University of Surrey

Test tubes in the lab Research in the ATI Dance Research

Closed form solution for the first natural frequency of offshore wind turbine jackets supported on multiple foundations incorporating soil-structure interaction

Jalbi, M Saleh and Bhattacharya, Suby (2018) Closed form solution for the first natural frequency of offshore wind turbine jackets supported on multiple foundations incorporating soil-structure interaction Soil Dynamics and Earthquake Engineering, 113. pp. 593-613.

[img]
Preview
Text
__homes.surrey.ac.uk_home_.System_Desktop_RG_Jalbi_Bhattacharya_Jacket_Closed_Form_2018.pdf - Accepted version Manuscript

Download (2MB) | Preview

Abstract

Offshore Wind Turbines (OWTs) are dynamically sensitive structures and as a result estimating the natural frequency of the whole system taking into effect the flexibility of the foundation is one of major design considerations. The natural frequency is necessary to predict the long-term performance as well as the fatigue life. Currently, jackets supported on multiple foundations (such as piles or suction caissons) are being considered to support WTG (Wind Turbine Generators) for deeper water developments. This paper presents a practical method to compute the natural frequency of a jacket supporting WTG by incorporating Soil-Structure-Interaction (SSI) based on closed form solutions. The formulation presented can be easily programmed in a spreadsheet type program and can serve as a convenient way to obtain natural frequency with least amount of input. The basis of this method is the Euler-Bernoulli beam theory where the foundations are idealized with a set of linear springs. In this method, a 3-Dimensional jacket is first converted into a two 2-Dimensional problem along the orthogonal planes of vibration which are essentially the principle axes of the foundation geometry. Subsequently, the jacket is converted into an equivalent beam representing its stiffness and a formulation is presented to find an equivalent beam for entire tower-jacket system. Using energy methods, an equivalent mass of the RNA (Rotor Nacelle Assembly)-tower-jacket system is also calculated and fixed base frequency of the jacket is estimated. To consider the flexibility effects of the foundation, a formulation for an equivalent rotational spring of the foundation is developed. A method to incorporate the mass of the transition piece is also presented. Finally, a step-by-step application of the methodology is presented by taking example problems from the literature which also serves the purpose of validation and verification.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Civil and Environmental Engineering
Authors :
NameEmailORCID
Jalbi, M Salehm.jalbi@surrey.ac.uk
Bhattacharya, Subys.bhattacharya@surrey.ac.uk
Date : 31 July 2018
DOI : 10.1016/j.soildyn.2018.06.011
Copyright Disclaimer : © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Uncontrolled Keywords : Natural Frequency; Jacket Structure, Multiple Foundations, Soil-Structure Interaction
Depositing User : Melanie Hughes
Date Deposited : 14 Aug 2018 12:11
Last Modified : 01 Aug 2019 02:08
URI: http://epubs.surrey.ac.uk/id/eprint/848925

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year


Information about this web site

© The University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
+44 (0)1483 300800