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Cracks could shorten bridge's life

Experts agree the Clearwater structure probably won't collapse, but they fear it could age prematurely.

By JENNIFER FARRELL
Published February 19, 2004

CLEARWATER - Hairline cracks discovered in concrete supports for the new Memorial Causeway Bridge could shorten the structure's life span, experts agreed Wednesday.

The cracks, found in four of its 16 supports, probably won't cause the $69.3-million bridge to collapse.

But a chief fear is saltwater intrusion, which could reach the columns' interior steel reinforcements, corrode them and cause the bridge to age prematurely.

"That's the kind of thing everybody should worry about, whether these cracks are going to corrode," said Henry Petroski, a professor of civil engineering at Duke University.

One cure for the cracks is filling them with epoxy, a procedure the same builder used last year to fix flaws on another concrete bridge project in Sarasota.

The cracks extend about 6 inches into the columns, as far as the first layer of steel reinforcements, state Department of Transportation engineers said. That leaves the columns vulnerable, said Petroski, who studies bridge failures.

"That's a major problem for a concrete bridge," said Petroski, who authored Engineers of Dreams, a book about great bridges.

PCL Civil Constructors, the Canadian contractor building the state project, has hired three engineering consultants to find a solution.

PCL vice president Jerry Harder, who works out of the firm's Tampa office, said Wednesday that he expects answers within a week.

Preliminary results show one of the columns suffered more damage than the others, Harder said.

"The other three are really pretty minor," he said.

The cracks were caused by flawed construction engineering that allowed the bridge spans to tilt too far out of balance when they were being poured, Harder said. Temporary supports meant to hold the roadway in place weren't designed properly, he said, and too much weight placed on the spans forced the permanent support columns to crack. "Concrete is a wonderful product," he said. "But it's brittle."

PCL Civil Constructors Inc. has rarely been forced to defend its work.

One of the leading general contractors in North America, the firm builds a range of projects - from office towers and airports to roads and bridges and industrial mills - with few complaints.

But locally, the firm has struggled at times.

In Clearwater, its Memorial Causeway Bridge project has suffered three structural flaws in 14 months.

DOT officials said Tuesday that the four columns supporting the bridge's tallest and widest span are so riddled with cracks they may have to be demolished and rebuilt.

Engineers are studying whether that section of the roadway might have to come down.

Another part of the roadway fell 7 inches this month when scaffolding underneath it buckled. In December 2002, crews used explosives to drop an 80-foot section of the bridge span after it fell a foot and twisted when a section of scaffolding failed.

In Hillsborough County, problems occurred with supports for an elevated bridge under construction in the median of the Lee Roy Selmon Crosstown Expressway. Inspectors discovered PCL did not build the columns to specifications, said PerryDawn Brown, spokeswoman for the Tampa-Hillsborough Expressway Authority.

But an engineering review found that the mistake didn't reflect unsafe work, Brown said. Rather, PCL had installed more steel reinforcements than were called for in the bridge plans, she said.

"They've done an outstanding job," Brown said. "We don't have any complaints."

In Sarasota, the state stopped work last year on a section of the John Ringling Causeway Bridge after inspectors found cracks in the concrete, according to the Sarasota Herald-Tribune.

PCL used epoxy to fix those breaches, Harder said.

In Clearwater, he said, some of the cracks are too small to be fixed with epoxy.

John Fisher, a professor emeritus of civil engineering at Lehigh University in Bethlehem, Pa., agreed that corrosion is a serious concern, but he said the problem is fixable.

"Those type of cracks are dealt with pretty well all the time in repairs," he said.

It is unclear whether epoxy alone could fix the problems in Clearwater. DOT officials must approve whatever solution PCL proposes.

PCL will cover any costs related to the problem, and the firm might tweak its methods before finishing the bridge, Harder said.

"When it's done," he said, "it'll be done right."

- Times researcher Kitty Bennett contributed to this report. Jennifer Farrell can be reached at 727 445-4160 or farrell@sptimes.com

[Last modified February 19, 2004, 02:00:25]


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