Thestrengthreserveduetorestrainedbendinginbrittle-matrixstructuresOriginalResearchArticle

Purelyflexural(i.e.,intheabsenceofmembraneforces)responseofstructureswithno-tensionorquasi-brittlematrixisrarelypossible.Whenin-planedisplacementsatslabsupportsarerestrained,importantcompressivemembraneforcesoccurfromtheverybeginningofthedeformationprocess.Theystrengthenseriouslythestructure(the“domeeffect”)butmakeitsresponseextremelyunstable.Therefore,theanalysisaimingatevaluationoftheultimatestrengthforsuchstructures,evenwhenbasedonasimpleelastic–plasticmodel,appearstobecumbersomeandfrustratingpotentialusers.Thecorrespondinggeometricallynon-linearprocedures,especiallyifcommercialfiniteelementcodesareused,becomeslowandcapricious.ThedirectFEMapproachtorestrainedbendingisstilloflimitedutilityforpracticalpurposesandsimplifiedmethodsareneeded,especiallyforrapiddiagnosticofmassiveconcreteslabs.