An alternative option to the traditional grouted joint for wind turbines is a direct steel-to-steel connection, also known as slip joint. In a recently published work, a proof of concept of a vibration-assisted installation and decommissioning technique of a slip joint was illustrated. Leveraging on the obtained results, the current study shows for the first time a decommissioning campaign carried out using a vibration-assisted technique applied on a prototype hydraulic wind turbine tower located in the North Sea, and connected to the monopile through a slip joint. The key aspect of the dismounting procedure is a priori knowledge of the resonance frequency clusters corresponding to the slip joint’s cross-sectional modes. Therefore, field hammer tests and experimental modal analysis were carried out inside the wind turbine tower. The identified frequencies and mode shapes were then compared with numerical ones estimated by a finite element model of the investigated structure. The comparison showed that a set of frequency clusters can be directly selected from a detailed numerical model. The preparatory work of the slip joint decommissioning was then executed by installing electric shaker devices, based on the dynamic identification results, and hydraulic jacks mounted inside the wind turbine tower. A first decommissioning trial was carried out in May 2019, while the final decommissioning was performed in August 2019. After analysing the measurements of the hydraulic pressures, displacements and excitation frequencies during the decommissioning campaigns, the results showed that it is possible to disconnect the slip joint if, in combination to a vertical static force, one of the identified cross-sectional mode shapes is excited. The vibration-assisted decommissioning proved to be a successful technique to dismount the connection in a controlled and straightforward manner.

传统的风轮机灌浆接头的替代选择是直接钢对钢连接，也称为滑动接头。在最近发表的工作中，说明了滑动接头的振动辅助安装和退役技术的概念证明。利用获得的结果，当前的研究首次显示了使用振动辅助技术进行的退役运动，该技术应用于位于北海的原型水力风力涡轮机塔架上，并通过滑动接头连接到单桩。拆卸过程的关键方面是对与滑动接头的横截面模式相对应的共振频率簇的先验知识。因此，在风轮机塔架内部进行了现场锤击测试和实验模态分析。然后将识别出的频率和模式形状与由研究结构的有限元模型估算出的数值进行比较。比较表明，可以直接从详细的数值模型中选择一组频率簇。然后，根据动态识别结果，通过安装电动振动筛装置并在风力涡轮机塔架内部安装液压千斤顶，进行滑环退役的准备工作。首次退役试验于2019年5月进行，而最终退役于2019年8月进行。对退役期间液压压力，位移和激励频率的测量结果进行分析后，结果表明可以断开滑移如果结合垂直静力，所识别的截面模式形状之一被激发。振动辅助退役被证明是一种以受控且直接的方式拆卸连接的成功技术。