Influence Line Diagrams

Influence Line Diagrams (ILD)
Influence line diagram is a diagram which represent the value of any particular function like Shear force, bending moment or axial force at particular point in the span of a structural member for the various positions of the point load on that structural member.
If you take a simply supported beam and you want to know the variation of the support reaction at one end with the variation of a particular point load from one end to the other end then drawing the Influence Line Drawing is the best option that you have.
Once you draw the ILD for the Reaction at one end, then you can find the value of the support reaction for any given point load at any particular position. It becomes very easy once the ILD is formed.