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Abstract
The main objective of this research was to create a finite element model for detailed three-dimensional stress analysis of an overhead optical ground wire (OPGW) typical of those used in transmission lines. The detailed model considers all possible mechanical effects, such as contact, friction, elongation, torsion, and bending for different end conditions.
The OPGW under study comprises four components: the external layer of fourteen aluminum alloy wires and ten inner aluminum clad steel wires, which are laid over an aluminum tube that houses a five-groove aluminum spacer. The optical fiber units are inserted in the aluminum spacer grooves. Three-dimensional solid elements are used to model the outer wires, the inner wires, and the aluminum spacer. The central aluminum tube is modeled with shell elements with large strain and deformation kinematics. All possible contacts between the components, with and without friction, are considered in the model.
The OPGW is assumed fixed at one end and pulled from the other with a prescribed displacement equivalent to the experimental elongation of 0.61% defined for all components.
The finite element analysis predicts that the responses of the outer and inner wires are in the linear range, however the aluminum tube and spacer are yielded under the prescribed displacement. Therefore, a multilinear stress-strain law is used in the model.
Two scenarios of loading were tested to apply the axial elongation on the wires; either only the central node or all the interior nodes of the wire cross sections are prescribed a maximum axial displacement.
Results of the finite element model are compared with those of the experiments performed at IREQ and with the analytical solutions of Machida and Durelli (1973) and Phillips and Costello (1973). The calculated axial forces of the cable in the coarse and fine mesh models are 61% and 70% of those predicted by the analytical solutions, respectively. However, the differences in stresses and strains of the coarse mesh model are in the range of ten percent only from the theoretical solutions.
The effective modulus of elasticity of the finite element model increases with tension. For the maximum elongation, the effective modulus obtained with the coarse and fine mesh models is 62% and 70% respectively of the equivalent modulus of elasticity calculated neglecting all three-dimensional effects.
This study shows the reliability and significance of using finite element modeling in predicting the detailed response of a complex cable, for which experiments and theoretical solutions are unable to yield complete results. (Abstract shortened by UMI.)
