As Las Vegas transforms itself into a more family-friendly tourist destination, mainstays of the strip are increasingly investing in non-casino amenities. The highest-profile new attraction, Caesars Entertainment's High Roller observation wheel, opened on March 31, providing a focal point for a new
retail, dining, and entertainment district known as The Linq.
Above, a rendering of the High Roller as envisioned by Arup.
Arup led the design of the High Roller, which at 550 feet is the tallest observation (or Ferris) wheel in the world. Our scope for the project included structural, geotechnical, mechanical, and electrical engineering, in addition to acoustic and fire/life-safety consulting. We also created the engineering reference designs and specifications for the cabins and mechanization system that operates the High Roller.
The original Ferris Wheel was built for the Chicago World Expo in 1893 in response to the Eiffel Tower, which had been unveiled in Paris in 1889. It proved extremely popular, and in the following century became a staple in amusement parks around the world.
Arup helped revolutionize this type of structure with the design of the London Eye, which opened in 2000 (hence its original name, the Millennium Wheel). Then the tallest in the world, it was called an “observation wheel” rather than Ferris wheel to distinguish its unique architectural design. In contrast to typical specimens, the cabins were mounted on the outside of the rim to provide an uninterrupted view in all directions, and the rim was supported by tensioned cables (much like a bicycle wheel), making it taller, lighter, and longer-lasting.
The new High Roller raises the bar yet again. It is more than twice as high as the original Ferris structure and all other wheels in the United States.
The enormous structure consists of 28 spherical cabins mounted to a single-element steel rim supported by 112 steel cables which mount to a 100-foot-long rotating hub. The hub rotates around two of the largest spherical roller bearings ever manufactured. The rotating structure rests on five canted steel legs which were carefully designed to integrate with the buildings and infrastructure on the heavily constrained site.
The completed attraction offers unparalleled views and entertainment near the center of the Las Vegas Strip.
As passenger experience is paramount to the High Roller's success, when The Hettema Group's architectural design of the cabins first began, Arup focused on optimizing the cabin shape for views and comfort.
While high-profile predecessors like the London Eye and Singapore Flyer feature oblong and cylindrical cabins, respectively, the High Roller's cabins consist of a sphere mounted high above a single tube for the rim. This allows many more people to fit comfortably inside the cabins (up to 40 can be accommodated at once) and an uninterrupted view in all directions.
The end result: A sense that riders are flying high above the Las Vegas Strip with no visible means of support.
The construction of the wheel began at the foundations, where the weight of the superstructure is transferred to layers of caliche, an extremely strong soil created by ancient floods that is unique to the Las Vegas desert.
Above the piles and pile caps, the steel structure is supported on massive concrete plinths, the largest of which is 35 feet tall. These massive concrete structures protect the legs of the wheel from potentially extreme events such as vehicle impacts, fires, blasts, and earthquakes.
The weight of the High Roller is supported on four inclined tubular steel legs, each of which is 270 feet long. Each support leg has three tuned mass dampers (supplied by Gerb) which were installed to reduce the potential vibration in Las Vegas’ strong winds. The legs contain internal ladders which provide access to the hub, spindle, and bearings for maintenance and inspection.
Lateral stability for the support structure is provided by the 315-foot-long brace leg, which acts like a kickstand. The brace leg includes a single tuned mass damper at mid height.
For additional safety, the steel legs are connected to the foundations via prestressed anchor rods which act as fuse for the structure, keeping it safe and stable during earthquakes.
At the interface between the rotating wheel and the fixed support structure are two massive spherical roller bearings (supplied by SKF). Due to manufacturing limitations, these 10-ton bearings have the largest load capacity that can currently be achieved for a roller bearing of their size.
To achieve the required performance from the bearings, Arup worked closely with SKF, American Bridge, and Japan Steel Works to develop a design that considered the tolerance requirements, structural capacity, manufacturing capabilities, and installation processes. (The tolerance of the machined interface for the bearings is so exact that it was limited by how accurately they could measure the smoothness of the surface rather than how accurately they could actually smooth it.)
The hub, spindle, and bearings were designed to work together as a single system, but had to be broken into three segments so that the pieces could be shipped to site and lifted into place. All field connections for the wheel were done by bolting the prefabricated components together on site. A single splice of the hub alone required a staggering 128 1.5” diameter bolts.
The 78-foot-long segment of the hub shown above was transported through the city by truck before being hoisted into place and connected to the rest of the hub at 285 feet in the air.
The end sections of the hub, spindle, and bearings were assembled onsite at ground level. The west hub spindle-bearing end was lifted into position first, followed by the center section of the hub. The spindle center was then threaded into the hub at height. Finally, the east end assembly was lifted into place, completing the support structure.
This complicated erection procedure was required because the combined weight of the hub and spindle —a massive 515 tons — was too much to lift with a single crane. The end sections of these components are heavy solid steel forgings and castings that needed to be extremely stiff to ensure the bearing could rotate smoothly and last for the design life of the structure.
After the support structure was in place, workers installed the 28 rim segments (one per cabin) at the 6:00 position. The tubular steel sections were then rotated forward using a temporary launching platform, giving the impression that the rim was growing up and around as the circle was completed.
This construction sequence was selected because it allows all the installation work to be done near the ground. However, it results in an unbalanced load when the structure is partially built. We worked closely with the wheel contractor, American Bridge Company, to ensure that the structure remained safe and stable in the temporary condition.
As each rim section was installed, it was held temporarily in place by cables and temporary steel struts. The 3-inch-diameter steel cables (supplied by Freyssinet) were left slack until the rim was fully assembled, at which point all the cables were tensioned to their target prestress levels.
Once the cables were prestressed, the tensions were fine-tuned to straighten the rim (much like truing a bicycle wheel). This construction methodology allows for the rim to be built to extremely tight tolerances, which is critical for the operation of the wheel.
As the project's primary goal was to create a comfortable and entertaining ride, Las Vegas' desert climate factored heavily into the cabin design. Arup designed a fully-integrated air conditioning system and collaborated with the cabin manufacturer, Leitner-Poma, to create an innovative spherical, double-paned glazing system.
The design took into account the need for the glazing to be tinted and reflective to limit the solar gain into the cabins, but not reflective enough to prevent passengers from photographing the stunning views in all directions.
Above, a cabin being installed on the rim.
Passengers enter and exit the cabins via boarding platforms located on either side of the wheel. As the wheel rotates continuously, the platform is curved to allow passengers to walk alongside the cabins as they move slowly past. Despite the enormous scale of the components, the distance between the boarding platform and the rotating cabins is a mere 2.5 inches.
Because the platforms were built prior to the wheel and by a different contractor, we helped coordinate the construction sequencing to ensure the two structures fit together properly and that entering and exiting the cabins would be smooth and easy.
At the interface of the platforms and the rim sit several large machines which operate the wheel. Arup produced the reference design for the mechanization system, which features equipment from Schwager Davis Inc.
The platform architectural design was by Klai Juba Architects, and they were constructed by WA Richardson Builders.
The cabins are completely surrounded by glass and spacious enough that everyone on board can circulate to see the best views.
Once at the top of the High Roller, riders enjoy stunning views of Las Vegas, including the Eiffel Tower at Paris, the Bellagio Fountains, Caesars Palace, The Flamingo, and many other landmarks of the Strip. During the day mountains and other spectacular natural features are also visible.
Caesars expects between five and six million patrons to ride the wheel each year.
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