ABSTRACT
We use the Method of Joints, Method of Sections, or Graphical Methods to determine the member forces within trusses, such as those in Figure 10.1 or Figure 10.2. Two assumptions reduce the number of variables to the available static equilibrium equations. First, members only carry axial load (along their length). Second, joints, where members connect, are pinned but free to rotate. The Method of Joints balances the loads and forces acting at a joint using the equilibrium equations presented in Chapter 5. The Method of Sections balances the forces acting on a section of a truss using both Equations (5.1) and (6.1) (i.e. the sum of forces and moments on an object must equal zero). Graphical Methods provide another method to balance loads, reactions, and member forces in a geometrical way using Maxwell diagrams. These provide a visual understanding of the individual member forces.
