If your talking bout your pecks, you can lie on your back on a bench, have your hands on the floor while holding weights, and lift them above your body keeping your arms straight. Try using larger weights and doing quick repetitions in reasonable sets, say 40-3, it depends on your size and weight and strength but your gonna want those tough if your worried bout protecting your ribs.

I don't even know if they do protect your ribs all that much! There's loads of stuff you can do other than what I just said, have a search on google for pectoral (i think thats how you spell it) exercises!

Good luck!