ABSTRACT
Offshore wind turbines (OWTs) are subjected to torsional loads because of off-centric horizontal loads from wind and wave action. Torsional loads are also generated from machine vibrations, and accidental collisions from ships and icebergs. The studies available in the literature for foundations supporting OWTs mostly account for lateral loads. In this paper, a continuum-based analysis for torsional dynamics of suction caisson foundations is shown. The Extended Hamilton′s Principle is applied to deduce the differential equations governing caisson and soil deformation, which are solved analytically in an iterative algorithm. The degree of accuracy of the analysis is assessed with an existing study in the literature. From the analysis, caisson-head stiffness for a few values of caisson slenderness ratio and typical range of caisson-soil stiffness ratios, and applied frequency are obtained and reported. The caisson-head stiffness reported can be used to obtain the natural frequency of the OWT structure.
