P35.005: Ductile Iron and Composite Structure Management

Full-Scale Cantilever Testing of Ductile Iron Poles: EPRI is expanding its research initiative focused on understanding the mechanical performance of ductile iron poles. Research conducted in 2025 revealed significant variability in the failure modes for ductile iron poles. In 2027, EPRI intends on expanding on this prior research to study the causal effects of pole geometry and design on ductile iron pole failure modes. Output from this research intends on helping engineers confidently evaluate the structural capacity of ductile iron poles and build towards a coherent design methodology for the material.

Finish Mechanical Testing on Accelerated Aged Composite Cross-Arms: For the last three years, EPRI has been engaged in accelerated aging of fiber reinforced polymer (FRP) composite crossarms at its laboratory in Lenox, MA. The target three-year aging cycle intends on finishing in late-2026 with mechanical testing results to be published in 2027. This research intends on providing insight into the long-term durability of FRP cross-arm subject to environmental stresses from UV and moisture exposure.

Develop Guidance on Geographic Variations in FRP Composite Weathering: Work plans to continue in 2027 to help utilities understand geographic variations in FRP composite structure weathering. EPRI intends to continue development of a framework to enable utilities to compare the relative weathering rates of FRP within their service territories and across North America more generally. This research aims to help utilities identify optimal regions for FRP deployments, and accurately account for potential material degradation to reach target service lives.

Effects of FRP Composite Materials Subjected to Outdoor Exposure: Work initiated in 2026 to evaluate the real world aging of fiber reinforced polymer (FRP) composite materials under outdoor exposure intends to continue in 2027. This multi-year effort examines the effects of UV radiation and moisture on FRP materials. EPRI has done extensive research on FRP aging in an accelerated laboratory environment, but correlations to outdoor exposure durations remain difficult. This initiative seeks to close the gap between real-world and accelerated aging of FRP materials, providing insights to transmission engineers on expected lifespans of FRP composite poles. Photo courtesy of Q-Lab.

Provide Cost and Performance Comparisons for Different Structure Material Types: This research effort is focused on helping engineers make the best decisions with regards to transmission structure material selection between wood, steel, concrete, fiber-reinforced polymer, and ductile iron. The Optimal Pole Material Selection Guide contains a qualitative review of each material type, representative structural designs, and pertinent design recommendations. In 2027, EPRI plans on expanding the guide to include steel lattice structures, comparing and contrasting their performance and cost relative to transmission pole solutions.

Provide Tools and Resources on The Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Ductile Iron & Composite Structures Transmission Resource Center: