The Queensferry Crossing

May 01, 2018
Forth Bridge Queensferry Crossing under construction
Forth Bridge Queensferry Crossing under construction.

The Queensferry Crossing near Edinburgh, Scotland, is the longest cable-stayed bridge in the world at more than 8,500 ft. It is one of the largest infrastructure projects in Europe, and it benefited from advanced reinforcement planning in 3D provided by the engineers from Leonhardt, Andrä und Partner (LAP) and Allplan Eng.

The challenge

Transport Scotland’s consultants from the Jacobs Arup joint venture were not given an easy task in developing a concept for the new bridge, which had to be an equal to the world cultural heritage Forth Bridge. 

A main span width of 2,132 ft stretches between 689-ft-high reinforced concrete towers. The spans of the side sections are 732 ft, and the foreshore bridges are 341 ft. Of the three pylons, the middle pylon proved to be particularly challenging. In the case of traditional cable-stayed bridges, the center pylon is back-anchored via rigid side sections located at the edge.

The solution

The planners achieved the back-anchoring of the central pylon by overlapping the stay cables by 479 ft in the middle of the respective section. This special feature of the structure achieved the necessary stabilization and allowed for a sophisticated and visually appealing bridge construction.

The reinforced concrete pylons taper from the upper edge of the foundation at 46 by 52 ft to the slim 24-by-16-ft tip. To plan the pylons, LAP created a complete 3D reinforce­ment model with Allplan Eng. The reinforcement of the individual pylon segments had to be placed precisely in the space due to the upward-tapering cross-section. This method placed high demands on the CAD software, which is why LAP also relied on Allplan Eng. for the reinforcement and design planning.

The Queensferry Crossing is the largest bridge for which 3D reinforcement planning was entirely created using Allplan Eng. Deadlines and costs were met because of the accurate and collision-free planning. Queen Elizabeth II officially inaugurated the bridge on September 4, 2017.

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