Nonlinear dynamics design for logically anti-collision device of offshore wind turbines
Offshore wind farms frequently experience ship collision incidents,leading to structural damage or even cessation of wind farm operations,with substantial economic losses.To mitigate the structural damage caused by ship collisions,this study proposes a novel all-steel quasi-negative stiffness elastic protective device,characterized by logistically changeable stiffness features passively based on the contact speed of the ship.Initially,a finite element numerical model of a single-pile foundation wind turbine collision with a ship was established.The calculations indicate that,compared to rubber protective devices,the novel protective device reduces collision force and tower top acceleration by 56.1%and 32%,respectively.A two-degree-of-freedom nonlinear dynamics model coupling the variable cross-section structure of offshore wind turbines with the quasi-negative stiffness device was further constructed.A multi-scale analytical method was consequently developed,effectively depicting the nonlinear energy exchange and dissipation processes during ship collisions.Analytical calculations closely match numerical solutions,scientifically delineating the"low speed ship approach with high stiffness-high speed collision with low stiffness"mechanical characteristics unique to wind turbine structures equipped with the novel protective device.An engineering method was established,featuring efficient design of key parameters through the analytical model and detailed design of specific components using the finite element model.Using a single-pile foundation structure of offshore wind turbines as a model,a logically anti-collision engineering design was implemented.
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