the top and the bottom wing wall were constrained, the centerofrotationspeciedcoincidedwiththeoneusedbyRevit.43Figure29: Rotatingthereferenceplane. ThetopwingwallisrotatedAgaintheoptionof selectingtheobjectsandmovingthemseparatelyisavailable.5.2 PositionIntuitively, onemightconsiderlockingthebridgeinpositionrelativetothebridge centerline le imported from Civil 3D, and use the centerline to move theentirebridge. However,afterthebridgedeckwascreatedwiththecenterlineas areference, there was nowayof constrainingthe bridge decktofollowthecenterline. Asaneect, theimportedcenterlinehadserveditspurposeandwasobsoleteintermsof usageinfurthermodelingprocesses. Awayofsomewhat constraining the bridge deck to the centerline was to create a modelline(alineonlyavailabletobecreatedinthehorizontal andvertical planewhichisvisibleinallviewsandcanbeusedasareferenceforotherobjects)andconstrainingpartsof thebridgetoit. Themainproblemwiththiswasthefactthatonecouldnotalignandlockthebridgedecksactualcenterlinewiththemodel linesincethebridgedeckhadaslope. Thus, theeasiestandmostlogical waytochangethepositionorrotationof thecenterlinewastosimplyselectthewholebridgewithallofitscomponentsandmove/rotateit.In gures 30, 31 and 32, the blue and yellow lines are the ones included in the442D underlay le showing the outlining of the bridge, while the bridge itself hasblacklines.Figure30: Thebridgeatitsoriginalposition45Figure31: ThebridgemovednorthalongtheroadFigure32: Thebridgerotatedcounter-clockwiseInthiscasetwodimensionsbecameinvalid, meaningoneormoreof therules whichthe dimensions needtofollowwere violatedas aresult of thechange. Theuserisabletoviewwhichdimensionsthathavebecomeinvalid46anddecidewhetherornottogothroughwiththeoperation(i.e. deletingthedimensions). Often,thedimensionsarenotcriticaltothemodel,andcanberecreatedifsodesired.5.3 SlopeAchange inthe slope of the bridge results inanelevationchange at thehighendof thebridge. Theslopechangeof thebridgedeckitself canbedonebyalteringtheelevationosetof thehighend, whichisasimpletask.Theprobleminthiscontextwasthatevenifthebridgedecksvisibilitywasconstrainedbythevertical cutsattheends, theobjectitself still remainedbeyondthesecuts. Theresultwasthattheosetvalueschosenwererelatedto the ends of the object, not the ends of the bridge deck as it was seen in themodel window. Thus, thebridgedeckroseatthelowendaswell. Ingure33thebluelinerepresentsthelengthofthebridgedeckobject, whichiscutwheretheabutmentbackwallstarts.Figure33: ThelowendofthebridgeroseApragmaticsolutiontothisproblemistocalculatetheosetswhichwillcreatethedesiredslopeof theportionof bridgedeckbetweenthetwocuts.Anotheristoshortenthebridgedeckobjecttoonlyslightlybeyondthecutplanes,whichwillmakethedierenceinosetoftheendsofthebridgedeckandthebridgedeckobjectalmostnegligible(theosetcanbechosentobeslightlylarger/smallerthantheactualosettocircumventthisproblem).Theconnectedobjectshavetobealteredaswell. Dependingonhowtheyare modeled and if they too have a slope, they might have to adopt the slope ofthe bridge deck. For the wing walls this means a change in prole is needed for47eachwingwall. Theabutmentbackwallswill needtohavealteredelevationosets at their ends too. If objects are connected to certain levels or referenceplanes, thesecanbechangedtoadapttothechangeinelevationofthehighend. Since the abutment back walls were modeled the same way as the bridgedeck,theextentsoftheabutmentbackwallobjectsneededtobesetequaltotheextentof thebridgedeckobjectforcoherencybetweenthebridgedeckandtheabutmentbackwalls. Ifnot,slightinaccuracieswereseenasaresultof thisdierence. Adrawbackbythisapproachwasthatthetwoabutmentbackwall objectshadthesameextents, thusoverlapping, whichmightcausecomplicationswheninteractingwithobjectsatalaterstage. Ingure34theinaccuracyeectispresented; theleftsideof thebackwall isslightlyhigherthanthebridgedeckattheinterfacebetweenthem,whereastherightsideisslightlylower.Figure34: InaccuracyattheabutmentbackwallsThe operation of changing the slope of the centerline might have been donemore eciently by changing the centerline in Civil 3D. This would remove theneedforosetchangesoftheobjectsinRevit.5.4 RadiusThisisalsoacasewherechangingthecenterlineinCivil3Dcouldbeagoodchoice. Theabutment wingwalls will onlyneedtoberotatedinorder toremainperpendiculartotheendsof theabutmentbackwalls, andthepierswill needtobe reworkedand/or movedslightlynomatter howthe bridge48deckattainsitsnewradius. Another approachistocreateamodel lineinthehorizontalplanewiththenewradiusasareferenceforanewbridgedeckbeam, beforesettingthecorrectheightosetsattheendsofthebridgedeckbeam. Thisisaveryquickoperationandgivesthesameresultasimportingthecenterlineagain. Iftheheightateachendofthebridgedeckremainsthesame, theslopealongthecenterlinewill receiveaminorchange. Dependingonthedesiredslope,theheightsmightneedtobechangedaswell.5.5 DepthofthepiersThisisanoperationveryeasilydoneinRevit,aslongastheuserhasdenedsuitablelevelsatwhichthepierscanspecifytheirbase, andthetopof thecolumnsareattachedtoeitheralevel orthebridgedeckwiththeuseofthetoolAttachTop/Base. TheAttachTop/Basetoolconstrainsanobjectstop/bottomtoanotherobject, suchthatiftheattachedobjectfollowsiftheobjectitsattachedtomoves. Theonlychangeneededtobedoneistosettheelevationofthebaselevelsappropriately,andthepierswillautomaticallyextend/shorten to adapt to the change. The foundation, which is also attachedtothelevel, will lowersuchthatitstopisalignedwiththelevel. Theusercanalsospecifyosetsfromthetopandbaselevels. Anotheraspectworthmentioningisthefactthatif thereisaterraingeometrywithinthemodel,piers can be lowered to the terrain with the Lower To Terrain tool, which isbasicallyaclickonabutton.Figure35: Piersatthehighendbeforethechangeindepth49Figure36: PierswithchangeddepthasdisplayedintheeldElevationatthetopleftcorner5.6 OrientationofthepiersAssumingthesuperstructureremainsthesame, theeasiestwaytodothisistosimplyrotateandmovethegivenpiertoitsdesiredorientation. Thebestway to do this is toselectthe components includedinthe pier inaplanview.When moving the pier, the columns will also move, and the bridge deck abovethecolumnswill mostlikelyhaveadierentelevation. If apierisattachedtothebridgedeckwiththeAttachTop/Basetool,thecolumnswillstillbeattachedtothebridgedeckafter thepier ismovedaslongasthecolumnsareabletointersect withthebridgedeck(i.e. as longas thecolumns arestill underneaththebridgedeck). Therelationshipbetweentheobjectswillstaythesamewithinthepieritselfbecausetheobjectsareallrotated/movedtogether. However, certainaspectsoftherelationsbetweenthepierandthebridgedeckmightchangeandhavetobedealtwithmanually. Dimensionsusedtoshowdistances, anglesetc. betweenobjectsinthepierandcertainpartsofthebridgedeckissuchacategory.5.7 SummaryofdesignchangesAfter testing the dierent design changes, the following conclusions were made:It is useful toconsider the potential changes whenmodeling. If theuser models smartly, cumbersomemanual operations maybeavoided.However, whenchangeswhichaectalargeportionof themodel needtobedone,itishardtomakealltheobjectsbehaveappropriately.50Goodmodelingsolutions taketimetoestablish, but it maybeworthitinthelongrun. Theknowledgegainedcanbetransferredtoothersituationsandprojects.Crudesolutionslikesimplymovingandrotatingobjectsmanuallyareoften just as good as creating rules for the objects to follow given a certainchange, especiallyif there are fewobjects that needtobe manuallyaltered.Inthecaseofanewslopeandanewradius, returningtoCivil3Dandmodifythe centerline there couldbe agoodidea. After the center-linehasbeenplacedandgiventhecorrecttopographicalplacement,thebridgedeckandabutmentbackwallsarethenreestablishedbysimplyclicking the objects onto the line, and new cuts to these objects are rela-tivelyquicklymade. Thisensuresthecenterlinepositioniscorrect,andthesameoperationswouldhavetobemadetothesurroundingobjectsregardlessofwhetherthechangewasmadethroughCivil 3DorinRe-vit. Asmentionedin3.2, SundtConstructionusuallymakesthewholebridge superstructure in Civil 3D. If modeled that way most of the designchangeswouldhavetobedoneinCivil3D.Evenif someof thedesignchangesmayrequireasmuchorevenmorework in Revit than they presently require in programs like Microstation,the benet from the automatic update of the changed objects in all viewsofthemodelmakestheworkloadlessinalmostanycase.6 ReinforcementofthebridgeAs mentionedinsection4.6, the reinforcement modelingwas done onthebasisof Norconsults2Drebardrawings, whichinturnweremadebasedonstructural analysis performed by Norconsult (section 2.2). Revit provides goodfunctionalityforreinforcementofconcretestructures. Inthecaseofstandardobjects theuser is abletoquicklyestablishthebasicreinforcement neededinanyconcreteobjectthrougheithertheareareinforcementtools(foroors,wallsorfoundations) orRevitsreinforcementextension(for moststandardobjects). For additional reinforcement and reinforcement of other objects,theuserhastoutilizetherebartool, whichoersnumerousrebarshapesaswellasthepossibilitytosketcharebarshapeformanual insertionofrebarinanobject. These tools can be combined; the user may use the area reinforcementtool or theextensiontoplacethebasicrebars intheobject, beforeaddingspecicrebarswiththerebartool. Inthecaseofnon-standardgeometry,therebar tool is the only applicable of these tools. Furthermore, when reinforcinga bridge structure which requires a vast amount of rebars, one will always have51theneedtoaddseveral rebarsinadditiontotheonesplacedwiththeotherreinforcementtools.6.1 TheareareinforcementtoolThisisaneattoolforquickreinforcementofstandardoors,wallsandfoun-dationslabs. Withasimpleclickonthetool Revitautomaticallypopulatestheselectedoor, wall orfoundationslabwithrebars, customizablethroughthepropertiespalette4.1. Ingure37, aoorreinforcedwiththearearein-forcementtoolisdisplayed. Thetoolcreatesrebarsinbothdirectionsatthetopandbottomof theobject. Inthepropertiespalettetotheleft, theusercan specify rebar diameter, hooks at the ends, major and minor rebar directionandspacingbetweenrebarsinthefourrebarsets. Atag, whichcanbeseenin the plan view, is automatically included (38) and will change if changes aremadetotherebarsintheareareinforcement.Figure37: Areareinforcementofaoor52Figure38: Areareinforcementtag6.2 RevitreinforcementextensionTheRevitreinforcementextensiongivestheusertheopportunitytoreinforcemorethanonlyoors, wallsandfoundationslabs. Fortheobjectsthatareable to be reinforced with the area reinforcement tool, the extension provides atleast the same functionality as the area reinforcement tool. An example of thistoolisshowningure39,whereabeamhasbeenselectedforreinforcement.53Figure39: Revitreinforcementextension,beamAlotof options, explainedwithgures, areavailableforquickestablish-mentofrebars. Theuserisabletoenterthismenuagainandmakechangestothereinforcement.6.3 TherebartoolInbridgedesignandespeciallywhendealingwithcastin-placeconcrete, thegeometryis most oftennon-standardandtherebar tool is byfar themostvaluableofthereinforcementtools. Thus,amajorfocusofthisthesiswillbeonthefunctionalityof thistool. Figure40showsthepanelsprovidedafterselectingtherebartool, wherethegeometryof theselectedrebarshapeandthespacingbetweentherebarsarechosen. RulesfortheorientationandthespacingoftherebarsareeasilymodiedthroughtheRebarSetmenu.54Figure40: RebaroptionsToplacerebars inanobject, theuser has tocreateasectionthat cutsthroughtheobject inwhichtherebars shouldbeinserted. Theplanethesectioninwhichtherebarswerecreateddenesrepresentstheworkplanefortherebarsinsertedwhileinthatsection. Therebarscanbeinsertedparallelto that work plane, parallel to the cover, or perpendicular to the cover (again,seegure40). Several sectionsindierentdirectionsandpositionsareoftenneededinordertoreinforceanobject,andtheuserneedstobecarefulwherethesectionsareplacedrelatedtorebarsalreadyplacedinordertoseetheminthatsection.6.4 ReinforcementofthesubstructureThesubstructureofthebridgeisnotverygeometricallychallenging,andtherebarsandfunctionalityoeredbytherebartoolweresucientformodelingtherebarsofthesubstructure. Beforeplacingrebars, theusercanmovetherebarstobeinsertedaroundtoget apreviewof wheretheywill beplacedwhen clicking them out in the model window. The rebars will snap to dierentlocationsintheconcreteobjectastheusermovesthemaround. ThecorrectamountandspacingbetweentherebarsarespeciedthroughtheRebarSetMenu, andthedirectionofthespacingisdeterminedbytheorientationandshapeof therebaroriginallyplaced(40). Theextentsof therebarsandtherebarsetscanbecustomizedinthemodelwindowaftercreationwiththeuseof shape handles, (blue triangles in gure 41) on top of the basic tools availablefor moving and altering an object (move, drag, rotate or altering of dimensionsinthepropertiespalette).55Figure41: RebarwithshapehandlesWiththediametersandlengthsoftherebarsshownproperly, theuserisabletoeectivelymovetherebarsaroundandtthemnexttootherrebarsappropriately. Whenrebarsareinsertedusingoneview,thoserebarsarealsovisible in the other views given the view range spans the area where the rebarsare situated. The user also has the possibility of changing the position, length,spacing etc. oftherebars fromother views,where the needfor changes mightbemoreapparent. If therebars areselectedinaviewbeforeswitchingtoanotherview,therebarsarestilldisplayedasselectedinthesecondview.56Figure42: Rebars,elevationviewFigure43: Rebars,frontviewTherebarsarealsoincludedinthe3Dview, wheretheusercanzoominand inspect the very details of the reinforcement to verify the correct positionofeverybar.57Figure44: Rebars,3DviewThis is very useful, not only to spot errors that would be dicult to discoverbylookingat2D-drawings;a3Dviewoftherebarsprovidesagoodoverview,which makes the people involved in the reinforcement work quickly get an ideaofthereinforcementplacement.Rebars bent in one plane are easily modeled with the rebar tool. The onlyreal issuewiththereinforcementofthesubstructurewastherebarsetsthatneededtocurve. Therebarsanchoredinthefoundationslabsandgoingupintothecolumns,followingthecurvatureofthecolumnsweresuchrebarsets(NumbersK24328andK24329ingure45).Figure45: RebarsanchoredinthefoundationThese rebars could not be modeled with the use of the Rebar Tool and theRebar Set Menu, as the spacing cannot follow a curve. Revit has a tool calledArrayGroupwhichissuitableforthisoperation. Bycreatingabarattheright position, the user can then click the Array Group tool, choose a centerofrotationaroundwhichrebarsaretobeplaced. Thentheuserspeciesthe58spanof therebar set andthenumber of rebars inthegroup, creatingtheappropriatedistancebetweentherebars. Figure46showsthearraygroupofrebarsfromatopviewofthecolumn.Figure46: RebarsfollowingtheshapeofthecolumnThenumberof rebarsaswell asthespanrangecanbemodiedatanytime. Eachrebarintherebargroupcanalsobemodiedseparately. Somecustomizationisneededinordertogettherightspacingbetweentherebars,asthespacingdependsonthespanrangeandnumberorrebars. Theprocesswould have been made easier by allowing the user to select the spacing betweenthe objects in the array group, which at this time has to be determined throughextracalculations.6.4.1 CoverDistanceIn Revit, the rebar cover (the distance from the edges of the concrete elementsthat denes aportioninwhichthereshouldbenorebar) is denedintheconcreteobjectitself, andtherebarcoverareawill beoutlinedwithagreendashedlineoncearebarobjectisselected,orarebarobjectistobecreated.Upon creation, the rebar objects snap to the dashed line and cannot be placedinawayresultinginaviolationoftherebarcoverdistance. However, whencreated, the user is able to move the rebars around regardless of the rebar cover,yettheobjectsstill snaptothedashedlinefortheusersconvenience. Onething to note about the rebar cover distance is that the rebar objects in Revit59donot includetheribs, thus onlythenominal diameter denes therebarsextents. InNorway, therebarsarenamedaftertheirnominal diameter, yettherealextentoftherebaristakenintoconsiderationwheninsertingrebars.Figure 47 shows the nominal diameter and the full diameter including the ribs.Thexinkxrepresentsthenominal diameter, andthenumberbelowistherealextentoftherebar.Figure47: NominaldiameterandrealextentsofrebarsWhen inserting rebars snapped to the rebar cover, they will be placed with adistance according to the nominal diameter, in practice resulting in a violationof therebarcoverdistance. Ingure48arebarwithanominal diameterof16mm is snapped to the rebar cover, which is set to be 75mm. Revit calculatesthe placement of the center of the rebar to be 83mm (75mm +16mm2) from theedgeoftheconcreteobject,whenitinfactshouldbe85mm(75mm+20mm2).Figure48: FalserebarcoverdistanceThe user is able to manually change the distance of the rebars after insertioninthemodel, butthisiscumbersome. Therebarcoverdistancecanonlybespecied to certain preset values in the properties palette (every 5mm rangingfrom10-100mm), thusonisnotabletospecifythesevaluesaccordinglyfortheconcreteobject. Also,therebarcoverdistanceneedstobedierentforarebarwithanominaldiameterof16andarebarwithanominaldiameterof20. It is possible to edit the diameter of the rebar objects in order to representthecorrectreal extentinthemodel. However, bydoingthis, thecalculationof theamountof rebarwill befalse. Revitkeepstrackof eachrebarinthe60model,andtheuserisabletoquicklyestablishasheetofthematerialusage,reinforcementareaof thebarsetc., whichisareallyuseful tool andrendersthetediousmanual calculationobsolete. If therebarareaisnotrepresentedcorrectly,thecalculationswillnotbecorrect.6.5 RebarDrawingsEventhoughRevit has therebar includedinthemodel, andthefact thattherebarcanbeinspectedinboth2Dand3Dviews,rebardrawingsarestillusefulwhengoingintothedetailsofthereinforcementwork. RebardrawingsinRevitaremadein2Dviews, usuallyinsectionscreatedforthatspecicpurpose. Wheninthesection,theusermakesuseofthetagtoolandsimplyclickstherebarsthat shouldbetagged. Inadditiontothetags, Revit hasseveral detail components and symbols which need to be used in the drawings.Regions of reinforcement canbe representedbydetail regions displayedinchosenpatterns. Textcanalsobeaddedifneeded. Rebardrawingsaremadein a specic way which people are familiar with, thus the rebar drawings madeinRevitshouldaimtofollowthesamestyleof annotation. However, sinceRevit has all the rebars includedinthe model, andthe rebars are actualobjectsandnotonlylinesonasheet,oneshouldalsobeawareofdierencesand look for opportunities to represent the drawings in a better way. In gure49, a typical rebar drawing is presented. This drawing shows the rebars in thepieratthelowendofthebridge.61Figure49: TheoriginalrebardrawingThe drawing is as clean as possible, usually only showing single rebars in therebar sets. The extents of the rebar sets are indicated by lines, and the amountof rebars in each rebar set is shown connected to the rebars that are displayedin the drawing. The region consisting of diagonal lines represents an area withverebarsetsgoingintotheplanedownwardsthroughthefoundation.All therebarscreatedareincludedinRevit, whichmeansthatthesamesectionasshowningure49will includeanabundanceof rebars, makingithardtogetanideaofwhereeachrebarissituated. Also,linesshowingwhichrebarstherebartagsarereferringtowillvirtuallybeunspottable. Figure50showsthesectioninRevitcorrespondingtothedrawingingure49.62Figure50: TopviewofthepierinRevitEvidently, inorder tocreateasensiblerebar drawing, onehas tomakesomeadjustmentstothesection. Firstly,therebartagsneedtobeplacedattherebarsinthesection. Secondly, itisdesirabletohidetherebarstaggedfromtheview, onlyshowingtheir extent withlines. This cannot bedonewiththehideelementcommand, thenormal tool usedforthisoperation,as therebar tagwill behiddenalongwiththeobject. Focus Softwarehasdevelopedseveral toolsintheirRevitAdvancedToolsextensiontoRevit,whichmakethereinforcementworkmoreecient. Oneof thosetoolsistheShow/Hide Rebar command, which hides the rebar in the view by changingthe visibility settings of the rebar without explicitly hiding the rebar using thehideelementcommand. Thus, therebartagremainsintheview, solvingthe problem. The tags do not show the extent of the rebar sets they annotate,andtheuserneedstomakeuseof rebardetail components. Therearebothtagsanddetail componentsincludedinRevit, andadditional objectscanbedownloadedfromAutodeskswebpage. FocusSoftwarehasalsomadeitsowntagsanddetailcomponentssuitablefortheconstructionbusinessinNorway,63andthesearetheobjectsusedinthisthesis. Aftersomecleanupwork, thesectionprovidesabetteroverviewofthereinforcementofthepier.Figure51: TopviewofthepierinRevit,aftercleanupandannotationThere are still some adjustments that could be made to this view; the rebarsgoing downwards from the column anchored in the foundation are all displayedin the view on the right hand side of the column. These could be displayed asdone in gure ??, and on the left hand side of the column. However, the rebarsare already created in Revit, and the procedure of representing them this wayonlyprovidesextraworkhidingthemintheviewandinsertinganadditionaldetailcomponent. Whentherebarsdonotcoincidewithotherobjectsintheviewonemightaswellkeepthemaslongasthecorrecttagisplaced. Thereareacoupleofotherthingstonoteaboutthisview. Therebarsanchoredinthefoundation, whicharesituatedattheendsof thecolumn, followingthecurvature,couldnotberepresentedwiththerebartoolalone(asdescribedin6.4). The rebar set had to be created using the Array Group tool, which hasadrawbackwithregardtotherebardrawing. Whenattemptingtotagtherebarset,therebarsweretreatedasseparate. Asaworkaround,onehasthepossibility of manually inserting a text annotating the rebar set properly. The64rebars are included in the overall schedule of rebars, such that calculations willbecorrect. Additionally,theyhavethesameschedulemark/positionnumber.Asaresult, theonlypartof themodel aectedbythisworkaroundisthisvery view, as the text will not update automatically if changes are made to therebarset. Nevertheless, thebestcasescenariowouldbethattherebartoolcould successfully represent rebar sets following a specic curve. Furthermore,thearraygroupshouldbeabletobetaggedas awhole. Theother thingrealizedthroughtaggingtherebarswasthefactthatseveralrebarsetscouldnotbetaggedtogether. Theregionrepresentedbythediagonallinesincludesve identical rebar sets. In the original rebar drawing (49), these are combinedandshownas35[516-24210]c500. Asolutionistotagall of therebarsetsindividually;howeverthereshouldbeawaytoincludealloftherebarsetsinonetag. Additionally, thespacinginRevit(51), wherethespacinglistedistheonebetweeneachrebarintherebarset,diersfromtheonedisplayedintheoriginaldrawing.6.6 RebardocumentationWhencreatingrebar, theamounts, schedulemark, lengthsetc. needtobeincludedinalistinorderforthemanufacturertoknowwhattoproduceandhowtolabeltherebarsmanufactured. ThisisveryquicklydoneinRevit. Alltherebarsusedarestoredinthedatabase,andwhencreatingalistspeciedtoshowinformationaboutrebars, thelistwill automaticallyincludeall therebars in the model. Afterwards, the user simply needs to add the appropriateelds to be shown in the list (bar diameter, bar length, total volume etc.). Theuserisabletospecifyrulesbywhichthelistissorted. FocusSoftwarehasdevelopedafunctionwhichautomaticallyassignsschedulemarkstorebars,relievingtheuserof thecumbersomeprocessof manuallyassigningschedulemarks.65Figure52: RebarlistsortedbyschedulemarkThe top row shows a problem related to the rebars created as array groupsinordertorepresentrebarsets(seesection6.4). Thegroupsarenotincludedcorrectlyintherebarlist,noraretheyassignedwithacorrectschedulemarkbyFocusSoftwaresschedulemarkfunction. Inthelistingure52, all therebars in the array group are included, with the right bar diameter and shape.However,thebarlengthandvolumeeldsareblank. Thereasonwasdiscov-eredtobethatthereweretwoarraygroups, bothhavingthesameschedulemarkbutdierentlengthsoftherebars. Whenassigningtherebarsinoneofthe array groups with a new schedule mark, the rebars were displayed correctlyintherebarlist.66Figure53: ArraygrouprebarsdisplayedcorrectlyintheRebarlistThesolutiontotheproblemwassimple, however, if theuser frequentlyneedstoresorttoarraygroupsinsteadofusingthetoolsalreadyprovidedforrebar by Revit, the result is a lot of additional work in order to both representtherebarsandkeeptrackoftheschedulemarks.Inadditiontothislist, FocusSoftwarehasdevelopedatool whichestab-lishes a rebar bending schedule showing information about the rebars includinggeometry. The rebar bending schedule automatically gathers the information,andasimpleclickonthetool generates thewholeschedule. If rebars areselected, onlythe selectedrebars are includedinthe schedule. The rebarbending schedule shown in gure 54 included 60 dierent schedule marks, andwascreatedwithinseconds. Thereductionintheamountofworkcomparedtotraditionalmethods,wherethiswouldhavetobedonemanually,ishuge.67Figure54: Excerptofarebarbendingschedule6.7 ReinforcementofthebridgedeckA major problemwiththe bridgedeckreinforcement isthe fact that thepathwhichasetofrebarsfollowcannotcurve. Severalrebarsweresupposedtobeperpendiculartothecenterlineof thebridgewithaxedspacingalongthecenterline,thuscurvingalongthecenterline. Rebarcreatedinacrosssectionperpendiculartothecenterlineatonelocationhavetherightorientationinthat section, however when multiple rebars are created from that rebar prolethroughtheRebarSetMenu, theaddedrebarswill beplacedparallel totheoriginalrebar,extendingtherebarsetinastraightline. Figure55showsthiseect; thesetofrebarsselectedwascreatedinthesectioncuttingthebridgeatthelefthandside, anddoesnotcurvewiththebridgedeck, butstretchesoutperpendicularlyfromthesection.68Figure55: RebarsetdoesnotcurvewiththebridgedeckThisalsoaectsthelongitudinal reinforcementif itiscreatedinacrosssectionofthebridge. Thesolutiontothisproblemis,atthemoment,averypragmaticone; arebar set canonlyspanaportionof thebridgebeforeanewrebarsetwithaslightlydierentorientationhastobeplaced. Althoughthisisnotdesirable,itisthebestsolutiongivenRevitscurrentfunctionality.Autodeskiscontinuouslyworkingwithrebarimprovements, andthisissueisprobablyonethat will begivenattentioninfuturereleases of Revit. Thelongitudinal reinforcementcanbecreatedinaplanview, whichenablestheusertoassignacurvetotherebarsusingthesketchrebartool. Theuserisalso able to assign a reference plane following the slope of the bridge as the workplane, such that the rebar is placed on that plane. The Rebar Set Menu cannotbeusedtoassignspacingbetweentherebarinthiscase, becausetheaddedrebarwill beplacedwiththespacingorientedvertically, nothorizontally. Inorder to create the wanted number of rebars horizontally, one has to manuallycopythebars. TheArrayGrouptool is suitablefor this operation. Bycreatingabar withthe appropriate curvature, the user canthenclicktheArray Group tool, specify the span of the rebar set and the number of rebarsinthegroup. However, afterinsertingasegmentof rebarsusingtheArrayGroup tool, the program started having performance issues (not responding),renderingmodelingalmost impossible. Also, rebars inthearraygrouparehardertocustomizeoncecreatedcomparedtorebarscreatedbythestandardprocedure. Rebars for this use are usually cut in lengths of 12000mm, and arenotpre-bentinthecaseof alargeradius(inthiscase600m). Thequestion69inthis regardis if therepresentationof sets of 12000mmstraight rebars issatisfactory. At the ends of each rebar set, there will be an inaccuracy becausethenextsetwillhaveadierentorientationinthehorizontalplane.Figure56: InaccuracyattheendsoftherebarsetsAnissue arose whentryingtoaddrebar tothe bridge deck; the rebarwas not placedontotheworkplanedenedbythesectioncreatedfor theinsertionoftherebar,butendedupatadierentlocationseeminglywithoutany connection to the section. In gure 57 the section and the added rebar aredisplayed. The section is indicated by the two arrows and the blue dashed line,andtherebaristhebluelineinthebottomsectionofthepicture(therebarishoveredoverwiththemouse,whichrevealstheobjectnameandtype).70Figure57: SectionandrebarnotcoincidingThe solution was to create a reference plane where the rebar was supposedtobeinsertedandsetthatreferenceplaneastheworkplanebeforeenteringthesectionandplacingtherebar.6.8 Post-tensioningreinforcementThecreationof thePTRis particularlydicult. It curves alongwiththebridgedeckaswellashavingdierentelevationsalongitslength.Figure58: OverviewofthePTRrunningalongthelengthofthebridge71Standardrebarshapesarenotapplicableforthisreinforcement, andten-sioned reinforcement behaves dierently and redistributes stresses and strains.Thesketchtooldoesnotwork,becauseitisconnedtoaplaneandhaslimi-tations determined by the section in which you draw the rebar, and there is nopossibilitytoattributearebarcurvatureintwoplaneswiththistool. Thus,other methods need to be considered. It is possible to create this kind of geom-etryusingtheIn-PlaceMasstoolwhichismentionedin4.2.1. Aportionofone of the PT tendons was modeled using this tool. Points were created alongthe length of the rebar with a spacing of 1000mm and given approximately therightelevation. Foreachpoint, bothareferenceplaneandasectionhadtobecreatedinordertoaddacircularproletoeachpoint. Thesectionswerecreated to view the specic point, and the corresponding reference planes wereneeded for the proles to be placed on. This way one was able to create a pathofcircularprolesforanIn-PlaceMasstofollow.Figure59: ThereinforcementasanIn-PlaceMassTheIn-PlaceMassobjectdisplayedingure59isnotcompletelyaccu-rate. However, it is possible to attain the correct geometry once enough pointsare added at the exact positions. Each point is assigned a host plane on whichthey are placed, and the points can be assigned an oset from that plane aftercreationtocontroltheirelevation. Byselectingaplanefollowingtheslopeofthebridge,oneisabletocontroltheelevationproleoftheobjectsatisfacto-rily. Eachpointcanalsobeselectedanddraggedtoapositionof theuserschoice. Yet,theprocedureisverycumbersomeduetothefactthatreferenceplanesandsectionsareneededforeachpoint, andthateverypointneedsto72be adjusted to create the desired geometry. Once the reference planes and sec-tions are placed in the model, they can be used for each of the post tensioningreinforcement objects since they follow the same curvature, which means theyonlyneedtobecreatedonceforalloftheposttensioningreinforcement.Figure60: PointswithreferenceplanesandsectionsThereis nowayof quicklychangingthegeometryof theobject; if theobject needs tobealtered, eachpoint aectedneeds tobealteredas well.Furthermore, theprolesassociatedwitheachpointarenotattachedtothepoints, andwill havetobemovedmanuallytoreectthechangeofpositionof thepoints. Also, toobtainacompletelyaccurateobject, theprolescre-atedateachpointneedtobeperpendiculartothedirectionof thepathbywhichtheobjectfollows. Thus, thereferenceplaneswill needtoberotatedslightly, whichrequiresalotofextraworkduetothefactthatnewsectionshas to be created perpendicularly to the reference planes in order to rotate thereferenceplanes. Figure61showsthisinaccuracyforfourpointswiththeiraccompanyingverticalcircularproles.73Figure61: In-PlaceMasspointsandprolesIt was concluded that this method was not feasible for the modeling of thePTR. However, therearemodelingengineerswhohaveworkedwithPTRinRevit, andtheyhavemanagedtocomeupwithfamiliesfromwhichobjectscanbeinserted[15]. ThesefamiliesarenotyetinthestandardRevitlibrary,andrequiremorethanamoderateamountofskilltomodel. ThePTtendonsin the examples shown of these families are limited to one or two spans with asmoothcurvefromtoptobottom, whichrequire3and5pointsrespectively.The PTR in the bridge modeled in this thesis has area where the reinforcementattens out altogether before rising towards the columns, thus more points areneededinorder tore