A supporting half-structure for an aircraft engine nacelle is provided that includes at least one longitudinal beam and a front half-frame, the beam and the half-frame being formed of composite materials. The half frame has an open section, and the half-structure defines a structure selected from the group consisting of: the beam and the front half-frame form a one-piece part; the beam has an extension with an open section, the shape of which matches that of the front half-frame, the extension being attached to the half frame; and the front half-frame has an extension with an open shape, the shape of which matches the beam, wherein the extension is attached to the beam.