摘要
对于海上风机部分埋入群桩基础,风机结构的高度将导致基础承受较大的倾覆力矩,因而在风机振动分析中需要考虑到基础的摇摆特性。为避免发生共振,风机结构第一阶自振频率应避开风轮转动频率(1P频率)和叶片通过频率(3P或2P频率)。目前关于风机结构动力特性的研究常常以底部刚性固定为假定,忽略了地基基础的影响,因而可能带来误差。结合既有研究成果,推导简化解析方法研究了部分埋入群桩基础的水平–摇摆耦合振动特性以及基础阻抗对风机结构共振特性的影响。首先,推导了采用动力Winkler地基模型的部分埋入群桩基础水平–摇摆动力阻抗,与精确解进行对比,验证了方法的正确性;其次,考虑基础阻抗的作用,推导了风机结构水平–摇摆振动方程;最后,通过简化方法和频域有限元方法对不同地基条件下某风机结构的共振特性及基础阻抗进行了计算和对比,研究了基础阻抗对结构共振特性的影响,并验证了简化方法的正确性。
The partially embedded pile groups bear tremendous moments generated by wind loads due to the large height of the offshore wind turbine structures. It is of great importance to consider the rocking vibration of the foundations in the lateral vibration analyses of wind turbine structures. In order to avoid resonance, which is very dangerous to high structures, the first-order natural frequencies of the wind turbine structures are always designed as away from 1P and 3P （2P） ones, so it is very important to calculate the natural frequencies of the wind turbine structures accurately during the design procedures. At present, the methods for calculating the dynamic characteristics of the wind turbine structures, including the natural frequencies, are usually based on the assumption of base fixity. Inaccuracies may occur in these methods for not considering the impedance of foundations. In this work, the coupled horizontal-rocking impedance of the pile group is derived and its impact on the resonance characteristics of the wind turbine structures is studied. First, a simplified method to determine the horizontal-rocking impedance of the pile group with dynamic Winkler model is proposed and verified by comparison against some published accurate solutions. Second, a lateral vibration equation for the wind turbine structures is derived with the consideration of the foundation impedance. Finally, through an example of wind turbine structure, the influence of the foundation impedance on the resonance characteristics of the structure is studied, and the proposed simplified method is verified by use of the finite element method.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2014年第2期286-294,共9页
Chinese Journal of Geotechnical Engineering
基金
教育部博士点基金项目(20110072110008)
