Prolonged　lateral　cyclic　loading　leads　to　soil　stiffness　degradation　around　offshore　wind　turbine　(OWT)　foundations,　which　reduces　the　system＇s　natural　frequency　and　increases　the　accumulation　of　foundation　rotation　angle.　Proper　evaluation　of　natural　frequency　and　rotation　angle　is　crucial　for　the　design　of　OWT　foundations.　This　study　develops　a　two-stages　numerical　approach　to　calculate　the　fundamental　frequency　of　OWT　systems　considering　the　foundation　stiffness　degradation　by　integrating　a　stiffness　degradation　model　of　soft　clays　with　a　simplified　three-spring　model.　Subsequently,　it　investigates　the　evolution　of　accumulated　rotation　and　natural　frequency　for　three　foundation　types—monopile,　monopod　bucket,　and　hybrid　monopile-bucket—throughout　their　service　life.　It　is　observed　that　the　hybrid　foundation　shows　the　smallest　rotation　in　the　first　cycle,　attributable　to　its　relatively　high　initial　stiffness　compared　to　the　other　two　foundations　with　the　same　steel　consumption.　However,　it　also　exhibits　the　highest　rate　of　cumulative　rotation　growth.　At　the　same　load　level,　the　monopod　bucket　foundation　exhibits　the　largest　cumulative　rotation　angle　due　to　its　lower　bearing　capacity,　and　the　degradation　of　natural　frequency　is　most　pronounced　for　monopod　bucket　OWT.　For　all　three　foundation　configurations,　increasing　either　the　pile　diameter　or　the　bucket　diameter　is　the　most　effective　approach　to　reduce　the　cumulative　rotation　angle　and　improve　natural　frequency　degradation,　while　maintaining　the　same　steel　consumption.　These　findings　should　be　considered　in　the　design　of　OWT　foundations.　©　2024　Elsevier　Ltd