Types of Loads on Structures

Different Types of Loads in Civil Engineering

Any structure must be created to be sufficiently strong to support any type of load at any moment during its expected lifetime. IS: 875–1987 is the Indian Standard Code that gives design considerations for various types of loads acting on a structure. These different types of loads have been listed below:

1. Dead Loads
2. Imposed Loads
3. Wind Loads
4. Snow Loads
5. Earthquake Loads
6. Other Loads

Types of Loads- Dead Loads (DL)

Dead loads are those types of loads that are permanent or immobile and are applied to a structure over its entire lifetime. Dead load is generally caused by the own weight of structural elements such as walls, roofs, beams, columns, etc., stationary equipment, and the weight of various materials.

The volume of each element is multiplied by the unit weight of the material used for that element to determine the dead loads for each structure. Unit weight of some of the materials commonly used in construction has been listed below:

Materials	Unit Weight
Brickwork	19 kN/m3
Timber	6 – 8 kN/m3
Plain cement concrete (PCC)	24 kN/m3
Reinforced cement concrete	25 kN/m3
Steel	78.5 kN/m3

Types of Loads- Imposed Loads (IL) or Live Loads (LL)

Imposed or live loads are those types of loads that change with time. Live loads consist of moving loads or movable loads such as the weight of the furniture, people occupying the floor etc. The designer appropriately assumes these types of loads. The minimum value of live loads for some of the important types of occupancy as per IS: 875–1987 has been mentioned in the table below:

Occupancy	U.D.L	Concentrated Load
Residential Buildings- Dwelling houses
All rooms and kitchens	2.0	1.8
Toilet and bathrooms	2.0	–
Corridors, passages, staircases	3.0	4.5
Balconies	3.0	1.5/m run concentrated at the outer edge
Residential Buildings- Hotels, hostels, lodging houses, dorms, residential clubs
Living rooms, bedrooms, and dormitories	2.0	1.8
Kitchens and laundries	3.0	4.5
Dining rooms, cafeterias, and restaurants	4.0	2.7
Baths and toilets	2.0	–
Educational Buildings
Classrooms and lecture rooms Dining rooms, cafeterias, and restaurants	3.0	2.7
Offices, lounges, and staff rooms	2.5	2.7
Toilets and bathrooms	2.0	–
Institutional Buildings
Bedrooms, wards, dormitories, and lounges	2.0	1.8
Kitchens, laundries, and laboratories	3.0	4.5
Dining rooms, cafeterias, and restaurants	3.0	2.7
Toilets and bathrooms	2.0	–

Types of Loads- Wind Loads

Wind loads are generally horizontal loads caused due to the movement of air relative to the earth surface. These types of loads are not considered for the design of small and low-rise buildings but are assumed for high-rise buildings. As per IS: 875 (Part 3), the design wind load depends upon wind speed, topography, location and shape of the structure, etc. The design speed of wind Vz at any height z can be calculated as

V_Z=k₁k₂k₃V_b

where k₁ = risk coefficient

k₂ = Coefficient based on terrain, height, and size of the structure

k₃ = topography factor

V_b = basic wind speed (m/sec)

The design wind pressure (p_z) at a height z is given as

p_z=0.6V_Z²

where V_Z is in m/s

p_z is in N/m²

Types of Loads- Snow Loads

The snow loads are to be considered for the buildings located in the regions where snow is likely to fall. These types of loads act vertically downward. A roof’s shape plays a significant role in the value of snow load. The design snow load on the plan area of the roof or any other area above ground can be calculated as-

S=μS₀

where S = design snow load

μ = shape coefficient

S₀ = ground snow load

Types of Loads- Earthquake Loads

Shocks due to earthquakes can cause movement of the foundation of structures. Due to these movements, additional inertial forces develop in the superstructure. Total vibration caused by an earthquake may be resolved in three mutually perpendicular directions. (one vertical and two horizontal directions). The movement in the vertical direction does not cause significant forces in the superstructure, but movements in horizontal directions need special consideration.

The type of soil, the size, and method of construction, as well as the duration and severity of ground motion, all affect how the building responds to ground vibration. The details of such estimates for structures standing on soils that will not noticeably settle or slide due to an earthquake are provided in IS 1893-2014.

Some Other Types of Loads

In addition to the types of loads already mentioned, some special types of loads and effects can affect the structure. Some of these loads have been listed below:

• Earth and Hydrostatic pressure: In the design of a structure, partially or fully below ground level, the pressure exerted by soil, water, or both must be considered.
• Erection loads: Special types of loads are generated during the erection of materials and equipment due to the impact of hoisting equipment.
• Accidental loads: These types of loads are a result of human action, including impact, collision, explosions, and fire.
• Settlement loads: These types of loads occur due to differential settlement of the foundations.

Important GATE Topics
Work Done By A Force	Motion Under Gravity
Dynamic Resistance	Static Resistance
Ideal Diode	Bettis Theorem
Work Done By A Constant Force	Application Layer Protocols
Castigliano’s Theorem	Portal Frames