Changing concepts completely can be the right solution, sometimes. If you have somehow built some bad will with your current concept, a concept change could even be necessary.
What would be the purpose of changing your concept? Is there a better market to be had than the demographic you currently appeal to? Occasionally, the demographics in an area can change and cause you to have to change with them. If your current concept doesn't have enough of a market in your area, then a change could be wise.
One thing you can't do, is simply change the name and the menu and claim to be a different restaurant. If you want a concept change to be effective, then you will have to shut down just as others have suggested. You'll need to choose new colors for your concept and redecorate with those colors and a decor that fits your new concept. You'll need a new logo, new signage, new uniforms, a new USP, and especially a new look on the exterior of your restaurant. You'll need to paint everything, change fixtures, reupholster furniture, landscape and think about changing the layout of your restaurant. You don't want to reopen looking like the same guy in a different suit.
Changing concepts is a big commitment, but it also can be just what you need to stir up new interest in an old restaurant.