Dynamic response of monopiles in sand using centrifuge modelling
Dynamic response of monopiles in sand using centrifuge modelling
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DOI：
10.1016/j.soildyn.2018.08.007
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发表时间：
2018-12-01
影响因子：
4
通讯作者：
Madabhush, S. P. Gopal
中科院分区：
文献类型：
--
作者：
Futai, Marcos Massao;Dong, Jing;Madabhush, S. P. Gopal
单桩基础是风力发电机最常用的海上基础之一。用1g试验和离心试验研究了它们的静力承载力、p-y曲线和循环荷载特性，但关于它们的固有频率，特别是离心试验的试验数据很少。海上风力涡轮机基础的设计在很大程度上取决于固有频率，因为循环载荷引起的共振可能导致损坏甚至故障。因此，了解自由振动下的振动台的动态响应是至关重要的设计。本文介绍了在离心机中进行的大直径单桩和小直径单桩试验的结果，首次直接测定了桩土系统的自振频率f（n）。实验方法被用来定义通过测量的加速度和力的时间历程和它们的快速傅立叶变换（FFT）下的力施加在一个控制的频率下的固有频率。通过离心试验研究了桩径、埋入长度、塔体自由长度和土体密度对f（n）的影响。在50 g离心试验中使用的相同模型也在1 g下进行了试验，以评估早期1 g研究与系统行为的相关性。在压电致动器的谐波加载期间，离心模型中的风力涡轮机转子的实测固有频率证实，必须考虑适当应力水平下的土壤结构相互作用，以获得正确的固有频率。将实验数据与理论解进行了比较，对这些系统的行为提供了重要的见解。
Monopiles are one of the most commonly used offshore foundation for wind turbines. Their static capacity, p-y curve and cyclic loading behaviour have been studied using 1 g tests and centrifuge tests, but there is little experimental data regarding their natural frequency, especially using centrifuge testing. The design of offshore wind turbine foundations is largely governed by natural frequency as resonance due to cyclic loading can cause damage and even failure. Understanding the dynamic response of the monopile under free vibration is thus critical to design. This paper presents the results of novel monopile (large diameter) and single pile (small diameter) tests in a centrifuge to for the first time directly determine the natural frequency (f(n)) of the pile-soil system. An experimental methodology was used to define the natural frequency via measured acceleration and force time histories and their fast Fourier transforms (FFT) under a force applied at a controlled frequency. The effects of pile diameter, embedded length, free length of the tower and soil density on f(n) were investigated in the centrifuge tests. The same models used in the centrifuge test at 50 g were also tested at 1 g in order to assess the relevance of earlier 1 g investigations into system behaviour. The measured natural frequency of wind turbine monopiles in centrifuge models during harmonic loading from a piezo-actuator, confirmed that soil structure interaction at an appropriate stress level must be taken into account to obtain the correct natural frequency. The experimental data was compared to theoretical solutions, giving important insights into the behaviour of these systems.