© Springer Nature Singapore Pte Ltd. 2019. With offshore wind turbines increasing in size, there is increasing interest in non-traditional support structures. New concepts include lightweight and flexible fiberglass composite towers that have potential benefits over traditional stiff steel towers. The aim of this paper was to assess how the combination of a more flexible wind turbine tower with an offshore concrete gravity base foundation would affect the dynamic response of the structure. The results focus on how the dynamic amplification factors (DAFs) change with varying levels of foundation stiffness during an extreme event (50 year return period extreme event).