First of all, Why do you need to know about Types of Loads on Structures?

Simple.

In order to construct buildings or structures to withstand any possible situation and loading conditions, you just need to know the typical loadings that are going to act on the structure.

Before starting to discuss the types of loads, let’s cover some basics. 

What are Structural Loads?

Actions or forces which cause stresses, deformations or displacements in a structure are known as structural loads. The forces may be the result of anything such as moving people, self-weight, other natural forces (wind, thermal, earthquake, snow), etc

Types of Loads

Based upon the sources of force, Types of loads will be classified as

  • Dead Load
  • Live Load
  • Environmental Loads
    • Wind Loads
    • Snow load
    • Earthquake Load
    • Thermal Loads
    • Settlement Loads
  • Special Loads

Types of Loads - Chart Diagram

Let’s see each one briefly…

Dead Load

Loads that are static or permanent relatively constant over the time period of a structure is known as Dead Load.

This includes self-weight of the structural components such as walls, beams, columns, roofs, and other immovable fixed parts of the structure such as plasterboards, flooring materials, wooden frames, etc.

Dead Loads can be calculated by multiplying the unit weight of materials used and their volume.

Dead Loads on typical structure

The dead load of the different material listed below

MATERIAL WEIGHT kN/m³
Wood 8 KN / m3
Brick Masonry 18.8 KN / m3
Plain Cement Concrete 24 KN / m3
Stone Masonry 25 KN / m3
Reinforced Cement Concrete 25 KN / m3
Steel 78.5 KN / m3
See the full list here

For Example, Dead Load of 3 m3 Plain Cement Concrete = Unit weight of PCC X Volume = 24 kN / m3 X 3 m3 = 8 kN / m3

Live Load

As the name suggests Live loads, on the other hand, consists of imposed loads on the floor which are temporary, changeable, and dynamic. 

Live loads vary. For Example,

  • People and Furniture Items are Live loads for Residential buildings.
  • Vehicles & pedestrians are live loads for bridges
  • Desks & students are live loads for educational buildings

Typical Live Loads in Office Building

You can refer IS 875 (part 2) -1987 for minimum Live Load Values.

Minimum Floor Live Loads for residential building as per IS Code

Minimum Floor Live Loads for residential building as per IS Code

DESCRIPTION LIVE LOAD kN/m²
Floors in Residential Buildings 2
Floors in Office Buildings 2.5 – 4
Floors of Banking Hall 3
Residential Staircase & Balconies 3
Floors of Educational Buildings 4
Factory Garages (Light) 4-5
Factory Garages (Heavy) 7.5

Environmental Load

Structural Loads that are caused by natural forces such as wind, snow, earthquake, and extreme temperatures are known as Environmental Load.

Typical Environmental Loads 

  • Wind Loads
  • Earthquake Load
  • Snow load
  • Thermal Loads
  • Settlement Loads

Wind Load

Pressures or stress-induced on a building by the wind blows is known as Wind Loads.

Why take wind load for consideration? Because while the wind blows it creates 3 types of loads which may cause the building to fail.

Wind Loads on building

  • Uplift Load – It creates a strong uplifting force, much like a kite flying high in the air. Pressures the structure to move upwards.
  • Shear Load – Pressures the building over the edge to tilt, which causes walls to crack.
  • Lateral Load – Horizontal force that makes the building go against the foundation and slides off.

It may not be required to calculate wind loads for a small or low-level rising building. 

However, it should be considered in the following situations.

  • High rise building  
  • Using lightweight material
  • Using critical design shapes (especially in elevations)
  • The occurrence of the hurricane in the particular region

If the structure is not enough to withstand the wind load, additional substructures or loads need to be imposed. The historical data of the locality usually determine wind load.

For more details on calculating the wind load, please refer to IS-875 (Part 3) -1987

Snow Load

Snow Loads are vertical loads that are imposed on the roof by snow during the snowfall.

These loads are considered only in snowfall areas mostly in northern or mountain regions all over the world.

Snow Loads are not the result of a single action. It occurs overtime on the roof during the wintertime. Snow deposits on the roof can easily move by wind forces causing unbalanced roof loads and drifting.

That imbalance of loads on the roof causes a critical loading force on the structures.

Refer IS 875 (part 4) – 1987 for Snow Loads on the structures. Snow Load Calculator – May be useful to calculate the loads.

Snow Deposit on Wooden Shed

Earthquake or Seismic Load

As the name suggests the load acts on the structure due to an earthquake is known as Earthquake load.

Seismic Acceleration

Due to the ground (movement) acceleration, the building moves back and forth which causes the structure to fail.

Earthquake loads are specific to the seismic region zone. The Bureau of Indian standards has published the seismic hazard maps for India. Every country has its own set seismic zone

According to BIS [IS-1893 (Part- 1): 2002], In India Seismic zone has been classified as four zones according to their past seismic history. Zone V is the most seismically active region, while zone II is the least.

Zone  Intensity
Zone II Low-intensity zone
Zone III Moderate intensity zone
Zone IV Severe intensity zone
Zone V Very severe intensity zone

Important Towns in India that have a very severe intensity zone are Bhuj, Darbhanga, Guwahati, Imphal, Jorhat, Kohima, Mandi, Sadiya, Srinagar, Tezpur.  

Structures in high seismic activity zones need to be carefully analyzed and designed to withstand the Earthquake loads.

Special Loads

Apart from the above 5 most common loads, there are some other special loads 

  • Settlement Loads – These types of loads occur when one part of the structure settles more than the other part of the structure. It is essential to design & study the soil conditions to avoid such settlements
  • Thermal Loads – Temperature that causes effects on buildings such as indoor & outside air temperature, underground heat & solar radiation is known as Thermal Loads
  • Flood Loads – These loads are caused by floods around the foundation. It causes erosion of soil and loss of load-bearing capacity of the building.  
  • Soil and Fluid Pressure – These loads occur due to high water flow on the soil. It eventually affects the density of soil which creates lateral uplift force.
  • Erection Effects – These loads include transportation of structural members or installation of structural members by the equipment. For Example, Metro Column Construction where the heavy vehicle used to erect the members in the place.

Conclusion

Hope now you understand the basics of types of loads that are acting on a building or any structure. If it helps you give a heart to this post. We really appreciate it!

Have doubts? drop a comment below.

Author

Satheesh is a Civil Engineer who has more than 9+ Years of experience in residential construction. He is the author, editor of Civil Planets

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