Moving a 122.5 m Arch bridge in 7 hours

Bridges are structures built to span physical obstacles, in order to provide a direct passage throughout such obstacle. Some time ago the U.S. navy faced the need to build a bridge in order to connect its existing base in Manama - Bahrain with new expansion properties located on the other side of the Sheikh Khalifa bin Salman Causeway. Initially this seems an ordinary building task; however, an in situ building would have meant to interrupt the causeway and nearby traffic for several days. Thus, it was decided to build the bridge at other location and then move it into place.

Image 1. Construction of the arch bridge over the Sheikh Khalifa bin Salman Causeway
Source: USACE

Moving the bridge

The bridge is a tied up bridge with a total length of 122.5 m and 10.6 m wide.

The bridge has a total high of 21.4 m and a total weight of more than 2650 metric ton.

Image 2. Arch bridge over the Sheikh Khalifa bin Salman Causeway
Source: ASCE

Initially the Army Corps planned to close the causeway some 48 hours in order to allow enough time to prepare the road for the move by removing the curb and median and then subsequently moving the bridge into place. However, Bahrain authorities said that the closure time should be limited to 7 hours.

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.
Image 3. Self propelled mobile transport used.
Source: USACE
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. During the move, each pair of mobile transports at opposite ends of the bridge were 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.

 One of the greatest concerns for engineers was to not place a lot of stress on the bridge. In order to monitor stress levels, 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.

References & Further reading
Bahrain bridge a first of Army Corps of Engineers
Bahrain bridge move huge engineering feat