Safest stuctural materia for big buildings

define 'safest'... There are many more hazards than fire. If you can coat wood to protect from a six hour file (or a two hour fire) then you could coat steel as well.

define 'big buildings'... 5 floors? 20 floors? 100 floors? How many sq metres? 100? 1000? 10,000?

define 'thick timber'... 12" x 12"? 24" x 24"?

ok, lets leave it to fire only to keep it simple

i dont think coating steel helps much because the problem is not that it gets melted but that it gets weakened and then bents

say 40-80 floors

well, say average size for tall buildings

the designer can deside keeping in mind the costs, usefulness etc. , but lets say that about the same size what would be with steel is steel used.

Actually the best way to learn about construction and structural sturdiness is by watching the demolition of old buildings!

You will see how some materials quickly come down with the wrecking ball (wood). And how it takes forever for them to tear down others (concrete with tons of rebar).

So find a demolition company in your area and call and ask where they are tearing something down. Then go watch.