3.4 Using Global Equilibrium to Calculate Reactions

To calculate the reaction forces for a determinate 2D truss, you simply have to apply the three equilibrium equations to the entire system. If there are more than three reaction components but the truss is still determinate, then you would have to likely split the truss into separate free body diagrams to solve for all of the unknown reactions. We will encounter this problem in frame analysis.

The process of finding reactions is identical to the process that was discussed in Section 1.2 for finding unknown forces using equilibrium. This process will be shown in an example to follow in the next section.