Performance of monocoque and semi-monocoque composite poles for transmission lines

Abstract

Poles play an important role in distribution of electrical energy. Other sectors such as telephone and internet also use their support to bring services to homes. Currently, poles are made of wood, reinforced concrete and steel. However, these materials are subject to problems such as rapid wood degradation, high weight and difficult installation for reinforced concrete poles and corrosion in steels. Some alternatives are adopted to minimize these problems, such as wood treatment, optimization of concrete structures and protection of steel surfaces. Another alternative is to look for different types of materials to supply all pole requirements. Composite materials, such as glass fiber-reinforced polymer (GFRP), have great advantages because they are resistant, light and insulating. Monocoque and semi-monocoque (commonly used in aircraft fuselages) structures allow reduction the final mass, which combined with the use of composite materials generates even lighter structures. In this work, four configurations of monocoque and semi-monocoque (using longitudinal stringers and transverse ring) structures in different combinations are analyzed. A parametric study identifies favorable configurations, which are later studied. The finite difference method is used for the calculation of the maximum deflections, to evaluate the adequate stiffness. The structural stability and the strength are analyzed using the commercial finite element software Abaqus. It is observed that, for fiber angles near the longitudinal pole axes, the resulting masses for the semi-monocoque poles differ little from the monocoque poles. However, for larger angles, there is a significant difference in the masses, which makes the semi-monocoque poles lighter. When rings are added or when these are combined with the stringers, there is a considerable increase on the pole ultimate strength