The method of sections can be used to determine member forces in a truss. It involves cutting or sectioning the truss and applying equilibrium equations to the cut parts. For example, a truss can be cut through members to determine the forces in those members by drawing and analyzing the free-body diagram of each cut section. Either the method of joints or method of sections can be used to analyze trusses.

1. THE METHOD OF SECTIONS
The method of sections is used to determine the loadings acting within a body. It is based on the
principle that if a body is in equilibrium then any part of the body is also in equilibrium. The method of
sections can also be used to “cut” or section the members of the entire truss. If the body passes through
the truss and the free-body diagram of either of its two parts is drawn, we can then apply the equations
of equilibrium to that part to determine the member forces at the “cut section.”
Example 1:
Determine the force in members GE, GC and BC of the truss shown in the figure. Indicate whether the
members are in tension or compression.
SOLUTION:

2. Example 2:
Determine the force in members in BF, BG and AB, and state if the members are in tension or
compression.

3. SOLUTION:
Reactions at A and G;

4. Procedure for Analysis
Either the method of joints or the method of sections can be used to determine the forces developed in
the members of a truss.
Method of Joints: Generally, if the forces in all members of the truss must be determined, the method
of joints is most suitable for the analysis.
Method of Sections: If only few member forces are to be determined, the method of sections may be
used.