TYPES OF LOAD ACTING ON BUILDING (IS : 875)

The loads acting on structures can be broadly classified as vertical loads, horizontal loads and longitudinal loads.

The Vertical Loads Consist Of :

1. Dead load : It is the self weight of structure which are transferred to structure throughout the life span. It majorly consists of the weight of walls, columns, beams, roofs etc.

Dead Load = volume of each section x unit weight of material

Sl. No	Material	Unit Weight Of Material
1	Plain Cement Concrete	18.8 kN/m3
2	Reinforced Cement Concrete	24 kN/m3
3	Brick Masonry	18.8 kN/m3
4	Timber	5-8 kN/m3
5	Stone Masonry	20.4-26.5 kN/m3

2. Live load : Live loads are either movable or moving load on building. It includes weights of movable partitions or furniture etc. The minimum value of live loads to be assumed are specified by the IS 875 (part 2)–1987.

Live Load For The Following Occupancies :

• Educational buildings

• Assembly building

• Institutional buildings

• Mercantile buildings

• Industrial buildings

• Business and office buildings

• Storage rooms

• Residential buildings–dwelling houses, hotels, hostels, boiler rooms and plant rooms, garages.

Imposed Or Live Load for different Occupancies :

IMPOSED OR LIVE LOAD ON STRUCTURE

However, reductions in assumed total live loads on floors may be made in designing columns, walls, their supports and foundations as shown in table below.

Number of floors carried by member under consideration	Reduction of total live load on all floors above the member under consideration  %
1	0
2	10
3	20
4	30
5-10	40
Over 10	50

3. Snow load : Load caused by the snowfall on the roof of the building. It is consider as vertical load acting on a building.

According to the IS 875 (part 4) – 1987, the minimum snow load on a roof area is obtained by the expression

Where

S = Design snow load on plan area of roof.

= Shape coefficient

S₀ = Ground snow load.

The Horizontal Loads Consist Of :

1. Wind load : It is the horizontal load caused by the blowing wind. Wind load is required to be considered in structural design especially when the height of the building exceeds two times the dimensions latreal to the exposed wind surface.

The calculation of wind loads depends on the two factors :

• Velocity Of Wind 
• Size Of The Building 

According to the IS-875 (Part 3) -1987) wind load calculating by the following expression : 

              

            V_z = k_1.k₂.k_3.V_b

Where k₁ = Risk coefficient
k₃ = Topography factor
k₂ = Coefficient based on terrain, height and structure size.
V_b = basic wind pressure is shown in a map of India. 

The design wind pressure is given by : 

p_z = 0.6 V²_z

where

p_z is in N/m² at height Z 

V_z is in m/sec. 

Note : wind pressure act uniformly up to the height of 30 meter, Above 30 m height, the wind pressure increases. 

2. Earthquake load :  It is the vibrational load on structure caused by the earthquake. This vibration occur in all three direction, but the movement in vertical direction do not cause forces in superstructure to any significant extent. But the horizontal movement of the building at the time of earthquake is to be considered while designing.

For monolithic reinforced concrete structures located in the seismic zone 2, and 3 without more than 5 stories high and importance factor less than 1, the seismic forces are not critical.