Apple Store: an all-structural glass staircase

Apple's Carrousel du Louvre Store was the first Apple store to open in France, before the Montpellier store. It is a genuine shop, unlike the virtual internet store. CSTB studied the helical staircase in Apple's new sales outlet and showroom in the context of an ATEx (Technical Experimental Assessment). This article takes another look at the structure designed entirely from structural glass, with its almost improbable lightweight and transparency.

The new 800 m² store in Paris is located at the end of the shopping centre in the largest museum in Europe facing the Louvre's inverted pyramid, and is a worthy successor to the very stylish design of the approximately 300 boutiques that the computer manufacturer has already opened in all parts of the world.  The glass staircase in the very centre of the store appears like a technological showpiece leading up to the mezzanine dedicated to software and accessories.  "A fairly unusual structure in France, according to CSTB's engineer Aurélie Bareille.  Although we often see glass steps or guard rails in projects, this is an entire structure made of a single material except for the handrails that contribute to the stiffness of the structure and the steel tie-rods that suspend the staircase stringers from the primary ceiling structure."

High performance glass

The 1.70 m long steps and the curved stringers, the small floor that acts as the landing, the two beams that stiffen it and the guardrails on the mezzanine are all made of three- or four-ply laminated glass and are assembled through individual connections sealed with resin.  Most of this highly stressed glass was made by intercalating a particularly high performance film between the laminations.  In this structure, the traditional PVB sheets were replaced by a single much thicker and also much stronger sheet.   "An ideal solution, except that it makes it difficult to perform an expertise on the structure," says Aurélie Bareille, adding that it is still very unusual to find glass using this type of intercalation on the construction market, and that it is reserved for exceptional projects.

Many tests on the various parts making up the staircase were made in CSTB laboratories and in the laboratories of the Seele Company responsible for their installation.  Everything was checked from drilled stringers assembled to each other by fishplates to the steps fixed to these stringers by means of metal inserts and bolts, to guarantee stability of the staircase and safety of users, even in the case of an accidental breakage of one of the glass components.  All elements of this staircase contribute to the strength of the structure, which means that a weakness in any one of them will necessarily weaken the entire structure.  As explained by Aurélie Bareille, "each part of the structure is structurally linked to the rest and contributes to the global stiffness of the structure."

Glass elements

  • The steps are made from annealed four-lamination SG glass.
  • The stringers are made from chemically toughened laminated glass.
  • The glass floor is made from quenched four-lamination SG glass.
  • The glass beams, that participate in the strength of the glass floor, are made from toughened laminated SG glass.
  • The mezzanine guardrails are made from toughened laminated SG glass.

Technical datasheet

Location:  Carrousel du Louvre, Paris
Client: Apple Retail France France EURL
Project Manager: Alpha International
Construction: SEELE
Inspection office: SOCOTEC