Yes. There are standards, they're the Building Codes. There are several versions of them that have come out over time, and they've been evolving with the advances in the science and engineering. When I was in Engineering school, we were generally taught off of a newer code than was in common use in the wild, but that transition was occurring in the couple of years that I was actually doing bridges.
In the case of bridges, you're going to get the basic Steel or Concrete code, maybe some federal guidelines if it's an interstate, definitely state DOT standards.
As for modern vs not -- There are definitely classes of bridges that I'd not consider modern. Anything with rivets, or sections that are built up by lots of little pieces (like the old style riveted trusses). Those aren't done anymore for several reasons: onsite labor is more expensive than shop labor, rivets are inconsistent and weak compared to bolts or welds, and the ongoing painting to control corrosion is a nightmare. In places like the West Coast, the older bridges are not built to current seismic standards, which have been evolving as quickly as the rest of the codes (e.g. tiedowns, base isolation, column jacketing). A lot of the older bridges also have details that aren't terribly good for fatigue performance.
There was definitely an inflection point, probably in the 80's where precast prestressed concrete started being the go-to design for more than just a plain old girder bridge over the interstate.
In the case of bridges, you're going to get the basic Steel or Concrete code, maybe some federal guidelines if it's an interstate, definitely state DOT standards.
As for modern vs not -- There are definitely classes of bridges that I'd not consider modern. Anything with rivets, or sections that are built up by lots of little pieces (like the old style riveted trusses). Those aren't done anymore for several reasons: onsite labor is more expensive than shop labor, rivets are inconsistent and weak compared to bolts or welds, and the ongoing painting to control corrosion is a nightmare. In places like the West Coast, the older bridges are not built to current seismic standards, which have been evolving as quickly as the rest of the codes (e.g. tiedowns, base isolation, column jacketing). A lot of the older bridges also have details that aren't terribly good for fatigue performance.
There was definitely an inflection point, probably in the 80's where precast prestressed concrete started being the go-to design for more than just a plain old girder bridge over the interstate.