Discussion of Concrete Pier Foundation Design for Transmission Structures

Concrete pier foundations for transmission structures are widely used with high-voltage transmission lines. Current design practice focuses on strength design ensuring the foundation and top structures are safe. However, the performance design criteria for deflection and rotation on top of this kind of pier foundation are not well defined in any major code or guide resulting in utility firms and engineering companies adopting their own differing criteria. This article discusses the development of appropriate performance criteria for foundation design relating to transmission poles. Common pitfalls faced by geotechnical and structural engineers during the design and analysis and ways to avoid them are also discussed. Current common practices and procedures for transmission structure foundation design are discussed together with the importance of adopting appropriate performance criteria to ensure the safety, economic feasibility, and aesthetics of the foundation. Finally, three case studies—tangent pole, light angle pole, and dead end pole—are conducted using the software applications PLS CAISSION, MFAD, and LPILE. The results are compared in terms of shear distribution, moment distribution, and deflection along the length of the pile foundation to establish the ways and extent performance criteria can affect the design.