The U.S. Open is one of the most exciting tennis tournaments of the year. A casting will help make it even better.
For two weeks every year, Arthur Ashe Stadium is the center of the tennis world. Located in Queens, New York, it serves as the main arena for the Open, hosting the biggest matches in one of the planet’s most important tournaments. Tens of thousands of ticket-buying spectators and millions more in a worldwide television audience see the stadium as it welcomes international stars like Serena Williams, Roger Federer and Novak Djokovic, adding importance to its functionality and appearance.
But currently, Ashe is undergoing a major renovation that will dramatically change its look and feel. It’s a renovation with massive and noticeable aspects, but also one made up of less-noticed but equally important phases.
Completed in 1997, the stadium was built without a roof. Because of this, matches were susceptible to the elements and the tournament schedule was often altered because of delays and cancellations. To fight the elements, the U.S. Tennis Association (USTA), the body that owns and operates the facility, announced in 2013 it was adding a retractable roof to the arena, following the lead of fellow major venues for Wimbledon and the Australian Open.
That roof, at a cost of a reported $100 million, is structurally independent from the stadium itself and is expected to be fully operational by the 2016 event in late August. The hulking steel frame was already in place for last year’s tournament, missing the plastic material that will eventually cover the roof and provide protection when inclement weather hits.
Of course, the project is much more complicated than simply slapping a roof structure over an existing arena. The new structure is supported by eight steel columns that are joined with ground-level concrete bases. Each base is a point where two diagonal braces are connected to a vertical steel column by cast steel connections. As fans walk into the arena, they stride right past the connections that are in place to help keep the roof up.
Enter CastConnex, Toronto, and then Bradken, Kansas City, Missouri.
Around February 2014, CastConnex, a supplier of castings and forgings with engineering and design capabilities, was contacted by steel fabricator Canam Group (Saint-Georges, Quebec, Canada). After a 2014 request from the New York City Design Commission, the USTA and the outside builders were tasked with creating the connections for the structure base that were strong and also attractive, since they are visible to spectators entering the arena.
CastConnex was tasked with delivering a custom-designed product, with the connections and braces in place by November 2014.
“From a structural perspective, the entire weight and lateral system of the roof goes through these connections,” said Carlos de Oliviera, principal, CastConnex. “On top of that, they have to look good, because of the architectural significance and how close people would be walking past them.”
According to de Oliviera, each of the connections weighs around 7,700 lbs. (3,492.7 kg.) and connects to 30-in. (76.2 cm.) diameter steel braces on one end. On the other, they’re welded to 40-in. (101.6 cm.) diameter columns.
“They’re kind of at that interface between the very large diameter bracing and columns,” de Oliviera said. “It transitions from the round brace down to the vertical thin plate, so it’s kind of like an organically shaped transition between the two geometries.”
The connections’ role is key.
“They’re structural components, so they support the weight of the roof. Also, when the wind blows – and the wind blows on the structure – they have to transmit those lateral forces down into the foundations,” de Oliviera said. “And then, heaven forbid if there was ever an earthquake where the ground is shaking, you’ll have inertial forces which are caused due to the weight of the structure and the motion of the ground.
“Those inertial forces have to be transmitted down into the foundations, so these are absolutely critical structural components.”
CastConnex is not a casting facility. It designs cast steel structural components for the construction of buildings and bridges, sourcing the components from steel casting facilities. In the past, CastConnex has designed components for exposed cast steel nodes for the Transbay Transit Center project in San Francisco and pin connectors with X-braces at the Whitney Museum of American Art in New York, among numerous other projects.
“From an architectural perspective, we can make geometries and connections that look very different than you would be able to, say, build out of flat plates and that sort of thing,” de Oliviera said.
Metalcasting also brings structural advantages as well, like a smooth force transfer between different shapes.
“Ultimately, what we can do is put the material where it ought to be for the flow of forces through a structural component, rather than trying to build up or stiffen platework. We literally shape the part as nature would shape it,” de Oliviera said. “Oftentimes when you do that, you end up with something that looks very elegant. That’s another way that we leverage the geometric freedom that casting offers to improve structural performance, but also to improve the aesthetic quality of connections.”
In the Ashe project, CastConnex turned to Bradken and its Atchison, Kansas, facility. The two companies had worked together in the past, and based on their strong professional relationship and the size and complexity of the part, Bradken was the right kind of facility for CastConnex.
“It’s increasingly difficult to have those relationships today when so many people try to commoditize an engineered component,” said Wayne Braun, director of business development – Industrial Products, Bradken. “The value added to that relationship put forward co-designing the component to yield the best results and lowest cost of quality.”
The components were cast via the nobake, sandcasting process in A9588050 steel, which is one of a number of standard grades for the structural market.
The two companies used a collaborative relationship to produce. There was feedback, give-and-take, input, and evidence of a strong professional relationship.
“Not everybody can do this because there are a lot of technical and quality back-and-forth between the two because of the importance of these components, not only the structural integrity but also the expectation visually,” Braun said. “In addition, the precision needs to be put in the weld-prep areas so that these castings fit into the plane. This allows them to be fabricated in position without creating potential dimensional issues at the fabricator when he goes to do fit-up.”
Braun said “getting off on the right foot” was important for the project. They didn’t want to get far along and find out the finished component was not up to the specs or did not match expectations. Representatives of different parts of the project’s chain were invited to see the castings and provide their own feedback.
“Getting that first article done and understanding that you’ve laid the part out properly, and have machined it within plane is why we do the 3-D overlay,” Braun said. “Or we’ll lay it out and then send them the file, and they will then put it in the envelope to make sure that it complies. Once you’ve got that locked down, then you can be sure your subsequent parts are going to yield the precision that’s required in the dimensional component.”
Other processes theoretically could have been used to create this component. Casting, however, brought many distinct advantages. Beyond the aesthetics, it holds an ability to handle a bigger range of challenges, not to mention the absence of weld joints, leading to more capability to handle stresses.
“One of the advantages is the ability to make shapes that are aesthetically pleasing to an architect,” Braun said. “If you combine those with the various grades and strengths that steel offers in addition to its weldability, it really gives you a number of options that allow you to cast shapes that are extraordinarily difficult or almost impossible to fabricate.”
Projects like these have another advantage: it can help a firm like Bradken continue to make its mark in the architectural world. Bradken is a member of the American Institute of Steel Construction, and Braun and de Oliviera have given co-talks on the use of steel castings and the benefits they can bring.
“We can say not only do we believe this, we’re actually doing it and we’ve done it in this example, this example and this example,” Braun said. “You don’t want somebody who’s never done one before that says ‘Yeah, I think we can cast that shape,’ because it’s about understanding what you’re casting, why you’re casting and what’s important on that casting.”