"The history and tradition of Texas Stadium was the biggest single influencer in the design of our new stadium," stated Jerry Jones, owner of the Dallas Cowboys. "From the signature shape of the roof and its opening above the field to the Ring of Honor, we wanted to maintain many of the signature elements that made Texas Stadium the cultural icon it is today."
The Jones family spent many hours studying sporting venues and other large structures worldwide.
"It would be hard to single out any one structure, because we learned from so many, be it a visual design element or a concept on space layout," Jones explained. "We spent a great deal of time studying the architecture of buildings across the country as well as Europe, Asia and Australia. And we didn't just focus on stadiums; we studied hotels, office towers, museums, and other public buildings as well. You have to look at both the vast design elements like the arch at Wembley Stadium while not forgetting to appreciate the details, like the subtle difference in the shade of the color of glass at the Nice Airport.
"One of those major spaces that partially inspired our end zone plaza design was the great public entries from the Underground station into Wembley Stadium in London. At Wembley we found that architect Norman Foster was able to take a sports stadium and turn it into a venue suited for hosting any range of events. That too was something we wanted to accomplish with our new home.
"On a more detailed design element, we were just as impacted by the details you can find when you look closely at a building," Jones continued. "We found a certain level of structural creativity in the fins of the Bloomberg Building in New York and the fritted glass in the designer boutiques of Louis Vitton and Chanel."
"Jerry Jones painted the vision of the stadium and the architects and engineers worked closely with him and the Jones family developing a design," said Mark Williams, project director and associate principle with the architectural firm of HKS, Inc. "HKS designed the preliminary concepts, conferring with structural engineers at Walter P. Moore to determine what was feasible. A lot of functional issues and aesthetic issues mesh themselves together in this concept and design."
"We wanted to provide more concourse width on the upper levels because there will be more people on the levels higher up in the building." That idea developed into the outward-canted exterior. "We determined that a 14-degree angle would allow the concourse on the upper levels to be wider than those on the lower lever, and because it sticks out farther, it shades the level below it, blocking the sun."
Yet Jones wanted the people inside to have the feeling that they were in an outdoor stadium, so that the glass skin and translucent retractable roof were designed to let in subdued natural light. And top center of the roof, Texas Stadium's famous hole-in-the-roof — a feature recognized worldwide — was carried over into the design of the new stadium with the modification of the world's largest retractable covering.
Manhattan Construction Company serves as the lead general contractor and construction manager for the Dallas Cowboys and Blue Star Development. Local minority firms Rayco Construction and 3i Construction are also members of the management team, adding project management staff to work side by side with Manhattan's project managers. This mentoring opportunity, promoted by Arlington's Fair Share agreement for contracting, is helping these two smaller contractors gain experience on large projects. Manhattan Construction, a 110-year-old company with expertise in large, complex projects such as The Ballpark at Arlington (Ameriquest Field) and Reliant Stadium in Houston, is proving to be an excellent choice as leader for this mentoring alliance.
Foundation and Structure
Once ground was broken in early 2006, it took only about four months for Mario Sinacola and Sons Excavating to move approximately 1.4 million cubic yards of sandy soil punctuated with native boulders that make up a Woodbine geological formation in the Dallas/Fort Worth mid-cities. Covering an area of about 14 acres, the 54-foot-deep stadium bowl will contain the football field and seats. Encountering the water table at approximately 20 feet required installation of a dewatering system, which remained in place as long as the bowl was open.
Olden Professional Services engineered the earth retention system, which included a massive 200,000 square feet of wall and 8,000 soil nails. The majority of this wall system is a permanent soil nail system with a precision tolerance temporary shotcrete face and a cast-in-place permanent concrete face. The soil nail system and anchors that were used consisted of epoxy thread bars with an additional double corrosion system applied by Olden. An innovator in soil retention technology, Craig Olden, Inc. developed their own installation system using modified Caterpillar-based integrated drills to install soil nails. The concrete reinforced bowl now serves as the foundation for the stadium structure.
Outside the bowl area, McKinney Drilling drilled the 60-foot-deep piers that support the massive stadium. The piers inside the bowl range only about 40 feet to 48 feet deep just to penetrate into the bearing strata.
Manhattan Construction Company has been self-performing the approximately $40 million of cast-in-place work for the 104-million-cubic-foot enclosed stadium — the largest enclosed stadium in the National Football League. The job will require 200,000 cubic yards of cast-in-place concrete with 22,000 tons of reinforcing steel. Dallas-based TXI is supplying the concrete, and Arrowhead Rebar is supplying the reinforcing steel.
Slanted columns constructed with slanted column forms like those that support the cantilevered stadium decks are becoming more commonplace, according to Mark Penny. "It was extra work and tricky for the guys installing the rebar and pouring the concrete," Penny commented. "It has made for some interesting challenges on assembling the curtainwall system."
A wind tunnel study performed by Star WDI in Canada reassured Walter P. Moore engineers that all the proposed materials worked for the wind loading, according to John Aniol, P.E. S.E., lead structural engineer with Walter P. Moore. "The report indicated pressures that varied from 30 psf [pounds per square foot] to 50 psf on the cladding," Aniol said. "That's not unusual for the DFW area. For an ordinary building, you can get wind pressures from the building codes, but for a complex building like this, we like to have a wind tunnel study."
Cast-in-place work has kept just ahead of precast element installation and connections. Heldenfels Enterprises, supplier of the precast riser elements, and its subcontractors, Precast Erectors, Inc. and Grout Tech, Inc., have completed detail work on the first phase, which included nearly three-quarters of the nearly 2,700 pieces of precast concrete in the specifications. This past February they began the second phase, which will comprise the East and West end zones along with the North and South field levels.
For all the stadium's grandeur, the feature that seems to most impress the contractors building it is the 660,800-square-foot roof, and more specifically the trusses that will support the massive retractable roof. The monumental trusses will also support a one-of-a-kind, 600-ton center-hung video board hanging 110 feet above the field.
"We worked on the design for the roof structure from April 2005 through July 2006," said Aniol. "The 16 months of design work culminated in a monumental arch — the world's longest single-span roof structure."
Because of the angle that the truss connects with the ground, traditional piles or piers could not provide the needed bearing strength for the concrete thrust blocks, or abutments, according to Penny. Instead, Walter P. Moore structural engineers designed a slurry wall box system.
"The monumental arch resists 19 million pounds of thrust from the arch," Aniol explained. "That load is delivered through the concrete thrust block, which is 11 feet thick by 25 feet wide, then transferred into the ground through a slurry wall box — a trench 30 inches thick and 70 feet deep by 145 feet long." Only about 30 percent of the abutment is visible above ground at the base of the truss arch.
Each boxed arch truss measures 17 feet wide by 35 feet deep and spans 1,225 feet. The 23 sections that make up each arch are composed of two X-framed sides of standard grade-50 steel with the two top and two bottom cord elements made of high-strength grade 65 steel, Aniol explained. The dense steel imported from Arcelor Co. in Luxemburg and fabricated by W&W Steel in Oklahoma City weighs 730 pounds per lineal foot. The elements are so heavy that only one 56-foot-long cord element can be shipped on each truck from Oklahoma City to Arlington. In all, the roof trusses will utilize about 6,500 tons of the high-strength grade 65 steel.
Derr Steel Erection Company of Euless is using six crawler cranes to erect the trusses: Manitowoc 18000 (660-ton basic capacity and Maxer heavy-lift attachment), a Terex-Demag CC 2800 (660-ton basic capacity and super-lift attachment), a Link-Belt LS-1018 (500 ton), a Link-Belt LS-918 (400 ton), a Liebherr LR1200SX (275 ton), and a Manitowoc 999 (275 ton).
"Our crews erected the two main arches from their abutments to the apex at the center of each arch," Bob Derr said, describing the process. "The arch sections (35 feet deep by 168 feet long) were assembled on site, and then erected across six sets of shoring towers. Each shoring tower is a braced steel frame approximately 50 feet wide and up to 265 feet tall. These towers were designed to carry the weight of each arch and resist the lateral loads that could be produced by storm winds in excess of 90 mph. Each arch was also stabilized laterally by the installation of 230-foot-long trusses that span from each arch to the concrete ring beam which forms the upper perimeter of the stadium bowl. Once the arches and the bracing trusses were completed, the arches were lowered by hydraulic jacks until they carried their own weight, and the shoring towers were then removed."
Derr also had a complimentary observation. "When the arches were connected at the center 'keystone' sections, we found that the length of each arch came within a fraction of an inch of the expected overall dimension, which was addressed with a minor amount of shimming at the joints. That kind of accuracy says a lot about the quality of the fabrication by W&W Steel and Manhattan's construction of abutments that were almost a quarter of a mile apart. Our ironworker crews and project staff have carefully monitored the position and alignment of the arches throughout the process."
K Post Company will be installing approximately 750,000 square feet of 60-mil PVC fully adhered Sika Sarnafil roof system with a 20-year warranty for the permanent roof. According to Tom Williams, project coordinator for K Post, handling the Densdeck and insulation at heights up to 350 feet are a challenge due to the higher wind speed at that elevation.
K Post will complete the top of one side of the oval roof. Once work begins on the other side, the retractable installation will begin. Then, they will slide a retractable panel to the middle to work on the permanent part underneath and do the same for the other side.
The retractable center and rack-and-pinion drives designed by Uni-Systems of Minneapolis were over a year in design and testing. The opening will measure 256 feet wide by 410 feet long. Two bi-parting mechanized roof panels — each measuring 63,000 square feet — will be driven by a rack-and-pinion drive system consisting of 64 7.5-horsepower electric motors, making it the first of its kind in the world. The open/close time will be 12 minutes.
Mark Williams was pleased to see the glass curtainwall going up in late December 2007. "Everything that has gone up to now has been concrete and steel trusses — the structure. The glass is a very elegant component of the design."
Not that the glass is to be taken lightly — the 5,071 glass panels that make up the skin of the stadium weigh more than 1 million pounds. And it is very special glass manufactured by Viracon. Each glass unit is comprised of two panes of .25-inch clear glass separated by a sealed air gap to provide insulation. The outer pane has a Low-E coating and a white ceramic frit on its inner surface. The frit will also allow the walls to act as a projection screen at night, according to Jack Hill of Blue Star Development.
"The glass frit varies from the bottom of the building to the top of the building," Hill described. "The coating at the bottom of the building is applied at a 90-percent density so that there is a 10-percent transmittance through it. That graduates to a 30-percent density at the top." The daylight color of the canted wall glass is, of course, gray with a hint of blue.
The cantilevered concrete decks form the foundation of the 14-degree canted exterior walls. Steel tubes are welded to weld plates anchored in the concrete decks, Hill explained. An aluminum mullion system attached to the steel tubing substructure holds the glass panels in place. Even the mullion aluminum is a customized color created by using PVDF resin and mica flakes — Valspar Cowboy Silver.
The aluminum curtainwall is a custom unitized system manufactured by Texas Wall Systems, Inc., an Oldcastle Glass Company, and is being installed by Haley-Greer, Inc.
The elegantly canted exterior wall is proving more of a challenge to the Haley-Greer workers than it was for the engineers and concrete contractors. According to Penny, the curtainwall installers are having a particularly interesting challenge. As each panel is lifted into place with a telescoping material handler, gravity dictates that it hangs in a vertical position. The installers, situated in the basket of another material handler, must manhandle each panel into place to make it land at the proper angle, attach the panel at the top, then get below the panel to push it in at the bottom to make it sit in its seat.
"In this unitized system, the panels come completely prefabricated," Penny described. "The workers put clips on the structure and lift the units into place. It's going much faster than a typical structural frame, especially on this slant, where they would otherwise have to build it all in place."
The stadium, progressing on schedule at an amazing rate, is scheduled to be complete in little more than one year — ready for the first Dallas Cowboys game in September 2009 and for Superbowl XLV in 1011.
"Overall, the process of building this new stadium has both educated and inspired my entire family," Jerry Jones concluded.