Arthur Ashe Stadium in Queens, New York is the largest outdoor tennis-only venue in the world, featuring 23,771 seats, 90 luxury suites, five restaurants and a two-level players’ lounge. But the United States Tennis Association (USTA), owner of the stadium, felt that something needed to be done to eliminate the frequent delays caused by inclement weather that disrupted the tournament over the past several years.

The solution was a lightweight retractable polytetrafluoroethylene (PTFE) membrane roofing system that can be easily be closed in under 10 minutes at the first sign of bad weather.

WSP USA was selected in 2011 to provide structural engineering services for the $100 million project, partnering with ROSSETTI, design architect of the retractable roof; and Birdair, Inc., which fabricated and installed the roof. Hunt Construction served as the general contractor and Hardesty & Hanover was the mechanization engineer.

The 236,000-square-foot roof was unveiled at an Aug. 2 ceremony featuring tennis legend Billie Jean King. The 2016 U.S. Open, which began Aug. 29, marks the first time an event at the stadium will have the retractable roof available.

“The new retractable roof allows the stadium to continue to offer open-air events, while providing all-weather protection for the players and fans,” said Ahmad Rahimian, project manager for WSP.

When the stadium was built and opened in 1997, the design did not include provisions for future installation of a retractable roof. So the designer and engineer had to find a way to construct a roof with minimal impact to the existing structure.

The answer? Construct a roof that doesn’t actually touch the stadium.

The roof structure was constructed using 6,500 tons of steel, resting on more than 1,700 self-supported structural beams. Although completely independent from the stadium, the roof structure blends seamlessly with the rest of the venue when it is closed.

“The primary challenge was the creation of a visually compelling structural design for the tennis world’s largest long-span retractable roof, on poor soil and within a tight budget,” said Yoram Eilon, project manager for WSP. “Our solution included the use of just eight columns – each composed of three steel structures – which were positioned outside the stadium’s footprint to support the lightweight fabric roof and maintained good sightlines for spectators.”

The original stadium featured a concrete-topped composite steel structure combined with precast hollow core slabs at the superstructure level, a cast-in-place slab at court level and steel frames spaced radially around the stadium.

Named after tennis champion Arthur Ashe, the stadium has been the main venue for the U.S. Open—one of the four annual grand slam tournaments for men’s and women’s professional tennis—since it opened in 1997.

WSP and ROSSETTI teamed up in the 1990s as the structural engineer and architect for the original $200 million stadium.

“WSP was the structural and MEP (mechanical, electrical and plumbing) engineer for the original Arthur Ashe Stadium and its predecessors in the ’80s and ’90s and we have a long relationship with the USTA,” Rahimian said.

The retractable roof is part of a five-year, $550 million transformation of the 42-acre USTA Billie Jean King National Tennis Center. Ongoing projects include a new grandstand stadium and a redesign of Louis Armstrong Stadium, both of which are currently in the works.

WSP and ROSSETTI are also teaming up as the structural engineer and architect for the Sponsor Pavilion, a 9,500 square-foot building that is expected to house sponsor display space on the ground floor with a 5,000-square-foot restaurant and bar terrace on the roof. Rahimian is principal-in-charge for this project, and Craig Tracy will serve as project manager.

The upgrades are scheduled for completion by 2018 and will add to the overall competition experience for both players and fans.