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1、ACIMATERIALSJOURNALTECHNICALPAPERTitleno.105-M69UnbiasedStatisticalComparisonofCreepandShrinkagePredictionModelsbyZdenekP.BažantandGuang-HuaLiThispaperaddressestheproblemofselectingthemostrealisticcomparisonsofthemainpredictionmodelsforcreepandcreepandshrinkageprediction
2、model,importantfordesigningshrinkageofconcreteandexplainwhyvariousnonstandarddurableandsafeconcretestructures.Statisticalmethodsofstatisticalindicatorshaveledtodubiousconclusions.ThesamestandardandseveralnonstandardtypesandaverylargeexperimentalfivemodelsasinReference7wi
3、llbestatisticallyevaluated:databasehaverecentlybeenusedtocompareandranktheexisting1.ModelB3,1995,whichwasapprovedastheinternationalpredictionmodels,butconflictingresultshavebeenobtainedby2721RILEMRecommendationandslightlyupdatedin2000variousinvestigators.Thispaperattempt
4、stoovercomethis9confusion.Itintroducesdataweightingrequiredtoeliminatethe(thismodelisarefinementofthe1978ModelBPandofitsimprovementasModelBP-KX13);biasduetoimproperdatasamplinginthedatabase,andthen2.ACImodel,8basedon1960sresearch,reapprovedbyexaminesBažantandBaweja’sMode
5、lB3,theACImodel,theCEBmodel,andtwoofGardner’smodels.ThestatisticsofpredictionACICommittee209in2008;errorsarebasedstrictlyonthemethodofleastsquares,whichisthe3.ModelofComitéEuropéenduBéton,labeledCEB,standardandtheonlystatisticallycorrectmethod,dictatedbythewhichisbasedon
6、theworkofMüllerandHilsdorf3(itwasmaximumlikelihoodcriterionandthecentrallimittheoremoftheadoptedin1990byCEB,12updatedin1999,28andco-optedtheoryofprobability,aswellastherequirementofnoncorrelationin2002forEurocode2);oferrors.Severalnonstandardstatisticalmethodsthathave204
7、.GardnerandLockman’smodel,labeledGL;andrecentlybeeninventedtoevaluatecreepandshrinkagemodelsare19alsoexaminedandtheirdeficienciesarepointedout.Theranking5.Gardner’searliermodel,labeledGZ.Sakata’smodel,18,22whosescopeissomewhatlimited,ofthemodelsthatensuesfromtheleast-squ
8、areregressionstatisticsisshowntobequitedifferentfromtherankingsobtainedbytheaswellasthecrudeoldmodelsof