Retractable Constructions: Scissor-Hinged Membrane Structures

Intelligent kinetic systems are being developed to address society’s increasing demand for flexibility in the built environment. The goal is to create spaces and objects that can physically re-configure themselves to meet changing needs, accentuating the dynamics of modern architectural space. Intelligent kinetic systems arise from the isomorphic convergence of three key elements: structural engineering, sensor technology and adaptable architecture. They are unique to the field of architecture where objects are conventionally static, use is often singular and responsive spatial adaptability is still relatively unexplored. We define kinetic architecture as buildings, or building components, with variable location or mobility and/or variable geometry or movement. (M.A. Fox, 2000) Over the last few decades many sports and entertainment facilities have been built across the world. In order to be economically profitable many of these (large-scale) venues require multi-purpose spaces that can be transformed to meet the specific needs of different activities. Retractable roof structures are a popular way to provide such adaptable environments. In technical terms these roofs are often referred to as “embedded kinetic structures”: they exist within a larger architectural whole in a fixed location and they can be physically re-configured (or maybe even re-configure themselves) in response to changing environmental or programmatic conditions. The goal of this research is to develop an efficient lightweight system for retractable roof structures that provides a fully fledged roofing solution in every possible configuration; not only in the final - completely closed - configuration but also in its most compact - completely open - form and every configuration in between. The base elements or building blocks of the proposed system are scissor-hinged-structures, structural membranes and pleated pneumatic artificial muscles. Structural membranes are wafer-thin construction materials that can resist external loading when sufficiently pre-tensioned. The pre-tension is applied to a specific, pre-determined three dimensional form and therefore retractable membrane structures were - until now - only to be used in their final (completely closed) configuration. Scissor structures are rigid systems of interconnected bars that can expand from a compact closed configuration to a much larger pre-determined form. Despite their promising inherent kinetic capabilities they have - for many reasons - not yet been successfully applied in adaptable architecture. In the proposed system, scissor structures are used as an adaptable load-bearing structure - or a series of reconfigurable beams - and structural membranes as a flexible cladding component. The membranes are attached to the hinges of the scissors and span between the scissor-beams, allowing themselves to be (un)folded in a wave-form during deployment. As the structural integrity and the architectural qualities of the roof depend greatly on the tension in the membranes, pleated pneumatic artificial muscles are used. These extremely lightweight actuating devices are integrated in such a way that they can manipulate the cables of the system and thereby control the tension in the membranes, keeping it at an acceptable level at all times and in every possible configuration of the structure. The final product of this research should be a design tool or a design methodology for the development of retractable roofs based on the investigated system.