Live Load

What Does Live Load Mean?

Live load is a civil engineering term for a load that is not constant, but changes over time.

Live loads can be caused by anything adding, removing, or relocating weight on a structure. This includes people walking across a surface and objects that can be moved or carried.

A live load can be uniformly distributed or act at a particular point, known as a point load. In the United States, a live load is expressed as pounds per square foot (PSF).

Safeopedia Explains Live Load

Live loads are factored into calculations of a structure's load capacity. The American Society of Civil Engineers (ASCE) allocates minimum live load requirements according to the intended use of a building or a temporary structure. For example, a house might require a live load of 1.5 kPa, while a dance hall might need to accommodate a live load of 5.0 kPa to factor in the greater number of people using the space at once and the type of activities carried out in it.

Construction approval for a structure depends on design and structural plans that fully account for the relevant live load requirements.

Temporary structures must also factor this in. The Occupational Safety and Health Administration (OSHA) publish and enforce official standards for the construction and maintenance of scaffolding, including load requirements.

Given the nature of construction work, scaffolding is subject to an almost constantly shifting load of workers, materials, and tools. To account for this, OSHA requires that scaffolds and their components must be able to support at least four times the maximum anticipated load.

Calculating Live Loads for Scaffolds

Before erecting scaffolding, its maximum live load should be calculated in order to ensure that it is built with the right type of tubing, bracing, and planks.

The live load on a scaffold will include the weight of the workers and the materials and equipment those workers will be using at a given time. These weights are approximations and should, therefore, be estimated as conservatively as possible to ensure that the scaffold can safely bear all the weight that will be placed on it.

There are various methods for calculating live loads, and employers should ensure they use the method approved by local building and planning authorities.

One of the simplest methods is to assume that there are up to ten workers on a scaffold at a given time. Multiply the average weight of a worker (erring on the heavier side) by ten. Then, assume that the material and equipment weight adds up to 1,000 kg. Divide the total weight by three, since each of the vertical posts of the scaffold bay are designed to bear a third of the total load. Multiply that result by the number of platforms on the scaffolding unit to get the scaffold's live load.