H&H and design partners Roughan & O’Donovan are teamed with BAM Farrans, a joint venture of BAM Nuttall Ltd. and Farrans Construction, to deliver a new double-leaf bascule bridge over the River Yare in Great Yarmouth, England. 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 movable structure is 25.2 meters wide, 68 meters long (center to center of trunnions) and provides 50 meters of navigational clearance. Named Herring Bridge, it will carry two carriageways and two footpaths, which will ease traffic congestion and improve reliability and time of travel.
Detailed design and construction documents were completed on an ambitious schedule for a 2023 opening. Each of the two bascule leaves is actuated by two pairs of hydraulic cylinders in a push-pull arrangement, powered by an energy-efficient closed-loop hydraulic system. The bridge’s structural system consists of twin steel box girders connected by transverse steel plate girder floorbeams and a steel counterweight box. Bridge control is semi-automatic by way of a programmable logic controller (PLC) based system.
After performing shop inspections of the fabricated leaves, H&H staff were onsite for installation as the bascule leaves arrived via barge from Belgium. Construction staging and coordination between the design team and contractor included detailed calculations of the bascule leaves weight and weight distribution for each stage of this highly choreographed installation. Each 770-tonne bascule leaf was carefully lifted and placed by a 1,800-tonne floating crane. Verification measurements of the bascule span trunnion assemblies were performed to confirm alignment prior to rotation in the upright position.