Considering the same frame using joint resolution highlights the advantage of the method of sections when only a few member forces are required.
In this technique (which can be considered as a special case of the method of sections), sections are taken which isolate each individual joint in turn in the frame, e.g.
In Figure 3.6 four sections are shown, each of which isolates a joint in the structure as indicated in Figure 3.7.
Since in each case the forces are coincident, the moment equation is of no value, hence only two independent equations are available. It is necessary when considering the equilibrium of each joint to do so in a sequence which ensures that there are no more than two unknown member forces in the joint under consideration. This can be carried out until all member forces in the structure have been determined.
Consider Joint G:
M fin lit r GH Isa zero member Member FG is a strut
Consider Joint F: substitute for calculated values, i.e. Ffg (direction of force is into the joint)
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