Aseismicdesignofstructure–equipmentsystemsusingvariablefrequencypendulumisolatorOriginalResearchArticle

Slidingisolationsystemshaveemergedasveryusefulvibrationcontroltechniquethatincorporateisolation,energydissipationandrestoringmechanisminoneunit.However,mostcurrentlyavailablesystemssuchasfrictionpendulumsystem(FPS)andpurefriction(PF)systemhavepracticallimitationsandareoflimitedeffectivenesswheninputexcitationlevelissignificantlydifferentfromitsdesignlevel.Toovercometheselimitationswhilepreservingtheadvantages,anewsystemcalledthevariablefrequencypendulumisolator(VFPI)hasbeendevelopedbytheauthors.TheisolationperiodofVFPIcontinuouslydecreaseswithincreaseinhorizontalslidingdisplacementwhichresultsinamorerobustisolationsystem.TheVFPIalsolimitsthemaximumforcetransmittedtothestructurebyprovidingarestoringforce-softeningmechanism.Inthispaper,ithasbeenshownthatisolatingastructureusingVFPIisveryeffectiveforvibrationcontrolofstructure–equipmentandotherprimary–secondarysystems.Anexamplefive-storeystructurewithequipmentmountedatitstophasbeenanalysedtodemonstratetheeffectivenessofVFPI.ItisshownthatVFPIprovidesbettervibrationcontrolpropertiescomparedtootherfrictionisolationsystems,andexcellentresponsereductionisobservedforawiderangeofequipmentpropertiesandexcitationcharacteristics.TheperformanceoftheexamplestructurewithVFPIhasbeencomparedwiththeotherfrictionalsystemssuchasFPSandPFsystem.