Oneofthemainconcernsinusingcommercialsoftwareforfiniteelementanalysesofdam-foundation-reservoirsystemsisthatthesimplifyingassumptionsofthemasslessfoundationareunreliable.Inthisstudy,anappropriatedirectfiniteelementmethodisintroducedforsimulatingthemass,radiationdampingandwavepropagationeffectinfoundationsofdamfoundation-reservoirsystemsusingcommercialsoftwareABAQUS.Thefree-fieldboundaryconditionisusedformodelingthesemi-infinitefoundationandradiationdamping,whichisnotabuilt-inboundaryconditioninmostoftheavailablecommercialsoftwareforfiniteelementanalysisofstructuressuchasANSYSorABAQUSandthusneedstobeimplementeddifferently.Thedifferentmechanismformodelingofthefoundation,earthquakeinputandfar-fieldboundaryconditionisdescribed.Implementationofthefree-fieldboundaryconditioninfiniteelementsoftwareisverifiedbycomparingitwithanalyticalresults.Toinvestigationthefeasibilityoftheproposedmethodindam-foundation-reservoirsystemanalysis,aseriesofanalysesisaccomplishedinavarietyofcasesandtheobtainedresultsarecomparedwiththesubstructuremethodbyusingtheEAGD-84program.Finally,themassedandmasslessfoundationresultsarecomparedanditisconcludedthatthemasslessfoundationapproachleadstotheoverestimationofthedisplacementsandstresseswithinthedambody.
