Civil Engineering Association

I need to do a research for my master's. I'm interested in the subject "free vibration response of railway bridges". Could somebody propose a research topic?????
If I'm in the wrong forum please guide me........
Thank you.....

I don't think free vibration only is good for master thesis, what is very interesting is the high speed train structure interaction in long suspension bridge. I think it is the best topic for railway bridge currently :)