Structural loads or actions forces, deformations, or accelerations applied to the structure or its components.

Loads cause stresses, deformations, and displacements in structures.

Engineers often evaluate structural loads based upon published regulations, contracts, or specifications.


The determination of the loads acting on a structure is a complex problem.

The nature of the loads varies essentially with the architectural design, materials, and location of the structure.

Loading conditions on the same structure may change from time to time or may change rapidly with time.

Loads are usually classified into two broad groups:-

  1. Dead loads
  2. Live loads

Dead loads (DL) are essentially constant during the life of the structure.

normally consist of the weight of the structural elements.

On the other hand, live loads (LL) usually vary greatly.

The weight of occupants, snow, vehicles, and the forces induced by wind or earthquakes are examples of live loads.

The magnitudes of these loads not known with great accuracy and the design values must depend on the intended use of the structure.

In structural analysis three kinds of loads generally used:

Concentrated loads that are single forces acting over a relatively small area.

for example, vehicle wheel loads, column loads, or the force exerted by a beam on another perpendicular beam.

Line loads that act along a line.

for example, the weight of a partition resting on a floor, calculated in units of force per unit length.

Distributed (or surface) loads that act over a surface area.

Most of loads distributed or treated

for example, wind or soil pressure, and the weight of floors and roofing materials.

Dead Loads (DL)

The structure first of all carries the dead load, which includes its own weight, the weight of any permanent non-structural partitions, built-in cupboards, floor surfacing materials, and other finishes.

It can worked out precisely from the known weights of materials and dimensions on working drawing.

Although the dead load can accurately determined, to make a conservative estimate to allow for changes in occupancy.

for example, the next owner might wish to demolish some of the fixed partitions and erect others elsewhere.

Live Loads (LL)

All the movable objects in a building such as people, desks, cupboards, and filing cabinets produce an imposed load on the structure.

This loading may come and go with the result that its intensity will vary considerably.

Wind Load (WL)

The wind has become a very important load in recent years due to the extensive use of lighter materials and more efficient building techniques.

A building built with heavy masonry, timber tiled roof may not affected by the wind load.

but on the other hand, the structural design of a modern light gauge steel framed building dominated by the wind load.

which will affect its strength, stability, and serviceability.

The wind acts both on the main structure and on the individual cladding units.

The structure has to be braced to resist the horizontal load and anchored to the ground to prevent the whole building from being blown away if the dead weight of the building is not sufficient to hold it down.

The cladding has securely fixed to prevent the wind from ripping it away from the structure.

Snow Load (SL)

The magnitude of the snow load will depend upon the latitude and altitude of the site.

In the lower latitudes, no snow would be expected while in the high latitudes snow could last for six months or more.

In such locations, buildings have to be designed to withstand the appropriate amount of snow.

The shape of the roof also plays an important part in the magnitude of the snow load.

The steeper the pitch, the smaller the load.

The snow falling on a flat roof will continue to build up and the load will continue to increase,

but on a pitched roof, a point is reached then snow will slide off.

Earthquake Load

Earthquake loads affect the design of structures in areas of great seismic activity,

such as north and south American west coast, New Zealand, Japan, and several Mediterranean.

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