Industry Sees New Bridge Launching Devices As a Way To Save Time, Money, Disruption.

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Author: Hampton, Tudor

The small, mostly European pool of suppliers offering segmental bridge launchers is crafting custom machines with complex, computerized operation and super-strong lift power. But that technical niche is expected to grow as the 30-year-old technology matures.

"We envision building bridges on the side of the road, picking them up one night and putting them over the top of traffic," says William Nickas, Florida Dept. of Transportation's chief bridge engineer. "It is not far away when you are going to rent specialized equipment to be brought in and utilized one night to avoid six-to-nine months of traffic switches and slowdowns."

That need is driving innovation. Udine, Italy-based DEAL supplied a $1-million, rubber-tire gantry that Zachry Construction Corp., San Antonio, used on the $261-million "High Five" interchange in Dallas (ENR 12/16/02 p. 21). The 70-ton-capacity machine finished setting deck segments over live traffic last summer and the project now is one year ahead of schedule, according to the Texas Dept. of Transportation. "We had to invent that piece of equipment because you couldn't do it with a crane or truss," says Aventura, Fla.-based Riccardo Castracani, North American representative for DEAL, a wholly-owned subsidiary of Rizzani de Eccher S.p.A.

In California, the San-Francisco-Oakland Bay Bridge features four, self-launching erection devices (SLEDs). They lift, hold and post-tension the east span's deck segments, weighing up to 750 tons, in balanced cantilever.

The project's Kiewit Pacific Co.-led joint venture has placed 25% of 452 segments. "We are still building the bridge," says Lorie Holte, segment erection specialist, who declined further comment due to a pending investigation into allegedly faulty foundation welds (see p. 12).

The SLEDS were designed by Guido A. Schwager, president of Schwager Davis Inc. They each weigh 350,000 lb and cost a total of $5.5 million. The diesel-over-hydraulic units operate four hoists, each reeved with a 10-part line of 1-3/8-in. wire rope, for a total line length of 1,600 ft. The units were fabricated in Newfoundland and assembled in Schwager's San Jose, Calif., shop. "The winches are all computer controlled," he says.

On the East Coast, another joint venture, Potomac Constructors LLC, is using two machines called "manipulators" to erect precast concrete pier segments for the Maryland approach of the $2.4-billion Woodrow Wilson Bridge. "We have approximately 200 segments in the air," says Alex Schmalz, Potomac general superintendent of Edward Kraemer & Sons Inc., Plain, Wis.

The $250,000, 22-ton manipulators hook to a 300-ton crawler crane mounted on a barge. Using hydraulic rams, remote controls position the segments for epoxy and post-tensioning.

The manipulators are scheduled by year-end 2007 to lift 472 of 616 segments weighing 45 to 100 tons. The sections are joined at sharp angles to create a 260°, V-pier radius. "We are erecting two segments a day per manipulator, three on a good day," says Schmalz.

Few companies offer such machines and safety is a greater concern after last year's deadly truss collapse at the Maumee River bridge in Toledo, Ohio. "It certainly raised our awareness," says J. David Nardon, vice president of Edward Kraemer & Sons.

But observers see more choices coming in the future. In 1989, concrete segmental bridges were a $500-million U.S. market annually. Today, that market is $5 billion, says Clifford L. Freyermuth, who manages the American Segmental Bridge Institute, Phoenix. "I would think that as the market grows, there is going to be a need for more suppliers," he says.

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PHOTO (COLOR): Picking. Oakland SLEDs are lifting 750-ton segments.

PHOTO (COLOR): Placing. Manipulators are remote-controlled.

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By Tudor Hampton