ABSTRACT

In order to understand and to predict cable effects on structures, three-dimensional numerical models for a stranded cable and a beam–cable system consisting of a cantilever beam and two connected cables are presented. The multibond graph formalism is used to model the coupled cable–beam system, with the cable and beam substructures using 3D rigid lumped segments. The stranded cables are modelled considering the bending stiffness, tension and sag due to self-weight. The generally applicable cable-structure modelling approach in this paper is applied to vibration-based non-destructive evaluation of electrical utility poles, where simulated modal testing of the pole-conductor system is required. Experimental parametrization of a stranded cable is carried out using specially designed apparatus to accurately measure the bending stiffness at different tensions, and to measure the axial stiffness and axial damping. A reduced-scale lab set-up and finite element models are developed for verification of the numerical models. Experimental free and forced vibration testing is performed on individual cantilever beam and stranded cable subsystems, and on the coupled cable–beam system to verify the numerical models in the frequency and time domains. It is concluded that the 3D bond graph models can be used to understand the interaction between cable and structure, allowing prediction of the in-plane and out-of-plane natural frequencies and time response of the connected pole. It is also concluded that by adding the cable to the pole structure, some modes emerge in the eigenvalue solution of the system which may be categorized as cable-dominated modes, pole-dominated or hybrid modes.

摘要

为了理解和预测电缆对结构的影响，提出了绞合电缆和由悬臂梁和两根相连电缆组成的束电缆系统的三维数值模型。多重键合图形式主义用于对耦合的电缆-梁系统进行建模，其中电缆和梁的子结构使用3D刚性集总段。对多股电缆进行建模时要考虑到由于自重引起的弯曲刚度，张力和下垂。本文中普遍适用的电缆结构建模方法适用于对电线杆进行基于振动的无损评估，其中需要对极导体系统进行模拟模态测试。使用专门设计的设备对绞合电缆进行了实验参数化，以准确测量不同张力下的弯曲刚度，并测量轴向刚度和轴向阻尼。开发了缩小规模的实验室设置和有限元模型以验证数值模型。在单独的悬臂梁和绞合电缆子系统上以及在耦合的电缆-光束系统上进行了实验性的自由振动和强制振动测试，以验证频域和时域中的数值模型。结论是，可以使用3D键合图模型来理解电缆与结构之间的相互作用，从而可以预测面内和面外固有频率以及所连接极点的时间响应。还得出结论，通过将电缆添加到杆结构中，