The basic requirement to be satisfied in structural design is that the foundation must be strong enough to support all the possible types of loads to which a building is liable to be subjected. Hence assessment of the design load is essentially the first step that should be taken before determining the type of foundation. The loads coming on the foundation of a structure can be classified into three different categories.
Dead load: This is the sum of loads comprising the self weight of the structure, footing, foundation and load of materials used for the various components of a building such as walls, floors, roofs etc. All permanent loads are included in dead loads. These loads can be calculated by finding weights of the cubical contents of the different materials used in the structure.
Live loadd: This is the movable load on the floor and hence it is variable. It is also known as super imposed load. It includes the load of persons standing on a floor, weight of the materials temporarily stored on a floor, weight on roof etc.
Wind load: Incase of tall buildings, the effect due to wind should be considered. The exposed sides of walls and roofs of the buildings are subjected to wind pressure. Wind pressure or wind loading is based on the measurements of wind velocities and characteristics of the structure acting as obstruction. In designing a structure and its foundation, separate as well as combined effect of imposed loads and wind loads are considered. The cross- walls and floors play an important part in stiffening the structure against wind pressure. In a building whose height is less than three times its width and it is adequately stiffened by cross-walls and floor, the effect of wind pressure is neglected. In case, the building is situated in coastal areas, the height of the building should not exceed two times the effective width for no wind effects.
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