A design flaw likely caused the collapse of a huge slab of a concrete canopy inside the long-term parking garage at Tampa International Airport in January, according to an engineering firm's investigation for the airport.
Walker Restoration Consultants found that girders holding up the canopy could not handle small movements of garage columns caused by changes in temperature. Bolts and rods connecting one girder to a column finally gave way, causing a 50- by 150-foot chunk of concrete to crash down.
"Their final analysis was that there was a flaw in the design process," said Louis Miller, the airport's executive director.
Before 2 a.m. Jan. 26, the slab dropped onto a ground-floor area of the garage where returned rental cars are cleaned and refueled. One car was crushed and two were damaged, but no one was injured. The collapse did not affect the structural integrity of the nine-story garage.
Tampa International hired Creative Contractors of Clearwater to design and build the canopy inside the existing garage in 2002.
Creative agreed to make all repairs at no cost and reimburse the airport for its expenses, including about $110,000 to clean up debris. Replacing the collapsed section of canopy and fixing remaining connections to the columns should cost about $300,000, Walker estimated.
The airport should give Creative the green light to start work Friday, said Louis Russo, senior director of planning and development. The company expects the job to take 10 weeks working 12-hour days, six days a week, he said.
No one at Creative was available to talk about Walker's report, which was released Monday afternoon.
The long-term garage was built in two halves with a gap in the middle open to the sky. Airport officials hired Creative to create a canopy that would shield rental car workers on the ground floor from the rain.
That required building the structure over an expansion joint in the garage floor. Like other concrete structures, parking garages expand in the heat and contract in cold.
In the chilly weather Tampa experienced a week before the incident, garage columns connected to either end of the girders could have moved as much as three-eights of an inch in opposite directions, the report said.
Over time, that could cause rods and bolts connecting the columns and girders to weaken, the report said. Walker suggested replacing the current connections with "slip joints" where bolts sit on Teflon pads, allowing them to move with the structure.