With that in mind, it makes perfect sense to make an office building out of reinforced concrete.
I grew up partly in an 18 story reinforced concrete building built in the 1920s. The apartment I lived in was recently sold for several million dollars.
Once, when there was a leak and the plaster came off, the underlying concrete was exposed and it scraped away like very weak sandstone.
How strong is the building and when will it collapse? Does anyone know? Is anyone testing?
I think the answer to both of those questions is "no". Everyone seems to assume they will stand forever. They won't.
None of the owners want to know that their investments are worthless. So nothing will be checked unless its required by law.
Also, buildings don't fall all of sudden. You would get a lot of cracks and problems before your building collapses
They certainly do in earthquakes. Even in areas that nominally don’t have earthquakes, some parts of the building code will surely be about ability to withstand a rare earthquake.