Civils, Utilities & Infrastructure integrated project planning. Precision planning to final execution
Four 900t strand jacks, two positioned at either end of the bridge, were used to take the full weight of the span so that the connection points could be cut.
For safety, lowering of the span was scheduled to occur during daylight hours, when visibility was better. Preparation was critical.
“ Before the initial lift, an‘ eyebrow cut’ was made above the pin to allow a small opening that enabled us to lift the span until we saw daylight,” said Bobby Martija, Mammoet Project Manager.
“ This gave us an opportunity to check the deflection of the bridge and ensure everything was stable. Once everyone was satisfied that all the clearances were correct, the cutting began”.
The night before the lowering operation, a barge was fully equipped with winches, support grillages, and Mammoet self-propelled modular transporters( SPMTs). Once secured beneath the bridge, a tightly managed 36 hour operational window began to lower the span and clear the navigation channel.
The span weighed 2,300 tonnes, a figure estimated from historical records. The engineers added a contingency to ensure the strand jacks had sufficient capacity in the event of a deviation.
The shaft was lowered nearly 50m using 54 strand wires. Because of their long length, it was critical that the correct strand jack configuration be used.
“ We had two ways of setting up the strand jacks. Initially, it was a simple umbrella configuration, with the strand wires resting on the deck of the bridge,” adds Martija.
“ We realized that this would be too time-consuming, with people required to manage and arrange them, so we decided it would be better to pre-coil the wires instead. We used two coilers( one for each strand jack), which we sub-assembled at our yard in Rosharon and brought directly to the site.”
Once the span was safely loaded onto the barge, it was shipped 10 nautical miles to a nearby dock, where it was offloaded and then placed onto supports.
For this phase, 2 x 54 lines of SPMT were used to lift the structure and transport it from the deck. Prior to lifting, the underside of the span had to be reinforced with steel.
Carrying out the welding at the start would have been a challenge and required people working at height. It was far easier and safer to perform this work on the deck of the barge.
Once the supporting steel had been welded to the span, it was driven by SPMTs and placed onto steel supports, ready for decommissioning.
Dependable support for complex projects
The successful removal of the Harbor Bridge center span reflects the strength of collaboration among the Harbor Bridge Project team and Mammoet.
This milestone underscores how coordinated expertise, innovative engineering, and disciplined execution can overcome the challenges associated with major civil infrastructure projects, while protecting workers, the public, and the environment.
Mammoet prides itself on finding the safest and most efficient method to overcome any heavy-lift or transport challenge, and on being flexible if plans change. Its systems and teams work hand in hand with those of its customers, overcoming engineering challenges together so that projects are completed in the best possible way.
Whether it’ s minimizing environmental impact or downtime, or making work environments safer, Mammoet is a dependable partner for complex civil and infrastructure projects. Having experienced engineers and specialist equipment to back this up is invaluable and ensured this bridge span removal was completed safely and on time.
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