What Is Imposed Load In Construction?
What Is Imposed Load In Construction?
Imposed load, also known as live load, is a temporary, changeable, or dynamic load acting upon a structure. The magnitude of these loads is typically related to the occupancy of the space or building where the load is applied.
Imposed loads are part of the total load sustained by a structure or member thereof that is applied to it after erection. Common sources of imposed loads include wind, rain and snow, occupants, furniture, and other belongings.
In the design of a structure, imposed loads are considered alongside permanent loads. The minimum values of live loads to be assumed are determined by codes and standards such as the American Society of Civil Engineers (ASCE). Reduction in total distributed imposed loads may be allowed in certain cases.
What Is Imposed Load Example In Construction?
Examples of imposed loads include vehicle traffic, occupants, furniture, and other equipment. Imposed loads are also known as live loads.
Imposed loads are typically related to the occupancy of the space or building where the load is acting. Understanding imposed loads is important in engineering design for structures such as buildings, bridges, and offshore platforms.
Other types of structural loads include dead loads (due to the self-weight of the structure), environmental structural loads, concentrated structural loads, line structural loads, and distributed structural loads.
In addition to permanent dead and imposed (life) loads, structures may also be subject to wind and snow loads as well as earthquake forces.
The magnitude of these additional forces will vary according to the design, use, location, and materials used in the structure. For example, buildings located in regions with heavy snowfall should be designed for snow loading.
What Is The Difference Between Live Load And Imposed Load?
The main difference between live load and imposed load is that live loads are temporary, changeable, and dynamic, while imposed loads are permanent and static. Live loads include forces from occupancy and intended use such as vehicle traffic, occupants, furniture, and other equipment.
Imposed loads are mainly associated with the weight of the structure itself or from other permanent attachments such as drywall or roofing materials. Examples of live loads include wind loads, snow loads, rain loads, seismic forces, etc.
What Is The Minimum Imposed Load?
According to IS 875, the minimum imposed load on roof trusses is 0.4 kN/m2. For sloping roofs up to 10˚, the imposed load is taken as 0.5 kN/m2 if access is not provided and 0.75 kN/m2 if access is provided.
For roofs of slope greater than 10˚, the imposed load is reduced by 0.02 kN/m2 for every degree rise in slope.
The live load considered for an inaccessible roof is 75 kg/cm2. IS 875 consists of five parts: Part 1 for dead loads, Part 2 for imposed loads, Part 3 for wind loads, Part 4 for snow loads, and Part 5 for special loads and load combinations.
How Do You Calculate The Imposed Load On A Slab?
To calculate the imposed load on a slab, you need to take into account the self-weight of the concrete, which is around 2400 kg/m3 or 24.54 kN/m3, as well as any additional loads such as live load, wind load, and floor finishing load.
For example, if the slab has a thickness of 150 mm and a floor finishing load of 1 kN per meter, then the slab load calculation would be 0.150 x 1 x 2400 = 360 kg which is equivalent to 3.53 kN.
If there is a 6″ thick wall with 3 meter height and 1 meter length, then the load can be measured per running meter equivalent to 0.150 x 1 x 3 x 2000 = 900 kg which is equivalent to 9 kN/meter.
The self-weight of bricks varies between 1500 to 2000 kg per cubic meter. For a 125 mm thick slab, each square meter would have a self-weight of 0.125 x 1 x 2400 = 300 kg which is equivalent to 3 kN.