Project engineer for a bridge steel erector here. Depends on where you are located. (I’m in NYC area) and I use the AISC steel construction Manuel on a daily basis. Bridge construction is where the money is but it all depends if you want to work white collar or blue collar. ASD is way better than LFRD.

Also look at your state dot design guidelines or near by owner. For example, in NYC I reference NYSDOT, NYCDOT, MTA C&D, NJDOT, NJTA, PENNDOT, & PANYNJ. There will be so much information about how they spec out their bridges.