For engineers, contractors and suppliers seeking a role in big sports stadiums, construction plans promising economy and speed are no longer value propositions, but “price of entry” requirements.

The principal supplier on the biggest ticket stadium under way — Chicago's new Soldier Field — offers more than timely dispatch of 1,600-plus riser, wall, floor and column member truckloads (note Precast Schedule box, page 22). Cretex Cos. Construction Products Group is using self-consolidating concrete (SCC) technology, coupled with the resources of J.W. Peters, Inc. (JWP) and three sister plants, to keep the job on its accelerated track. Soldier Field's rebuilding must culminate in time for the 2003 season of the Chicago Bears, the prime tenant and a National Football League charter franchise.

Cretex Construction's part covers a 4,526-piece package — with separate stadium ($14 million) and north parking structure ($22.5 million) supply contracts — of conventional precast/prestressed members, plus tub sections lining the base of elevated seating sections. Soon after securing the stadium contract, JWP found that those sections, more than any in the package, required creativity and scheduling execution.

“The presence of drainage channels and sloped back edges, and highly visible fascia sections to remain exposed, led us to casting the tubs upside down,” says Tim Daniels, production superintendent for Burlington, Wis.-based JWP, which is fabricating stadium components and the north parking structure's higher load double tees. “Self-consolidating concrete was the only way to ensure uniformity of mix distribution around the tubs' heavy reinforcement and strand and achieve architectural-grade finishes for the exposed surfaces.”

Considering the complexity of the tub units, casting them upside down was about the only way they could be poured, he adds. Consolidation of concrete back into all formed areas and around the embeds and reinforcement would have been difficult without the use of the highly fluid mixes.

The tubs run the length of the stadium sidelines along second and third seating levels. The Chicago office of Thornton-Tomasetti Engineers approved the mix specification for the 146 pieces — totaling about 1,150 yd. of material — after routine acceptance testing and a review of the industry's limited SCC standards library. The SCC mixes have exhibited compressive strengths of 8,100 to 9,800 psi, about 12 to 22 percent higher than mixes used for companion precast. In addition to test results with those figures, the JWP quality control staff capped off its submittals to Thornton-Tomasetti with ASTM C 94-modeled guidelines for SCC production.

GAME PLAN

Although siting and scheduling have steered every professional sports venue built since at least 1990, Soldier Field has required project principals to meet a new and very site-specific challenge: Construction in 20 months or less of a 65,000-seat venue bounded by a limestone-clad, concrete landmark. An 80-year old World War I veterans memorial owned by the City of Chicago Park District, Soldier Field lies in a Roman colonnade-flanked, U-shaped structure.

Now rising inside the historic structure's footprint is an open-air stadium with extensive skybox seating, supersized video equipment and other trappings. A $600 million-plus price tag includes a fully concealed 3,500-car parking structure abutting the stadium's north end. Topped off with trees and landscaping in a park-like setting, the four-level facility will reportedly be the largest precast parking structure built below ground in the United States, with 2,750 pieces.

The January 2002-September 2003 schedule hinged partly on demolition of an existing stadium bowl. Work was delayed by the regular 2001-2002 season going one week past schedule — to make up for the NFL's postponement of September 16-17 games — and a 13-3 season that placed Chicago in the playoffs for a January 20 showdown with Philadelphia (Eagles 33, Bears 19). The Bears relocated for the current season to Memorial Stadium at the University of Illinois, Champaign.

Reports from Cretex Construction's site staff indicate that precast erection for stadium and north parking structure are about 50 percent complete (as of mid-November) and on pace for scheduled completion early in 2003. Seating and scoreboard installations, along with interior skybox and concourse area work, figure to consume much of the time leading up to the Bears' September 28 home opener.

A HOUSE DIVIDED?

Elk River, Minn.-based Cretex Construction Products Group spans flagship companies J.W. Peters, Inc., Burlington, Wis., and Iowa Prestressed Concrete, Des Moines, plus PBM Concrete of Rochelle, Ill., and Raider Precast of West Burlington, Iowa. The latter two companies were acquired in October 2001 and positioned Cretex Construction with leverage unrivaled for a population center like Chicago.

Serious as they are about the nuts and bolts of the Soldier Field rebuilding, company insiders can joke about split loyalties surrounding the NFL franchise — the Chicago Bears — around which the contract revolves.

From a headquarters deep in Minnesota Vikings territory, Cretex Construction is overseeing four plants staffed with Bears, Vikings and Green Bay Packers fans. Packers-loyal JWP is handling the bulk of work for the Bears' new home; it is also shipping fat-stem double tees for the top level of an underground parking structure adjacent to the stadium's north end. However, much of that facility is being built with columns and tees from 1) PBM, the main supplier and one whose staff is loaded with Bears faithful; and 2) IPC and Raider, both in a state where support is divided between Vikings and Bears.

SOLDIER FIELD PROJECT PRINCIPALS

Owner
Chicago Park District

Contractor
Turner/Barton Malow/Kenny Joint Venture

Architect
Lohan Associates/Wood & Zapata Joint Venture

Engineer
Thornton-Tomasetti Engineers

Precast suppliers
J.W. Peters, Inc. (stadium)
Iowa Prestressed, PBM, and Raider Precast (north parking structure)

Precast erectors
International Erectors Inc., Kenosha, Wisc. (stadium)

Precast Services Inc., Twinsburg, Ohio (parking)

STADIUM PRECAST

Piece	Quantity
Risers	1,292
Tubs	146
Walls	142
Vomitories	98
Slabs	50
Stairs	34
Spandrels	21

TUBS

JWP ordered three Bonnybrook Custom Steel forms to fabricate tub sections in six sizes. The self-consolidating concrete mix specification was based on Master Builders' 3200 HES or 3030 NS (+ VMA) superplasticizers. It facilitated the upside down casting scheme, greatly elevating quality assurance for structural and architectural points.

RISERS

The risers are fabricated with 1½- to 4-ft.-deep legs. JWP staff notes that the 4-ft. depth — driven by the sections' 62-ft. spans and vibration-dampening requirements — sets a new record for such conditions.