Authorities say a 950-ton pedestrian bridge that collapsed onto a six-lane highway killing at least six people had undergone a “stress test” just before and the cables were being tightened when it pancaked onto traffic below.
After hours of searching for possible survivors amid tons of rubble, Miami-Dade Police Detective Alvaro Zabaleta said Friday that the operation “has turned from a rescue to a recovery operation.”
At least six people were killed in the accident Thursday afternoon. Four were found dead at the scene, and at least nine others were injured and taken to a hospital.
The $14.2 million pedestrian bridge was lifted into place Saturday and scheduled to open in 2019 to provide safe passage over Southwest Eight Street, also known as U.S. Highway 41, between the community of Sweetwater and the campus of Florida International University.
National Transportation Safety Board chairman Robert Sumwalt III said a team of specialists have started investigating the collapse.
Miami-Dade Mayor Carlos Gimenez said one factor in the accident may have been the stress test that had just been conducted before the main span gave way.
Sen. Marco Rubio, R-Fla., who had just left the scene before the accident, tweeted that cables that suspend the bridge had loosened and “were being tightened when it collapsed.”
Amjad Aref, a researcher at University at Buffalo’s Institute of Bridge Engineering, told the Miami Herald that stress testing normally involves placing carefully calibrated weights on the span and measuring how the structure responds to ensure it’s within safe parameters.
One part of the bridge, which spanned 174 feet, came down on the driver’s side of a car, killing the female driver but not the passenger, said Jenna Mendez, a sergeant with the Sweetwater Police Department. Another part fell on the hood of a car with a husband and wife inside — safe.
“They said they felt everything on their feet, but they were able to pull back and get out of the car,” Mendez said. “They were very lucky.”
Rubio, an adjunct professor at the school, noted the pedestrian bridge was intended to be an innovative, “one-of-a-kind engineering design.”
Renderings showed a tall, off-center tower with supporting cables attached to the walkway. When the bridge fell, the main tower had not yet been put in place, and it was unclear what builders were using as temporary supports.
The project was a collaboration between MCM Construction, a Miami-based contractor, and FIGG Bridge Design, based in Tallahassee. FIGG is responsible for the iconic Sunshine Skyway Bridge across Tampa Bay.
FIGG’s statement Thursday said the company was “stunned” by the collapse and would cooperate with the investigation.