1. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China 2. Zhejiang Electric Power Design Institute, Hangzhou 310012, China
For jacket supported offshore wind turbines (OWTs), numerical calculations and analysis were performed to investigate the dynamic responses of the whole structures under extreme cyclic loadings of typhoon condition. The series of pile-soil interaction models (p-y, t-z, Q-z) in the code of American Petroleum Institute (API), an elastoplastic t-z model considering the cyclic degradation of strength and stiffness axially in the pile-soil interface as well as an elastoplastic p-y model representing the lateral behaviors were used in the numerical simulations. Results show that the largest proportion of the anti-overturning moment at the mudline of jacket supported OWT is provided by the t-z spring. A negative contribution to the anti-overturning moment may be caused by the p-y spring, and the main function of p-y spring is to resist the horizontal loadings. The contribution from the Q-z spring is small and negligible. The rotation response at the top of jacket foundation may increase obviously with the consideration of the cyclic degradation effect of t-z spring. Considering the coupling degradation effects of the t-z and p-y springs, the translation of the jacket foundation will be more obvious and the displacement response at the top of the foundation will increase significantly. Thus the effects of the pile-soil cyclic degradation should be considered adequately in the engineering design.
Fig.1Schematic diagram of model for jacket supported offshore wind turbine
模型参数
数值
内摩擦角φ/（°）
39
地基弹性模量ηh/（N·m?3）
3.4×107
p-y曲线形状参数hs
0.1
刚度衰减参数αd
0.001
有效重度γ'/（KN·m?3）
10.4
Tab.1Parameters of elastoplastic p-y model
Fig.2Elastoplastic t-z model considering cyclic degradation
模型参数
数值
模型参数
数值
δ/（°）
21.5
B
2.5
z50/mm
0.5
a
0.04
h
4.0
b
0.5
τr/τu0
0.317
Tab.2Parameters of elastoplastic t-z model after calibration
Fig.3Comparison of simulation results of t-z model and interface shear test results under constant normal stiffness
计算工况
p-y模型
t-z模型
Q-z模型
1
API
API
API
2
API
弹塑性
API
3
弹塑性
API
API
4
弹塑性
弹塑性
API
Tab.3Calculation cases for different pile-soil interaction situations
模型
φ/（°）
δ/（°）
Nq
A
γ'/（KN·m?3）
p-y模型
39
?
?
0.9
10
t-z模型
?
21.5
?
?
10
Q-z模型
?
?
20
?
10
Tab.4Parameters of p-y, t-z, Q-z models from API code
几何参数
数值
转子、轮毂、机舱集中质量/t
466.8
塔筒长度/m
73.0
塔筒底部直径/m
5.5
导管架部分高度/m
44.6
导管架顶部根开/m
12.0
导管架底部根开/m
22.0
桩长/m
50.0
桩径/m
2.0
桩壁厚/mm
30.0
Tab.5Parameters of jacket supported offshore wind turbine
Fig.4Schematic diagram of moment caculatuion of jacket foundation at mudline
Fig.5Time history of contribution of different springs to anti-overturning moment at mudline
Fig.6Time history chart of rotation response at top of jacket foundation top
Fig.8Time history chart of vertical displacement response at top of jacket foundation
Fig.7Time history chart of horizontal displacement response at top of jacket foundation
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