Pile Fixity Length Estimation of the Offshore Wind turbine’s Jacket Substructure Under Lateral Loading Considering Nonlinear Soil-Pile Interaction

Modeling the soil-pile interaction by Finite Element Method (FEM) might be a time-consuming process and re-quired fully detailed soil properties that are not easily accessible. Instead, there are alternative modeling methods such as apparent fixity model, coupled springs model, and distributed springs model. In the apparent fixity model for pile foundation systems a fixity length level below the seabed is designated for the pile to be fixed at. It is assumed that whole structure consist of the pile and support structure is cantilevered at corresponding fixity length level with-out surrounding soil and has a lateral deflection similar to a pile penetrated into the soil. In this study the apparent fixity length of the piles sustaining the OC4 offshore wind turbine jacket on the seabed is calculated by applying anon-linear soil-pile interaction analysis follow-on a dynamic response analysis of the structure under lateral excita-tions. Regarding stiffness coefficients, different apparent fixity lengths are obtained. Moreover, it is demonstrated that the calculated fixity lengths take smaller values than piles’ critical lengths.

Keywords:

Offshore wind turbine , Jacket , Soil-pile interaction , Fixity length