The concept illustrates a moving experience.
By Helen Elias
UK structural engineers Ramboll Whitbybird has unveiled its innovative design solution for a self-supporting air inflated structure that, when manufactured, will be one of the world’s largest lightweight demountable performance venues. It isn’t just the size and scale of this iconic arena (along with a complex array of video projection equipment, five huge screens and an internal structure needed to support large stages, video projection and a surround sound kit) that engages the attention. It’s the massive fabric structure itself, a building that will be seen touring the world’s major cities in years to come, a sleek streamlined white auditorium, designed in response to a complex architectural form and created in a distinctive palette of lightweight materials.
Oslo-based Various Architects was commissioned by the Norwegian cultural organization, Arts Alliance, to design a lightweight 3,500-capacity mobile performance venue with a clear, wide span internal volume. No internal supports were to obstruct views of the stages, from anywhere in the auditorium. The structure had to be easily built within a two-week construction slot and be easily demountable. Furthermore, it had to be transportable, so the engineers needed to keep the structure’s shipping weight and volume to a minimum. A worldwide tour of the venue, presenting “ID: Identity of the Soul,” a five-screen cinematic performance based on the work of Scandinavian playwright Henrik Ibsen and Arabic poet Mahmoud Darwish, is planned for 2009, giving focus to the design and development schedule. With all this at the back of their minds, and a futuristic visual design concept, Various Architects talked to Stephen Melville, a director of the engineering consultancy Ramboll Whitbybird.
Various Architect’s design concept for the 3,900m2 transportable venue was minimal, sculptural and complex — a challenging oval structure rising in height from 10m at each end to 17m in the center over a 90m length, and spanning 60m at its widest point. The internal 2,000m2 performance space is enclosed by a public circulation plaza and front-of-house and back-of-house facilities. The interior spaces are enclosed by a self-supporting inflatable PVC structure that is braced with a lightweight aluminum structural frame and enclosed by a lightweight cable roof. The entire ensemble touches the ground lightly, with speaker racks suspended from the columns and refillable water tanks providing foundation enough, avoiding the need for anchoring into the surface below or transporting heavy weights.
Enclosing the space was the first issue to resolve. After investigating a number of different options, Melville and his team evolved an innovative fabric roof solution based on the principles of a bicycle wheel. A 6m-tall ring beam truss with central tension ring spans 70m by 36m to provide a column-free roof for the performance space.
Cables supporting the translucent fabric roof are tensioned from the high-level radial truss to clearly span the space below. Specifying standardized components for the lightweight roof reduces manufacturing complexity while allowing ease of construction and makes the whole structure more easily transportable. Columns of standard tubular aluminum staging components support the roof truss and distribute loads to the ground.
The defining form of the venue is created through an air-inflated structure assembled from four massive air-filled curved forms. These sections are constructed from inflated tubes formed into hexagons; The central space of each hexagon is filled with an air-inflated translucent cushion that allows diffused light to filter into the circulation spaces. The inflated forms are kept at a constant internal air pressure by pumps attached to a sensor.
To help cut costs and improve manufacturing efficiency, the hexagon members are designed to be the same length. To get a random pattern that fitted to the form of the structure, special pieces were made at the vertices where the elements connect. A 2-D CAD model was created to accurately populate the surface of the form with the hexagons, locating precisely where each hexagon would be placed and ensuring alignment at the adjoining surface edges.
After completing the design, Ramboll Whitbybird worked closely with contractor Tectoniks to develop the air-inflated hexagons using a thin 1mm thick white PVC architectural fabric that is inherently waterproof and fire-proof, as well as being 100% recyclable. “The advantage of this material is that when the hexagons are deflated, they collapse into a very small space,” explained Stephen Melville. “Our mock-up of just two hexagons stood at about 5m high and 6m when it was inflated, yet the whole thing packed down astonishingly easily into a bag the size of a small holdall.” The full-sized sample panel allowed the team to develop the most suitable manufacturing process and allowed the engineers to see how the massive structure would look and feel. The benefits of this lightweight, easily transportable material were obvious to the design team: the entire venue packs into 30 standard 40-ft. shipping containers for transportation. Melville estimates that the biggest volume of the entire structure when built — the hexagon façade itself — packs into just five or six containers.
Breaking the façade into four sections gives the whole structure an inherent versatility. The venue can be offered for future use at full size or in smaller configurations ranging from 1,500 to 3,900m2, and with or without a roof. There will be two interchangeable roof coverings to help the building adapt to different climates and weather: a mesh roof for shade, and a solid PVC roof for rain protection. With the detailed design now finished, manufacturing is underway in the UK, with the deployment of this innovative demountable building set for the end of 2009.