A case structure interposed between the engine and the nacelle of the aircraft is provided. The case structure includes: a ferrule surrounding the engine and including a plurality of segments; at least one radial arm ensuring connection to the nacelle; and a plurality of attachment devices for securing the plurality of ferrule segments together or with at least one radial arm. The plurality of attachment devices includes an articulation device configured for ensuring coupling of the lifted-rotated-pushed type ensuring after disengagement of the ferrule segment, its pivoting about a pivot axis parallel to a longitudinal axis of the engine and then its blocking in a disengagement position.