Stepped timber frame with invisible seams
Wooden beams make up the stepped structure of the huge roof covering the Aqualagon, the future water park of Marne-la-Vallée. The beams were made by Arbonis, using an innovative assembly technique, which received a favorable ATEx assessment in early 2016.
About 30 kilometers outside of Paris, Disneyland Paris and Pierre & Vacances - Center Parcs are building a vast tourism complex called Villages Nature®. Aqualagon will be one of its flagship facilities. Designed by architect Jacques Ferrier, this 9,000-sq.-meter covered water park, with a roof inspired by step pyramids, is nearly 30 meters high. The wood/steel structure of this big top has 52 beams spread in a step-like design, made by Arbonis with an innovative assembly technique.
Original assembly technique using glued rods
Each 15-meter-high beam, with a span of approximately 40 meters, looks like one piece. But each beam is actually a combination of almost ten invisibly connected pieces of glued laminated timber. These elements are assembled in a workshop, with rods anchored in the wood with resin, using 9,500 rods and 5.5 tons of resin. The design is aesthetically pleasing, but is this assembly rigid and solid enough to support a tall wooden building?
Assessing the resistance of the system
The C&E Ingénierie consulting firm, a partner of Jacques Ferrier for the design of the structure, consulted the CSTB very early on to obtain a Technical Experimentation Assessment (ATEx) for its unusual assembly technique. The CSTB checked the suitability of the sizing of the structure, which falls outside the scope of the Eurocode 5 rules, the European standard for calculating the design of timber structures. The CSTB also assessed the proposed reinforcement method: adding rods to provide rigidity and reinforce the sections of glued laminated timber that are subject to the most stress, without needing to use additional materials.
The CSTB also examined the methods of manufacturing in the factory, especially the anchoring, to ensure that there was a good connection between the timber, the epoxy resin and the metal rods. To do so, the CSTB used the results of mechanical tests carried out on the rods themselves and on the complete assemblies. Arbonis had this tensile testing done by Lermab, a multidisciplinary laboratory of the University of Lorraine.