The principle of virtual work has very wide application. But the following are important from the subject point of view:
1. Application of Principle of Virtual Work on Beams Carrying Point Load:
Consider a beam AB, simply supported at its supports and subjected to a point load W at C as shown in fig:
Let RA = Reaction at A and RB = Reaction at B.
First of all, let us assume the beam to be hinged at A. Now consider an upward virtual displacement (y) of the beam at B. This is due to the reaction at B acting upwards as shown in fig.
2. Application of Principle of Virtual Work on Lifting Machine:
We know that in the case of lifting machines, the effort moves downwards, whereas the load moves upwards. In such cases, the virtual works done by the effort and that by the load are found out.
3. Application of Principle of Virtual Work on Framed Structures:
In a framed structure, first of all assume that the member to be removed. Now find out the virtual works done by all the remaining members of the frame and the force in the member, assumed to be removed.