An aircraft fuselage barrel (10) includes a skin (12) and a shear tie (18). The shear tie (18) resides within and is integrally formed with the skin (12). The shear tie (18) is separate from and configured for frame attachment thereon. A multi-ring system (79) for fuselage barrel formation includes a mold (68) with a ring (50). The ring (50) has width (W2) approximately equal to a separation distance (D) between two adjacent fuselage frames (22) and includes a module (52) that has a circumferential length (L1) that is greater than a circumferential distance between two fuselage longerons (14). A support structure (80) is coupled to and supports the mold (68). A method of forming the aircraft fuselage barrel (10) includes constructing the support structure (80). Rings (86) of the mold (68) are attached to and over the support structure (80). The mold (68) is constructed. Material is laid-up onto the mold (68) to integrally form the one-piece fuselage barrel (10) including a Hat-configured longeron (14).