A numerical study on the effect of asymmetry on underwater noise emission in offshore monopile installation

Offshore wind energy holds significant promise as a solution in the energy transition. However, installing offshore pile foundations can generate substantial levels of underwater noise, posing potential risks to marine life. This paper examines the influence of asymmetric impact forces and pile inclination on producing underwater noise and seabed vibrations based on cases of a small- and large-diameter monopile. The study focuses on scenarios involving inclined and eccentric forces and tilted piles. The analysis reveals that non-symmetrical conditions significantly impact the sound pressure levels around the ring frequency of the pile due to various noise generation mechanisms. However, it is observed that the vertical component of the impact force predominantly contributes to the generation of underwater noise, primarily due to its considerably higher amplitude.Dynamics of StructuresOffshore EngineeringHydraulic EngineeringEngineering Structure

Correction to: A mode-matching method for the prediction of stick-slip relative motion of two elastic rods in frictional contact (Acta Mechanica, (2022), 233, 2, (753-773), 10.1007/s00707-021-03132-z)

In the original publication, Eqs. (11) and (17) are published incorrectly, and this has been corrected as follows: (Formula presented.) The original article has been revised.Dynamics of StructuresOffshore EngineeringEngineering Structure

Dynamic Response Of Two Interacting Extensible Barsin Frictional Contact

In this paper, a new model is developed to describe the nonlinear dynamics of twoaxially deformable bars sliding relative to each other in which the interaction is governed byfriction. The first bar is fixed at one end and is subjected to a distributed normal force perpen-dicular to its axis to activate friction at the common interface, while the second bar is allowed toslide relative to the fixed one. A semi-analytical solution method is developed in which only thenonlinear interaction is addressed numerically. The dynamic behaviour of the bars is expressedas a summation of vibration modes including the necessary rigid body mode to allow for thepermanent sliding of one bar relative to the other. This results in a computationally efficientscheme without compromising the accuracy of the solutions. The developed model can be usedin pile driveability studies. In this case the fixed bar resembles the soil column while the secondbar describes the dynamics of the driven pile.Offshore EngineeringDynamics of StructuresEngineering Structure

A mode-matching method for the prediction of stick-slip relative motion of two elastic rods in frictional contact

This paper presents a computationally efficient mode-matching method to predict the relative axial motion of two elastic rods in frictional contact. The motion is of the stick-slip type and is non-uniform along the rods. The proposed method utilizes the piecewise linearity of the problem in time and space. The original set of nonlinear partial differential equations describing the dynamics of the coupled system is first reduced to a system of linear, per time interval, ordinary differential equations by means of modal decomposition. The global modes are used for one of the two rods, while for the other rod, different modes are identified per time interval based on the regions in stick or slip phase. Subsequently, the system response is obtained by combining the piecewise linear solutions. A comparison of the solution method proposed with standard numerical techniques shows its advantage both in terms of computational time and accuracy. Numerical examples demonstrate the capability of the method to analyse cases involving either harmonic- or impact-type forces that drive the relative motion. Although the discussion in this paper is limited to the one-dimensional configuration, the approach is generic and can be extended to problems in more dimensions.Dynamics of StructuresOffshore EngineeringEngineering Structure

Vertex corrections to the anomalous hall effect in spin-polarized two-dimensional electron gases with a Rasha spin-orbit interaction

Applied Science

A Mode Matching Technique For The Seismic Response Of Liquid Storage Tanks Including Soil-Structure Interaction

The paper establishes a computationally inexpensive method to deal with the dynamic response of liquid storage tanks subjected to seismic excitation including dynamic soil-structure interaction. The tank is modelled as a thin shell, the stored liquid is described asan inviscid and incompressible fluid and the soil medium is modelled as an elastic continuum.The dynamic response of the tank-liquid-soil system is derived in the frequency domain usingdynamic substructuring and mode matching. The tank vibrations are first expressed in terms ofthe in-vacuo shell modes while the liquid motion is described as a superposition of linear po-tentials. The soil reaction to the plate of the tank is derived on the basis of a boundary integralformulation with the excitation field being the seismic free-field ground motion. Due to its highcomputational efficiency, the proposed method is suitable when a large number of simulations isrequired as is the case in seismic risk analysis. It overcomes the limitations of most mechanicalanalogues used nowadays, while at the same time maintains an accuracy comparable to that offinite element models within a fraction of the computation time of the latter.Offshore EngineeringDynamics of StructuresEngineering Structure

Gentle Driving of Piles (GDP) at a sandy site combining axial and torsional vibrations: Part I - installation tests

Gentle Driving of Piles (GDP) is a new technology for the vibratory installation of tubular (mono)piles. Its founding principle is that both efficient installation and low noise emission can be achieved by applying to the pile a combination of axial and torsional vibrations. Preliminary development and demonstration of the proposed technology are the main objectives of the GDP research programme. To this end, onshore medium-scale tests in sand have been performed on piles installed using both impact and vibratory driving methods (including GDP). After presenting the development of a purpose-built GDP driving device and the geotechnical characterisation of the site, this paper covers the execution of GDP installation tests. Focus is on the installation performance of GDP-driven piles, which is discussed with the aid of structural and ground monitoring data. The comparison between piling data associated with GDP and standard axial vibro-driving points out the potential of the proposed installation technology, particularly with regard to the beneficial effect of the torsional vibration component. The findings of this study encourage further development of the GDP method and its future extension to offshore full-scale conditions.Dynamics of StructuresOffshore EngineeringMacromechanic LaboratoryGeo-engineeringEngineering Structure

Experimental identification of the dynamic behaviour of pile-soil system installed by means of three different pile-driving techniques

A novel pile-driving technique, named Gentle Driving of Piles (GDP), that combines axial low-frequency and torsional high-frequency vibrations has been developed and tested recently. During the experimental campaign, several piles were installed onshore, making use of the GDP shaker. Besides those, a number of additional piles were installed using conventional pile-driving techniques, i.e. impact piling and axial vibratory driving. After the completion of the installation phase, the installed piles have been subjected to impact hammer tests with the following goals. First, the in-situ dynamic properties of the pile-soil system have been identified. Second, the post-installation soil state has been investigated, along with its evolution in time for each pile driving scenario. Preliminary analyses, of the data collected during the impact tests show dissimilar trends in the overall dynamic response between the piles installed with impact hammer and those installed with the axial and the GDP shakers.This observation suggests a difference in the post-installation dynamic behaviour of the pile-soil systems related to different pile-driving techniques. In this paper, a first attempt is made to identify the differences in the overall pile-soil dynamic behaviour of the piles installed by means of the three different pile-driving techniques.Dynamics of StructuresOffshore EngineeringEMSD CE&GGeo-engineeringBusiness RelationsEngineering Structure