长周期海域地震作用下近海单桩式风机结构响应与荷载预测分析

Structural response and load prediction analysis of offshore monopile wind turbine under long-period offshore earthquake actions

摘要

海上风机结构向高柔化、深水化发展，海域地震动存在着显著的长周期成分，将对风机结构安全形成巨大威胁。为了探索海域长周期地震动作用下海上风机的结构动力响应特性，本研究以美国可再生能源实验室（National Renewable Energy Laboratory，NREL）开发的5 MW单桩固定式风力发电机作为研究对象，首先基于K-NET数据库并结合海域地震动长周期成分特性指标β_l将海域地震动进行分类；随后运用OpenFAST开源软件，考虑湍流风-地震联合作用时正常运行、停放风机和紧急停机3种工况，提取并分析了风力机的塔体运动响应和塔体地震荷载，重点关注了海域地震动长周期成分效应的影响；最后，基于已有荷载预测模型，并根据海域地震动长周期特性影响效应，提出了一种精度更高的塔身极端荷载预估模型。结果表明:海域长周期地震动作用下风机的塔体运动响应和塔体地震荷载都远大于常规地震动作用下的结果；当地震强度较小时，气动作用使结构响应增大，当地震强度较大时，气动作用中的阻尼效应使塔架的结构响应降低；考虑地震动长周期效应提出的荷载预估模型能用于更精确的海域地震动作用下塔架极端荷载计算。

Abstract

The offshore wind turbine structures are becoming more flexible and extend to deeper waters. At the same time，historic data show that offshore earthquake contains abundant long period components，which poses great challenges to the dynamic safety of monopile offshore wind turbines. This study focuses on a 5 MW monopile fixed offshore wind turbine developed by the National Renewable Energy Laboratory（NREL）of the United States and mainly investigates the long-period seismic motion effect on structure dynamic response characteristics of large offshore wind turbines. First，the seismic motions in the K-NET database recorded in offshore stations are selected and classified using a characteristic index β_l describing their long-period component feature. Then，under the combined action of turbulent wind and seismic motions，the OpenFAST open-source software is utilized to examine three operational conditions，i.e.，regular operation，parked status，and emergency shutdown. The dynamic responses and tower loads are extracted and analyzed，and the emphasis is put on the effect of the long-period-component feature of the seismic motions. Finally，a more precise extreme load prediction model considering the long-period-component feature for the tower is suggested based on existing models. The results demonstrate that the movement and seismic loads of the wind turbine are much greater under long-period seismic motions in offshore locations than normal seismic actions. The aerodynamic effect increases the dynamic responses when seismic intensity is low. However，the aerodynamic effect，mainly the aerodynamic damping，lessens the dynamic responses when the seismic intensity is high. The extreme loads on offshore wind turbine towers under the long-period offshore seismic motions can be more precisely calculated using the proposed prediction model in this work.

关键词

海域长周期地震动 / OpenFAST软件 / 近海单桩风机 / 结构动力响应 / 气动阻尼

Key words

long-period offshore earthquake / OpenFAST software / offshore monopile wind turbine / structural dynamic response / aerodynamic damping

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基金资助

国家自然科学基金资助项目(51809084)

中央高校基本科研业务费资助项目(JZ2022HGTB0237)