"Would curved roofed concrete shapes like bomb-proof hangars, only round, do the job?"

That's a good question, Penny. I've been wondering the same thing since I saw a video which discussed a tornado which hit a suburb of Chicago several years ago. (I can't remember the name of the town.) The video showed many homes in ruins, yet a Catholic church made of curving concrete surfaces seemed to have nothing wrong with it but chipped paint.

No doubt the windows were shattered, but the building seemed to be fine.