Document Type : Research
Associated professor of Civil Eng., University of Guilan, Guilan, Iran.
PhD candidate of Civil Eng., University of Guilan. Guilan, Iran.
Offshore wind turbines (OWT) are considered as one the most promising ways of harvesting green energies in the world. OWTs are dynamically sensitive as their loading frequency is close to their natural frequency, allowing a narrow band of frequency to avoid resonance. Therefore, precise estimation of their natural frequency (fn) can be crucial. Soil-structure interactions (SSI) can be of great importance in estimation of dynamic characteristics of OWTs. In this study, a standard offshore wind turbine is modeled using FLAC-3D in two cases of fixed-base, i.e. with no SSI and another case with full system of soil and structural parts to estimate the effects of SSI on the natural frequency of the OWT systems. The result showed that modeling the OWT in the fixed base state results in overestimation of the system’s natural frequency for 20 percent which can be misleading in the design process. Besides, the damping ratio was largely underestimated in the fixed base condition due to the main contribution of soil damping. Therefore, the importance of soil-structure interactions was emphasized in modeling and design of offshore wind turbines.