I am a little late to this party. Nice looking bridge. I had to read the whole 22 pages in one sitting, so may have missed a lot.
I am wondering one thing about the load calculations on the downward force of the bridge trusses which the side rails appear to have compensated for.
Where the angle iron is welded to the thin box tubing, and the crossmembers for the boards are placed, isn't the load actually on the angle iron, and the angle iron puts a twisting load on the crossmembers? Since the truss tubes are thin walled material, and the angle iron is supported by only one side of the tubing, won't the angle iron attempt to bow the inner side of the main beams towards the center of the bridge, thereby changing all of the straight down calculations of the support members?
David from jax