Influence-Line -diagram-(Truss)

Influence Line diagram (ILD) for Truss members

         ILD represents how Axial force changes overtime in each members of truss when unit load moves from one side to another i.e.  Effect of unit moving load on member if truss.

Q. How do we draw ILD for truss member ?

Note : Since we are dealing with moving load so we need to determine path of travel for load.

Here in this both figure Red marking members are the path of travel .

Concept involved in drawing ILD in truss :
To draw the ILD for specific member we find the axial force in the member every time the unit load visit the joint .




Here , in above figure Orange Dot shows the joints which Unit load visits.
Thus to draw ILD for particular member , we need to do calculation for that member by placing unit load on each of the joints which the unit load visit .

Note : When unit load is just above the supports Axial Force at every member is Zero.

To understand on detail we will solve few Examples :


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Influence Line Diagram for beams  Standard and Muller Breslau Method