17.4: Applications of Stress
Consider a structure made of a boom and a rod designed to support a load. These two components are connected by a pin and stabilized by brackets and pins. The boom and the rod are detached from their supports to assess the different stresses imposed on this structure, and a free-body diagram is drawn. Then, all the forces applied, including the load acting on the structure, are identified. The reaction forces exerted on both the boom and the rod are computed using the equilibrium equations.
The reactions at point P cause compression in the boom, and those at point R cause tension in the rod. Both members are two-force members, subjected to forces at only two points. The lines of action of the resultant forces acting at each of these two points are equal and opposite, and they pass through both points. The forces exerted on the joint by these members can be determined using a force triangle. The normal stress that arises from the axial force on the boom is determined by dividing the prevailing force on the member by the cross-sectional area of the boom. Similarly, the normal stress acting on the rod is calculated.
