Abstract: What is proposed is an inwardly articulated form assembly for forming concrete core-wall structures having a rectangular shape in which a primary form structure having fixed seamless corners is presented to the wet concrete; after the concrete has set, a secondary support structure which effects a compound movement when activated by a lever assembly connected thereto causes the primary form to articulate inwardly in a progressively centripetal movement towards the interior of the core-shaft about vertically extending double hinge structures connecting parts of the secondary support structure near respective corners thereof.