工程管理外文文献.docx

工程管理外文文献.docx

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工程管理外文文献

StudyonTheoryofReliabilityAnalysisinConstructionRiskManagement

DENGTiejun&QIUYike

（CollegeofCivilEngineering,HunanUniversity,Changsha410082,Hunan,China）

Abstract:

Thestateoftheartofreliabilityanalysisforconstructionsystemsisinvestigated.Itispointedoutthatmostofthecurrentresearchinconstructionreliabilityanalysisarelimitedtoasinglespecificgoalormanagementproblem.Startingfromthetheoryofsystemengineering,theconceptofreliabilityforconstructionsystems,whichisdifferentfromthereliabilityofstructuraldesignbutcloselyrelatedtoitisdefined;andtherelationshipbetween“GoalSubsystem”and“ProcedureSubsystem”ispresentedbytakingintoaccountofthefeaturesofconstructionpractice.Analgorithmofthereliabilityanalysisforthe“GoalSubsystem”and“ProcedureSubsystem”isproposed,andtheapproachesforimprovingthesystemreliabilityareexplored.Theclassificationofreliabilitylevelsanditsrelationshipwithconstructionriskmanagementarealsopresented,andthepossibilitiesoffutureapplicationofthereliabilitytheoryinconstructionriskmanagementdiscussed.

Keywords:

reliabilityanalysis;constructionriskmanagement;systemsengineering;theclassificationofreliabilitylevels

1Introduction

Since1916BarChartwasinventedbyH.L.Ganttandappliedintotheflowproduction,flowproductionmethodswasextensivelyadoptedintheorganizationoftheengineeringconstruction.Till2000GabrielA.Barrazaproposed‘S’and‘SS’curvestomodeltheengineeringconstruction.Thatmodelextendedthedeterministiccost-schedulecontrolmethodintoaprobabilisticmodel.Basedontheprobabilisticanalysisforthereliabilityofcost-schedulecontrolusingprobabilitytheoryandmathematicalstatisticaltechniques,thismethodcangivearationalframeworkforthedecisioninengineeringconstruction}}}.Allthisprovesafactthatconstructionreliabilityhaslongbeenstudiedandappliedintheconstructiontechnologyandmanagement.However,thepreviousresearchesstudiedthecontrolandmanagementonlyofasingleobjectiveamongthewholeobjectivesystemforconstruction.Theydidn'tconsidertheuniquecharacteristicsoftheengineeringconstructionasawholesystem;thereforetheyfailtoinstructthepracticalissuesoccurringintherealconstructionprojectmanagementbasedontheirreliabilityanalysis.

Themodernconstructionisanincreasinglycomplicatedprocesssystem.Fromtheviewofsystemengineering,eachprocedureortaskinanengineeringprojectcanonlybeaccomplishedaftermeetingsimultaneouslyseveralobjectivesunderbothexternalandinternalconstraints.Aswaspointedout[2],foranengineeringprojectunderreasonableeconomicconstraint,itsperformancecanbedefinedintermsof

（1）degreeofmeetingthequalitystandards,

（2）assuranceofmeetingthetimedurationrequirement,（3）credibilityofconstructionsafety,and（4）satisfactionofmeetingthesiteenvironmentrequirement.Hence,thereliabilityofaconstructionprojectreferstothefeasibility,possibilityandsafetyofthewholeproductionactivities.Thatis,inordertoguaranteethereliabilityofaconstructionproject,wehavetoassurethefeasibility,possibility,credibilityandsafetyofaprojectunderspecifiedconditions.Generally,however,allthefactorsaffectingtheaccomplishmentoftheprojectarerandomvariables.DenotedbyPt，thereliabilityofconstructioncanbemathematicallymeasuredbytheprobabilityof‘meetingthedesignrequirement’or‘meetingthepre-specifiedprojectperformanceaccordingtotheprojectplanning’.Associatedwiththereliabilityofconstructionisitsprobabilityoffailure,denotedbyPf.Thetwoeventsareexclusive,i.e.,Pt+Pf=1，orPt=1-Pf，where0≤Pt≤1，0≤Pf≤1.Obviously,thereliabilityofconstructioncanalsobedescribedbythenrobabilitvoffailureofaconstructionproject,thatis,wecanjudgethereliabilityofaprojectfromitsprobabilityoffailurebeinglessthantheacceptablerisklevel.Asaresult,itisdesirabletoapplytheprincipleofreliabilityanalysisontotheengineeringriskmanagement,aimingtoimprovetheabilityofriskaversionforanengineeringproject.

Asectionshouldbeprovidedtobrieflyintroducetherestofthepaper.

2ReliabilityAnalysisofConstructionObjectiveSystems

TheperformanceofanengineeringconstructionactivitycanbedefinedintermsofQuality（Q）,TimeDuration（T）,Safety（S）,Normal（N）andCosts（C）.Accordinglythereliabilityoftheconstructionactivityshouldbeexpressedasahierarchymulti-objectivesystem,withfirstlayerbeingTimeDuration（T）,Safety（S）,Normal（N）,andsecondlayertheCosts（C）.Figure1demonstratestherelationshipamongtheobjectives.

Fig.lRelationmodelforobjectivesystemofconstructionactivity

Asfarasaspecificconstructionprocedureisconcerned,therearesomedifferenttaskstorealizeacertainobjectiveinthefirstobjectivelayer,say,Y}.Therelationshipofthesetaskscanbecategorizedasfollowingcases.

（1）Independence.Eachtaskisindependentfromtheothers,andeachcontributessomehowtotherealizationoftheobjective.However,whenthesetasksapplysimultaneously,thefollowingtaskhelpstherealizationofthecontributionfromtheprevioustask.Forexample,inthecastingofmassconcrete,thefollowingseparatetaskscontributeindependentlytothetemperaturecontrol,whichistheobjectiveoftheconstructionprocedure:

addingtheconcreteadditivetoreducethehydrateheat,coveringtheplasticinordertokeepwarm,embeddingcoolingpipelines,etc.

（2）Logicalcorrelation.Onlyaftertheprevioustaskcanthefollowingtaskbegin.Forexample,therelationbetweenlocalizationofformworksandthemeasure/lininginestablishingtheformworksofreinforcementconcretemembercastinsitu.（3）Thecombinationofthe

（1）and

（2）,i.e.,thetasksarebothindependentandlogicallycorrelated.

Hence,forcase

（1）,ifdenotebyφij（0≤φij≤1）theeffectivenessoftheit"task。

。

therealizationofobjectiveYi，then

⑴

Wherepti（n）isthereliabilityofobjectivewhenntasksareindependent.

Forcase

（2）whenmtasksareapplied,

pti（m）=min{φik/k=1,2,3,……,m}⑵

wherepti（m）isthereliabilityofobjectivewhenmtasksarelogicallycorrelated.

Forcase（3）,thetargetreliabilitycanbecalculatedfromequation

（1）and

（2）.

SupposethecostsoftheithtaskareCijforcase

（1）andCikforcase

（2）,respectively.Thenforcase（3）whichisthecombinationofcase

（1）andcase

（2）,thetotalcostforrealizingtheobjectiveY}inthefirstlayeris

⑶

Forcase

（1）,aftertheprevious（n-1）tasks,theadditiveeffectivenessfromthenthtask,whichcanimprovethereliabilityoftheobjectiverealization,canbederivedfromequation

（1）:

⑷

wherePfi（n-1）,Pfi（n1）areprobabilitiesoffailureafter（n-1）andntasks,respectively.

Therefore,forcase

（1）,weshouldchoosethemosteffectivetaskamongthealternativesbasedonthereliabilityofobjectwhichhasalreadypossessesaftertheprevioustasks.Insodoing,thefollowingtaskscanbereduced,andthecostsdeductedaccordingly.Forcase

（2）,however,weshouldguaranteethequalityofeachtask.Itisnotacceptabletoimproveunreasonablytheeffectivenessoftasksbecauseitwillincreasethecosts.

3ReliabilityAnalysisofProcedureSubsystem

3.1ReliabilityCalculationofProcedureSubsystem

Productasconstructionoutputismanufacturedaftertheconstructionprocedures;thereforetheunitofconstructionsystemisconstructionprocedure.Inthecontextofreliabilityanalysis,theunitconstructionprocedurespartitioningthewholeprojectcanbemodeledasaseries-parallelsystem;thesub-divisionproceduresforaunitconstructionprocedurecanalsobemodeledasseries-parallelreliabilitysystem.Basedonthereliabilityanalysistheory,theprobabilityofreliabilityofaseriesconnectionsystemwheneveryprocedureisindependentistheproductofprobabilityofeachprocedure:

⑸

wherejisnumberofconstituentconstructionproceduresoftheseriesconnectionsystem,j=1,2,…，n.

Becauseeachpartoftheparallelsysteminfluencesthefeasibilityofconstructionschemeandthusthereliabilityofconstructiondirectly,whichisaparallelconnectionnon-redundantsystem,therefore,theprobabilityoffailureofaparallelconnectionconstructionsystemistheminimumoftheprobabilitiesofbranches,i.e.:

Pt=min﹛Pk，k=1，2，3，……﹜⑹

WherePkistheprobabilityoffailureofkthbranch.

comestoaseries-parallelsystem,thereliabilityofthewholesystemiscalculatedaftertheprobabilityofseriesconnectionbranchandparallelconnectionbrancharecalculatedbyequation（5）and（6）separately.

3.2ReliabilityImprovementApproachestoProcedureSubsystems

Mostoftenmodeledreliabilitysystemsforconstructionproceduresareseries,parallelandseries-parallel.Fortheconstructionprocedurewithseriesbranches,theprobabilityofreliabilityistheproductofthereliabilityofeachconstituentsystemasshowninEq.（5）.Herein,toenhancethereliabilityofthesystem,thereliabilityofeachconstructionproceduremustbeenhanced.Inaddition,emphasisshouldbeputonthoseconstructionprocedures,thereliabilityofwhichcanbeguaranteedbysomeeasymeasures.Fortheconstructionprocedurewithparallelconnection,however,itisknownfromEq.（6）thatnotonlyshouldweenhancethereliabilityofthesystemaswedoforseriesconnectionsystem,butalsoweshouldminimizethedifferenceofeachconstructionproceduretooptimizethemeasuresforreliabilityimprovement.

Inaddition,numberofconstructionproceduresofproceduresubsysteminfluencesthereliabilityoft