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Wednesday | 30 May, 2012 | 12:42 pm

Stealing bases

By Lynn Stanley

Firm chooses steel for new 24,000-seat baseball stadium

June 2012 - According to the Baseball Almanac, the first all concrete and steel baseball park opened in Philadelphia on April 12, 1909. The project cost $457,167.61.

Steel has continued to play a key role in America’s favorite pastime and proved to be the material of choice for HDR Architecture when the firm took on a $131 million project to design TD Ameritrade Park in Omaha, Neb. The 24,000-seat stadium’s sleek, clean profile marks the gateway to downtown, housing the NCAA Men’s College World Series and serving as home field for the Creighton University baseball team. The city also has positioned the stadium as a showpiece to help spur future urban development and enhance Omaha’s reputation as one of America’s top-flight sports communities.

Uncommon size
A 24,000-seat baseball stadium is uncommon at the college level, says John Savage, PE, SE, LEED AP and senior structural engineer for HDR. The design had to combine the characteristics of a typical 6,000-seat AAA ballpark with the amenities of a major league field. HDR had to include thousands of square feet of space not usually found in college ballparks. The NCAA, broadcast media and College World Series Inc., among other users, had very specific input regarding the fan and player experience the facility needed.

Architecturally, HDR collaborated with Populous to design the stadium. As the lead structural engineer, HDR also worked with structural engineering consultant Thorton-Tomasetti, Kansas City, Mo. HDR is an Omaha-based global firm providing architecture, engineering, consulting, construction and related services. The firm has completed projects in 60 different countries. Program and user demands for TD Ameritrade Park created special challenges for the structural design.

“We chose structural steel because of its versatility, open, light appearance and its ability to shorten construction time and reduce costs,” says Savage. “The project had to be designed and built in less than 24 months and getting the structural steel frame erected on time was critical to meeting the opening day deadline. The geometry of the stadium meant we had to pay special attention to outlining and coordinating the steel elevations. It took nine radius points, for example, to define the stadium’s curved layout. Since much of the steel was exposed to view, detailing needed to be clean to maintain aesthetics. The right coating system also was critical to keep the steel from rusting.”

Clean connections
Exposed connections were evaluated to meet both structural and architectural requirements. “In keeping with the stadium’s modern design, we wanted the steel to look as sleek as possible,” says Savage. “That meant connections needed to be as clean as possible. We were able to achieve this by welding the majority of connections between truss members at the upper seating bowl to eliminate the need for gusset plates and bolts.” During the shop-drawing preparation process, fabricator Drake-Williams Steel was able to provide feedback that allowed HDR to further simplify details and make fabrication easier, Savage says. HDR used the Ram Structural System, fully integrated engineering software for building analysis, design and drafting of steel and concrete structures along with Revit Structure to shorten construction time. HDR provided Drake-Williams with a CIMSteel Integration Standard file for use in their early mill order package. Steel detailer Midwest Detailing used the CIS 2 file to create shop drawings without having to recreate the geometry of the steel frame, a step that further contributed to a time savings. “Overall a six-week head start was achieved with the ability to import files to the fabricator and detailer,” says Savage.

Steel framing
The structure’s framing system used braced frames for lateral loads and composite steel framing for gravity loads. Because much of the concourse and suite-level structure was left exposed, with occupied space below, the design used a split slab concept for these areas. Large cantilevers with exposed truss work support precast concrete risers for the upper seating bowl. Steel beams frame the roof level and support a metal roof deck. Portions of the roof used a composite slab to deaden noise and vibration from multiple mechanical condensing units, which cool the building’s indoor areas. For the canopy above the roof, HDR used Versa-Dek, a metal deck product that provides inherent strength with the aesthetic appeal of a dovetail shape. The Versa-Dek product also was factory finished with a custom paint color to match the other exposed steel in the stadium.

To complete the project, Drake-Williams fabricated 3,233 tons of structural steel sourced from Nucor Steel. Sustainable features included storm water retention, reflective roofing to reduce heat, energy usage controls and a curtain wall to allow daylight wherever possible. The firm wanted the design and feel of the stadium to incorporate and reflect the experience of the student athlete, the fan and the patron, says Savage. It also wanted the design to symbolize the long history and traditions of Omaha’s baseball fans.

HDR’s ability to employ advanced tools to implement a creative structural steel design made it possible for TD Ameritrade Park to open in 2011, despite a short schedule and difficult geometry. “On opening day of the 2011 College World Series, the stadium showcased the sporting event but it also highlighted another star—structural steel,” says Savage. MM

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