Chapter B Concrete Structures

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1、BConcreteStructuresB.1IntroductionInthissectionanumberofcasestudiesinconcreteareexaminedunderimpactandexplosionconditions.Inmostcases,theresultsobtainedfromempiricalformulaeandfinite-elementanalysisarecomparedwiththoseavailablefromexperimentsandsitemonitoring.Someconcretestructureshavebeena

2、nalyzedlateroninothersectionsaswell.Thechoiceisbasedsimplyontheirusage.Impactsandexplosionsorblastsdemandthattheeffectsofthestrainrateofconcretemustbeincludedintheglobalanalysisofconcretestructures.Thetextgivesnumerousdataonthissubject.TableB.1givesthevaluesofstrainratesforconcreteundercomp

3、ression,tensionandbendingconditions.B.2ConcreteBeamsB.2.1ReinforcedConcreteBeamsAreinforcedconcretebeamwhichhasalreadybeentestedinthelaboratorymustbeanalyzedsothatabasisisestablishedforthevalidationofthenumer-icaltools.Ohnuma,ItoandNomachibeamswerechosenforthiswork;over18beamshavebeenanaly

4、zed.FigureB.1showstheimpactloadingsystemwhichgeneratesimpactonspecimensbyahigh-speedstrikinghammer.Thestrik-inghammerisahardsteelcylinderwithadiameterof98mm.Theweightofthehammeris70kg.Themaximumvelocitywasrestrictedto50ms−1.FigureB.2showstherelationshipbetweenimpactforceandimpactvelocity.T

5、hebendingfailureoccurredatlowvelocityandshearingfailureoccurredathigh-velocityimpact.Theload–timefunctionadoptedisshowninFig.B.3.FigureB.4showsthefinite-elementmeshschemeadoptedforA-20,A-30andA-50beams.Velocitiesrangingfrom0to30ms−1forthesameimpactwerechosen.Theimpactforceswerecalculatedand

6、areplottedonFig.B.2;astrainrateof20s−1878BConcreteStructuresTableB.1.Strainratesforconcreteunderconditionsofcompression,tensionandbendingTestapparatusforMaximumstrain−1highstrainratesrate(s)UndercompressionAnytypeofcompressionDropweight10.00Dropweight2.00Dropweight20.00Hydraulic0.50SplitHo

7、pkinson1,000.00Pressure(bar)120UndertensionUni-axialtensionCompressedair-driven0.05loadingSplittingtensionHydraulic0.20Uni-axialtension‘Pelletmethod’—high20.00velocityprojectileUni-axialtensionSplitHopkinson(bar)0.75Uni-axialtensionwithConstantstrainrate0.01Eff