I did a very similar project for my Foundations of Engineering class (easiest class i'll ever take
).
I used a program called west point bridge designer. It was made for a contest but your entry was optional. I'm not much of a civil engineer, but search for the program and see if it helps you any more. It has a load test and three or four different metal to use in several different sizes. Thats all I can help you with. Good luck.
