The load which almost retains its magnitude and point of application throughout the life of the structure is called Dead Load. This load is usually the self weight of the structure which is estimated by multiplying volume of a member with the standard weight of the material of Construction. This load constitutes a bigger part of the total load on a structure. The load due to persons occupying the structure and their belongings is called Live Load whose magnitude and point of application changes with time. In case of bridges, live load consists of weight of vehicles moving over the bridge. Other types of loads are Wind Load, Earthquake Load, and Temperature Loads.
This is type of dead load which is due to self weight of the member to be designed. For design, a reasonable value of self load depending on past experience is assumed in the start which is then compared with the actual self weight at the end. Corrections in design are made if necessary.
All external loads, leaving the self weight, acting on the member to be designed are called imposed or superimposed loads, including live load, wind load, earthquake load, etc. Part of dead load may also act as imposed load.
The maximum intensity of load expected during the life of the structure depending upon a certain probability of occurrence is called service load. No additional factor of safety or overload factor is included in the service loads.
Service loads increased by some factor of safety or overload factor are called factored loads.
The load due to persons occupying the building and their belongings like furniture, dresses, books and kitchenware, etc. is called live load. It changes in magnitude as well as point of application with time.
The load exerted by the wind speed and its air density onto a building. With high velocity winds, low pressure areas are created on the building which creates suction pressure.
Typical Live Loads
|Occupancy or Use||Live Load (kg/m^2)|
|Private apartments, School classrooms.||200|
|Fixed-seats, assembly halls, Library reading rooms.||300|
|Movable seats assembly hall||500|
|Wholesale stores, Light storage warehouses.||600|
|Library stack rooms.||750|
|Heavy manufacturing, heavy storage warehouses, sidewalks and driveways.||1200|