Consider the planar truss shown in the figure (not drawn to the scale) Neglecting self-weight of the members, the number of zero-force members in the truss under the action of the load P is

Consider the planar truss shown in the figure (not drawn to the scale) Neglecting self-weight of the members, the number of zero-force members in the truss under the action of the load P is Correct Answer 8

Concept:

Planar Truss: When all the members and nodes of a truss lie within a 2-dimensional plane it is called a planar truss.

Members of a truss carry only axial force. If the member of a truss does not carry any force under some specific load conditions, those members are called zero-force members.

Identification of zero-force members:

1) If at any joint two members are non-collinear and no load is acting at the joint, then both the members will be zero-force members.

e.g.

Using property 1 explained above, at joint D members CD and EC are zero force members. Similarly, EF and EC are zero force members, and at joint C, CF and BC are zero force members,

At joint F;

Key Points

Force in member GA can also be found using the fact that truss members carry the only axial force and if the axial deflection of any member is zero that member will be a zero force member.

In the given truss, due to hinge at A and G no axial deformation of the member AG is possible.

Hence GA is a zero force member.