Airframes are indeed designed to withstand most things nature can throw at them.
The main danger to passengers comes from cabin baggage and loose objects (such as duty free bottles) which may fly around the cabin during violent turbulence.
I had the horror of meeting an inbound GB Airways aircraft from Alicante that had encountered the phenomenon known as "clear air turbulence" (where the aircraft hits turbulence without prior warning) and the cabin interior resembled a charnel house! Several of the passengers had been injured by duty free bottles flying around the cabin, and by the wheels of tumbling trolley bags!
For this reason, I was very surprised when the main airlines relaxed the weight limits on cabin bags - personally, after witnessing some pretty horrific looking injuries, I would have liked to have seen all trolley bags or rollaboards banned as carry-on baggage!
Commercial pressure, as always, wins!