Designing Kitchens and Bathrooms - safety bars in shower

is there code on how high or low these should be installed-i am aware i need to use bracing inside the walls-and not just drywall anchors for these..

The American Disabilities Act gives guidelines, but as far as encoding them, it may be a local issue. Quite often a horizontal, or slightly off horizontal bar on the back wall of the tub/shower about knee high will give "helpable" support upon rising from the tub. In addition, I like to install a vertical one where one exits the tub/shower, and (believe it or not), I use one as a towel rack adjacent to the back of the tub, and usually across from the toilet. Remember, when you fall you would grab a feather if you thought it would stop your fall.