Theory of triangulation
Triangulation involves the use of triangular shapes to give stability to structures. It relates particularly to pinned or hinged structures. Usually these types of structures offer no resistance to bending moments when a force is applied.
Members trying to resist bending do not need to be as strong. However they can easily be pushed out of shape by external forces and hence are not in equilibrium, ie ∑FH≠0.∑FH≠0 is used to show that the total of the horizontal forces is not zero.