Stainless steel rises to 3,835m by helicopter.
In the valley, several months of studies have been necessary for the realisation of this structure, faceted and covered with care and precision, an essential requirement imposed by the extreme weather conditions. Matt and durable, the material of the envelope is a response to the climate and the environment.
With its summit at 4,810 metres, the Mont-Blanc becomes the holy grail of thousands of alpine mountaineers every year! Built at an altitude of 3,835m, the “refuge du Goûter” shelter constitutes the last stage of the normal – or royal – route before the final ascent., The shelter was built in 1962 and has been the object of intense usage but is now under menace from the advancing glacier. It is being replaced by a new audacious construction, in the form of an ovoid placed perpendicularly to the ridge over an advanced rockface. The shape and location are two radical options taken to minimise the amount of snowdrift buid-up and allowing the west wind to slip freely over the cliff. Identifiable by its thick folded stainless steel body, a snow melter tank with eight anti-stagnation devices completes the installation.
Aerodynamic faceted ellipsoid
The definition of the form is part of a dual approach of study of aerodynamic phenomena and descriptive geometry. From the proposed eliptic plan comes an ellipsoid of revolution which is divided into 2x16 segment planes and 32 facets per level, giving a total of 128 facets for this building composed of four levels; technical rooms on the ground level, a common room on the entrance level and dormitories on the last two levels.
This decomposition of the volume into rectangular or trapezoidal storey-height facets has contributed to strengthening the construction elements and to keep them under the maximum weight that can be lifted with a helicopter. The structure of the construction isolated from the ground is a timber framework with dowelled assembly, chosen for its light weight. The whole frame rests on a platform linked to a metal structure forming pillars, which in turn are located by 69 steel stakes anchored to a depth of 8 metres into the rock. The installation has been designed to withstand winds of up to 260km/h and a load pressure of 400 kg/m2 and a vacuum pressure of 600 kg/m2 (studies conducted in the Cemagref wind-tunnel in Grenoble).
Shock-resistant matt cladding
With temperatures as low as – 40 ° C, the idea is to create an environment akin to a soup-tin with a capacity of 120 persons. Aside from the cocoon-like interior and the varied equipment designed to provide the required autonomy and of course, the extreme environment, specific research has been conducted in order to choose the exterior cladding. This had to be an evaluation of several types of metallic “skins”, in terms of their characteristics; deformation, resistance, visual aspect, fabrication, ease of installation and recyclability.
A 304L grade austenitic stainless steel siding proved ideal for the extreme conditions encountered in the pure mountain air and was compatible with the budget of the construction project. A four month study was necessary in order to define the details of the assembly and determine the profile of each facet to allow for easy assembly on-site. A novel assembly technique was devised, using a Z shaped profile of the steel bands on the upright and flat junctions, to insure constant flatness of the cladding, with hollow junctions of the same type of steel as the facets. Additional difficulties came from the windows and photo-voltaic panels which had been installed prior to the cladding.
Another imposed requirement in this protected and very popular site constantly over-flown by medical or surveillance helicopters, was to prevent unwanted shiny reflections that may dazzle pilots. The external cladding was made from 304 grade stainless steel with a Uginox top coating, 0.5mm thick for the covering and 0.8 and 1.2mm thicknesses for the sides. Each facet is “lit” by sunshine, just like the faces of the Mont-Blanc itself, as the sun runs its course through the day.