Achieved Reliability of the North American Design Approaches for Transmission Overhead Structures

Structural reliabilities of three reference transmission overhead structures: a suspension steel lattice tower, a tangent H-frame wood structure and a self-supporting steel pole structure, designed according to the stipulated deterministic approaches of the American National Electrical Safety Code (NESC C2-2002) and the Canadian Standard (CSA C22.3 No. 1-2001) were assessed. Structural reliabilities of these reference structures, designed according to an alternate Canadian approach based on reliability-based design, were also assessed. The paper presents the achieved reliability for the reference structures, considering two balanced load scenarios: wind only and wind combined with ice. Similarities and differences between the NESC C2 and the CSA C22.3 design approaches are discussed