Jalali Mohammad Hadi, Rideout D Geoff
Faculty of Engineering and Applied Science, Memorial University, Canada.
J Vib Control. 2022 Jun;28(11-12):1520-1535. doi: 10.1177/1077546321996936. Epub 2021 Mar 10.
Interactions between cable and structure affect the modal properties of cabled structures such as overhead electricity transmission and distribution line systems. Modal properties of a single in-service pole are difficult to determine. A frequency response function of a pole impacted with a modal hammer will contain information about not only the pole but also the conductors and adjacent poles connected thereby. This article presents a generally applicable method to extract modal properties of a single structural element, within an interacting system of cables and structures, with particular application to electricity poles. A scalable experimental lab-scale pole-line consisting of a cantilever beam and stranded cable and a more complex system consisting of three cantilever beams and a stranded cable are used to validate the method. The frequency response function of a cantilever ("pole") is predicted by substructural decoupling of measured cable dynamics (known frequency response function matrix) from the measured response of the assembled cable-beam system (known frequency response function matrix). Various amounts of sag can be present in the cable. Comparison of the estimated and directly obtained pole frequency response functions show good agreement, demonstrating that the method can be used in cabled structures to obtain modal properties of an individual structural element with the effects of cables and adjacent structural elements filtered out. A frequency response function-based finite element model updating is then proposed to overcome the practical limitation of accessing some components of the real-world system for mounting sensors. Frequency response functions corresponding to inaccessible points are generated based on the measured frequency response functions corresponding to accessible points. The results verify that the frequency response function-based finite element model updating can be used for substructural decoupling of systems in which some essential points, such as coupling points, are inaccessible for direct frequency response function measurement.
电缆与结构之间的相互作用会影响诸如架空输配电线路系统等索结构的模态特性。单个在用电杆的模态特性很难确定。用电锤敲击电杆得到的频率响应函数不仅会包含电杆本身的信息，还会包含与其相连的导线和相邻电杆的信息。本文提出了一种普遍适用的方法，用于在电缆与结构的相互作用系统中提取单个结构元件的模态特性，尤其适用于电线杆。使用由悬臂梁和绞合电缆组成的可扩展实验规模的杆线以及由三根悬臂梁和一根绞合电缆组成的更复杂系统来验证该方法。通过将测量得到的电缆动力学（已知频率响应函数矩阵）与组装好的电缆 - 梁系统的测量响应（已知频率响应函数矩阵）进行子结构解耦，来预测悬臂梁（“电杆”）的频率响应函数。电缆中可能存在不同程度的垂度。估计得到的电杆频率响应函数与直接测量得到的频率响应函数的比较显示出良好的一致性，这表明该方法可用于索结构，以滤除电缆和相邻结构元件的影响，从而获得单个结构元件的模态特性。然后提出了一种基于频率响应函数的有限元模型更新方法，以克服在实际系统中某些部件难以安装传感器的实际限制。基于对应于可测点的测量频率响应函数生成对应于不可测点的频率响应函数。结果验证了基于频率响应函数的有限元模型更新可用于某些关键点（如耦合点）无法直接测量频率响应函数的系统的子结构解耦。
