LARGEST RETRACTABLE ROOF OVER A TENNIS STADIUM IN THE WORLD
Every August for the US Open, Arthur Ashe Stadium hosts elite tennis athletes, crowds of fans, and sponsors for a two week period. At 23,771 seats, Arthur Ashe Stadium is the primary tennis stadium on the Billie Jean King National Tennis Center Campus and is the largest tennis stadium in the world.
At the turn of the 20th century, the site was a dumping ground for coal ash for all of Manhattan. Over time, the built-up ash caused long-term settlement issues at the site. These poor, marshy soil conditions made adding a retractable roof to the stadium nearly impossible as the weight of the structure would be too heavy for the ground to support.
Arthur Ashe Stadium was originally designed by ROSSETTI in 1997, but was not designed to have a roof. Rain hindered play during the US Open for five consecutive years, causing United States Tennis Association (USTA) to consider adding a roof over Ashe Stadium. The USTA's four critical design objectives included: structural integrity, financial viability, operational functionality, and aesthetically pleasing.
After an intensive R+D effort in collaboration with WSP Parsons Brinckerhoff, a global engineering firm based in New York City, the team created an innovation solution to combat the poor soil conditions. The design created a structure totally independent of the existing stadium, essentially building an umbrella over the structure to shield the court and spectators.
In 2013, the ROSSETTI design team began deep research into the functionality of a free-standing retractable roof over Arthur Ashe Stadium. The original Saddledome Scheme did not work as the roof would not be able to close during rainfall or with winds going more than 25 MPH. Due to these major issues, the design team continued its research and created several schemes for a Bi-Parting Fixed Fabric Shell Concept.
Original Saddle Dome Scheme
Bi-parting Fixed Fabric Shell - Schematic Design 1
Bi-parting Fixed Fabric Shell - Schematic Design 2
CREATING THE STRUCTURE
The main support for the retractable roof features eight steel columns that surround the stadium's perimeter. These tree branch-like columns sit on massive concrete bases, each of which is supported by approximately 24 piles driven 175 to 200 feet in the ground for maximum support. The pilings are so deep, a Manhattan skyscraper could be built on the foundation. Additionally, the structure is engineered to withstand hurricane-strength weather. Utilizing the independent columns was the most efficient way to minimize the impact to the existing stadium as they are able to stand on their own to support the roof without touching the current stadium. In addition, the isolated foundation elements allowed the project to avoid much of the dense, underground infrastructure from not only the current campus, but also the site’s history as the home of the 1939 and 1964 World’s Fairs.
Four catenary trusses form the framing system that supports the roof, each spanning 460 feet to form the opening of the retractable panels, weighing 1 million pounds each. The trusses use a lenticular truss configuration that span between the eight column supports.
Between the main trusses and a perimeter truss is a series of secondary one-way trusses, which are configured in a radial direction that support the fabric roof.
A third layer of structure in the roof plan creates a diaphragm, which are "X" braces coupled with circumferentially running beams. The last layer is the framing for the gutter around the perimeter of the roof. All these elements, together with the main and secondary trusses form the structural shell for the roof.
While a 7,000 ton roof structure could have easily been designed to appear clunky, Arthur Ashe Roof was specifically designed to be aesthetically pleasing, appearing thin and elegant in terms of overall proportion for that much weight. The structure supports 190,000 SF of polytetraflouroethylene (PTFE) fabric, a Teflon coated membrane installed by Birdair that is light in weight yet incredibly durable in keeping out the elements, especially the sun. While it allows outdoor quality of daylight transmission, it blocks 90% of the solar radiation.
To satisfy one of USTA's objectives for the structure to be aesthetically pleasing, ROSSETTI's design intent was respectful to the iconic stadium, aesthetically taking its cues from existing architecture. The roof gives the appearance of being an integral part of the stadium, designed to look as if it was original to the Stadium, built in 1997. In reality, the roof is completely independent from the existing stadium, making it visually and physically as light as possible.
As the roof opens and closes it's what you don't see that's the most fascinating. Computers keep tabs on over 4 dozen sensors simultaneously tracking not only the precise movement of the roof down to the 1/8”, keeping it in perfect alignment but also, wind speeds, seismic activity, motor speed, torque and voltage and more. Engineered to open and close within 7 minutes, the roof's creative design and technological components allows Arthur Ashe Stadium to continue to feel like an outdoor stadium and operate on-demand. At the same time, a separate system of sensors and thermal cameras measure a multitude of environmental data at hundreds of discrete locations, including temperature and humidity both in the seating bowl and outside the stadium to ensure the comfort of the nearly 24,000 people seated inside.
RAIN IS NO LONGER AN ISSUE FOR THE US OPEN
In addition to the new roof, the stadium features new seating for 23,771 fans, state-of-the-art broadcast and audio systems, 90 luxury suites, five restaurants (including media and player dining), and a two-level players' lounge. With the completion of the retractable roof over Arthur Ashe Stadium and the other enhancements on campus, the Billie Jean King National Tennis Center is expected to draw an extra 10,000 people/day during the US Open, increasing attendance to 1.2 million visitors. This will boost the economic impact numbers well above the current $756 million and increase the global TV viewing audience. Rain is no longer an issue for the US Open, allowing for a more enjoyable experience for athletes, fans, and sponsors.