土木工程外文翻譯

外文翻譯EstimatingFutureHighwayConstructionCostsC.G.Wilmot,M.ASCE,1andG.Cheng,P.E.2Abstract:TheobjectiveofthisresearchwastodevelopamodelthatestimatesfuturehighwayconstructioncostsinLouisiana.Themodeldescribesoverallhighwayconstructioncostintermsofahighwayconstructioncostindex.Theindexisacompositemeasureofthecostofconstructionlabor,materials,andequipment;thecharacteristicsofcontracts;andtheenvironmentinwhichcontractsarelet.Futureconstructioncostsaredescribedintermsofpredictedindexvaluesbasedonforecastsofthepriceofconstructionlabor,materials,andequipmentandtheexpectedcontractcharacteristicsandcontractenvironments.Thecontractcharacteristicsandcontractenvironmentsthatareunderthecontrolofhighwayagencyofficials,canbemanipulatedtoreflectfuturecost-cuttingpolicies.ApplicationofthemodelinforecastingtohighwayconstructioncostsinLouisianashowsthatthemodelcloselyreplicatespastconstructioncostsfortheperiod1984–1997.Whenappliedtoforecastingfuturehighwayconstructioncosts,themodelpredictsthathighwayconstructioncostsinLouisianawilldoublebetween1998and2015.Applyingcost-cuttingpoliciesandassuminginputcostsare20%lessthananticipated,themodelestimateshighwayconstructioncostswillincreaseby75%between1998and2015.Keywords:Highwayconstruction;Costs;Estimation.onStateDepartmentsofTransportationarerequiredtopreparehighwayconstructionprogramsthatdescribetheirplannedconstructionactivityintheshortterm.Thereisusuallyconsiderableinterestintheprogramfromlocalauthorities,politicians,andinterestgroups.Draftprogramsaretypicallypresentedtothepublicandtovariousagenciesatthelocal,regional,state,andfederallevelforcommentandreview.Ultimately,aprogramwillbeapprovedbythestatelegislatureandwillbecometheformalprogramofconstructionofthestateDepartmentofTransportationuntilanewprogramisdevelopedinthenextcycleafewyearslater.Becauseindividualprojectsareofconsiderableimportancetopoliticiansandindividualinterestgroups,itiscommonthatprogressonaconstructionprogramiscloselymonitored.Anydeviationislikelytobequeried,andtheSecretaryofthestateDepartmentofTransportationoraseniorofficialinthedepartmentwilloftenhavetodefendthesituationpubliclyorinthestatelegislature.Thiscanleadtoperceptionsofincompetenceanderosionofsupportfromthelegislatureandthepublic.Topreparereliablehighwayconstructionprograms,roadauthoritiesmusthaveaccurateestimatesoffuturefundingandprojectcosts.Whilefuturefundingisobviouslyneverknownwithagreatdealofcertainty,itisoftentheestimationofprojectcoststhatcauseupsetsintheexecutionofconstructionprograms.Inaccuratecostestimationisonesourceoferror,butanother,theescalationincostofaprojectovertime,isanothersourcedisruptiontotheprogramthatisusuallynotanticipatedandcateredfor.Typically,whenprojectsarecosted,theircostsareestimatedintermsofthecurrentcostoftheproject,andthisestimateisnotadjustedfortheyearinwhichtheprojectisscheduledforimplementation.Thesecostincreasescanbesignificantandare,ofcourse,cumulativeacrossprojects;also,theyriseatanincreasingrateeachyearintothefuture.Estimatingfuturehighwayconstructionisthefocusofthispaper.ThemodeldevelopedinthisstudywasdevelopedwithdatafromtheLouisianaDepartmentofTransportationandDevelopment~DOTD!andisthereforeparticulartothatstate.However,themethodologyemployedcouldbeemployedinotherareas.MeasuringProjectCostsWhenconstructioninthefieldlagsbehindplannedconstructionintheconstructionprogram,itisusuallybecausetheprojectsthathavebeenconstructedhavecostmorethananticipated.Thisisnotrandomvariationofactualcostsaboutestimatedcosts,because,clearly,underestimateswouldcanceloutoverestimatesovertimeinsuchasituation.Rather,itisevidenceofaattheoveralllevel,whichismucheasiertomeasurethanattheindividualprojectlevel.Inthepast,changeinoverallconstructioncostshasbeenmeasuredintermsofconstructionindices.Theseindicesareweightedaveragesofthecostofasetofrepresentativepayitemsovertime.Theyhavebeenusedtodisplaycosttrendsinthepast.However,thereisnoreasonwhycostindicesmustberestrictedtodisplayingpasttrends;theycanalsoportrayfutureoverallcosts,providedtherepresentativepayitemsonwhichtheindexisbasedcanbeforecast.Apredictiveconstructioncostindexwasadoptedinthisstudytodescribethechangeinoverallconstructioncostsinthefuture.Theformulationoftheindexisdescribedlaterinthepaper.PastIncreasesinConstructionCostsWhenthechangeinoverallconstructioncostsinthepastisobserved(asmeasuredbypopularconstructioncostindices),itisapparentthattheychangesignificantlyfromyeartoyearandthatthechangescansometimesbequiteerratic.Thecommonassumptionthatconstructioncostschangewiththerateofinflationcanleadtopoorestimatesoffutureconstructioncost.Toillustrate,theFederalHighwayAdministration’sCompositeBidPriceIndex,anindexofoverallhighwayconstructioncosts,isplottedinFig.1togetherwiththeConsumerPriceIndex(CPI),acommonexpressionofgeneralinflation.TheFHWACBPIfortheentirenationandforLouisianaaloneisplottedinthediagram.Allindiceshavebeennormalizedtoavalueof100in1987forcomparisonpurposes.Fromthediagram,itisclearthathighwayconstructioncostschangeerraticallyandevendisplaydifferentshortandlong-termtrendsfromtothoseoftheCPI.ItisalsoapparentthatconstructioncostchangesaredifferentinLouisianafromthoseinthenationasawhole.Whilenotshownhere,reviewoftheFHWACBPIfromotherstatesshowsthatmanyofthemshowadeviationfromnationalvalues.PastMethodsofForecastingHighwayConstructionCostForecastingfuturehighwayconstructioncostshasbeenachievedinbasicallythreewaysinthepast.First,unitratesofconstructionsuchasdollarspermilebyhighwaytypehavebeenusedtoestimateconstructioncostsintheshortterm.However,thismethodhasgenerallybeenfoundtobeunreliable,becausesiteconditionssuchastopography,insitusoil,landprices,environment,andtrafficloadsvarysufficientlyfromlocationtolocationtomakeaveragepricesinaccurateestimatesofthepriceofindividualprojectsorevenofallprojectsinaparticularyear.Second,extrapolationofpasttrends,ortime-seriesanalysis,hasbeenusedtoforecastfutureoverallconstructioncosts(Koppula1981;Hartgenetal.1997).Typically,constructioncostshavebeencollapsedintheseanalysestoasingleoverallexpressionofconstructioncostsuchastheFHWACBPIortheEngineeringNewsRecord’sBuildingConstructionIndex~ENRBCI!orConstructionCostIndex~ENRCCI!.However,thesetypesofmodelsareusuallyonlyusedforshort-termforecastingduetotheirrelianceonthenotionthatpastconditionsaremaintainedinthefuture.Third,modelshavebeenestablishedthatdescribeconstructioncostsasafunctionoffactorsbelievedtoinfluenceconstructioncosts.Therelationshipbetweenconstructioncostsandthesefactorshavebeenestablishedfrompastrecordsofconstructioncosts.Typically,themodelsestablishedinthismannerhavebeenusedtoestimatethecostofindividualcontracts.Thesemodels,withtheirrelationalstructure,aretheonlymodelsexpectedtoprovidereliablelong-termestimates.Themodeldevelopedinthisstudyisofthistype.ProposedConstructionCostModelItisclearthattherearenumerousfactorsthataffectconstructioncosts.However,itisstrikingthatmostconstructioncostmodelsdevelopedinthepasthaveusedonlyafewofthemanyinfluentialfactorsidentifiedabove.Onereasonforthisisthatinformationisgenerallynotavailableonmanyfactorsindatasetsusedtoestimatemodels.Anotherreasonisthatinformationonthequalitativeconditionssurroundingeachcontractisdifficulttoobtain.Theseareproblemsthatprevailinmostcircumstancesandaredifficulttoovercome.Tomitigateagainsttheeffectofanincompletesetoffactors,twostrategiescanbeemployed.First,itmaybepossibletorepresentsomeoftheabsentfactorsbysurrogatevariablesthatareinthedataset.Forexample,asmentionedearlier,annualbidvolumehasbeenusedinthepastasaninversemeasureofthelevelofcompetitionprevailingintheconstructionindustryatthattime (Herbsman1986).Similarly,thenumberofplanchangeseachyearcanserveasameasureofdesignquality.Second,ifthemodelingofconstructioncostischangedfromestimatingthecostofindividualprojectstoestimatingoverallconstructioncostseachyear,themodelingtaskissimplified.Thisisbecauseitisnolongernecessarytotrytomodelindividualprojectsinwhichconditionsinflatethepriceinonecaseanddeflateitinanother,sincesuchconditionswouldtendtocancelthemselvesoutamongprojectsinthesameyear.Forexample,firmsthatreducetheirbidpricesinanefforttowinaparticularcontractcouldbebalancedoutwithinthesamefiscalyearbythosethatincreasetheirpricesbecausetheyalreadyhaveenoughworkandarenotparticularlyinterestedinwinningthecontract.Similarly,thosefirmswithexpertiseinthetypeofconstructionrequiredwillbebalancedoutbythosewithlowlevelsofexpertiseinthatarea.Thus,itisgenerallymoretolerabletooperatewithfewerrelevantfactorswhenmodelingattheaggregateoroveralllevelthanwhenmodelingatthedisaggregatelevel.Theobjectiveofthisstudyistoestablishamodel,estimatedonhistoricalquantitativedata,thatincorporatesasmanyrelevantvariablesaspossibleandiscapableofestimatingthefutureoverallcostofhighwayconstructiononanannualbasis.ThemodelisintendedtoassesstheimpactofalternativefutureconditionsonhighwayconstructioncostsandassistofficialsoftheLouisianaDOTDtoidentifymanagementpoliciesthatwillhelplimittheincreaseinhighwayconstructioncostsinthestate.Itwasalsotheperceptionofthoseinterviewedthatcontractsletinthefourthquarterofthefiscalyeartendedtoresultinhigherbidprices.Thiswasbecausetherewasatendencyforprojectstoaccumulateinthefourthquarterduetovariousdelays,andtheincreasedvolumeofprojectsresultedindecreasedcompetitionamongcontractors.ModelStructureThemodeldevelopedtopredictoverallhighwayconstructioncostsinthisstudyisbasedonfivesubmodelsofpriceestimation.Eachsubmodelestimatesthepriceofapayitemrepresentativeofcostmodeladominantconstructionarea.Dominantconstructionareaswereidentifiedfrompastexpenditureindifferentareasofhighwayconstruction.FromtheLouisianaDOTDdatafortheperiod1984–1997,itwasfoundthatmorethan50%ofallhighwayconstructionexpenditureoccurredintheareasofasphaltconcretesurfaces,Portlandcementconcretesurfaces,excavationandembankment,structuralsteel,structuralconcrete,andreinforcingsteel.Interestingly,theseconstructionareasareidenticaltothoseusedtoestimatetheFHWACBPI.Thestructuralsteelconstructionareawasnotincludedinthemodeldevelopedinthisstudy,becausemorethan98%ofexpenditureinthisconstructionareawasbidasalumpsumineachcontractwithnorecordoftheamountofsteelincludedinthebid.Thismadecomparisonofthecostofstructuralsteelamongcontractsimpossible.Theotherfiveconstructionareasincludedinthemodelwereallrepresentedbypayitemswhosepriceswereexpressedintermsofrates,whichpermittedcomparisonamongcontracts.AschematicrepresentationoftheoverallmodelwithitsfivesubmodelsisshowninFig.2.Eachsubmodelestimatesthepriceofarepresentativepayitemfromeachofthefivedominantconstructionareas.ThecontributionofeachsubmodeltotheoverallmodelisaccomplishedbycombiningthepricesoftherepresentativepayitemsinanindexsimilartothatoftheFHWACBPI.Inthiscase,becausetheformulationisslightlydifferentfromtheFHWACBPIandisconstructedspecificallytoreflectpastandfutureoverallconstructioncostsinLouisiana,itisnamedtheLouisianaHighwayConstructionIndexandisdefinedasionModelperformanceisideallyvalidatedusingdatanotusedintheestimationofthemodel.Inthiscasenosuchdatawasavailable.Dividingtheexistingdatasetintotwoportionstoestimatethemodelononeportionandusetheotherforvalidationwasnotpractical,giventhelimitedsamplesizeinsomeofthesubmodels.Forexample,theconcretepavementsubmodelhasatotalofonly212observations,andestimatingthesubmodelonthehighlyvariabledataonfewerobservationswouldreducetheaccuracyoftheestimates.Thus,theperformanceofthemodelwasassessedbyobservinghowwellitreproducedobservedconstructioncosts.Usingthesamedataasthatonwhichthemodelwascalibrated,theestimatedandobservedLHCIvaluesfortheperiod1984–1997areshowninFig.3.The95%confidencelimitoftheobservedLHCIisalsoshowninthefiguretoillustratethattheestimatedLHCIvaluesare,forthemostpart,containedwithinthe95%confidencelimitoftheobservedLHCIvalues.ThechisquaredtestofthesimilarityoftheestimatedandobservedLHCIvaluesindicatesthatasignificantdifferencecouldnotbeobservedatthe99%levelofsignificance.InvestigatingthebehavioroftheconstructioncostindexinFig.3revealsinterestingreasonsbehindtheobservedbehavior.Reviewingthedataandobservingitsimpactontheforecaststhroughthemodelallowsananalysttodeterminetheprimarycausesofchangeinconstructioncostsduringcertainperiodsinthepast.Forexample,themaincauseofthedecreaseinconstructioncostsobservedintheperiod1984–1986canbetracedbacktoadeclineinlaborandpetroleumcostsduringthatperiod.Therapidincreaseinconstructioncostsfrom1995to1996wasprimarilyduetoacombinationofrisingpetroleumcostsandanincreasedproportionofsmallercontracts.Thedropinconstructioncostsobservedimmediatelyfollowingthisevent(i.e.,in1997)wasmainlytheconsequenceofanincreaseintheaveragesizeofprojectsfromdurationofprojects.ConclusionsThisstudyhasshownthattheliteratureindicatesthatacomprehensivesetoffactorscontributestothecostofhighwayconstruction.Inthisstudy,themostinfluentialfactorswerefoundtobethecostofthematerial,labor,andequipmentusedinconstructingthefacility.However,alsoaffectconstructioncosts.Inparticular,contractsize,duration,location,andthequarterinwhichthecontractisletwerefoundtohaveasignificantimpactoncontractcost.Bidvolume,bidvolumevariance,numberofplanchanges,andchangesinconstructionpractice,standards,orspecificationsalsomakeasignificantimpactoncontractcosts.Otherfactorsareexpectedtohaveanimpactonconstructioncostsbutwerenotincludedinthisanalysisbecausenodataontheirvalueswereavailable.Themodeldevelopedinthisstudyreproducespastoverallconstructioncostsreasonablyaccuratelyattheaggregatelevel.Predictedoverallconstructioncostsarenotsignificantlydifferentfromobservedcostsatthe99%levelofsignificance.Thisaccuracyislargelytheresultoftheaggregatelevelatwhichconstructioncostsaremeasuredinthisstudy;attheindividualcontractlevel,thesubmodelscaptureonlybetween42and72%ofthevariationinthedata.Itissuspectedthatmuchofthisvariationisduetounobserved,essentiallysubjectivefactorsthatinfluencethebidpricesinindividualcontracts.However,someoftheseidiosyncraticvariationsattheindividualcontractlevelaverageoutintheaggregationprocess.ThismodelcanbeusedbyhighwayofficialsinLouisianatotestalternativecontractmanagementstrategies.Increasingcontractsizes,reducingthedurationofcontracts,reducingbidvolumeandbidvolumevariance,reducingthenumberofplanchanges,andreducingtheproportionofcontractsletinthefourthquarterallservetoreduceoverallconstructioncosts.Highwayofficialscanassesstheimpactofstrategiestheybelieveareachievablebyapplyingthemodel.Mostimportantly,though,themodelcanassistinestimatingfutureconstructioncostsandprovidingthemeanstoproducemorereliableconstructionprograms.AssociateProfessor,LouisianaTransportationResearchCenterandDept.ofCivilandEnvironmentalEngineering,LouisianaStateUniv.,BatonRouge,LA70803-6405.CivilEngineer,GEC,Inc.,9357InterlineAve.,BatonRouge,LA70809.C.G.Wilmot,M.ASCE,andG.Cheng,P.E．EstimatingFutureHighwayConstructionCosts．JOURNALOFCONSTRUCTIONENGINEERINGANDMANAGEMENT?ASCE/MAY/JUNEingindesign’.WorldComputing,Vol.26(1),pp74–76.ISO(1994).ISO10303-1Part1:Overviewandfundamentalprinciples,InternationalOrganizationforStandardization,Geneva,Switzerland.edmodeltosupportdistributedcollaborativedesignofbuildings’.AutomationinConstruction,Vol.7(2–3),pp177–188.LeeH.K.,LeeY.S.,KimK.H.andKimJ.J.(2007).‘Acost-basedinformationmodelforaninteriordesigninalarge-scalehousingproject’,ICCIT07,2007InternationalConferenceonConvergenceInformationTechnology,PosterSessions:Session4.ofConstructionEngineeringandManagement,Vol.123(2),pp113-120.公路建設(shè)造價(jià)的未來C.G.Wilmot,M.ASCE,1andG.Cheng,P.E.21聯(lián)合教授，路易斯安娜運(yùn)輸研究中心和國(guó)家環(huán)境工程局，路易斯安娜國(guó)立大學(xué)2注冊(cè)工程師據(jù)公路建設(shè)造價(jià)索引，該模型介紹了中所有公路建設(shè)的工程費(fèi)用。這索引是一份綜合定額，和項(xiàng)目環(huán)境基礎(chǔ)上的預(yù)測(cè)價(jià)格。在公路管理機(jī)構(gòu)控制下的項(xiàng)目特征和項(xiàng)目環(huán)境能可根據(jù)未來的成本削減政策來操作處理。公路造價(jià)預(yù)算模型在路易斯安娜的運(yùn)用表現(xiàn)出這模型幾乎是1984—1997年時(shí)建設(shè)造價(jià)模型的重現(xiàn)。未來在運(yùn)用公路造價(jià)預(yù)算時(shí)，該模型預(yù)測(cè)路易斯安娜的公路造價(jià)將在1998年到2015年間的增加兩倍。在應(yīng)用削減成本政策和假設(shè)投入的資關(guān)鍵詞：公路建設(shè)，造價(jià)，預(yù)算立項(xiàng)中成為國(guó)家交通部的正式建設(shè)項(xiàng)目。辯護(hù)。這會(huì)導(dǎo)致使人不相信你的能力，并使來自立法機(jī)構(gòu)和公眾的支持受到?jīng)_擊。明顯，預(yù)留資金永遠(yuǎn)不能確保，通常是對(duì)在建設(shè)項(xiàng)目實(shí)施中引起混亂的項(xiàng)目造價(jià)的評(píng)估。不準(zhǔn)確的造價(jià)意見是一個(gè)錯(cuò)誤來源，但另一方面，不斷過時(shí)的工程造價(jià)是另一個(gè)使項(xiàng)目失敗的項(xiàng)目造價(jià)估量當(dāng)某領(lǐng)域建設(shè)落后于建設(shè)計(jì)劃中的進(jìn)度，通常是因?yàn)橐呀?jīng)建造的項(xiàng)目費(fèi)超過了預(yù)期費(fèi)用。實(shí)際費(fèi)用相對(duì)于預(yù)算不是隨意變動(dòng)的，因?yàn)楹苊黠@在這種情況下過低估計(jì)與過高估計(jì)會(huì)相互抵消。而且，這是所有項(xiàng)目全部過低評(píng)價(jià)的證據(jù)。這樣的好處是能在一般水平估量，這比在特別的項(xiàng)目水平估量容易得多。費(fèi)用項(xiàng)目的平均造價(jià)。他們已經(jīng)習(xí)慣于根據(jù)過去造價(jià)。但是無法解釋造價(jià)索引必須嚴(yán)格表現(xiàn)過去趨勢(shì)的原因，他們同樣能表現(xiàn)未來一般造價(jià)，預(yù)備建立索引的典型費(fèi)用項(xiàng)目，能預(yù)測(cè)。預(yù)算造價(jià)索引在本研究中被用于解釋未來在一般建設(shè)造價(jià)的變化。索引的簡(jiǎn)化公式會(huì)在下文中提到。建設(shè)造價(jià)的增長(zhǎng)歷史當(dāng)過去一般建設(shè)造價(jià)中的變化被注意到了(如被普通建設(shè)造價(jià)索引估量)，很明顯這年復(fù)一年變化得很顯注而且有時(shí)非常沒規(guī)律。通常建設(shè)造價(jià)隨通貨膨脹率變化的設(shè)想會(huì)對(duì)未來建設(shè)造價(jià)做出錯(cuò)誤的判斷。舉個(gè)例子，公路管理聯(lián)合會(huì)(FHWACBPI)的綜合投標(biāo)價(jià)格索引是關(guān)區(qū)分為對(duì)于整個(gè)國(guó)家和只對(duì)路易斯安娜。所有索引已經(jīng)因相似目的在1987年根據(jù)100標(biāo)準(zhǔn)規(guī)范。從表中清楚看到公路建設(shè)造價(jià)變化不規(guī)律，甚至呈現(xiàn)趨向于CPI變化的不同長(zhǎng)短期。而且很明顯建設(shè)造價(jià)變化在路易斯安娜和整個(gè)國(guó)家是不同的。沒有在此顯示的，其他國(guó)家FHWACBPI的評(píng)論表明其中一些與國(guó)家標(biāo)準(zhǔn)有偏差。過去公路建設(shè)預(yù)算方法單位建設(shè)價(jià)格已經(jīng)用于短期預(yù)算(HartgenandTalvitie1995；Stevens1995)。但是經(jīng)常發(fā)現(xiàn)格對(duì)特殊工程，甚至對(duì)特殊年份的所有工程進(jìn)行不準(zhǔn)確造價(jià)有很大差異(HartgenandTalvitieetal.1997)。通常，建設(shè)造價(jià)在僅對(duì)一般造價(jià)描寫的分析中已失去意義，如FHWACBPI，工程新紀(jì)錄之建筑工程定額(ENRBCI)，或建設(shè)造價(jià)定額(ENTCCI)。但是，這些模型通常只造價(jià)描述為影響造價(jià)的功能因素。建設(shè)造價(jià)和這些因素之間的關(guān)系已經(jīng)從過去的建設(shè)造價(jià)紀(jì)于提供不規(guī)律長(zhǎng)期判斷的唯一模型。本研究中就是這個(gè)模型。地點(diǎn)、工程類型、項(xiàng)目持續(xù)時(shí)間和項(xiàng)目規(guī)模對(duì)單個(gè)項(xiàng)目造價(jià)有重大影響。Herbsman(1986)表示，除材料費(fèi)，人工費(fèi)和機(jī)械費(fèi)，每年的項(xiàng)目總量(i.e.,theso-calledbidvolume)影響項(xiàng)目?jī)r(jià)格。這是智慧的提議，價(jià)位影響競(jìng)爭(zhēng)(至少在短期內(nèi))，反過來，這也影響項(xiàng)目?jī)r(jià)格。Olsen和Epps(1981)表示出價(jià)量年復(fù)一年的變化影響出價(jià)價(jià)格。其他人認(rèn)為政府法令，計(jì)劃變動(dòng)，承造方管理團(tuán)隊(duì)的質(zhì)量，提高竣工安全及時(shí)間的項(xiàng)目信息對(duì)建筑造價(jià)有影響(Koehnetal.1987;ElhagandBoussebaine1998).也有人說質(zhì)量因素，如建造企業(yè)的表里如一，建造者的需求，以及建造者與管理機(jī)構(gòu)的關(guān)系都會(huì)對(duì)建造有很大影響(Fayek1998)。建設(shè)造價(jià)模型很顯然有很多因素影響造價(jià)。然而令人吃驚的是過去大部分造價(jià)模型只用了一小部分重要因關(guān)于每個(gè)項(xiàng)目質(zhì)量情況的信息很難獲得，在大多數(shù)情況下成功和很難克服都是問題。例子，如早先提到的，過去每年的出價(jià)規(guī)?？勺鳛樵u(píng)價(jià)那時(shí)建設(shè)產(chǎn)業(yè)競(jìng)爭(zhēng)力水平的反因子 (Herbsman1986)。同樣的，每年計(jì)劃的改變量能評(píng)價(jià)設(shè)計(jì)質(zhì)量。其次，如果建設(shè)造價(jià)模型勝的企業(yè)會(huì)在同一年以因此提價(jià)來達(dá)到平衡，因?yàn)樗麄円呀?jīng)做了足夠的工作而且不急于求成。少的因素在整體水平比在處于崩潰水平建立模型更好。公路造價(jià)增長(zhǎng)的警務(wù)的管理。變化的信息。項(xiàng)目書及其變動(dòng)和每年計(jì)劃改變的總數(shù)都是從原始資料中獲得的。次是面談，另兩次通過電話會(huì)議交談。面試官有一份問題單去控制面試，但回答人也可選擇回答范圍。這會(huì)確認(rèn)實(shí)施中的變化，如更堅(jiān)硬的道路設(shè)計(jì)能容納更多交通量，欄桿下鋪磚便于除草，注意沖蝕控制，欄桿末端處理變化，增加臨時(shí)交通線的用處。不管怎樣，因?yàn)檫@些些會(huì)談，這對(duì)以后瀝青水泥的出價(jià)增長(zhǎng)立即負(fù)起了責(zé)任。變化包括聚合改性瀝青的介紹和提高材料種類測(cè)試程序的應(yīng)用。這些變化是所期待的，同時(shí)也推廣使提高瀝青水泥的造價(jià)大約會(huì)談洞察到項(xiàng)目承包在四分之一財(cái)務(wù)年中會(huì)使報(bào)價(jià)更高。因?yàn)橛幸粋€(gè)趨勢(shì)是在四分之一年中會(huì)積累各種障礙，工程量的提高會(huì)減少承造者間的競(jìng)爭(zhēng)。關(guān)于過去和未來建設(shè)資金的資料是從多種來源獲得的。貿(mào)易局的經(jīng)濟(jì)研究處公布了工業(yè)雇傭和收入的歷史記錄，用來評(píng)價(jià)每個(gè)工業(yè)部門的工人人均工資。這個(gè)信息用來確定1980-1997人薪資提供信息。1987年過去和預(yù)測(cè)的工人薪資水平被編成了一份反映每100勞動(dòng)力價(jià)值的統(tǒng)計(jì)表。1984-2015年間公路建設(shè)器材和材料價(jià)格資料來源于一家信息資源公司(DRI)。見表一典型支付項(xiàng)目混合資源中的替代變量建設(shè)設(shè)備建設(shè)機(jī)器路基材料建設(shè)用沙/碎石/石料AA級(jí)水泥水泥原料和相關(guān)產(chǎn)品瀝青混凝土精制石油產(chǎn)品和建設(shè)用沙/碎石/石料變形強(qiáng)型鋼模型結(jié)構(gòu)混凝土加強(qiáng)木棍和碳評(píng)價(jià)子系統(tǒng)組成。每個(gè)子模型評(píng)價(jià)一個(gè)建設(shè)優(yōu)勢(shì)娜DOTD1984-1997年間的資料可以發(fā)現(xiàn)超過50%的公路建設(shè)費(fèi)用用于瀝青混凝土表面，波特蘭水泥混凝土表面，坑道和路基，鋼結(jié)構(gòu)，混凝土結(jié)構(gòu)和固型鋼。有趣的是，這些建設(shè)地FHWACBPI的，因?yàn)榉ū容^。模型中其他五項(xiàng)都由支付項(xiàng)目表示，其價(jià)格用比率表示更易比較。每個(gè)子模型的建立是為了降低當(dāng)年描述各種建設(shè)投資的可變支付項(xiàng)目?jī)r(jià)格，考慮中的項(xiàng)目特征和那時(shí)良好的項(xiàng)目環(huán)境使項(xiàng)目很順利。在模型中嘗試盡可能多的獨(dú)立的各類因素使一般模型中影響建設(shè)造價(jià)的因素盡可能綜合和敏感。所示。每個(gè)子模型從五個(gè)優(yōu)勢(shì)建設(shè)區(qū)域評(píng)價(jià)一個(gè)選擇性支付項(xiàng)目的價(jià)格。整體模型的每個(gè)子模型的貢獻(xiàn)是整合了與FHWACBPI的索引表相似的索引表中的可選擇性支付項(xiàng)目的價(jià)格。在這里，因?yàn)檫@形式和FHWACBPI有細(xì)小的差別而且是有效性型一共只有212項(xiàng)觀測(cè)值，信息多樣但觀測(cè)值相對(duì)較少會(huì)降低對(duì)模型評(píng)價(jià)的精確度。所以模型執(zhí)行以觀察它怎樣重新觀測(cè)建設(shè)造價(jià)來評(píng)估。Fig3用模型測(cè)量出來的資料，1984-1997年間評(píng)價(jià)和觀察的LHCI值如Fig3所示。LHCI的信用限制。LHCI評(píng)價(jià)和觀測(cè)值相似性測(cè)驗(yàn)表明顯著的不同點(diǎn)在99%不能被注意到。預(yù)先計(jì)劃的影響，這使分析家找到了在過去一些時(shí)期中建設(shè)造價(jià)改變的主要原因。舉個(gè)例子，觀察1984-1986年間建設(shè)造價(jià)下降的主要原因要追溯到那段時(shí)期勞動(dòng)力和石油價(jià)格的下降。后建設(shè)造價(jià)的下跌(i.e.,in1997)主要原因是1996年承包的項(xiàng)目平均規(guī)模的增大和項(xiàng)目平本研究已經(jīng)表明論文說明了公路建設(shè)造價(jià)的一個(gè)系列綜合原因。研究表明最有影響力的因素響工程造價(jià)。特別要指出，項(xiàng)目規(guī)模，持續(xù)時(shí)間，地點(diǎn)和項(xiàng)目投資對(duì)建設(shè)造價(jià)的影響也是非計(jì)說明書的改動(dòng)也能起到很大影響。其他會(huì)產(chǎn)生影響的因素不包括在本分析中因?yàn)槿狈ο嚓P(guān)可利用的數(shù)據(jù)。確地重現(xiàn)了過去普通建設(shè)造價(jià)。建設(shè)預(yù)算在99%的重要性上與決算相差無幾。相較于個(gè)別項(xiàng)目，子模型只能獲得資料中42%—72%的變化程度的情在整體過程中被平均。這模型判斷出到2015年如果過去的趨勢(shì)被推斷或通貨膨脹率作為評(píng)價(jià)未來建設(shè)造價(jià)依據(jù)，那么路易斯安娜的公路建設(shè)造價(jià)增長(zhǎng)會(huì)比預(yù)期更快。根據(jù)模型預(yù)測(cè)，即使經(jīng)濟(jì)情況比預(yù)期更舊可能會(huì)流行，。建設(shè)造價(jià)中工程增加的主要原因是石油生產(chǎn)和建設(shè)機(jī)器價(jià)格的預(yù)期增長(zhǎng)?？赡軙?huì)較緩慢。謝本論文中運(yùn)用的研究成果來自于路易斯安娜運(yùn)輸研究中心。向他們和來自路易斯安娜運(yùn)輸發(fā)展局工作人員的幫助表示衷心的感謝。來源：C.G.Wilmot,M.ASCE,andG.Cheng,P.E．EstimatingFutureHighwayConstructionCosts．JOURNALOFCONSTRUCTIONENGINEERINGANDMANAGEMENT?ASCE/MAY/JUNEUsingWeibullAnalysisforEvaluationofCostandSchedulePerformanceKhaledM.Nassar1;HordurG.Gunnarsson2;andMohamedY.Hegab,P.E.3Largeamountsofmoneyarelosteachyearintheconstructionindustrybecauseofpoorscheduleandcostcontrol.Fewcontractorsspecifyandfollowsystematicschedulemonitoringpractices.Traditionally,theearnedvaluemethodEVMisusedtocontrolandmonitorscheduleperformanceusingthescheduleandcostperformanceindiceswhichcomparethebudgetedcostofworkperformedtowhatwasoriginallyscheduledorwhatisactuallyexpended.Thispaperpresentsastatisticalapproach,namelyWeibullanalysis,toevaluatestochasticallythescheduleperformanceofconstructionordesignprojects.TheapproachcanbeusedinconjunctionwiththeEVMtoenhancetheevaluationandcontrolofscheduleperformance.Weibullanalysisisacommonmethodforfailureanalysisandreliabilityengineeringusedinawiderangeofapplications.Inthispaper,theapplicabilityofWeibullanalysisforevaluatingandcomparingthereliabilityofthescheduleperformanceofmultipleprojectsispresented.Thevariousstepsintheanalysisarediscussedalongwithanexampleinwhichtwoprojectsareanalyzedandcompared.TheauthorsconcludethatWeibullanalysishasseveraladvantagesandprovidesarelativelyrobustandeffectivemethodforconstructionmanagerstobettercontrolandmonitortheirprojects.Constructionprojectsareseldom“on-schedule”allthetime.Theamountofworkperformedontheprojectusuallyfluctuatesfromoneperiodtotheother.Infact,accordingtothe“80/20”rule.suggestedbythe18thCenturyeconomist,Pareto80%oftheeffortwillbeexpendedduring20%oftheprojectduration.Thiscreatesasignificantproblemintryingtomonitortheactualperformanceoftheprojectscheduleandspecificallytryingtodecidewhetherornottheprojectcanfinishontime.,thereliabilityoftheprojectscheduleperformance.TheearnedvaluemethodEVMisoftenusedasaprojectcontroltechniquetoprovideaquantitativemeasureofscheduleperformance.IntheEVM,thescheduleandcostperformanceindicesC/SPIareusedforconstantmonitoringoftheproject’scostandschedulebasedonanoriginalcriticalpathmethodCPMscheduleChang2001.Unfortunately,CPMschedulingingeneralcreatesanunrealisticexpectationregardingprojectscheduleperformance.Startingaprojectonedayandexpectingthattheprojectwillfinishonanexactdatesometwoorthreeyearsinthefutureisunrealistic.Therefore,thereisaneedtoextendscheduleanalysistechniques,liketheEVM,toprovidemeansforprobabilisticallyanalyzingthescheduleperformanceandmeasuringtherisksinvolved.Inothermanagementdomainslikesoftwareprojectsandbusinessmanagement,toolsfromtheareaofreliability,availability,andmaintainabilityRAMengineeringarenowusedtopredictandavoidsuddensystemfailures.RAMengineeringisemergingasthenewestdisciplineinproductdevelopmentduetonewaccurate,quantitativemethods.Weibullanalysisisforemostamongthesetools.Weibullanalysisisawidelyusedmethodinthefieldofmanufacturingandindustrialengineering.Ithasmainlyservedforsimulatingfailureratesorlifetimeofcertainproducts.Byusingthisparticularanalysisonecanmakepredictionsaboutproduct’slife,comparethereliabilityofcompetingproductdesigns,andmanagesparepartsinventoriestonameafewcommonindustrialapplicationsDorner1997,1999.TheobjectiveofthisstudyistodiscussandpresenttheapplicabilityofWeibullanalysisforevaluatingscheduleperformanceusingcostandperformanceindicesC/SPIandtoprovideconstructionmanagerswithaneffectivetoolforstochasticallyevaluatingtheC/SPI.AnumberofprobabilistictechniqueswerecheckedagainstthedatausingAnderson-DarlingmeasureADvalueandtheWeibulldistributionwasfoundtobethebestrepresentativeforevaluatingscheduleperformanceandcostperformancehavingthelowestADvalue.Inthispaper,anexampleisprovided,inwhichtwoprojectsarecomparedandanalyzed.ThefirstpartofthispaperbrieflycoverstheEVMandperformanceindices.ThesecondpartdiscussestheWeibulldistribution,it