Static load is the mechanical load applied to an assembly or object slowly. There is no time i.e. the static load will not change with time, therefore it can be used to do tests to find the maximum loads that can be applied to structures, like bridges or floor loads in tower blocks. Static load can also be used to work out the strength of materials of various types.
Static loads are different to dynamic loads where the line of forces acting on the structure are applied very quickly and changeable. So for example a car park where there are no moving vehicles is being affected by static loading, but when the vehicles start moving the load becomes dynamic.
Both types of loading can be used to define safety factors to structural designs. So a structure having a load limit of half the maximum capacity would have a safety factor of 2.
To understand static loading more we can compare it to dynamic loading.
Static Loading vs Dynamic Loading: what is the differences?
Structural analysis looks at both static and dynamic loading, as Structural Analysis is determining how physical structures will behave when a force acts on it.
In this case the load on the structure can be any object such as the people on a top floor or vehicles parked on a slab, to natural forces such as wind and snow, to geological forces such as earthquakes.
Whether the load being applied is a static or dynamic situation depends on the action of the forces. If they are applied very quickly they are dynamic, if they are acting on the structure slowly they are static.
Dynamic analysis determines dynamic load and static analysis determines static loads.
The equation of force shows us that dynamic loads apply a greater force to structures than static loads. The concept of sudden decelerating force can also increase force, in the example where a wrecking ball strikes a building.
There are examples of where research into dynamic and static loading would appear to contradict. This has been studied particularly on buried pipe.
Some studies into buried pipe indicate that the amounts of displacement on buried pipe would experience much greater than what pipe experiences exposed to long-term moving loads.
The studies have also shown that the ratio of pipe displacement for static loading versus dynamic loading becomes less with pipe stiffness. In any case, the standard position is that dynamic loads apply more force than static loads.
Structural engineering uses the equation of force to determine the force due to a dynamic load, since primarily we want to provide a safety margin. An example is a roadside crash barrier aimed at preventing errant vehicles from leaving the road.
Dynamic loads may also change over time so it is often easy in structural engineering load calculations to use the static loading measures in place of dynamic loading with guidelines used to establish capacity to dynamic load forces as a separate entity.
Materials and Load Tests
Every material has a limit of how much compression or tension stress it can handle before it yields or permanently deforms. There is a set of fundamental material properties that can be tested to determine how much stress the material can handle.
Stress is the measure of the force per unit area in a cross section of the material. When stress reaches beyond what the material can handle, microscopic fractures form and grow until the material experiences failure and breakage. The point at which the material breaks is known as the ultimate tensile strength of the material.
Unique material strengths and properties help determine the applications the materials can be used for.
Examples of Static Loading
Static loads, or dead loads, occur over time and are a category of load that encompasses many different types.
For instance, if people are talking in a lift waiting for the doors to close, the people create a static load as the people and lift are not in motion to one another.
However, the instant the people move in the lift it becomes dynamic load as the stresses in the lift change depending on where the people are in the lift. Different loads also produce different stresses from a fixed load such as walking as opposed to jumping or up and down.
Other types of static loads include filing cabinets or furniture that is placed on a floor or buildings on a bridge.
FAQs
What is an Example of a Static Load?
Examples of static loads are the weight of a building bearing upon the ground or a car parked along the side of a road. However, if the car begins to move it becomes a dynamic load.
What is Static Loading in a Structure?
Static loading in a structure is defined as any load that exerts itself on a structure whether the weight of furnishings or another stationary load. For example, a crane placed on top of a building is a static load (until it moves!).
What is a Static Load Called?
Static loads are often referred to as dead loads or holding loads.
Conclusion
Static loading is defined as any load that is applied slowly to an assembly, object or structure. Static loads are also those loads that remain consistent, and do not move whatsoever. Static loads are used to measure the maximum load capabilities of various structures and objects and ultimate tensile strength of materials.
Dynamic loads, on the other hand, are loads that are applied quickly with changes in time, such as a cars driving across a bridge, or people dancing up and down on a dancefloor or the weight of snow piling on top of a roof.