Types of Loads
Dead Load:
is the gravity load or weight of constant magnitude and fixed position that act permanently on the
structure. Such load consists of the weights of the structural system itself and of all other material and
equipment permanently attached to the structural system.
For a building:
the dead loads include the weights of the columns, beams, girders, the floor slab, roofing, walls, and
other miscellaneous attachments.
Live Load:
is the structural (typically gravity) load of varying magnitude and/or position caused by the use of the
structure. Since the position of a live load may change, each member of the structure must be designed
for the position of the load that causes the maximum stress in that member.
For a building:
→ uniform live loads: which depend on the purpose for which the building is designed
→ minimum concentrated live loads: must be considered in the design of an automobile parking deck
For some types of buildings having very large floor areas, many codes will allow
a reduction in the uniform live load is allowed when the structure under consideration has large floor
areas. This is related to the fact that the prescribed live load will not occur simultaneously throughout
the entire structure at any one time.
For a bridge:
→ Highway bridges:
-live loads on bridge resulted from traffic
-Specification for truck loadings on highway bridges are reported in the LRFD Bridge Design
Specifications of the American Association of State and Highway Transportation Officials (AASHTO)
→ Railroad bridges:
-Specified in the Specifications for Steel Railway Bridges published by the American Railroad
Engineers Association (AREA).
-Train loadings involve a complicated series of concentrated forces.
Snow Load:
is applied at roof due to snow and can be severe
Snow load depend on
1-building’s shape
1-roof geometry
3-wind exposure
4-location
5-importance
6-the structure being heated or not
Wind Load:
-Occurred in structures that block the flow of wind
-The effect of wind on a structure depends on:
1-the density and velocity of the air
2-the angle of incidence of the wind
3-the shape and stiffness of the structure
4-the roughness of its surface
Wind loadings can be calculated by either a static or a dynamic approach
Earthquake Load:
Earthquake load resulted from the ground’s motion
Earthquake load depends on:
1-the amount and type of ground accelerations
2-the mass and stiffness of the structure
Earthquake loadings can be calculated by either a static or a dynamic approach
Hydrostatic and Soil Pressure
is the pressure resulted from retaining water, soil, or granular materials