ABSTRACT
This chapter talks about the equilibrium principles considered in to the forces analysis involved in structures. For such forces to be in equilibrium there must be no resultant force. The triangle law can be used to determine when three concurrent forces are in equilibrium. Bow's notation is a useful method of labeling the forces in a truss and it aids the construction of force polygons. The spaces between the members and their external forces and reactions are labeled using letters or numbers when working in a consistent direction. Each joint in a structure will be in equilibrium if the structure is in equilibrium, thus the analysis of trusses by the joints method involves considering the equilibrium conditions at each joint, in isolation from the rest of the truss, by analysis of the horizontal and vertical components of the forces. Force diagrams are drawn for the forces at each joint, taken in sequence, recognizing that some polygon elements for one joint.
