Darden Restaurants Inc. is testing a new bar concept called Atrium that serves a dual-branded Olive Garden/Red Lobster location. The venue, in North Carolina, is not designed to be stand-alone concept. Rich Jeffers, a spokesman for the Orlando, Fla.-based Darden said the company is testing the idea of giving the shared bar area a more unique identity. Since March 2011, Darden has opened six dual-branded locations, which the company calls “synergy units” designed to work in markets that don’t have population density to support a single brand location.