What are the Types of Structural Loads?

Snow Loads

Snow loads are environmental loads applicable to structures expected to receive snowfall.

Snow can accumulate and be deep as a ten-story building. If snow collects on top of a structure, it creates additional loads on the building. Like wind loads, there are many factors to consider, and the calculation will depend on the code.

Earthquake (or Seismic) Loads

Earthquakes generate seismic loads that engineers must anticipate.

The computation of earthquake loads will depend again on the structural regulation. Since earthquakes are unpredictable, the codes will provide many approaches to computing them. Some factors to consider are the probability of an earthquake, its strength, and the distance to the nearest fault lines.

Earth Loads (or Pressure)

For tunnels, retaining walls, or below-grade structures, soil pressure (or soil-lateral loads) is another load to consider. It is the structural load due to soil and structure interaction.

The computation of soil pressure will require a sufficient understanding of soil mechanics. Structural codes will also have other requirements for this load type.

Water Loads (or Pressure)

Water and ice are a concern for some, such as dams, tanks, flood barriers, bridges, offshore platforms, and coastal structures. It is the structural load due to water and structure interaction. Examples of these loads include:

• Hydrostatic pressure
• Uplift loads in soil from the water table
• Rain or ponding loads from accumulated water on the roof or building surface
• Flood loads
• Dynamic loads such as wave impact
• Floating ice (solid water) are loads that can hit offshore platforms

Some of these loads can cause damaging effects, such as scouring to bridge piers. The computation of these loads will again depend on the structural codes and accepted practices.

Self-Straining Loads

Other loads one should consider are self-straining forces. These forces typically expand or contract structural elements. These include: 

• Temperature changes due to heat
• Creep and shrinkage of concrete
• Moisture change in materials
• The differential settlement, such as observed in soil

Summary

Let's summarize:

There are many ways how to classify structural loads.

Dead loads are permanent forces acting on the structure, either self-weight or superimposed.

Loads that change in position and magnitude are live loads. Examples include floor-live loads, roof-live loads, and moving loads.

Wind loads are environmental loads due to the wind.

Snow loads are environmental loads applicable to structures expected to receive snowfall.

Earthquakes (or Seismic) Loads are loads that an earthquake produces.

Earth load (or pressure) is a structural load due to the soil and structure interaction.

Water load (or pressure) is a structural load due to the static or dynamic water and structure interaction.

Self-straining loads are forces that typically expand or contract structural elements.