The libraries at my university are broadly set up so that every floor has a different noise level. At the top are the silent study areas, there's a floor or two in the middle where you're allowed to chat, and the ground floor is usually a cafeteria/rec room kind of setup. Seem to work quite well in my experience!
On the downside, the engineering/science library currently only has 3 toilets operational thanks to renovation works. In a building designed to hold hundreds of people. Round exam time, when everyone's been drinking a lot of coffee, it can get... quite bad.