H&H, in partnership with Roughan & O’Donovan, is designing this new double-leaf bascule bridge over the River Yare in Norfolk County, England, a design-build project being led by a joint venture of contractors BAM Nuttall and Farrans Construction. The Norfolk County Council prioritized this infrastructure investment to attract investment in the area, create jobs, and improve the quality of life of the community. The new bridge is 25.2 meters wide, 68 meters long (center to center of trunnions), and will carry two carriageways of vehicular traffic in each direction along with two footpaths. This vital connection will ease traffic congestion and improve reliability and time of travel.
H&H is responsible for the detailed design of the bascule leaves along with the counterweights, trunnions, live load shoes, span locks, hydraulic operating machinery, and electrical control systems. The movable span structural system consists of twin steel box girders with an integrated orthotropic steel deck and steel cross girders.
Each of the two bascule leaves is actuated by two pairs of hydraulic cylinders assembled in a push-pull arrangement. All cylinders are powered by a closed-loop hydraulic system. A pair of fixed displacement pumps coupled to 110kW electric motors powers each leaf. Each pair of cylinders is connected to the structure at a longitudinal operating girder. The push-pull of the cylinder strokes imparts the rotation to operate each of the bascule leaves.
Bridge control is semi-automatic by way of a programmable logic controller-based system. The speed and direction of bridge operation are controlled by varying the rotational speed and direction of the pump motors that power the hydraulic cylinders. This is all accomplished using variable speed drives.
The final design was completed in March 2021, and construction is underway.
