SimulatingstructuralcollapseofaPWRcontainmentOriginalResearchArticle

NNCLimitedwassponsoredbytheHealth&SafetyExecutive(UK)toconductfiniteelementanalysistosimulatetheover-pressurisationtestsconductedona1/4scalemodelofapre-stressedconcretecontainmentvessel(PCCV)bySandiaNationalLaboratories.Thetestsandtheresultsindicatedthreedistinctstagesofstructuralresponseasthevesselapproacheditsfailureload.Thefirststagewasessentiallyanelasticresponse.Thesecondstagedisplayednonlinearbehaviour,whichstartedafteronsetofsubstantialconcretecrackingandinvolvedlocalyieldingorfractureofstructuralcomponents.Thethirdstageinvolvedextensiveconcretecrackingandrapidincreaseinstrainsleadingtoglobalstructuralcollapse. Thispaperdiscussestheengineeringjudgmentusedtodevelopthe3Dfiniteelement(FE)globalmodel,whichwassuccessfullyanalysedtopredictthefailuremode.Forthelimitstatetest(LST),itwasshownthatthelinerrupturesbeforestructuralcollapse.Forthestructuralfailuremodetest(SFMT),theasymmetricbehaviourwassuccessfullypredicted,identifyingtheweakareainthevesselwherethestructuralcollapsewasinitiated.Thiswaspossiblebecausethe3Dmodelsimulatedtheinteractionoftheessentialstructuralfeaturessuchasthetendons,buttresses,liner,penetrationsandthebasemat.Explicitmodellingofthepost-tensionedtendonsallowedthemodeltoaccommodatefrictionalloss,simulatingrealisticreductioninthepre-stresslevelsincertainareas.Detailedmodellingofthepenetrationsandbuttressessimulatedlocalstiffeningofthecylindricalwall.Themaximumdeflectionwasexpectedatthemid-heightofthewallintheareaawayfromlocalstiffeningandwherethepre-stresslevelshadreducedduetofriction.ThisweakareawasidentifiedbytheFEmodelandwasconfirmedbythetest.