Structural assessment of lattice steel towers used in power transmission lines

Resumo

The lattice steel towers have been widely used as supports for overhead power transmission lines.
These towers have become essential elements to the transmission systems and their stability contributes to a
better functioning and electrical safety. In this research work, a three-dimensional latticed structural system,
composed by primary and redundant members was adopted to represent the steel towers. In current design
practice, redundant members are not included in the finite element models and a linear analysis is performed for
the structural design. Considering this methodology, several design recommendations indicates that the forces
acting on the redundant members can be up to 2.5% of the forces on the primary elements (main elements).
Therefore, the main objective of this investigation is to develop an analysis regarding the redundant member’s
structural behaviour of lattice steel towers used in power transmission lines, having in mind the assessment of
the forces, as well as the design on these elements. Hence, five different steel towers associated to a 500 kV
transmission line were investigated and a nonlinear analysis was performed aiming to determine the forces
values acting on the redundant members and comparing with those calculated according to the design standards
(linear analysis). The global structural behaviour related to the redundant elements failure was also studied, as
well as the influence of the angle between the members, having in mind the forces values. The results obtained
along this analysis have shown relevant quantitative differences between the forces values established by the
design standards and those calculated through a nonlinear analysis based on finite element models.