Demountable CLT theatre structure
The ABBA Arena Auditorium forms the seating areas for the ABBA Voyage concerts and incorporates entrance and bar areas, vertical circulation, fire escape corridors, and technical zones. It has a footprint of about 80 x 50m, is four storeys tall, and consists of 1650 unique cross-laminated panels of dimensions up to 9.9m long. It sits within, and structurally independent of, the arena's steel-framed enveloping walls and roof.
Xylotek joined the project team during its design development, initially as a design consultant, to develop a solution wholly in mass timber (as an alternative to a steel-framed approach). Having proven the viability of a cost-effective, demountable scheme of cross-laminated wood, we were appointed for its full design, fabrication and installation. We worked with CLT supplier Hasslacher who produced and machined each of the unique panels, which were delivered, just in time, in batches to the Stratford site.
The original scheme had around 144 tonnes of steel + 630m3 of CLT; our scheme has 900m3 of CLT, which approximately halves the embodied carbon.
The project presented exciting challenges. The non-orthonogal design – derived from the overall hexagonal form of the Arena - added significant geometric complexity compared to more conventional regular orthogonal CLT structure. We therefore established a rigorous process of 3d geometric modelling and data handling, integrating fabrication and install-sequence information into the model from the outset, and working closely with Hasslacher to provide CADCAM ready data. Given the geometric complexity, it was decided that a separate installation drawing was needed every panel. These were produced with programming help from Mule Studio.
The project presented exciting challenges. The non-orthogonal design – derived from the overall hexagonal form of the Arena - added significant geometric complexity compared to the more conventional regular orthogonal CLT structure. We, therefore, established a rigorous process of 3d geometric modelling and data handling, integrating fabrication and install-sequence information into the model from the outset and working closely with Hasslacher to provide CADCAM-ready data. Given the geometric complexity, it was decided that a separate installation drawing was needed for every panel. These were produced with programming help from Mule Studio.
Another challenge was maximising the structure's ease of disassembly to allow for its future relocation. CLT panels are typically joined with many large screws, which are challenging to remove. To address this, we developed – with our sub-consultant engineers Corbett & Tasker - a system that mainly uses bolted connections. The use of glulam ‘ledger’ elements and ‘Idefix’ recessed connectors –combined to enable adjoining CLT panels to be structurally joined, even when one face is inaccessible. We believe this approach has broader potential for lifecycle considerations of CLT buildings in making dismantling and reusing CLT panels possible (and so keep its captured carbon out of the atmosphere for longer).
The 600-tonne auditorium structure has no groundwork! Driven again by the need for accountability, the CLT structure is carried on over 300 JackPad portable foundations, which sit directly on the tarmac of the existing car park on the site. Each JackPad was adjusted vertically to account for variation in the carpark level and keep the CLT structure level. The large number of pads means that bearing pressures are kept low. The auditorium is thus wholly demountable.
The fire protection of the CLT was of critical importance. It was achieved through spray-applied spread-of-flame treatments (applied by ATOL Construction), which were used partly in situ on the assembled structure and partly onto panels pre-assembly (in a neighbouring marquee) for panels where accessibility would be difficult when assembled.
The Arena in Stratford, London, hosts the virtual ABBA Voyage concerts and is designed to be demountable for future relocation. Xylotek also carried out the production of the external timber rainscreen.