Walking into Abu Dhabi’s new Louvre Museum, one is immediately greeted by a flood of dappled light created by the stunning, multi-layered lattice covering the interweaving interior spaces of the building. The intricate geometric dome is both reminiscent of traditional Arabic architecture screens and crucial in achieving Architect’s Jean Nouvel’s vision for a “rain of light.” But what went into the design and construction of the building’s most striking element, and how does it function structurally? Ateliers Jean Nouvel worked for over one year in close collaboration with BuroHappold Engineering to develop a design which is both an architectural and structural masterpiece. We spoke with Andy Pottinger, Associate Director at BuroHappold, to understand the dome in more depth.
When first establishing a suitable pattern for the geometric dome, a vital concern was creating an arrangement avoiding the appearance of a traditional space-frame. "Initial studies related to geodesic approaches (based on triangles) and orthogonal approaches (an approximately square grid)," explains Pottinger. "But all of the designs studied clashed with the architectural base pattern of four triangles surrounding a single square." After a few different iterations, nothing felt quite right. So, one afternoon the designers started from scratch and decided to embrace this architectural pattern. "Instead of adding long straight lines we added further squares and triangles and the result is what you can see above the Museum today," says Pottinger.
Each of the 8 layers of cladding in the dome now consists of these repeating star-like shapes. Every layer, however, is respectively scaled and rotated to add complexity and perception of randomness from a geometrically logical pattern:
Ateliers Jean Nouvel produced maps showing where higher and lower levels of light were desired, and these were used to create maps of luminance at plaza level. This allowed us to ascertain a percentage transparency through the cladding required and to develop a tool for automatically varying the widths of the cladding elements to gain the required transparency. We did this alongside Ateliers Jean Nouvel for all 8 cladding layers, covering approximately 200,000 square meters.
Altogether, the dome comprises 10,968 individual elements, 7,850 individual stars, 8 cladding layers, and weighs more than 7,000 tons, supported by two layers of steelwork ("we consider the dome to have 10 layers," says Pottinger). To support all of this, four support towers are hidden among the various room structures within the museum to achieve a floating appearance, which was vital to the vision of the dome:
Initially, the dome had 5 irregularly spaced supports. The structural demands created by this support arrangement were pushing us towards a form that would have clear lines of strength; but avoiding clear lines of strength was a key part of our brief because it would create the appearance of a space frame supporting a cladding system. A truly integrated piece of art was desired, so we suggested a reduction of supports to four, so long as we could position them at the corners of a perfect square.
The dome itself was carefully designed to be self-sufficient, evading the necessity of a lateral restraint, and further employs a triangulated rim structure to prevent the dome from spreading. To ensure that each of the four supports was equally loaded, the dome is actually symmetrical along one axis. Such patterns are hard, though not impossible, to detect from the museum below, something which Pottinger identifies as one of the most rewarding aspects of the design:
"At certain times in the design the layers of the cladding were not separated as they are now, but we feel the separation was an inspired decision by the architects—rewarding the visitor who looks long enough at the dome and can begin to understand the logic."
Considering the massive size and weight of the dome, the physical construction of it proved to be a difficult task. "Waagner Biro, based in Vienna, did an extraordinary job," confirms Pottinger—workers formed the dome in 85 "super-size" components which were then lifted onto over 120 temporary towers, each one different due to the irregular spaces below. Once assembly was completed, the entire dome was lifted by synchronized hydraulic jacks over 600 millimeters vertically to sit on their permanent bearings.
And the engineering marvels of the dome don't stop at the end of construction. In order to ensure that the structure can be maintained, the design team has developed several access strategies. A walkway around the perimeter of the dome allows entrance to an extensive network of inner walkways. Furthermore, a walkable stainless steel mesh exists across the entire bottom surface with strategically-placed service islands which allow access to the top surface:
The full bottom and top surface of the dome can be accessed and cleaned in this way. We feel that the precise and considered detailing of these accesses and services give the architecture of the dome another layer of depth.
