透射边界-地基-风电结构地震响应与破坏模式

近海风力发电结构是由无限域地基、基础及上部结构组成的体系,有限域透射人工边界和地震动输入模式直接影响结构体系的动力响应。首先,建立透射人工边界-地基-基础-塔筒结构和固定边界-地基-基础-塔筒结构的有限元模型;然后,简要澄清了透射边界地震动输入之所以采用外力而不采取地震动物理量(加速度、速度和位移)的原因所在;最后,对给出的3种作用模式:(1)固定边界地震动输入,(2)只考虑外源输入波作用,(3)同时考虑外源输入波和内源振动的散射波作用,分别进行计算分析和比较。通过数值计算并结合理论分析,(1)澄清了对透射边界采用外力进行地震激励输入的方法的原因,这种输入方法合理可靠,符合实际情况;(2)在地震波等效荷载的生成中,针对圆形横截面地基提出了一种阻尼力、刚度力的便捷性生成方法,大大减小了工作量;(3)从自身振动特点及阻尼设置角度,解释了地震作用下采用透射边界比采用固定边界时风电结构响应减小的原因;(4)指出了地震作用下透射边界地基模型在结构动力响应与倒塌计算中内源振动反射的不容忽视性。

Research on seismic response and failure modes of system of transmitting boundary-soil-wind power structures

Offshore wind power structure is the system of superstructure-foundation-infinite domain soil. Dynamic response of structure system is directly affected by transmitting boundary of the model and seismic motion input mode. Firstly, finite element models of tower tubes-foundation-soil-transmitting boundary and tower tubes-foundation-soil-fixed boundary are established. Then, the reason why force instead of acceleration, velocity and displacement is used for seismic input in the model while transmitting boundary is briefly clarified. At last, the following modes are analyzed, i.e. (1) seismic input of fixed boundary; (2) external source wave motion is considered only; (3) external source wave motion and scattering force caused by endogenous oscillation are both considered. Analysis results show that: (1) the reason why force is used for seismic motion input in the model with transmitting boundary is clarified; and the method of seismic motion input is in accord with the actual situation; (2) a convenient method of the generation of stiffness force and damping force is proposed for the foundation of circular cross-section; and it can greatly reduce the workload; (3) the reason that dynamic response of offshore wind power structure is smaller using transmitting boundary than using fixed boundary is explained from the viewpoint of vibration characteristics of model and the damping; (4) the indispensability of endogenous oscillation in seismic response and failure modes of structure using transmitting boundary is pointed out.