Buckling Strength of Wood Power Poles Using Finite Elements

The buckling strength of wood electric‐power transmission and distribution structures is examined using finite‐element analysis. The elastic and geometric stiffness matrices for a simple beam element are used to form a generalized eigen problem. The eigen problem is solved for the buckling strength of poles of constant diameter and various end fixities. There is good agreement with Euler's formula even for models consisting of relatively few finite elements. Critical buckling loads are also calculated for tapered poles with circular cross sections. The results agree closely with the buckling loads predicted by Gere and Carter's formulas. The buckling strength of a tapered pole is often approximated by using a pole of constant cross section with the cross section equal to that at one‐third the distance from the small end. This method is shown to be very conservative. The numerical analysis is extended to several practical examples including a single‐pole tangent structure, dead‐end structures guyed two ways and one way, multilevel guyed structures, and an H‐frame.