Apart from planes hitting them, wasn't the collapse of the World Trade Centre towers partially down to structural metal failure caused by rusting and deterioration?
I thought that, in theory, the towers were strong enough to be hit by a plane. But the frame was not up to standard, thus causing the total collapse rather than just localised damage.
I am now keeping a close eye on the PFI build going on outside my window.
The cladding looks like one gust of wind will take it off.
In a previous hospital I asked the estates department if I could borrow a masonry drill to put a cable through a wall. They told me to poke it with a long screwdriver. It worked!! A lot of breeze and not much block in modern structures.