사질토 지반에 설치된 버킷기초의 비선형 강성 매트릭스 산정사질토 지반에 설치된 버킷기초의 비선형 강성 매트릭스 산정

Abstract

Bucket foundations are increasingly used for supporting offshore wind turbines (OWT). The design of bucket foundation for OWT is usually governed by combined loads from wind and waves. For the combined load analysis, it is important to predict and input the stiffness of the foundation appropriately. So far, the elasticity of stiffness of gravity type shallow foundations has been proposed through previous studies, but there is a lack of research considering the nonlinearity of actual ground. Further, in the case of the bucket foundation, there is no clear design formula or method for predicting the rigidity of the foundation. In this study, the stiffness matrix of the bucket foundation embedded in a sandy soil is developed by performing the FE analysis considering the non-linearity of the soil. Hardening Soil model of PLAXIS 3D program is adopted and the input parameters are estimated by the stiffness reduction curve (G/Gmax) to match the small strain behavior of the soil. The stiffness matrix of the bucket foundation is considered by adopting lumped model with six degree of freedom. The stiffness matrix calculated by the Hardening Soil model is compared to the Mohr-Coulomb model. The non-linear stiffness matrixes for three different length-to-diameter ratios and five different friction angles are developed. Also, the dimensionless stiffness matrixes of all cases are presented in this study.