Elioth

Elioth work along with the Arema / GFC / SCAU / IOSIS for the renovation and expansion of the Stade Velodrome in Marseille on environmental issues, steel design and roof membrane design.

To host matches for Euro 2016, the Velodrome changes its look and expands its capacity. At the heart of the project is the roof over the stadium: it unifies the stadium, protects the spectator under its curves and highlights the role of the stadium in the city.

Elioth _SCE took part in the early stages of project design of the roof: the structural design follows as closely as possible the architectural concept. The wide span structure (280 x 210m) follows a radial pattern that showcases the evolution of curves in space, while offering straight elements of structure. It is covered by a white, translucent, smooth shell.

The energy strategy of the renovation operation of the stadium and its surroundings, which aims at the Low Consumption Building label, was developed in competition phase by Elioth _EE, including new energy sources (photovoltaic, fatal energy recovery loop, heat exchange on the effluent from the nearby STEP) at the core of the project. At the same time, an overall model of the stadium has been set for digital wind tunnel testing at the competition stage by Elioth _EE, to quantify and ensure the comfort of spectators in the wind on all tribunes. The water saving issues were also a significant part of the project, with the conversion of existing buried tanks on the outskirts of the lawn (1400 m3) into rainwater retention and storage tanks to ensure 100% of watering needs of the lawn without consuming water.

This project was an opportunity to implement the large-scale geometric parametric modeling tool Rhino Grasshopper, in conjunction with finite element calculation softwares (GSA, through SSI, but also Ecotect). The use of these technical tools has enabled real-time updating of the computational models, depending on evolution of the architectural project. Starting from a simple definition – three curves in space, Elioth relied on a parametric geometry to generate and re-generate the model in a few minutes, for a framework of thousands of members.

This flexibility has allowed a precise optimization of the project parameters – frame height and position of the support nodes.

The physical wind tunnel testing conducted on a model of the stadium were post-processed using simplified transfer functions of the behavior of the steel structure. This work, in conjunction with the CSTB, addresses static pressure and dynamic amplifications due to wind, for a consideration of the charges closer to reality.

Elioth _SCE finally completed work to optimize the structure in compliance with its non-hierarchical shell design. The 4 mega-columns underlying the 60 000m ² of steel truss have been the object of special attention / reflection. Their primary structural role, moreover in a seismic zone, associated with the project constraints (preserving the existing concrete structure, audience evacuation and firefighter access through these elements) requested the cooperation of Elioth _SCE / Iosis Mediterranée / Industry during phase APD-PRO.

The membrane cover was designed and calculated by Elioth _SCE during phases APD and PRO. Several options were considered to cover the stadium with a PTFE fabric or an ETFE membrane. The architectural appearance, especially reading volume and curves of the stadium, is highlighted by an innovative design of flat membrane stretched over the frame. A preliminary study of quantification and adjustment of the slope of the roof has ensured an efficient flow of rainwater to prevent the membrane from sagging. Despite this adjustment, the slightly curved spans of membrane required an advanced computation to model their behaviour and prevent accumulation of snow.

The southern side of the stadium may include a transparent area to let sunlight through to the lawn. The outline of the transparent area (in the shape of a water drop) was the object of a genetic algorithm optimization. By linking a 3D model of the roof (Rhino Grasshopper + + Galapagos) with the sunshine modeling tool (Ecotect), a constrained optimization has been implemented by Elioth _LAB. The needs of the lawn and the quantization parameters of solar energy have been established by Elioth _EE.

The phase PRO, issued in February 2011, fits into a schedule that leads the beginning of the erection works in summer 2011 for delivery in 2014.