Abstract
Recent developments in the construction of offshore wind turbines have created the need for a method to detect whether a monopile foundation is plastically deformed during the installation procedure. Since measurements at the pile head are difficult to perform, a method based on measurements at a certain distance below the pile head is proposed in this work for quantification of the amount of plasticity. By considering a onedimensional rod model with an elastic-perfectly plastic constitutive relation, it is shown that the occurrence of plastic deformation caused by an impact load can be detected from these measurements. Furthermore, this plastic deformation can be quantified by the same measurement with the help of an energy balance. The effectiveness of the proposed method is demonstrated via a numerical example.
Highlights
In recent years, the number of offshore wind farms has considerably increased to meet the demand for energy from renewable resources
Compared to a grouted connection, a bolted connection is more sensitive to material damage inflicted by the pile driving process since the wind turbine is directly connected to the pile head
This work focuses on using the measurement data from these sensors to detect and quantify plastic deformations inflicted by the pile driving process
Summary
The number of offshore wind farms has considerably increased to meet the demand for energy from renewable resources. Compared to a grouted connection, a bolted connection is more sensitive to material damage inflicted by the pile driving process since the wind turbine is directly connected to the pile head. A method to detect and quantify the damage caused by the pile driving process is essential in order to assess the structural health of a monopile. F(t) x = 0 x = a x, u x = L Figure 1: Sketch of the pile driving process (left) and the mathematical one-dimensional model (right). This work focuses on using the measurement data from these sensors to detect and quantify plastic deformations inflicted by the pile driving process. The monopile is modelled by the one-dimensional rod theory [4], which includes the Rayleigh-Love correction term [5] to account for stress wave dispersion expected for. The input energy of the hammer is governed by the impact velocity of the ram v0
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