Structural loading calculations of wood transmission structures

The most critical task in the design of any structure is to determine the loads that the structure must withstand. In the case of transmission line pole structures, currently there are two available methods commonly utilized to calculate the environmental loads: wind and ice. The first method is suggested by the National Electrical Safety Code (NESC). This is an ultimate stress method where all factors of safety are included in the loads. The second option, recommended by the American Society of Civil Engineers (ASCE), calculates the forces that must be resisted by the structure and may be used in an ultimate strength method, where wood is the pole construction material. This later technique may also be used in a load and resistance factor design (LRFD) with other common materials. This paper compares the advantages and limitations of the two methods. Numerical examples will be provided showing how the design may differ depending upon which method is employed.