I broke the chainstay of my steel '89 HardRock just by riding over the 1 1/2-2" high lip of a driveway where it meets the road. I was 117 pounds too.

I'm pretty sure it was accumulated stresses from jumping curbs and dirt jumps though. I no longer ride like that, and so far my aluminum and steel bikes have held up just fine. Well, except for the two steel Sun EZ-3 recumbent delta trikes I used to own. I babied those bikes, but I have a feeling they broke because my super Clyde friend owned them at one time. He was almost 470 pounds, riding a bike with a 300 pound weight limit. Even though he didn't ride them very much, he may have stressed the frames. Or they're just poorly-designed bikes. The fact that they both had only a 5-year warranty on the frame speaks volumes.