Adesignofsemi-submersibleplatformismainlybasedontheextremeresponseanalysisduetotheforcesexperiencedbythecomponentsduringlifetime.Theexternalloadscaninducetheextremeairgapresponseandpotentialdeckimpacttothesemi-submersibleplatform.Itisimportanttopredictairgapresponseofplatformsaccuratelyinordertocheckthestrengthoflocalstructureswhichwithstandthewaveslammingduetonegativeairgap.Thewindloadcannotbesimulatedeasilybymodeltestintowingtankwhereasitcanbesimulatedaccuratelyinwindtunneltest.Furthermore,fullscalesimulationofthemooringsysteminmodeltestisstillatuffworkespeciallythestiffnessofthemooringsystem.Owingtotheabovementionedproblem,themodeltestresultsarenotaccurateenoughforairgapevaluation.Theaimofthispaperistopresentsensitivityanalysisresultsofairgapmotionwithrespecttothemooringsystemandwindloadforthedesignofsemi-submersibleplatform.Thoughthemodeltestresultsarenotsuitableforthedirectevaluationofairgap,theycanbeusedasagoodbasisfortuningtheradiationdampingandviscousdraginnumericalsimulation.Inthepresenteddesignexample,anumericalmodelistunedandvalidatedbyANSYSAQWAbasedonthemodeltestresultswithasimple4linesymmetricalhorizontalsoftmooringsystem.Accordingtothetunednumericalmodel,sensitivityanalysisstudiesofairgapmotionwithrespecttothemooringsystemandwindloadareperformedintimedomain.Threemooringsystemsandfivesimulationcasesaboutthepresentedplatformaresimulatedbasedontheresultsofwindtunneltestsandsea-keepingtests.Thesensitivityanalysisresultsarevaluableforthefloatingplatformdesign.
