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.
In first-world countries/states with earthquakes, the answer to this is often yes and yes.
A good article from 2000 in Christchurch discusses the issues: https://www.canterbury.ac.nz/media/documents/event/Hopkins-L...
The article is relevant because Christchurch had a major earthquake in 2011. I know of quite a few older buildings that were retrofitted that did not even need to be demolished (most buildings are designed to just survive a major earthquake, but often they need to be demolished due to damage, similar to writing off cars after accidents).
Christchurch did have regulatory failures because many older buildings were known to be unsafe (e.g. only meeting 10% of current code/regulations), but owners could defer fixing them up to code almost indefinitely. But that regulatory failure is being addressed in other parts of the country e.g. Wellington.
The South Island of New Zealand is overdue for a magnitude 8.2 Earthquake which will devastate many towns on the West Coast, and will affect the whole country indirectly. https://www.stuff.co.nz/the-press/news/90364889/magnitude82-...
You can sometimes see where concrete of a building has been tested for example a circular hole about 10cm across is left where a sample was taken.
If interested, next time you meet a civil engineer or someone working in the relevant department that deals with the building codes will often know relevant details about your location.