Subject: How do you efficiently design and rehabilitate a bridge?

A small, secluded village recently experienced a 500 year flood and one of 
the main streets out of town had its bridge lifted off its bearings and 
washed downstream. After inspection by the county engineer, the 
abutments for the existing bridge were determined to be reusable. The 
orginal bridge was built in 1936 using steel riveted beams. The village 
wants to moderanize the bridge using current specifications and 
loadings. The village requests that the group determine the most 
economical steel beam design, determine the deck thickness, calculate 
the reactions at the abutments and prepare a cost estimate for the 
construction of the new steel beams, paint for the beams and concrete 
rock. 
This problem is not for homework, but a problem I'm faced in an 
upcoming engineering competition. Really what I need to know are certain 
equations that might be necessary and any information that would be 
helpful. 
thank you

Re: How do you efficiently design and rehabilitate a bridge?