When presented with a structural engineering problem where multiple types of loads are present, it is usually more simple to obtain the forces (reactions, shear, bending moments, etc.) by treating each load separately, solving, and then combining the final forces together directly. This concept is known as superposition.
What is Superposition?
If we have a structural problem with multiple loads, we can just solve considering each load acting individually, find the shear forces and bending moments, and then just summate the final results from each load scenario (or load case). This works because the loads are INDEPENDENT, the value of one does not rely on the value of the others.
Example
Let's consider the example below:
We can simplify this and analyse as two seperate loading cases, ① and ②:
The final combination is just the direct summation of the forces.
Concluding Remarks
This is an important fundamental principle in structural engineering that helps us simplify many problems and also combine results from different analyses.