Dear Nala,
Kindly do the following:
1. Go through all the Caeasr manuals. You will get nearly all the answers of basic questions from there. For Expansion joints read Chapter 5 of Caesar Applications Guide.
2. Read EJMA as mentioned by shr.
3. Go through coade newsletter May 1993 and Dec 1993 for information on Expansion joints.
4. Utilize the search option on the forum. That's the most powerful tool for learners.
5. Take help from any experienced stress engineer in your company.

All the best.