@palallin posted:Question: does your load calculation account for the weight of the bridge elements themselves?
No the static load of the bridge structure is not included. I considered possible live loads only. If this was for real, you would need to estimate the weight and distribution of all static loads and add them in. It would be a somewhat iterative process, but doable.
You would also need to consider the lateral loading imposed if the train was heavily braking whilst on the bridge. I did a rough run for that scenario, and interestingly there was no added loads on the bridge members; the lateral load was borne by the left end fixed support point.
Joe; I think your "single grandchild" test load would be plenty to insure structural integrity! 
Nice bridge by the way!
Rod
