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ARIZONA CARDINALS STADIUM - · PDF fileLocated in Glendale, which is just outside of Phoenix, the new Arizona Cardinals stadium has an ... “Stadium Roofs Offer Much More Than Shelter.”

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Text of ARIZONA CARDINALS STADIUM - · PDF fileLocated in Glendale, which is just outside of Phoenix,...


    PowerPoint by: Mike Benkert



    The new Arizona Cardinals football stadium, designed by Peter Eisenman is not set to openuntil mid August of 2006, but is already gaining recognition for its innovative architecture and engineering.The stadium sits in the middle of the Arizona desert where the unique climate and landscape act asdriving forces behind many of the design and construction decisions made in the building.



    Located in Glendale, which is just outside of Phoenix, the new Arizona Cardinals stadium has anexterior skin that is representative of a barrel cactus. This form is carried out around the perimeter of thestadium by way of 21 pairs of alternating metal panels and vertical glass slits 1. These shimmering metalpanels serve to reflect the shifting desert light and the glass slots give patrons a spectacular view of thehorizon from any level of the exterior 2. The rounded form of the barrel cactus also manifests itself in thebulbous nature of the stadium as a whole.



    In addition to the design representations of the local climate, many of the programmaticnecessities were also directly influenced by the desert climate. In a region where 100 degree temperaturesare commonplace from the spring until fall, air conditioning systems are essential for almost all buildings inthe greater Phoenix area including stadiums. This problem calls for either a dome or a retractable roofstructure, and in a climate where many days are also 70 to 80 degrees and sunny, an open-air stadium isoften desired, hence the retractable roof.

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    Unfortunately, retractable roofs add a lot of extra cost to a building project and as the spanincreases (which is necessary to get sunlight to the grass field), the price of construction and materials alsoincreases, so instead of increasing the span of the retractable roof, Eisenman elects to equip the newArizona Cardinals football stadium with North Americas first retractable natural grass playing field that slidesout of the stadium to get the proper sun exposure, which saves about $50 million dollars in construction cost3. The long span roof trusses, super columns, retractable roof system, and retractable field make the newArizona Cardinals football stadium in Glendale stand out as one of the unique structural feats in the world.

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    Holding up the roof of the new Arizona Cardinals football stadium are two curved BrunelTrusses, spanning 700 feet with a maximum depth approaching 90 feet in some areas 4. The word truss isactually misleading in describing the spanning element of the roof in that the top chord acts like an arch,while the bottom chord acts like a cable. This is actually more efficient in that the two chords work inconjunction and as a result, require only slender struts between them instead of heavy diagonal elements ofa traditional truss 5. The top chords of the trusses are pieced together from pre-fabricated 20 x 20 steelcross-sections (weighing more than 70 tons a piece), while the bottom chords are considerably thinner insection. These elements along with the rest of the roofs structural frame were assembled at ground levelbefore being hoisted 120 feet in the air by a jacking system implanted within four super columns used to liftand support the Brunel Trusses 6.





    Since the 156-foot concrete super columns were required to perform the roof lift, they needed tobe built before a lot of the seating bowl could be completed and therefore, were viewed as freestandingelements during their design 7. The most critical design considerations for the super columns according toengineer Dean Purdy, were the forces and moments imposed at the top of the columns due to jacking 8.Each column acts as its own jacking frame and there are 2 jacks per super column. Each jack consists of 54cable strands and each strand is about 145 long 9. The jacking assembly itself has the capacity to lift theEiffel Tower 10. During the roof lift, hydraulic pressure was used to grip and lift the cables in 18 incrementsuntil the Brunel Trusses were lifted 122 to 158 above the stadium floor. At that point, steel transfer girderswere installed in the notches at the top of the super columns and the trusses were lowered 2 to their finalresting height 156 above the floor 11. To correspond to the forces and moments imposed at the top of thecolumns due to jacking; each super column is 17.5 wide and 12 deep 12.

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    Riding over the arched top chord of the Brunel Truss, the Arizona Cardinals stadium retractableroof is the first in the United States to run along a curved arc 13. As a result of the arced path taken by the tworoof panels there are more inherent risks that dont surface in the typical flat track retractable roof system. Aselectrician Lennart Nielsen puts it, if the brakes were to release [in a flat track roof system] and the motorsdidnt start up for some reason, the roof would simply remain in place. However, at the Cardinals newstadium [with its sloped roof track] if the brakes were released and the motors didnt start up, the roofsections would fall into the parking lot 14. The roof itself consists of two movable panels suspended betweentwo parallel tracks and each panel rests on eight two-wheeled carriers 15. The roof moves with cables alongthe roof rails that are wound around motorized drums connected to the panels. There are four drums perpanel and each drum houses four motors, which aid in propelling the panels to speeds reaching mile perhour 16. The roof takes 12 minutes to open and close and is made from a translucent Bird-Air fabric thatgives the stadium an open, airy feel even when the roof is closed 17.

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    While Eisenmans stadium design features many innovative structural elements that make standout amongst other venues, Architectural Record states that, The most unique feature of the Glendale,Arizona stadium [is] a natural grass field that can be moved on a 234 by 400 foot, 12 million pound tray 18.Such rollout natural grass playing fields have been utilized in some Asian and European venues, butCardinals Stadiums combination of a retractable roof and field is the first of its kind in North America 19. Thefield tray itself rests on 13 rail tracks and moves in and out of the stadium on 542 wheel assemblies, amongwhich, 76 are powered by 1-horsepower motors 20. The average travel speed of the tray is 11.5 feet perminute and the total travel distance, which takes about 65 minutes to move both inside and out, isapproximately 741 feet 21. The tray, which is equipped with a sophisticated irrigation and drainage system,remains outside the stadium getting maximum sun exposure until game days, when the field is moved backinside the stadium 22.




    To correspond to the bulbous nature of the barrel cactus and the desert climate of Glendale,Eisenman uses structure not only to support Cardinals Stadium, but as an aesthetic expression. A greatexample of this is in the roof system where the structure expresses a feeling of lightness. The curved roofform achieved through the use of arched roof panels and trusses represents a light and airy bubble despiteweighing thousands of tons. The curved Brunel Trusses also feel lighter in that the bracing is thinner andmore widely spaced than a typical truss as a result of the arch and cable characteristics of the chords.Design moves like this show a great understanding for the ramifications the structural system has on abuilding. This attention to detail, along with the regional and organic design features and implementation ofnew building technologies make Cardinals Stadium somewhat reminiscent to the works of the late FrankLloyd Wright. Unfortunately, like many of Frank Lloyd Wrights buildings, this particular venue has a fewprogrammatic issues that are worth discussing.



    While the rollout grass field cuts down on costs that would otherwise be spent on making alarger span retractable roof, the seating capacity takes a serious hit in that there is no permanent seatingbehind the south end zone where the field slides in and out of the structure. Also, with the development ofgrassy (a.k.a. field) turf in recent years, it is debatable if the rollout field is even necessary. Nevertheless,the overall integration of modern structural systems and sleek design in Eisenmans Cardinals Stadium,makes for a great pie