Laterally Loaded Piles With Wings: In Situ Testing With Cyclic Loading From Varying Directions

2013 ◽  
Author(s):  
Christina Rudolph ◽  
Jürgen Grabe
Keyword(s):  
Large Scale ◽  
Load Level ◽  
Lateral Loading ◽  
Offshore Wind ◽  
In Situ Tests ◽  
Laterally Loaded Piles ◽  
Offshore Wind Turbines ◽  
Loading Direction ◽  
Laterally Loaded

The application of piles as foundations for offshore wind turbines yields new requirements for the design. Wind and waves induce a cyclic lateral loading on the pile which changes direction corresponding to the meteorological conditions. Cyclic lateral loading on piles results in accumulated displacements, depending on the cyclic load level and load characteristics. The deformation can increase significantly due to a varying loading direction. Under such loading conditions the pile can drift sideways even if the loading is symmetric. Wings attached to the pile shortly below the seabed have been known to reduce deformations on laterally loaded piles as they locally enlarge the diameter on which the soil resistance is activated. They also change the cross-section of the pile from a circular shape to a star-shape. This might reduce the drifting of the pile. A series of large-scale in-situ tests has been carried out in order to identify the effects of changing loading direction as well as the applicability of winged piles to reduce deformations. Two tubular steel piles (one of them equipped with wings) have been installed and subjected to high-cyclic lateral loading from varying directions. In this paper the in-situ tests and their results are presented.

scholarly journals In Situ Lateral Load Tests on Instrumented Bored Piles in Loessial Soils

2017 ◽  
Vol 13 (1) ◽  
pp. 1-11
Author(s):  
Sebastian Drăghici ◽  
Anatolie Marcu
Keyword(s):  
Large Diameter ◽  
In Situ Tests ◽  
Laterally Loaded Piles ◽  
Natural Moisture Content ◽  
Load Tests ◽  
Bored Piles ◽  
Strength And Stiffness ◽  
Laterally Loaded ◽  
Plaxis 3D

Abstract The aim of the paper is to provide some aspects regarding the behaviour of laterally loaded piles in loessial soils, by presenting and analysing the results of several in situ tests on large diameter bored piles in this type of soil. The major feature of loess is that it exhibits a massive decline of its strength and stiffness parameters when it comes into contact with water, leading to the collapse of its structure even under self-weight and creating difficult conditions for foundations. The load tests were performed both in natural moisture content loess and also in saturated loess. The results obtained by means of instrumentation are back-analysed using current analytical methods and also by finite element method using a numerical model in the geotechnical computation software Plaxis 3D.

Installation and lateral loading tests of suction caissons in silt

2011 ◽  
Vol 48 (7) ◽  
pp. 1070-1084 ◽  
Author(s):  
Bin Zhu ◽  
De-qiong Kong ◽  
Ren-peng Chen ◽  
Ling-gang Kong ◽  
Yun-min Chen
Keyword(s):  
Wind Turbines ◽  
Large Scale ◽  
Lateral Loading ◽  
Offshore Wind ◽  
Scale Model ◽  
Moment Capacity ◽  
Offshore Wind Turbines ◽  
Rotation Center ◽  
Cone Penetration Tests ◽  
Caisson Foundations

A number of potential offshore wind turbines in China will be constructed in sandy silt seabeds, and the mono-caisson foundation is an important choice for these offshore wind turbines. A program of large-scale model tests on suction installation and lateral loading of caisson foundations in saturated silt were carried out in a large soil tank at Zhejiang University. Test results of installation resistance during suction installation show that the seepage effect is limited in silt, and the suction required to penetrate the caisson can be well predicted based on the sleeve friction and cone resistance of cone penetration tests. The deformation mechanism and soil-structure interaction of a caisson subjected to lateral loads were investigated. The instantaneous rotation center of the model caisson at failure was at the depth of about four-fifths of the skirt length, almost directly below the lid center. Based on the assumption of a common position of the instantaneous rotation center and dominating resistance forces on the caisson, an analytical expression for the ultimate moment capacity was presented.

Development of a CFD-CSD Coupling Technique for Large Scale Offshore Wind Turbines

2020 ◽  
Author(s):  
Auraluck Pichitkul ◽  
Lakshmi N. Sankar
Keyword(s):  
Fluid Dynamics ◽  
Renewable Energy ◽  
Wind Turbines ◽  
Large Scale ◽  
Time History ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Renewable Energy Resources ◽  
Aerodynamic Loads ◽  
Offshore Wind Turbines

Abstract Wind engineering technology has been continuously investigated and developed over the past several decades in response to steadily growing demand for renewable energy resources, in order to meet the increased demand for power production, fixed and floating platforms with different mooring configurations have been fielded, accommodating large-scale offshore wind turbines in deep water areas. In this study, the aerodynamic loads on such systems are modeled using a computational structural dynamics solver called OpenFAST developed by National Renewable Energy Laboratory, coupled to an in-house computational fluid dynamics solver called GT-Hybrid. Coupling of the structural/aerodynamic motion time history with the CFD analysis is done using an open File I/O process. At this writing, only a one-way coupling has been attempted, feeding the blade motion and structural deformations from OpenFAST into the fluid dynamics analysis. The sectional aerodynamic loads for a large scale 5 MW offshore wind turbine are presented, and compared against the baseline OpenFAST simulations with classical blade element-momentum theory. Encouraging agreement has been observed.

Load Mitigation Using Slotted Flaps in Offshore Wind Turbines

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Shilpa Thakur ◽  
K. A. Abhinav ◽  
Nilanjan Saha
Keyword(s):  
Large Scale ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Dynamic Link Library ◽  
Trailing Edge ◽  
Offshore Wind Turbines ◽  
Trailing Edge Flaps ◽  
Bottom Structures ◽  
Unsteady Effects ◽  
Bem Theory

This paper focuses on load mitigation by implementing controllable trailing-edge slotted flaps on the blades of an offshore wind turbine (OWT). The benchmark NREL 5 MW horizontal axis OWT is subjected to coupled stochastic aerodynamic-hydrodynamic analysis for obtaining the responses. The OWT is supported on three different fixed-bottom structures situated in various water depths. Blade element momentum (BEM) theory and Morison's equation are used to compute the aerodynamic and hydrodynamic loads, respectively. Presently, the load reduction obtained by means of the slotted flaps is regulated using an external dynamic link library considering the proportional-integral-derivative (PID) controller. BEM theory is presently modified to account for unsteady effects of flaps along the blade span. The present analysis results show reduction up to 20% in blade and tower loads for the turbine with different support structures on implementing controllable trailing edge flaps (TEFs). This study can form the basis for evaluating the performance of large-scale fixed OWT rotors.

scholarly journals The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

2015 ◽  
Vol 8 (4) ◽  
pp. 3481-3522 ◽  
Author(s):  
P. J. H. Volker ◽  
J. Badger ◽  
A. N. Hahmann ◽  
S. Ott
Keyword(s):  
Large Scale ◽  
Wind Farm ◽  
Mesoscale Model ◽  
Wind Farms ◽  
Simulation Models ◽  
Offshore Wind ◽  
Offshore Wind Farms ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. We describe the theoretical basis, implementation and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.

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