Eislast

Eislast (ice load) is a term used in structural engineering to denote the load exerted by ice that accumulates on exposed surfaces of structures in cold climates. It encompasses the weight of ice that forms from freezing precipitation, glaze ice, or frost, and it can affect buildings, bridges, transmission lines, towers, roofs, and other fixed infrastructure.

Ice can accrue in various forms and distributions. Clear ice, glaze ice, and rime ice may develop on horizontal, sloped, or vertical surfaces depending on weather, wind, and surface roughness. The resulting ice mass adds vertical and sometimes horizontal loading, which can be highly nonuniform. Loads may be uniform over a surface or concentrated where ice forms along edges, protrusions, or joints. Dynamic effects occur when ice forms rapidly, departs in sheets, or impacts components during shedding or wind-driven movement.

Characterizing Eislast involves estimating the mass of ice per unit area and its distribution. A common simplification treats the load as q = ρi · h · g, where ρi is the ice density (approximately 900 kg/m³), h is the ice thickness, and g is the acceleration due to gravity. In practice, thickness can vary from millimeters to several centimeters or more, and the load is often combined with other actions such as snow, wind, and thermal effects. Because ice formation is climate- and location-specific, engineers typically use local climate data, experience, and applicable codes or standards to determine representative Eislast values for design.

Standards and practice vary by country and project type. Eislast is treated as a variable action in many regions, with regional climate data or design guidelines informing worst-case scenarios, load combinations, and safety factors. Provisions for ice loads may be included in national annexes or specialized guidelines for structures in cold climates.

See also: snow load, wind load, load combinations, climate design.

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