| Popis: |
The growth of offshore wind turbines pushes the size of monopile foundations and with that the size of anvils that are used to install monopiles. The current simulation programs that are used to predict the pile driveability rely on simple models to represent the anvils. Those models are shown to be inaccurate, especially for anvils > 5.5 m, which reflects directly on the accuracy of the driveability prediction result. Also for pile driving noise emission predictions the force wave that travels through the pile must be estimated accurately, including its high-frequency content, which is not possible with the currently available impact pile driving simulation programs. To overcome this shortcoming, a novel anvil modelling approach is proposed, based on the Mode Displacement Method, which is a Reduced Order Modelling approach. The resulting anvil models are robust and universally applicable since the methodology relies only on a FE model and just a single parameter to defines the model frequency content. A comparison of the simulation results with the novel anvil model to FEA results shows that all relevant behaviour during impact is caught very accurately by the application of the proposed anvil model. Instead the former lumped-mass anvil model results in a large overestimation of the impact force in the impact simulation with an 8 meter anvil, and also relevant high-frequency effects in the force wave are not captured with that model. A validation of the new anvil model based on PDA measurement data from the installation of a wind turbine monopile in the North Sea shows a good match between simulation and reality. |
