Types Of Load
The types of loads acting on structures for buildings and other structures can be broadly classified as vertical loads, horizontal loads and longitudinal loads. The vertical loads consist of dead load, live load, and impact load.Types of loads acting on the building structure.
- Dead load
- Imposed loads
- Wind loads
- Snow Loads
- Earthquake forces
- Shrinkage, creep and temperature effect
- Other forces and effects
Dead Load
Dead loads in the building include the weight of all permanent constructions, like roofs, floors, walls, partition walls, beams, columns, balcony's footing. These loads shall be assessed by estimating the quantity of each material and then multiplying it with the unit weight. The unit weights of various materials used in building constructions are given in the code IS 875 -1987. It includes an exhaustive list. For example, under the heading 'brick masonry', it has four types like common burnt clay bricks, engineering bricks, glazed bricks and pressed bricks. Under the heading plain concrete, there are 10 groups. The commonly used values by the designers are listed in the table.Unit weight of Important Building Materials used by designers
Imposed Loads
the loads which keep on changing from time to time are called as imposed loads, common examples of such loads in a building are the weight of the persons, weights of the movable partition, dust loads and weight of furniture. Their loads were formerly known as live loads. these loads are to be suitably assumed by the designer. It is one of the major loads in the design. The minimum values to be assumed are given in IS 875 - 1987. It depends upon the intended use of the building. These values are presented for square more of floor area. The code gave the value of loads for the following occupancy classification:
- Residential building
- Education building
- institutional building
- Business and office building
- mercantile buildings
- Assembly buildings
- Industrial buildings,
- Storage rooms
The code gives uniformly distributed loads as well as concentrated loads. The floors are to be investigated for both uniformly distributed and worst position of concentrated loads. The one which given worst effect is to be considered for the design but both should not be considered to act simultaneously.
In a particular building, the Imposed load may change from room to room.
Some of the important values are presented in the table, which is the minimum values and wherever necessary more than these value are to be assumed.
Table Minimum Imposed load to be considered.
Wind Loads
The force exerted by the horizontal component of wind is to be considered in the design of buildings. It depends upon the velocity of wind and the shape and size of the building. complete details of calculating wind load on structures are given in IS 875 -1987.Using color code, basic wind pressure Vb is shown in a map of India. The designer can pick up the value of Vb depending upon the locality of the building
To get the design wind velocity Vz the following expression shall be used
Vz = k1 k2 k3Vb
where K1= Risk coefficient
k2 = Coefficient based on terrain, height and structure size.
K3= Topography factor
The Design wind pressure is given by
Pz= 0.6 Vz2