News: Bahrain bridge move huge engineering feat
Story by Nathan Herring
WINCHESTER, Va. - Middle East District engineers and contracted personnel, moved an approximately 450-foot long, 2,650 metric ton tied-arch suspension bridge across a major roadway at the Naval Support Activity Bahrain, located in the capital city of Manama.
The move, which took place in late-January, was the first of its kind in the Middle East.
The flyover bridge, another name for an overpass, was moved roughly 270 yards across the Khalifa Bin Salman Causeway, which is equivalent to the size and traffic use of the Washington Beltway in Washington, D.C. The bridge now connects Naval Support Activity Bahrain, known as NSA I, to the U.S. Navy port facility, known as NSA II.
In order to move the massive bridge, self propelled mobile transports were used. These machines, two twelve axle units on each corner, lifted the bridge at its bearing points and safely moved it onto pre-constructed abutments.
Before the move, support beams were installed at each end and the bridge was suspended from the beams using two-inch diameter high-strength rods, eight at each end. In addition to the support beam installation, a roadway analysis was completed on the causeway to ensure that the pavement could withstand the weight of the bridge, which weighed more than 3,000 metric ton once the beams were installed.
It also took about two hours to place concrete pads that protected underground utilities and remove the median, said Roger Thomas, chief of business operations division.
During the move, each pair of mobile transports at opposite ends of the bridge was manually controlled and each set of wheels, 48 sets on each transport, could be adjusted and turned individually. This had to be done before each segment of the move.
An operator had to go into a computer and set all of the axles for that particular transport, said Roger Thomas, chief of business operations division.
“It took a lot of set-up time and each move had to be carefully calculated,” said Mike Allen, structural engineer.
The move was not without complications. A number of mechanical issues caused unexpected delays, including two broken hydraulic cylinders that had to be replaced in one of the transports.
“We had such a high caliber group that could plan for and overcome problems,” Thomas said. “If we didn’t have that, we wouldn’t have been successful.”
One of the greatest concerns for engineers was to not place a lot of stress on the bridge.
“Concrete doesn’t bend,” Thomas said.
In order to monitor stress level, engineers used both hi-tech and lo-tech methods. They monitored tire pressure of each wheel using computerized sensors. Engineers also attached laser pointers to one end of the bridge on each side and four-inch diameter targets to the other end. They did the same across the width of the bridge on each end as well.
“As the bridge moved, they monitored the lasers to make sure they stayed inside the targets at all times,” Allen said. “The laser pointers were especially needed during turning.”
In addition to the special precautions, the bridge itself was designed to withstand the rigors of the move, which took about a year to plan, Thomas said.
The move took place overnight and traffic was rerouted during that time. The Ministry of Transportation in Bahrain gave engineers a seven hour window to complete the move, but extended the time frame due to the mechanical issues. The move was completed around 8:45 a.m. and the road reopened to traffic around 9 a.m.
The flyover bridge was built off-site and moved into place to avoid a prolonged road closure, which could have lasted months instead of hours.
Currently, personnel need to travel up to 60 minutes through heavy traffic in the city to reach the port facility, which is currently undergoing expansion, Allen said.
“NSA Bahrain has significantly expanded with the ongoing construction of our port facility,” said Capt. David J. Meron, commanding officer of NSA Bahrain. “This bridge will make it possible for emergency vehicles, pedestrians, and electric carts to quickly and easily transit between facilities, enhancing our ability to support our tenant commands, their missions and ongoing operations.”
Allen was relieved to see the bridge moved into place.
“It was vindication for all the tedious planning and pre-work to finally see it in place,” he said.
Thomas credits the team for the success of the move and says he was glad to be a part of it.
“There were a lot of moving parts in this project,” he said. “It’s a once and a lifetime feat and the pinnacle of an engineer’s career to even be a small part of this project.”