PROBLEM STATEMENT 

Hints and Discussion Thread

For Part A
Follow the four-step plan:

1. Equilibrium: FBD and equilibrium equation for connector C. Assume all members in tension in your FBD. You should recognize that the problem is INDETERMINATE.
2. Force/elongation equations:  Write down the e = FL/EA equation for each of the three rods.
3. Compatibility equations: You should have two equations: one saying that 1 and 2 have the same displacement, and the second saying that 1 and 3 have equal but opposite displacements.
4. Solve: At this point, you should have a sufficient number of equations to solve for the three rod loads.

For Part B: You should recognize that the elongations for (1) and (2) for Structure I have opposite signs.

Any questions? Ask (and answer) questions here.