The new Meadowlands Stadium

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    Figure 1: Rendering of the new Meadowlands Stadium (Courtesy 360 Architecture, Inc.)

    Within the largest metropolitan area in the United States, home to nearly 20 million people, the previous 33-year-old-stadium for the New York Jets and New York Giants NFL professional football teams was in dire need of replacement. After several attempts at building their own separate facilities, the Jets and Giants decided to continue their relationship by sharing in the use of one stadium. This time they are not tenants, but joint owners of a 100 percent privately financed, $1.6-billion state-of-the-art sports and entertainment facility in East Rutherford, N.J.

    With an impressive 2.1 million square feet and approximate footprint dimensions of 750 feet by 900 feet, and boasting 82,500 seats for football games, this is the second largest NFL stadium. The stadium contains seven levels, three of which house 217 luxury suites, and another three spacious concourse levels with all the expected amenities in a new, world-class sports facility. Each corner of the seating bowl features a 30 foot by 120 foot LED scoreboard that uses the latest technology. Construction on the stadium began in May 2007 and was completed in the spring of 2010, months ahead of schedule.

    Site description and foundations
    The stadium site is located in the Meadowlands Complex in East Rutherford, N.J., which is approximately six miles west of Midtown Manhattan. The Meadowlands site is within one of the largest urban wetlands on the Eastern Seaboard. The land is owned (as was the old Giants Stadium) and will be leased from the New Jersey Sports and Exposition Authority, a New Jersey state agency. The new stadium is positioned less than 50 feet from the old stadium, which partially dictated the overall scheduling of the stadium construction since the old stadium was being used for football games and other events during construction. Development of the stadium within the already developed area of the old stadium’s parking lot did not have any adverse impact on the wetlands ecosystem.

    Subsurface conditions, as classified in the International Building Code, are characterized as a site class ‘E.’ This classification, along with the code-prescribed spectral response accelerations, resulted in a borderline seismic category D building, which would have had significant cost penalties for the structural, architectural and mechanical systems. Thornton Tomasetti, Inc. suggested to ownership that a site-specific seismic investigation be performed, in hopes of lowering the classification to category C. The investigation was ultimately performed and the reduced criteria confirmed, saving the owner millions of dollars and reducing the overall construction time.

    Poor subsurface conditions, which included fill from Hudson River dredging as well as marsh deposits, necessitated the use of a deep foundation system consisting of concrete-filled, closed end, driven steel pipe piles. In total, approximately 5,000 piles were used consisting of 13-3/8 inch diameter pipe piles each with a 150-ton capacity for main column pile caps; and 9-5/8 inch diameter 75-ton capacity framed slab support piles. Pile caps ranged from two pile groups up to 24 piles per cap, and from depth of 3 to 7.5 feet. Columns in the lateral load resisting system could potentially undergo uplift. Therefore, 1-5/8-inch diameter threaded bars embedded 25 feet into bedrock with 175-kip uplift capacity were used. From two to 10 tie-down anchors were used, depending on uplift loading.

    Slab support piles were located between column support pile caps at approximately 25 feet on center for the typical service level slab to reduce the required thickness. The field slab was designed to support up to six feet of soil for special conditions, such as motor cross and monster truck events, and therefore required slab support piles at 12 feet on center. Only one expansion joint was used to separate the central field slab from the remainder of the service level slab. To account for concrete shrinkage, seven shrinkage strips were used, at which the concrete was not poured up to 180 days from adjacent pours. Framed slab thickness varied from 10 inches to 12 inches with an additional 12 inch haunch at pile support locations for punching shear capacity.

    Design/build
    In December 2006 the owners entered into a design-build contract with Skanska Building USA as the project was in the middle of the design development phase. Skanska assumed the contracts of the design team and was tasked to have the stadium fully designed and constructed in just over three years. To achieve this, multiple early release packages for structural steel and foundations were required. The first of which was a 3,250-ton steel mill order in December 2006 that consisted of grade 65 heavy wide flange members (jumbo shapes) that were produced overseas. This early release was necessary because of the long lead time to obtain the members, and to address the concern of a possible one-year mill shut down for retooling. This initial design issuance was released 11 months before the 100 percent construction documents were completed. Besides the typical uncertainties in nailing down a design without coordinated architectural drawings, Thornton Tomasetti had to study options for a proposed roof, but later never materialized due to financing issues. The initial mill order package was followed by another three mill order releases that were delineated based on the erection schedule, and multiple foundation packages. Hitting the ground running was also critical due to the vast number of steel projects with a similar timeline that were planned to undergo construction in the same region. In the New York metropolitan area, the New York Yankees, New York Mets and the New Jersey Red Bulls all were building steel stadiums, plus large scale commercial buildings in New York City were in the pipeline. This caused concern as to whether the necessary structural members could be procured when required. Fortunately, finding a qualified erector to build the stadium was not an issue, as Skanska’s sister company Skanska USA Civil performed the erection services.

    The success achieved in meeting such an aggressive schedule was only possible with the strong, dedicated and cooperative design/build team. An essential team member was the steel fabricator, Canam Group. They were brought on at the beginning of the process to procure the steel and assist in the development of the most efficient and timely design suited to their fabrication preferences and meeting the erection scheme and timeline developed by the erector and Skanska Building USA. For example, Canam preferred that the spandrel members supporting only façade loads be made up of built-up ‘I’ shape plate members instead of standard wide flange members that were reinforced or tube members. Also, they provided input on where they preferred to see bolted versus welded connections, and other specific connection materials and details.

    Building information modeling (BIM)
    Critical to the procurement of steel at such early stages was the development of a building information model (BIM) by Thornton Tomasetti. This BIM was created using Tekla Structures software concurrent with the design analysis model (Figure 2). The overall stadium was divided into three portions that established the mill order packages, which were defined by the erection schedule. Each portion of the model was developed in two stages. The first stage included basic member geometries, material sizes and specifications. Then an initial version of the model was handed over to the fabricator to develop the bill of materials and to adjust any discrepancies relative to the printed plans (produced in Revit Structure, as seen in Figure 2) provided with the model. Concurrent with the fabricator’s use of the model, Thornton Tomasetti moved into the second phase of modeling, during which connection information was added for the main members. At set dates, the Tekla model was handed over to Canam, and they took ownership and subsequently created approximately 16,000 shop drawings. The drawings were submitted to and returned by the design team electronically via Skanska’s project extranet, which helped expedite submittals.


    Figure 2a

    Figure 2b
    Figures 2a and 2b: A Tekla model view of a partial frame (2a) and a construction photo.

    Close collaboration between the engineer and fabricator was required to allow for simultaneous use of the model and for it to be useful to the fabricator, with minor adjustments. Criteria for setting up the model in a format that worked between both offices were necessary. Ultimately, the development of the model shaved months off the schedule, eliminating the additional time necessary for a fabricator to develop a bill of materials from only a set of paper drawings, as traditionally done in a design-bid-build project. This collaboration led to the eventual design, detailing, fabrication and erection of 15,000 pieces of steel weighing 26,000 tons in 27 months, with a 17-month erection schedule.

    Figure 3: 3D view from Thornton Tomasetti’s Revit model

    During the construction phase Thornton Tomasetti developed the Tekla model further to include the precast seating units, and Skanska had the mechanical systems added for purposes of clash detection and clash prevention. This model, coupled with radio frequency identification (RFID) tagging of the precast pieces, was also used by Skanska to track the progress of the precast manufacture, shipment and construction. The BIM proved to be invaluable in the coordination of a project of this scale with so many team members and systems.

    Superstructure description
    Multiple structural framing schemes were evaluated by the project team, including all-concrete, all-steel and hybrid systems. To meet the aggressive schedule, as well as accommodate local market conditions, an all-steel scheme was determined to be the most suitable.

    To provide for a design that balanced efficiency as measured in steel tonnage with that of the construction schedule, Thornton Tomasetti suggested that the bent spacing be increased beyond the typical spans found in football stadiums. Most new football stadiums have spans of 42 feet to 46 feet (The old Giants’ stadium had approximately 30 foot bents). The New Meadowlands Stadium has spans, outboard of the lower bowl, that range from 44 feet to 55 feet. A study conducted by Thornton Tomasetti compared the cost of the structural steel framing for a 30-foot bay versus the proposed spans. It was determined that, even though the 30- foot bays resulted in a savings based on material cost alone for the floor framing due to lighter beam members, it was far outweighed by the additional erection costs from the 50% more members (steel and precast) that had to be erected, and additional fireproofing and/or painting costs.

    The main structural system consists of 52 radial bents (Figure 4) that vary in spacing due to the radial geometry, but range from 26 feet at the lower bowl to 55 feet at the perimeter grid. The column spacing along the bent varies from 25 feet to 46 feet. The bents consist of wide-flange rolled steel columns and girders, except for the larger spans and cantilevers, which require the use of built-up plate girders or trusses. The floor framing system consists of composite slabs 4.5 inches thick of normal weight concrete topping over 3-inch metal deck. Floor beams vary in depth, but generally are 24 inches deep and are spaced 9 feet to 10 feet on center and span the radial bent girders.

    The stadia units of the seating bowl are made of concrete precast double or triple units, with 7 1/4-inch thick risers and 4-inch thick treads. These units span to the steel raker beams that are part of the radial bents. Depths of risers varied as dictated by necessary sightlines, increasing in depth with height. The riser depths range from approximately 8-½ inches to 22-½ inches and contain drop stems below the tread to provide the required strength and stiffness to minimize vibration issues. Total stadia unit depths range from 30 inches at the lower bowl to 36 inches at the upper bowl, which contains the longer spans.


    Figure 4a

    Figure 4b
    Figure 4a and 4b: Typical sideline bent section (4a); and typical endzone bent (4b)

    To achieve a practical, cost-effective design, only four expansion joints were used throughout the stadium. One expansion joint was placed in each “corner” of the stadium (Figure 5). The majority of steel structures in this region, particularly open-air structures, would be limited to a distance between expansion joints of 300 feet to 400 feet. The new stadium has expansion joints up to 670 feet apart. If Thornton Tomasetti was to break up the stadium to the typical range, there would be eight expansion joints that would run through the suites and premium club spaces. In addition, more lateral bracing members would be required to stabilize the individual structures. Expansion joints range from nine to 26 inches to accommodate seismic drifts.

    Even in the few locations with expansion joints, the design seeks to maximize useable space and keep a clean look. Expansion joints in most buildings would typically require a double column (taking up useable floor space), or one column with a bracket with slide bearings to support beams on the other side of the joint (expensive and a maintenance headache). For the new stadium, a single column was used on one side of the joint, with cantilever beams extending from adjacent columns to the other side of the joint. Cantilevers ranged in span, but the largest is a 27-foot span. A study performed to evaluate the cost effectiveness of this solution determined that the additional material cost required for the large cantilevers was offset by the savings in fabrication costs of expensive brackets and slide bearings that require many fitted stiffeners with large welds.

    Figure 5: Typical Plan highlight expansion joint locations.

    Lateral load resisting system
    The four expansion joints divide the stadium into four individual structural buildings, one at each endzone and each sideline. The resulting buildings are regular in plan, allowing for a simple lateral system. The lateral load-resisting system consists of ordinary concentrically braced frames in each principal direction for each building segment. Frames extend the full height of the main building from the foundations up to the Concourse 3 Level. Above the Concourse 3 level a combination of braced frames and moment frames are used to work with the architectural layout.

    The 7 ½-inch total thickness slab on deck (4 ½ inch NWT concrete on 3-inch deck) is used as the structural diaphragm spanning between braced frames to distribute the lateral loads. A mat of #4 rebar at 12 inch on center each way is used for shear reinforcement of the slab, plus 8-#7 rebar were placed at the perimeter for chord reinforcement. In some cases, the diaphragm is required to span over 200 feet between braced frames.

    A wind tunnel test by RWDI provided the design wind forces for the main lateral resisting structural system and for the components and cladding. In most cases, seismic forces govern the design of the lateral system. As noted previously, a site-specific seismic study was performed by Langan Engineering and Environmental Services, which allowed for a reduction in design seismic forces and a lowering of the seismic design category from D to C. In addition, Thornton Tomasetti performed a 3-D dynamic analysis model using CSI SAP software using the spectral response spectrum obtained from the site-specific study. This analysis resulted in the reduction of design base shear and overturning moment by approximately 15 percent. This reduction translated into a similar reduction in tonnage for the braced frame member columns and braces, as well as a reduction in piles and tie-down anchors.

    Even with the one-third decrease in seismic forces confirmed by the site-specific study and dynamic analysis, there were still a significant number of perimeter columns requiring uplift tie-down anchors. Due to the significant cost of the tie-down anchors, Thornton Tomasetti performed studies using varying lateral load-resisting structural systems to reduce the seismic forces by increasing the response modification coefficient ‘R.’ It was determined that these other systems would allow for elimination of the uplift anchors, but would require special detailing requirements to meet the seismic ductility demands. This special detailing would increase material and fabrication costs associated with the braced-frame connections that would have to be designed for the full tension capacity of the member. Typical connections for each system (Figure 6) were designed by Thornton Tomasetti’s in-house connection design engineers and priced and evaluated by the design-build team for cost and schedule impacts. Ultimately, an R=3 with no special seismic detailing was determined to be the most economic solution.


    R=3 CONNECTION

    R=6 CONNECTION
    Figures 6a and 6b: Comparative connection designs for R=3 vs. R=6 seismic systems

    Conclusion
    A bit of innovative thinking, along with a strong professional design and construction team under a design/build delivery method, allowed the building of a state-of-the-art stadium months ahead of an already aggressive schedule. A major contribution to this achievement was the use of BIM, which will likely continue to provide useful information for the operation of the facility for decades to come.

    Figure 7: Stadium during construction.
    Project team members
    Owner: New Meadowlands Stadium, LLC, East Rutherford, N.J.
    Structural engineer: Thornton Tomasetti, Inc., Newark, N.J.
    Design-Build contractor: Skanska USA, Parsippany, N.J.
    Architect of record: Ewing Cole, Philadelphia, Pa.
    Design architect: 360 Architecture, Inc., Kansas City, Mo.
    Geotechnical engineer: Langan Engineering and Environmental Services, Inc., Elmwood Park, N.J.

    Armindo Monteiro, P.E, LEED AP, vice president and project manager for project, and Anjana Kadakia, P.E., LEED AP, principal and project executive for project are in the Newark, N.J. office of Thornton Tomasetti, Inc. Tom Scarangello, P.E. is chairman of Thornton Tomasetti and served as principal-in-charge of the project.