Tuesday, October 16, 2012

LIVE LOADS IN A BUILDING: on floors, on roofs.

Live loads, also called as super-imposed loads, consisi of moving or variable loads, due to people or occupants, their furniture, temporary stores, machinery etc.


Live loads on floors shall comprise of all loads other than dead loads. The minimum live loads on different floors for different uses shall be as given in Table 1.2. The loads specified in Table 1.2 are uniformly distributed static loads in kg/m2 ( kN/m2) on the plane area and provide for normal effects of impact and acceleration, but do not take into consideration special concentrated loads, snow loads and other loads.

In the case of multistoreyed buildings, the following reductions in live loads may be made in designing column, walls, piers and foundations

No reduction shall be made in ihe case of warehouses, garages, and other buildings used for storage purposes, and for factories and workshops, designed for 500 kg/m2 (5 kN/m2). However, for bulidings, such as factories and workshops, designed for a live load of more than 500 kg/m2 (5 kN/m2), the reduction given above may be made, provided that the loading assumed for any column, walt etc, is not less than that which would have been if ah floors had been designed for 500 kg/m(5 kN/m2) with no reduction.


*the lower value of 250 kg/m2 (2.5 k N/mZ) should be taken where separate storage facilities are provided and me higher value of 400 kg/m2 (4 kN/m2) should be taken where such provisions are laking.

Note 1. In the above table, a reference to a floor includes a reference to any part of that floor, and a reference to ‘slabs’ includes boarding and beams or ribs, spaced not farther apart than one metre between centres, and a reference to ‘beams’ means all other beams and ribs. 

Note 2. Under loading class No. 250, the reference to ‘light work rooms’ envisages roorns in which sorne light machines (for example, sewing machines, used for by milliners or tailors) are operated without a central power-driven unit, that is, the machines are independently operated either by hand or by srnall motors.

Under loading dass No. 400, the reference to ‘workrooms’ generally envisages the installation of machines operated with central power driven unit with individual machines being belt driven.

Note 3. ‘Fixed seating’ implies that the removal of the seating and the use of space for other purpose is improbable. The maximum likely load in this case is, therefore, closely controlled.

Note 4. The loading in workshops, warehouses and factories varies considerably and so these loadings under the terms ‘light’ ‘medium’ and ‘heavy’ are introduced in order to allow fon more economical designs but the terms have no special meaning in themselves other than the live load fon which the relevent floor is designed. It ts, however, important, panticularly in the case of heavy weight loads, lo assess the actual loads lo ensure that they are not in excess of 1000 kg/m2 (10 kN/m2) in case where they are in exccss, the design shall be based on the actual loading.

Note 5. The load classification fon stairs, corridors, balconies and landings provide fon the fact that these often serve several occupancies and are used fon transporting the furniture and goods.


Table 1.3 gives lives loads on flat roofs, sloping roofs and curved roofs.

Roofs of buildings used for promenade or incidental assembly purposes shall be designed for a minimum load of 400 kg/m2 (4 kN/m2) or heavier, it required.

Snow Load: It the roof is subjected to snow load, it should be designed for the actual load due to snow or lot the live loads specified in Table 1.3, whichever is more severe. Actual load due to snow will depend upon the shape of the roof and its capacity to retain the snow; and each case shall be treated on its own merits. In the absence of any specific information, the loading due to colletion of snow may be assumed to be 2.5 kg/m2 (25 kN/m2) per centimetre depth of snow.

Loads due to rain: On surfaces whose positioning, shape and drainage system are such as to make accumulation of rainwater possible, loads due lo such accumulation of water and the live loads for he roofs as given in Table 1.3 shall be considered separately and the more critical of the two shall be adopted in the design.


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