Bending Around (Sprint) Center. Written by George F. Wendt and David Landis, P.E. of Walter P. Moore

Bending Around (Sprint) Center
By David Landis of Walter P. Moore and George F. Wendt of Chicago Metal Rolled Products
In Modern Steel Construction magazine, July 2008

DESIGN

The $276 million Sprint Center arena opened last October to a sell-out crowd cheering for Elton John and received rave reviews. This unique state-of-the-art arena is Kansas City’s newest downtown landmark and the centerpiece for the city’s downtown revitalization. Sprint Center arena was designed by a consortium of the nation’s leading sports facilities architectural firms who took the name Downtown Arena Design Team (DADT). The unprecedented team was comprised of HOK SVE, Ellerbe Beckett, 360 Architecture, and Rafael Architects. Walter P Moore, a leading sports facility engineer, was structural engineer of record. Together, this design team brought a level of leadership, passion and experience like no other.

This 18,500 seat state-of-the-art multipurpose arena is expected to host over 100 events per year and was designed with flexibility as a primary goal. Sprint Center will accommodate NBA basketball, NHL hockey, AFL arena football, concerts, circuses, and many other performances and special events. With retractable and variable rise seating to optimize sight lines, the arena can be reconfigured quickly to accommodate different events. The roof structure also gives Sprint Center extraordinary flexibility to host a wide variety of shows and stage configurations. In addition to code live and snow loads, the long-span roof was designed to support up to 425,000 pounds of show rigging for concerts plus an 80,000-pound scoreboard, four 8,000-pound speaker clusters and nearly a half mile of catwalk loaded with sports lighting, spotlights, and electrical and sound equipment.

Sprint Center’s most notable aesthetic design feature is its distinctive cladding system. Curved both vertically and horizontally, the faceted cladding system was designed to allow dramatic views inward and outward and is somewhat reminiscent of a pillowed crystal bowl. The faceted glazing, as well as varied frit patterns applied to the glazing, transforms the building’s appearance as sun angles and light conditions change throughout the day. At night, the arena glows like a colorful ornament, exhibiting the activities inside and beckoning to the surrounding city.

Walter P Moore investigated numerous schemes for structural support of the cladding with the architects and construction manager. In response to the architect’s desire for an elegant and non-distracting support structure, a system of curved vertical and horizontal pipe was selected. Curved horizontal 16” diameter HSS span up to 50 feet and are supported by curved vertical 16” diameter HSS spanning up to 48 feet. The horizontal HSS are moment connected with end plates to reduce deflections. Using moment connections enabled the engineer to economically minimize member sizes while still meeting strength requirements and deflection limits. End plate connections with oversized holes allowed for reasonable erection tolerances while providing economical moment connections.

The curtain wall support frame was designed and detailed such that it did not provide support for any of the floors or roof. Since the curved frame supports only the cladding system, it was not required to be fireproofed. However, the curtain wall system did need to accommodate floor and roof live load deflections and building drifts due to wind and seismic loads. Design building drifts and support frame movements to be accommodated by the cladding system were outlined on the structural drawings.

FABRICATION

AISC member Schuff Steel Midwest had responsibility for the entire structural steel package and engaged fellow AISC member Hillsdale Fabricators an Alberici Enterprise in St. Louis for fabrication of the curtain wall support frame. AISC Roller/Bender member Chicago Metal Rolled Products earned the contract from Schuff Steel and Hillsdale Fabricators to curve 750 tons of the16 inch diameter pipe that gives the structure its unique shape. According to the site architect, Craig Milde of DADT, “The steel really helped give the glass enclosed arena its unique shape. Refining the geometry to attain the desired enclosure shape was most challenging – 9 radius points in each of the four arena quadrants.”

With full-service plants in both Chicago and Kansas City, Chicago Metal was able to minimize construction time and cost because each plant contributed to the project. For example, raw material more readily available in Chicago was curved in Chicago then sent to Hillsdale Fabricators in St. Louis who in turn shipped the parts to Kansas City to be erected. On the other hand, material purchased in Kansas City that was shipped to Schuff’s facility in Ottawa, Kansas, was curved in Kansas City. As the project progressed, Chicago Metal was in frequent contact with the fabricators to insure that everything was fitting up well.

According to George Wendt, President of Chicago Metal, “we are so proud to have contributed to this iconic structure that will be the pride of Kansas City for years to come. We opened our plant in Kansas City to curve steel for customers west of the Mississippi with quicker delivery, lower freight costs and increased capacity. We are happy that the new Kansas City facility achieved these goals with its work on the Sprint Arena.”

During fabrication, the design, fabrication and erection teams collaborated extensively. Numerous planning meetings were held to discuss fabrication and erection issues, including geometry coordination, acceptable tolerances, erection sequence, and support frame movements expected due to thermal changes and construction progress. Clips for the curtain wall mullion attachments were welded to the curved horizontal pipes in Hillsdale’s fabrication shop. Ensuring that the geometry of the fabricated curved steel and the curtain wall matched when erected was critical. Craig Milde, on-site DADT architect, visited both Chicago Metal and Hillsdale Fabricators to monitor progress. Wendt also visited Hillsdale Fabricators.

The curtain wall support frame was primed in the shop. The final coating was applied in the field after erection.

ERECTION

Walter P Moore developed an erection sequence during design to minimize support frame deflections during curtain wall erection – adjacent bays of curved horizontals and their moment connections had to be completed prior to erecting a bay of curtain wall. Erection of the 2,204 fritted trapezoidal glass panels of many different sizes lagged erection of the steel frame by several bays.

To simplify erection, Walter P Moore designed compact connections that allowed for reasonable fabrication and construction tolerances. The bases of the curved verticals are connected with pin assemblies. Connections to the upper concourse floor and roof are made with slip-critical bolts in oversized holes. The curved horizontals are moment connected with end plates with slip-critical bolts in oversized holes and shim plates. With few exceptions, erection of the curved steel frame proceeded smoothly.

Construction tolerances for the curved steel frame were reduced from those in the AISC Code of Standard Practice to facilitate connection of cladding system. Any point along the steel support frame had to be erected to within 1” of the design location in any direction.

Greg Peterson of Hillsdale Fabricators reported that Chicago Metal did a great job curving the steel: “the pipes fit their fixtures perfectly.” Craig Milde, the on-site architect reported, “the first four verticals were delivered yesterday afternoon. I watched the first one be set this morning. You must have done good work: it slid right into place.”

TEAMWORK

From the initial decision on the part of the architectural firms to form a consortium of some of the leading stadium and arena design firms though the design process to curving, fabricating, and erecting the curtain wall, teamwork and constant communication were the hallmark of this project. Numerous planning sessions during design, fabrication and erection helped construction of the doubly curved curtain wall system and support steel proceed smoothly. The resulting structure, Sprint Center arena, shines brightly as the achievement of that collaboration and is Kansas City’s new jewel.

Owner: City of Kansas City, Missouri

Developer: Anschutz Entertainment Group and Icon Venue Group

Construction Manager: M.A. Mortenson Company

Architect of Record: Downtown Arena Design Team: HOK Sport, Ellerbe Becket, 360 Architecture, Rafael Architects

Structural Engineer of Record: Walter P Moore

Steel Fabricator: Schuff Steel Company and Hillsdale Fabricators an Alberici Enterprise

Steel Detailer: Dowco Consultants

Steel Erector: National Steel Constructors

Curtain Wall Supplier: Architectural Wall Systems

Roller/Bender: Chicago Metal Rolled Products

About the authors:
David Landis, P.E., is Senior Principal and Design Director in the Kansas City office of Walter P Moore and has been involved in the structural design of over 30 sports facilities. Walter P Moore is a multidisciplinary consulting engineering firm based in Houston, TX. DLandis@WalterPMoore.com.

George Wendt is President of Chicago Metal Rolled Products, a national leader in curving structural steel, steel sheet and steel plate for the construction industry. Founded in 1908, Chicago Metal operates full-service plants in Chicago and Kansas City. GWendt@cmrp.com.