[sgc]

It's not that rare, I see it several times a year.

It is presumed that all foundation bolts are shot after about 50 years on any foundation in terms of their seismic performance. If you pull out an old foundation from say the 1950s, the bolts are almost invariably either totally corroded through or just a thread in the middle.

For a building basically sitting in saltwater, I would expect there to be widespread reinforcing steel failure at that age without proof to the contrary. Which is certainly one of the big reasons why they require recertification, although obviously the 40 year recertification schedule has proven to be woefully inadequate.

This will probably not wind up being more interesting than a failure to have rigorous enough inspection schedules and people dragging their feet to do what obviously had to happen. Those items appear far more important that the somewhat reduced amount of reinforcing steel compared to drawings at this point. It seems like relatively pedestrian negligence.