Design of Self-Supporting Rotegrity Structure Using Notched Elements

Abstract

Consisting of linear elements, reciprocal frame structures are three-dimensional (3D) self-supported structures that can be rapidly assembled. This feature renders them suitable for both temporary and permanent uses. Considered as a type of deployable frame, such structures can be used in architectural and engineering applications. As a subset of reciprocal frame structures, rotegrity structures can be advantageous, owing to their structural form. In this work, a spherical rotegrity structure is constructed on a geodesic sphere through its transformation to a reciprocal structure with mutually supporting elements. Instead of the bolted connections commonly used in practice, a notched connection is proposed to facilitate the construction process of the self-supporting rotegrity structure. The parametric modeling of the rotegrity structure is created in Grasshopper, and two prototypes, having circular and rectangular cross sections, are built. In each prototype, two sets of elements, called Type A and Type B, are used, the linear member lengths and cross sections of which are identical. The cross sections of the members of the two prototypes are different. To assemble the prototypes, first, a number of elements are fabricated through 3D printing and tested in terms of their self-supporting capabilities and connections. Then, stainless steel pipes and wooden bars are used for Prototypes I and II, respectively. It is found that Prototype I, composed of circular hollow section profiles, is unstable, owing to the rotation of elements and because it requires the use of stabilizers. Conversely, Prototype II, which consists of rectangular cross-section elements, becomes stable when the last element is installed in the right place and did not require any additional attachment.