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Construction Corner - Using robots for bridge work

0 227 Infrastructure

by Journal Of Commerce last update:Oct 9, 2014

Problems in getting experienced, qualified welders has forced the builder of the new Tappan Zee bridge, north of New York City, to turn to robotic welders.
Korky Koroluk
Korky Koroluk

A handful of welders and their robot equipment have been on the job for several weeks now, welding together steel piles before they are driven into the bed of the Hudson River.

Some of the largest piles are eight feet in diameter, so welding them can take a long time.

But, the robotic welders work faster — sometimes twice as fast as manual welders, and might be doing a better job.

And, depending on the size of the pile, a dozen or more robots can be attached to a track and circle around the pile as they weld.

Four-man crews monitor the robots as they work, and inspect the finished welds.

The robotic welders came from Wilkinson Technologies, in Lafayette, La., a firm that specializes in using robotic welders on large pipes for caissons for off-shore oil rigs, drilling platforms and bridges.

The Tappan Zee bridge replacement will cost $3.9 billion. It will be a twin-span, cable-stayed structure alongside of the original cantilever bridge built in 1952-55. That one cost only $81 million, with a projected service life of 50 years.

The replacement is being built under a design-build contract which gives Tappan Zee Constructors (TZC) financial incentives for finishing the job early and under budget. TZC would be held responsible, however, if the project goes over budget. There are also stiff penalties if the bridge isn’t finished on time in 2018.

Across the country, in Oakland, Calif., bridge welders have been in the news for the last several years, as Caltrans, the state’s transportation department, wrestled with welding faults in box girders for the new Bay Bridge suspension span.

The girders were prefabricated in China, and there have been stories for several years of deficiencies in the welding and inspection, plus an obstinate refusal on the part of the Chinese contractor to do much about the problems.

The Sacramento Bee has followed the story closely. Now, with the $6.5-billion structure in service, four years late and $3.9 billion over its 2003 budget, the paper has taken a long look at the project’s problems.

Not least among them, was the fact that the Chinese company hired to build the box girders had never built a bridge, or even parts of a bridge. The Shanghai Zenhua Port Machinery Co. (ZPMC) Ltd., is a maker of giant cranes for container ports.

Caltrans agreed to use ZPMC, because it had a reputation as fast and cost-effective, offering savings of about $250 million compared to the competing bidder.

Trying to hurry the project along, Caltrans allowed cracks or suspect welds. Two senior engineers challenged quality assurance practices. One was reassigned to other work; the other’s contract was allowed to lapse.

The Bay Bridge oversight committee put pressure on Caltrans to speed up the job, despite evidence that quality control had broken down.

Tony Anziano, chief executive for the project, is a lawyer, not an engineer or a project manager.

He made at least 64 visits to Shanghai trying to sort out the quality control mess. While in the city, he stayed at one of the city’s most luxurious hotels, at $470 a night.

His travel expenses during the period were more than $300,000.

To prepare its report, the Sacramento Bee reviewed more than 100,000 pages of construction records and e-mail. It gained access to at least one engineer’s work diary. In the end, its report runs to more than 5,000 words, with many photographs.

Many experts have predicted that the faulty welds will lead to expensive repairs in the future. It seems likely, then, that this investigative report is likely not the end of the story.

Korky Koroluk is a regular freelance contributor to the Journal of Commerce. Send comments or questions to editor@journalofcommerce.com.

last update:Oct 9, 2014

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