Kinematic response of flexible suction caissons for offshore wind turbines to vertically incident shear waves

Abstract

This paper presents the translational and rotational kinematic interaction factors of flexible suction caissons considering structural and soil properties relevant to the seismic analysis of offshore wind turbines. Kinematic stresses developed along the foundation skirt are also presented and analyzed. The parametric analysis performed considers four height-to-diameter ratios between 0.5 and 2, three skirt thickness-to-diameter ratios between 0.5% and 2.0%, and four different relevant skirt-soil stiffness ratios for sand soils. The foundations are as- summed to be founded in homogenous and non-homogeneous soils, and they are considered to be subjected to vertically-incident shear waves. The kinematic response of the foundations is computed through an advanced boundary element - finite element coupled numerical model. It is found that the kinematic interaction factors are fundamentally independent of the skirt-soil stiffness ratio. It is also found that the general pattern of the kinematic interaction factors is analogous to that of piles, and that significant filtering of the seismic input motions can be observed. Results are presented in ready-to-use dimensionless plots. Regarding kinematic stresses, shell-like or beam-like behaviour is observed depending on height-to-diameter ratio of the skirt.