Nonlinear behavior of wood pole structure

Wood pole structure has been widely used in North America for power lines 230kV and below. This paper is intended to examine the nonlinear behavior of an unguyed single wood pole structure. For this purpose, an extensive parametric study is made by using three methods: an analytical one, a numerical (FE) one, and a semi-empirical (manual) one. As a result, it is found that wood poles usually behaves like “slender” cantilevers so that buckling or stability plays an important role; a nonlinear FE software assuming linear material can predict the buckling load of a pole subjected to a purely vertical load (as may be encountered under the ideal load case of Ice-Only), by applying a small, fictitious lateral load to trigger the buckling; a pole´s strength usage as computed from such a FE software may behave like a “switch” when the load is predominantly vertical. That is, it may jump quickly from a low usage value to a high usage value when the pole is approaching its buckling load. These phenomena are the natural results of the non-linear behavior of wood pole structures.