Mook; I'm no bridge engineer either, but I have played one at a model rr in the past.

Some of your words sounded almost prophetic and my reaction to the bridge picture was "Holy Crap, Batman!".

It occurs to me now this was a ballast deck bridge and at the time they probably used heavy timbers under that ballast, wood ties, all creosoted, and the ballast now soaked with year after year of you name it, including curve grease, loco lube, etc, etc.
Pilings may be ok but the bridge feel off it pedestals? Don' know.
Notice the ballast deck is 'hasta la vista'.