Engineers saw the new Memorial Causeway bridge "see saw" in high winds, officials say.
By JENNIFER FARRELL
Published April 15, 2004
[Times photo: Kinfay Moroti]
A diver working for PCL Civil Constructors maps underwater cracks on a pylon under the new Memorial Causeway Bridge on Wednesday.
CLEARWATER - A section of the new Memorial Causeway bridge supported by a cracked concrete column was seen shifting in heavy winds this week, leading the U.S. Coast Guard to stop boat traffic under the bridge for more than six hours.
The state Department of Transportation said it asked the Coast Guard to keep boaters away from the construction site Tuesday morning as a precaution. Later, an engineering consultant for the bridge builder said the roadway was built to withstand winds of as much as 100 mph, officials said.
Still, crews began installing beams to secure the swaying span on Wednesday.
DOT spokeswoman Marian Scorza called the agency's request to close the Intracoastal Waterway "purely precautionary."
It is the first time in memory the Coast Guard has taken such a step for a bridge under construction, said Petty Officer Robert Suddarth. Depending on wind conditions, the agency might do it again, he said. "I don't know how real the concern was that the bridge was going to come down, but we didn't want to take the chance," he said. "It was really just a safety issue. If something were to happen, we wouldn't want a boat out there."
PCL Civil Constructors, the Canadian firm building the bridge, could not be reached for comment.
Engineering experts said it is difficult to assess the significance of the motion in the bridge without reviewing detailed designs, but the issue is the latest in a series of setbacks for the $69-million bridge.
It was was planned as a showpiece but has been marred by construction blunders and a flawed redesign. Six of 16 concrete columns are cracked, including those that hold up the highest and longest spans over the harbor's main channel.
Engineers are studying how to fix them, and the DOT has said at least four columns may have to be demolished and rebuilt along with the roadway above.
In February another section of the roadway fell 7 inches after temporary scaffolding buckled. Crews are working to buttress the faulty scaffolding so they can figure out how to repair the roadway.
In December 2002, crews used explosives to demolish an 80-foot section of the bridge span after it fell a foot and twisted when another section of scaffolding failed.
This month, a DOT report showed that all the spans have minor cracking, the result of a revamped engineering design that didn't account for high bending forces during construction.
Such a track record made state officials extra cautious about the bridge moving in the wind, Clearwater City Manager Bill Horne said. "They were just being overly cautious, I think," he said. "I think they're being very mindful about what could happen."
Engineering crews working for the state noticed the roadway "see saw" up to 2 inches Monday morning before lunch, according to Bill Adams, a senior project engineer with Parsons Brinckerhoff Construction Services, Inc.
As winds gusted to 50 mph, one span over the main channel nearest the existing bridge was seen shifting up and down, he said.
"It was noticeable," Adams said. "We didn't know how much higher the winds were going to get."
Because of weather forecasts for high winds in the area, crews from Parsons Brinckerhoff were watching the bridge around the clock, Adams said. He said they noticed the bridge begin to move when gusts reached 35 mph. By about 5:30 a.m. Tuesday, winds began picking up again, and the DOT contacted the Coast Guard when speeds reached 38 mph, according to Adams.
Coast Guard and Florida Fish and Wildlife Conservation Commission crews patrolled the area from 5:45 a.m. to 11:55 a.m. to keep boaters from passing under or too near the bridge.
Adams and Scorza said they were unable to say whether the bridge had been damaged further by the wind gusts and they declined to address questions about its strength.
Lawrence Kahn, a professor of civil engineering at Georgia Institute of Technology contacted by the St. Petersburg Times, said it is impossible to know if a 2-inch shift is excessive without reviewing detailed designs. For instance, the Golden Gate Bridge in San Francisco was designed to sway up to 15 feet, he said.
Adams said crews will continue to monitor the bridge, but forecasts have called for decreasing winds.
In the event winds pick up again, Suddarth said the Coast Guard may take action.
A diver working for PCL Civil Constructors maps underwater cracks on a pylon under the new Memorial Causeway Bridge on Wednesday.
