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1、外文原文Response of a reinforced concrete infilled-frame structure to removal of two adjacent columnsMehrdad Sasani_Northeastern University, 400 Snell Engineering Center， Boston， MA 02115, United StatesReceived 27 June 2007; received in revised form 26 December 2007; accepted 24 January 2008Available on
2、line 19 March 2008AbstractThe response of Hotel San Diego， a six-story reinforced concrete infilledframe structure， is evaluated following the simultaneous removal of two adjacent exterior columns。 Analytical models of the structure using the Finite Element Method as well as the Applied Element Meth
3、od are used to calculate global and local deformations. The analytical results show good agreement with experimental data。 The structure resisted progressive collapse with a measured maximum vertical displacement of only one quarter of an inch （6。4 mm). Deformation propagation over the height of the
4、 structure and the dynamic load redistribution following the column removal are experimentally and analytically evaluated and described. The difference between axial and flexural wave propagations is discussed. Threedimensional Vierendeel （frame） action of the transverse and longitudinal frames with
5、 the participation of infill walls is identified as the major mechanism for redistribution of loads in the structure. The effects of two potential brittle modes of failure (fracture of beam sections without tensile reinforcement and reinforcing bar pull out） are described。 The response of the struct
6、ure due to additional gravity loads and in the absence of infill walls is analytically evaluated. c 2008 Elsevier Ltd。 All rights reserved。Keywords： Progressive collapse; Load redistribution; Load resistance； Dynamic response; Nonlinear analysis; Brittle failure1. IntroductionTheprincipalscopeofspec
7、ificationsistoprovidegeneralprinciplesandcomputationalmethodsinordertoverifysafetyofstructures。The“safetyfactor”，whichaccordingtomoderntrendsisindependentofthenatureandcombinationofthematerialsused，canusuallybedefinedastheratiobetweentheconditions。Thisratioisalsoproportionaltotheinverseoftheprobabil
8、ity(risk)offailureofthestructure.Failurehastobeconsiderednotonlyasoverallcollapseofthestructurebutalsoasunserviceabilityor,accordingtoamoreprecise.Commondefinition。Asthereachingofa“limitstate”whichcausestheconstructionnottoaccomplishthetaskitwasdesignedfor。Therearetwocategoriesoflimitstate：(1）Ultima
9、telimitsate，whichcorrespondstothehighestvalueoftheload-bearingcapacity。Examplesincludelocalbucklingorglobalinstabilityofthestructure；failureofsomesectionsandsubsequenttransformationofthestructureintoamechanism；failurebyfatigue；elasticorplasticdeformationorcreepthatcauseasubstantialchangeofthegeometr
10、yofthestructure；andsensitivityofthestructuretoalternatingloads，tofireandtoexplosions。（2）Servicelimitstates，whicharefunctionsoftheuseanddurabilityofthestructure。Examplesincludeexcessivedeformationsanddisplacementswithoutinstability;earlyorexcessivecracks;largevibrations；andcorrosion。Computationalmeth
11、odsusedtoverifystructureswithrespecttothedifferentsafetyconditionscanbeseparatedinto：（1)Deterministicmethods,inwhichthemainparametersareconsideredasnonrandomparameters.（2）Probabilisticmethods，inwhichthemainparametersareconsideredasrandomparameters.Alternatively,withrespecttothedifferentuseoffactorso
12、fsafety，computationalmethodscanbeseparatedinto：（1）Allowablestressmethod，inwhichthestressescomputedundermaximumloadsarecomparedwiththestrengthofthematerialreducedbygivensafetyfactors。(2）Limitstatesmethod，inwhichthestructuremaybeproportionedonthebasisofitsmaximumstrength。Thisstrength，asdeterminedbyrat
13、ionalanalysis，shallnotbelessthanthatrequiredtosupportafactoredloadequaltothesumofthefactoredliveloadanddeadload（ultimatestate）.Thestressescorrespondingtoworking(service）conditionswithunfactoredliveanddeadloadsarecomparedwithprescribedvalues(servicelimitstate).Fromthefourpossiblecombinationsofthefirs
14、ttwoandsecondtwomethods，wecanobtainsomeusefulcomputationalmethods。Generally，twocombinationsprevail：（1)deterministicmethods,whichmakeuseofallowablestresses。（2）Probabilisticmethods，whichmakeuseoflimitstates。Themainadvantageofprobabilisticapproachesisthat，atleastintheory，itispossibletoscientificallytakeintoaccountallrandomfactorsofsafety,whicharethencombinedtodefinethesafetyfactor。probabilisticapproachesdependupon:（1)Randomdistributionofstrengthofmaterialswithrespecttotheconditionsoffabricationanderection（scatterofthevaluesofmechanicalpropertiesthroughout
