Numerical study on the deformation response of the monopod bucket foundation under lateral loads

The monopod bucket foundation is one of the promising foundation types for the offshore wind turbine. An accumulated deformation of foundation should not exceed the tolerance value and should be within the service limit state requirement. Under long-term cyclic loads from wave, current and wind, it is essential to evaluate the stability and permanent deformation of the foundation during 20-year service life of offshore wind turbine. The current semi-empirical methods mostly used for estimating accumulated rotation are proposed by Zhu et al. (2013) and Foglia et al. (2014). These methods consist 2 parameters, Tb (dimensionless ratio of maximum cyclic moment) and Tc (dimensionless ratio of minimum cyclic moment). The results of model tests show that Tb and Tc are related to Dr (relative density of soil). However, the suggested method to determine the deformation parameters Tb and Tc is still not presented. In this study, a numerical model programmed with finite element method collaborated with stiffness degradation model proposed by Achmus et al. (2009) is established to duplicate the deformation of monopod bucket foundation in model test results of Foglia et al. (2014). The relationship between Dr and 2 deformation parameters, Tb and Tc, can be determined by the numerical model presented in this study.