A Parametric Structural Genome: Using Computational Design to Manage Compound Tolerances of Multiple Materials to Create the World's Largest Double Curved Outdoor LED Screen

Las Vegas’ Sphere has the capacity to entertain a seated audience of up to 18,500. The interior features the largest, high-resolution LED screen in the world, paired with 164,000 speakers as well as 4D features, including scent and wind. The exterior, meanwhile, is wrapped in 580,000-sq.-ft of programmable lighting made up of approximately 1.2 million LED “pixels”. This presentation will focus on the spherical layering of the Sphere, making it possible to fit a high-fidelity display screen on top of a 500 ft diameter sphere in an extreme climate. Surrounding the performance venue itself is the geosphere exoskeleton that’s known as the “Exosphere”. Outboard of this primary structural steel, which is based on geodesic triangulation, is a layer of curved secondary structural steel known as “Trellis,” which was preassembled into mega-panels on the ground and flown into place. On top of the Trellis sits the tertiary layer, which is the carrier of the LED pixels themselves. This layer, known as “Lattice,” is made out of extruded aluminum, panelized off-site, and cold-warped in place to fit the Trellis panels’ curvatures prior to their installation. 

Access to relevant data is essential for high-quality, fact-based decision-making. While engineers have always approached their work in this manner, the modern project workflow has brought about a specific, significant change. Client expectations have grown beyond the concept of a “final” deliverable to now include a continuous influx of data upon which they base key business decisions. Engineers are now purveyors of data just as much as they are consumers of it. On Sphere, the engineering team implemented parametric design early in the design process to help make informed decisions. Early conversations were held regarding fabrication and erection with W&W/AFCO Steel, contracted to deliver primary and secondary steel packages, as well as with SACO Systems, the party responsible for the design and fabrication of the exterior LED solution. This open dialog early in the process enabled informed decisions through the incorporation of realistic fabrication and erection considerations and costs into the optimization functions. Through detailed estimates by W&W/AFCO together with casting manufacturer Cast Connex for a cast steel node option, a comparative analysis was developed, which showed that casting the nodal connections of the Exosphere offered significant technical advantages over conventionally fabricated nodes.

By design, the goal at completion was for the Exosphere’s geometry to generally be within 2 in. of the target geometry and for out-of-tolerance between any two adjacent nodes to be less than L/500. From this – itself quite ambitious for a project of this size – superstructure tolerance target, the team needed to get down to glass curtain wall-like tolerances at the outermost layer supporting the LEDs. Extensive simulation showed that anything beyond +/- 10 mm out of the position of any given LED pixel would distort the overall image. Added to this were also challenges from differential movements of metals during the ~180°F temperature swings that are not uncommon in a desert climate. Making it all ultimately come together while staying within acceptable tolerances could only have been achieved using data-rich, high-fidelity parametric models of all the constituent systems, as well as robust protocols for data sharing and interpretation. Las Vegas Sphere was envisioned to awe the spectator and to elevate the entertainment experience to a new level, and thanks to the collaborative, computational design-aided process and creative thinking that was poured into its design and construction, it now stands as an architectural and structural landmark.