Natural frequency of offshore wind turbines on rigid and flexible monopiles in cohesionless soils with linear stiffness distribution

被引:41
作者
Darvishi-Alamouti, Saeed [1 ]
Bahaari, Mohammad-Reza [1 ]
Moradi, Majid [1 ]
机构
[1] Univ Tehran, Coll Engn, Sch Civil Engn, POB 11365-4563, Tehran, Iran
关键词
Natural frequency; Monopile; Subgrade reaction; Slenderness ratio; Rayleigh method; DYNAMIC-RESPONSE; PILES; SAND;
D O I
10.1016/j.apor.2017.07.009
中图分类号
P75 [海洋工程];
学科分类号
0814 ; 081505 ; 0824 ; 082401 ;
摘要
A simplified method is introduced to obtain the fundamental frequency of offshore wind turbines supported by monopile foundations. Soil-pile interaction is modeled based on Winkler approach and concept of beam on elastic foundation. The soil is considered to have linearly varying modulus of subgrade reaction along depth which is a typical assumption for cohesionless soils. Rayleigh method which is based on conservation of total energy of the system is utilized. Firstly the natural frequency of the system with rigid pile is derived and then an innovative procedure is introduced to take pile flexural stiffness into consideration. Comparison between results of the present method with those of a numerical FE model for a typical 2 MW wind turbine structure shows excellent agreement for rigid pile and flexible pile with small value of slenderness ratio. The agreement is also good for flexible pile with higher slenderness ratios. A parametric study is carried out to investigate the effect of important parameters of foundation including pile slenderness ratio, pile aspect ratio and pile mass on the system natural frequency. (C) 2017 Elsevier Ltd. All rights reserved.
引用
收藏
页码:91 / 102
页数:12
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