土木工程外文翻译原文.docx

1、土木工程外文翻译原文外文原文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 2008Av

2、ailable online 19 March 2008AbstractThe response of Hotel San Diego, a six-story reinforced concrete infilled-frame 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 E

3、lement Method 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 he

4、ight of the 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. Three-dimensional Vierendeel (frame) action of the transverse and longitudinal

5、 frames with 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 o

6、f the structure 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. IntroductionTheprincipa

7、lscopeofspecificationsistoprovidegeneralprinciplesandcomputationalmethodsinordertoverifysafetyofstructures.The“safetyfactor”,whichaccordingtomoderntrendsisindependentofthenatureandcombinationofthematerialsused,canusuallybedefinedastheratiobetweentheconditions.Thisratioisalsoproportionaltotheinverseo

8、ftheprobability(risk)offailureofthestructure.Failurehastobeconsiderednotonlyasoverallcollapseofthestructurebutalsoasunserviceabilityor,accordingtoamoreprecise.Commondefinition.Asthereachingofa“limitstate”whichcausestheconstructionnottoaccomplishthetaskitwasdesignedfor.Therearetwocategoriesoflimitsta

9、te:(1)Ultimatelimitsate,whichcorrespondstothehighestvalueoftheload-bearingcapacity.Examplesincludelocalbucklingorglobalinstabilityofthestructure;failureofsomesectionsandsubsequenttransformationofthestructureintoamechanism;failurebyfatigue;elasticorplasticdeformationorcreepthatcauseasubstantialchange

10、ofthegeometryofthestructure;andsensitivityofthestructuretoalternatingloads,tofireandtoexplosions.(2)Servicelimitstates,whicharefunctionsoftheuseanddurabilityofthestructure.Examplesincludeexcessivedeformationsanddisplacementswithoutinstability;earlyorexcessivecracks;largevibrations;andcorrosion.Compu

11、tationalmethodsusedtoverifystructureswithrespecttothedifferentsafetyconditionscanbeseparatedinto:(1)Deterministicmethods,inwhichthemainparametersareconsideredasnonrandomparameters.(2)Probabilisticmethods,inwhichthemainparametersareconsideredasrandomparameters.Alternatively,withrespecttothedifferentu

12、seoffactorsofsafety,computationalmethodscanbeseparatedinto:(1)Allowablestressmethod,inwhichthestressescomputedundermaximumloadsarecomparedwiththestrengthofthematerialreducedbygivensafetyfactors.(2)Limitstatesmethod,inwhichthestructuremaybeproportionedonthebasisofitsmaximumstrength.Thisstrength,asdet

13、erminedbyrationalanalysis,shallnotbelessthanthatrequiredtosupportafactoredloadequaltothesumofthefactoredliveloadanddeadload(ultimatestate).Thestressescorrespondingtoworking(service)conditionswithunfactoredliveanddeadloadsarecomparedwithprescribedvalues(servicelimitstate).Fromthefourpossiblecombinati

14、onsofthefirsttwoandsecondtwomethods,wecanobtainsomeusefulcomputationalmethods.Generally,twocombinationsprevail:(1)deterministicmethods,whichmakeuseofallowablestresses.(2)Probabilisticmethods,whichmakeuseoflimitstates.Themainadvantageofprobabilisticapproachesisthat,atleastintheory,itispossibletoscien

15、tificallytakeintoaccountallrandomfactorsofsafety,whicharethencombinedtodefinethesafetyfactor.probabilisticapproachesdependupon:(1)Randomdistributionofstrengthofmaterialswithrespecttotheconditionsoffabricationanderection(scatterofthevaluesofmechanicalpropertiesthroughoutthestructure);(2)Uncertaintyof

16、thegeometryofthecross-sectionsandofthestructure(faultsandimperfectionsduetofabricationanderectionofthestructure);(3)Uncertaintyofthepredictedliveloadsanddeadloadsactingonthestructure;(4)Uncertaintyrelatedtotheapproximationofthecomputationalmethodused(deviationoftheactualstressesfromcomputedstresses)

17、.Furthermore,probabilistictheoriesmeanthattheallowableriskcanbebasedonseveralfactors,suchas:(1)Importanceoftheconstructionandgravityofthedamagebyitsfailure;(2)Numberofhumanliveswhichcanbethreatenedbythisfailure;(3)Possibilityand/orlikelihoodofrepairingthestructure;(4)Predictedlifeofthestructure.Allt

18、hesefactorsarerelatedtoeconomicandsocialconsiderationssuchas：(1)Initialcostoftheconstruction;(2)Amortizationfundsforthedurationoftheconstruction;(3)Costofphysicalandmaterialdamageduetothefailureoftheconstruction;(4)Adverseimpactonsociety;(5)Moralandpsychologicalviews. Thedefinitionofalltheseparamete

19、rs,foragivensafetyfactor,allowsconstructionattheoptimumcost.However,thedifficultyofcarryingoutacompleteprobabilisticanalysishastobetakenintoaccount.Forsuchananalysisthelawsofthedistributionoftheliveloadanditsinducedstresses,ofthescatterofmechanicalpropertiesofmaterials,andofthegeometryofthecross-sec

20、tionsandthestructurehavetobeknown.Furthermore,itisdifficulttointerprettheinteractionbetweenthelawofdistributionofstrengthandthatofstressesbecausebothdependuponthenatureofthematerial,onthecross-sectionsandupontheloadactingonthestructure.Thesepracticaldifficultiescanbeovercomeintwoways.Thefirstistoapp

21、lydifferentsafetyfactorstothematerialandtotheloads,withoutnecessarilyadoptingtheprobabilisticcriterion.Thesecondisanapproximateprobabilisticmethodwhichintroducessomesimplifyingassumptions(semi-probabilisticmethods).As part of mitigation programs to reduce the likelihood of mass casualties following

22、local damage in structures, the General Services Administration 1 and the Department of Defense 2 developed regulations to evaluate progressive collapse resistance of structures. ASCE/SEI 7 3 defines progressive collapse as the spread of an initial local failure from element to element eventually re

23、sulting in collapse of an entire structure or a disproportionately large part of it. Following the approaches proposed by Ellinwood and Leyendecker 4, ASCE/SEI 7 3 defines two general methods for structural design of buildings to mitigate damage due to progressive collapse: indirect and direct desig

24、n methods. General building codes and standards 3,5 use indirect design by increasing overall integrity of structures. Indirect design is also used in DOD 2. Although the indirect design method can reduce the risk of progressive collapse 6,7 estimation of post-failure performance of structures desig

25、ned based on such a method is not readily possible. One approach based on direct design methods to evaluate progressive collapse of structures is to study the effects of instantaneous removal of load-bearing elements, such as columns. GSA 1 and DOD 2 regulations require removal of one load bearing e

26、lement. These regulations are meant to evaluate general integrity of structures and their capacity of redistributing the loads following severe damage to only one element. While such an approach provides insight as to the extent to which the structures are susceptible to progressive collapse, in rea

27、lity, the initial damage can affect more than just one column. In this study, using analytical results that are verified against experimental data, the progressive collapse resistance of the Hotel San Diego is evaluated, following the simultaneous explosion (sudden removal) of two adjacent columns,

28、one of which was a corner column. In order to explode the columns, explosives were inserted into predrilled holes in the columns. The columns were then well wrapped with a few layers of protective materials. Therefore, neither air blast nor flying fragments affected the structure.2. Building charact

29、eristicsHotel San Diego was constructed in 1914 with a south annex added in 1924. The annex included two separate buildings. Fig. 1 shows a south view of the hotel. Note that in the picture, the first and third stories of the hotel are covered with black fabric. The six story hotel had a non-ductile

30、 reinforced concrete (RC) frame structure with hollow clay tile exterior infill walls. The infills in the annex consisted of two withes (layers) of clay tiles with a total thickness of about 8 in (203 mm). The height of the first floor was about 190800 (6.00 m). The height of other floors and that of the top floor were 100600 (3.20 m) and 1601000 (5.13 m), respectively. Fig. 2 shows