Wind and Ice Loads on Transmission Structures: A State of the Art Review

Climactic loads imposed on transmission conductors include ice, wind and ice concurrent with wind. Structural reliability under these loads depends on the statistical variation of applied loads and associated resistances. Analytical treatment for combined wind and ice effects is difficult given the different probability distribution functions of ice thickness and wind speeds. Existing design codes and guidelines are somewhat inconsistent in defining what actually applies for low and extreme winds. This paper reviews the present state of the art in research on wind speed and ice thickness distributions, associated risks, forecasting models, MRIs (recurrence intervals), field-based weather records and databases. The main inference from this study is that low to moderate winds should be modeled with a probability distribution different from that of extreme or hurricane winds. Reasonable reliability design procedures for combined ice and wind loads can be developed for utility structures with proper statistical assumptions.