Form Finding and Analysis of an Active Bending-Pantographic Bamboo Space Structure

This paper presents the form finding and structural analysis of an active bending-pantographic bamboo space structure that integrates self-stressed active bending arches, tensile pantographic grids and supporting bipods. The structure was designed to roof an open-aired amphitheater in the tropical climate. The structure has a self-supporting behavior and a mobile assembly procedure, applying the hinged flexible connection (HFC) mechanism. The structure was developed initially through small-scale physical models, then, on computer models and full-scale prototypes. Empirical models were used to determine the minimum bending radius of the arches and served to embed data for the computer models. The active bending arch (ABA) applied Phyllostachys aurea bamboo rods subjected to axial loads up to the elastic limit of strain on the beams. Steel cables and diagonal rods were connected to the curved beams, avoiding buckling in the plane of the arches. Modular pantographic grids were deployed over the ABA, generating double curved space frames with free- form geometries. The coupling of active bending arches and pantographic grids resulted in a hybrid structure, with mutual operation of bending-active and form-active structural modules. The developed structure used bio-based materials for a sustainable engineering design, with lightweight techniques and low-carbon footprint.