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Live Load

Live loads or super-imposed loads consist of moving or variable loads. It could be 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 load on different floors for different uses shall be as given in Table 2. The loads specified in Table 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 multi-storeyed buildings, the following reductions (stated in Table 1) in live loads may be made in designing column, walls, piers and foundations:


Table 1

No. of floors earned by member under consideration

Percentage reduction of total live load on all floors above the member under consideration

1

0

2

10

3

20

4

30

5 or more

40

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No reduction shall be made in the 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 buildings, such as factories and workshops, designed for a live load of more than 500 kg/m2 (5 kN/m\ the reduction given above may be made, provided that the loading assumed for any column, wall etc. is not less than that which would have been if all floors

had been designed for 500 kg/m(5 kN/m2) with no reduction.


Table 2

Live Load On Floors (IS: 875-1964)

Loading Class No.

Type of floors

Min. live load per metre2 of floor area

Alternative minimum live load

200

Floors in dwelling houses tenements, hospital wards, bed rooms and private sitting rooms in hostels and dormitories.

200 kg/m2(2 kN/m2) 

Subject to a min. total I load of 2.S times, the values in col. 3 for any given slab panel and 6 times the value in col. 3 for any given beam. This total load shall be assumed uniformly distributed on the entire area of the slab panel and the entire length of the beam.

250

Office floor other than entrance halls, floors of light workrooms.

250*-400 kg/m2(2.5-4 kN/m2) 

300

Floors of banking halls, office entrance halls and reading rooms

300 kg/m2(3 kN/m2) 

400

Shop floors used for display and sale of merchandise ; floors of workrooms generally floors of classrooms in schools ; floors of places of assembly with fixed seating; restaurants; circulation space ill machinery halls ; power stations etc., where not occupied by plant or equipment.

400 kg/m2(4 kN/m2) 

500

Floors of warehouses, workshops, factories and other buildings or parts of buildings of similar categories for light weight loads; office floors for storage and filling purposes; floors of places of assembly without fixed seating; public rooms in hotels, dance halls, waiting halls etc.

500 kg/m2(5 kN/m2) 

750

Floors of warehouses, workshops, factories and other buildings or parts of buildings of similar categories for medium weight loads.

750 kg/m2(7.5 kN/m2) 

1000

Floors of warehouses workshops, factories and other buildings or parts of buildings of similar categories for heavy weight loads, floors of book stores and libraries, roofs and pavement lights over basements projecting under the public footpath.

1000 kg/m2(10 kN/m2) 

Garage Light

Floors used for garages, for vehicles not exceeding 2.5 tonnes (25 kN) gross weight.

slab

400 kg/m2(4 kN/m2) 

The worst combination of actual wheel loads, whichever is greater.

beams

250 kg/m2(2.5 kN/m2) 

The worst combination of actual wheel loads, whichever is greater.

Garage Heavy

Floors used for garages, for vehicles not exceeding 4 times the gross weight.

750 kg/m2(7.5 kN/m2) 

Subject to a minimum of one and a half times maximum wheel load but not less than 500kg (5kN) considered to be distributed over 75 cm2.

Stairs

Stairs, landing not considered for class 200 loading but not liable to overcrowding.

300 kg/m2(3 kN/m2) 

Subject to a minimum of 130 kg (1.3 kN) concentrated load at the unsupported end of each step for stairs constructed out of structurally independent cantilever steps.

Stairs, landing and corridors for class 200 loading but liable to overcrowding, and for all other classes.

500 kg/m2(5 kN/m2) 

Balcony

Balconies not liable to overcrowding:

For class 200 loading

300 kg/m2(3 kN/m2) 

For all other classes

500 kg/m2(5 kN/m2) 

Balconies liable to over crowding

500 kg/m2(5 kN/m2) 

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

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 rooms in which some 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 small motors. Under loading class 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 vary considerably and so these loadings under the terms 'light' 'medium' and 'heavy' are introduced in order to allow ;for more economical designs but the terms have no special meaning in themselves other than the live load for which the relevant floor is designed. It is, however, important, particularly in the case of heavy weight loads, to assess the actual loads to ensure that they are not in excess of l000kg/m2 (10 kN/m2); in cases where they are in excess, the design shall be based on the actual loading.

Note 5:

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

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LIVE LOADS ON ROOFS

Table 3 gives live 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, if required.

Snow Load:

If the roof is to snow it should be designed for the actual load due to snow or for the live loads specified in Table 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 collection 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 which have positioning, shape and drainage system in such a way as to make accumulation of rainwater possible, loads due to such accumulation of water and the live loads for the roofs as given in Table 3 shall be considered separately and the more critical of the two shall be adopted in the design.


Table 3

S. No.

Type of roof

Live load measured on plan

Minimum live load measured on plan

1.

Flat, sloping or curved with slopes up to and including 10 degrees

  1. (a) Access provided

150 Kg/m2 (1.5 kN/m2)

375 Kg (3750 N) uniformly distributed over any span of one metre and 900 kg (9000N) uniformly distributed over the span in the case of all beams.

  1. (b) Access not provided except for maintenance

75 Kg/m2 (7.5 kN/m2)

190 Kg (1900 N) uniformly distributed over any span of one metre width of the roof slab and 450 kg (4500N) uniformly distributed over the span in the case of all beams.

2.

Sloping roof with slope greater than 10 degrees.

(a)For roof membrane sheets or purlins – 75 kN/m2 less 2kg/m2 for every degree increase in slope over 10 degrees

(b) For members supporting the roof membrane and roof purlins such as trusses, beams, girders, etc. - 2/3 of load in (a)

(c) Loads in (a) and (b) do not include loads due to snow, rain dust collection, etc. and the effects of such loads shall be appropriately considered.

Subject to a minimum of 40 Kg/m2 (400 N/m2)

3.

Curved roof with slope at springing greater than 10 degrees

(75- 345ОҐ2) kg/m2 where ОҐ=h/l

h = height of the highest point of the structure measured from its springing, and

I = chord length of the roof if singly curved and shorter of the two sides if doubly curved.

Subject to a minimum of 40 kg/m2.

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Note:

For special types of roofs with highly permeable and absorbent material, the contingency of roof material increasing in weight due to absorption of moisture shall be provided for.

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