What exactly are "modern design standards" required by bridges? When did the modern era start? Is there really a major moment in bridge design where the standards changed? Is there even broad agreement on what these standards are?
(Side note: the bridge pictured in the article is the Bridge of the Gods, just upstream of Bonneville Dam on the Columbia River. There's going to be more than bridge problems if the flow of the river takes out that bridge.)
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.
"The AASHTO LRFD Bridge Design Specifications are intended for use in the design, evaluation, and rehabilitation of bridges, and are mandated by the Federal Highway Administration for use on all bridges using federal funding."
It is over 2000 pages long without errata. It is updated yearly with major updates less frequently.
It's fine for skyscrapers. The Empire State Bldg isn't going anywhere. It's dumb for thin flexible skyscrapers that will accumulate microfractures in a relatively short time span and whose steel structure is insufficient to support the building in the face of significant concrete degradation.
Microfractures =/= global strength loss. Additionally, the concrete itself tends to strengthen over time. I guess I just don't understand what failure mode you are worried about.
There are thousands of slender concrete structures that have been in service (thus far) without issue.
(Side note: the bridge pictured in the article is the Bridge of the Gods, just upstream of Bonneville Dam on the Columbia River. There's going to be more than bridge problems if the flow of the river takes out that bridge.)