A recent collaborative effort between transport company Mammoet, Flatiron/Dragados, and the Texas Department of Transportation has accomplished the safe and effective removal of the center span of the historic US 181 Harbor Bridge center span.
Now with the brand-new, 3,300-foot US 181 Harbor Bridge already carrying traffic across the Corpus Christi Bay after opening last fall, work is underway to safely remove the original structure built in 1959. Removing the historic truss-style steel center span as one piece required, according to a Mammoet press release, careful planning and safety considerations.
Flatiron/Dragados coordinated parts of the center span removal including marine operations, construction sequencing, and safety planning, while Mammoet advised on the operation to determine the safest and most effective method.
Ultimately, the team determined a lift-and-lower method to remove the entire 2,535-ton center span was the safest and lowest-impact option when compared to piece-by-piece removal and controlled explosive demolition. Key benefits to this method included fewer workers required to operate at height, a lower environmental impact, more efficient navigation, and faster reopening of shipping lanes.
This process was accomplished using four 900-ton strand jacks positioned in pairs at both ends of the bridge to take the center span’s weight while connection points were cut. This included an initial “eyebrow cut” to check the bridge’s deflection as the lift began to ensure stability.
The shaft was lowered almost 165 feet using 54 strand wires, which were pre-coiled to save time and reduce the number of required workers. The full lowering happened during a 36-hour window after a barge was secured beneath the bridge with winches, support grillages, and Mammoet self-propelled modular transporters.
The successfully lowered bridge was moved via barge 10 nautical miles and offloaded onto supports at a dock, where it will be decommissioned, after the underside the span was reinforced with steel while on the barge deck.
According to TxDOT, the decision to replace the old Harbor Bridge considered many factors, such as the old bridge’s lack of shoulders, steep grade, a high accident rate and an outdated 138 feet of navigational clearance.
The new $803 million US 181 Harbor Bridge is 3,295 feet long between the transition piers and has a center span length of 1,661 feet. The structural profile includes 698 precast concrete box girders, 84 delta frames and 76 pairs of permanent stay cables.
Drivers get three lanes in each direction with a median barrier, shoulders, and a bicycle and pedestrian shared-use path. Larger ships are now able to enter the Port of Corpus Christi with the new bridge’s 205 feet of clearance.
The structure, billed by its developer Flatiron/Dragados as the longest concrete segmental cable-stayed bridge in North America, required a collective 10 million man-hours to complete.
