Numerical determination of equivalent damping parameters for a finite element model to predict the underwater noise due to offshore pile driving

Start Page
605
End Page
610
Citation
Euronoise: 605-610 (2015-06)
Contribution to Conference
Euronoise 2015 
Due to the massive construction of offshore wind parks in the German North Sea, an increasing attention has been directed to underwater noise. In particular, limiting values for the sound pressure level during construction have been introduced by the German authorities to protect marine life. State-of-the-art technology for the erection of the wind turbines is impact pile driving. Hence, a reliable prediction technique for the noise due to pile driving with an impact hammer becomes increasingly important. At present, different numerical methods are under development for these kinds of forecasts. The most common approach used to calculate the sound pressure in the area close the pile is the finite element method (FEM). In several publications, an equivalent damping in the embedded part of the pile is chosen to take the losses, e.g. the plasticity of the soil, into account. In this contribution, a method to determine the equivalent damping with the "Wave Equation Analysis of Pile Driving" (WEAP) is shown. During a drivability study performed with WEAP, the Rayleigh damping coefficients are extracted. Finally, these coefficients are validated by comparing predicted values calculated with the FEM to measured data.