﻿ 大型海上风机吊装船的桩腿结构设计与强度分析
 舰船科学技术  2023, Vol. 45 Issue (19): 40-43    DOI: 10.3404/j.issn.1672-7649.2023.19.007 PDF

Structural design and strength analysis of pile legs for large offshore fan hoisting ship
ZHAO Cheng-yuan
China Classification Society, Beihai 536000, China
Abstract: Large offshore fan hoisting ship is a special ship used to install offshore fan. The design and strength analysis of its pile leg structure are very important to ensure the safe operation of the ship. Since the pile legs of the fan hoisting ship are shaped steel materials, the forms of material failure include material yield and buckling of thin-walled parts. This paper first introduces the checking criteria of steel yield strength and buckling strength, then introduces the pile leg structure of large offshore fan hoisting ship, and conducts load modeling of wind power pile legs combined with the wave dynamics model. Finally, the strength analysis and simulation of the pile leg of the fan hoisting ship are carried out by using the finite element calculation software ansys-workbench.
Key words: offshore fan hoisting ship     pile leg     strength     yield strength     Ansys-workbench
0 引　言

1 风机吊装船桩腿的S-N曲线法疲劳强度计算

S-N曲线表征材料的疲劳特性，S-N曲线的一般形式为：

 ${S_r}{N_r}^m = A \text{。}$

 图 1 风机吊装船的桩腿结构材料S-N曲线 Fig. 1 S-N curve of pile leg structure material of fan hoisting ship

1）忽略低于疲劳极限的应力，低于疲劳极限的值产生的损伤忽略不计；

2）只考虑循环对称应力，应力极限比值 $\dfrac{{{\sigma _{\max }}}}{{{\sigma _{\min }}}} \ne 1$

3）当前交变应力的疲劳损失具有独立性，如果循环次数为n，则疲劳损伤为n/N

4）疲劳损伤与应力加载顺序无关。

 ${D_0} = \frac{{{N_L}}}{A}\int_0^{ + \infty } {{S^m}} \frac{h}{q}{\left( {\frac{S}{q}} \right)^{h - 1}}\text{d}S = \frac{{{N_L}}}{A}{q^m}\Gamma \left( {1 + \frac{m}{h}} \right) \text{。}$

2 风机吊装船桩腿的强度设计与校核准则

 $\left[ \sigma \right] = \frac{{{\sigma _s}}}{S} \text{。}$

 $\frac{{{\sigma _{{a}}}}}{{\left[ {{\sigma _{{a}}}} \right]}} \leqslant 0.15，\frac{{{\sigma _{{a}}}}}{{\left[ {{\sigma _{{a}}}} \right]}} + \sqrt {\frac{{\sigma _{{{by}}}^2}}{{{{\left[ {{\sigma _{by}}} \right]}^2}}} + \frac{{\sigma _{bz}^2}}{{{{\left[ {{\sigma _{bz}}} \right]}^2}}}} \leqslant 1.35 \text{，}$
 $\begin{split} & \frac{{{\sigma _{{a}}}}}{{\left[ {{\sigma _{{a}}}} \right]}} > 0.15，\quad \frac{{{\sigma _{{s}}}}}{{\left[ {{\sigma _{{a}}}} \right]}} +\\ & \sqrt {{{\left[ {\frac{{{C_{{{mg}}}}{\sigma _{{{by}}}}}}{{\left( {1 - \frac{{{\sigma _{{a}}}}}{{{\sigma _{{s}}}}}} \right)\left[ {{\sigma _{by}}} \right]}}} \right]}^2} + {{\left[ {\frac{{{C_{{s}}}{\sigma _{{{bz}}}}}}{{\left( {1 - \frac{{{\sigma _a}}}{{{\sigma _{{s}}}}}} \right)\left[ {{\sigma _{{{bz}}}}} \right]}}} \right]}^2}} \leqslant 1.35 \text{。} \end{split}$

 $\frac{{{\sigma _a}}}{{\left[ {{\sigma _a}} \right]}} + \sqrt {\frac{{\sigma _{by}^2}}{{{{\left[ {{\sigma _{by}}} \right]}^2}}} + \frac{{\sigma _{bz}^2}}{{{{\left[ {{\sigma _{bz}}} \right]}^2}}}} \leqslant 1.35 \text{。}$

 图 2 桩腿材料的应力应变特性曲线 Fig. 2 Stress-strain characteristic curve of pile leg material

3 风机吊装船桩腿的屈曲设计与校核准则

 $\left[ {{\sigma _{\varepsilon r}}} \right] = \frac{{{\sigma _\varepsilon }}}{{{S_\varepsilon }}} \text{。}$

 ${\sigma _\sigma } = \left\{ {\begin{array}{*{20}{l}} {{\sigma _E},{\sigma _E} \leqslant \frac{{{\sigma _\varepsilon }}}{2}}，\\ {{\sigma _s}\left( {1 - \frac{{{\sigma _t}}}{{4{\sigma _\varepsilon }}}} \right),{\sigma _E} > \frac{{{\sigma _\varepsilon }}}{2}} \text{。} \end{array}} \right.$

1）静载工况

 ${S_\varepsilon } = \left\{ {\begin{array}{*{20}{l}} {1.667 + 0.265{\lambda _0} - 0.044\lambda _0^2,{\lambda _0} \leqslant \sqrt 2 }\text{，} \\ {1.917\lambda _0^2,{\lambda _0} > \sqrt 2 } \text{。} \end{array}} \right.$

2）组合工况

 ${S_\varepsilon } = \left\{ {\begin{array}{*{20}{l}} {1.250 + 0.199{\lambda _0} - 0.033\lambda _0^2,{\lambda _0} \leqslant \sqrt 2 } \text{，}\\ {1.438\lambda _0^2,{\lambda _0} > \sqrt 2 } \text{。} \end{array}} \right.$

 ${\lambda _0} = \sqrt {\frac{{{\sigma _g}}}{{{\sigma _\varepsilon }}}} 。$
4 风机吊装船桩腿结构的设计与强度分析 4.1 大型海上风机吊装船的桩腿结构设计

1）桩腿的形状和尺寸

 图 3 海上风机吊装船的状态结构设计示意图 Fig. 3 Schematic diagram of state structure design for offshore wind turbine lifting vessel

2）桩腿的连接方式

3）桩腿的支撑系统

4.2 风机吊装船桩腿强度分析的载荷边界条件

1）垂向波浪弯矩

 ${M_c} = \frac{1}{5}{f_0}{K_0}{C_o}{L^2}B{C_1} 。$

2）水平波浪弯矩

 ${M_S} = \frac{1}{4}{f_0}{L^{9/4}}\left( {B + 0.29B} \right){C_0}\left( {1 - \cos \left( {\frac{{2{\text π} x}}{L}} \right)} \right) 。$

3）重力及附加作用力

 ${P_c} = \frac{1}{2}{B^{0.65}} + 3{C_0}{C_1} + D\cdot g 。$

4.3 风机吊装船桩腿结构的有限元模型建立

1）定义材料属性

2）网格划分

 图 4 海上风机吊装船的桩腿结构有限元模型 Fig. 4 Finite element model of pile leg structure foroffshore wind turbine hoisting ship
4.4 风机吊装船桩腿结构的有限元应力分析

 ${{D}} = \frac{{{v_0}{T_d}}}{{\bar a}}\sum\limits_{s = 1}^{{N_m}} {{p_n}} {q_n}\Gamma \left( {1 + \frac{m}{{{h_m}}}} \right) 。$

 图 5 吊装船桩腿结构有限元强度校核云图 Fig. 5 Finite element strength verification cloud diagramof the pile leg structure of the lifting vessel

5 结　语

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