In April 2018, work completed on the Wirral Dock Bridge replacement.
Located in the United Kingdom, the 30-metre bridge was designed with a single lift point on the embankment of the River Mersey. To allow for the weight of the bridge, and to reduce the size of the counterweight, the constructors used MagnaDense concrete.
The ‘A’ Bascule bridge
The project is located at the site of the well-known Four Bridges, connecting Birkenhead with Wallasey. With a construction dating back to the 1930s, the bridges were outdated and in need of replacement. The new ‘A’ bridge replaces the old bridges and allows vessels to access Wirral docks.
The ‘A’ bridge is known as a bascule bridge, and functions as a replacement for the earlier constructions. They constructed the bridge using stainless steel, a pre-cast composite deck and two hydraulic cylinders, lifting the bridge into the air from one location. To allow for the construction of new foundations, the bridge now lifts from the opposite side of the river. Constructed by Dawnus Construction, the pre-constructed steel and concrete bridge was floated into its location via the river.
All bascule bridges require counterweights to ensure stability and have two large hydraulic cylinders to operate. Due to the requirement for the entire 30-metre bridge to lift from one side of the river, the counterweight needed to achieve a density of 3.2 t/m3. To attain this using standard concrete would have a large steel box and an enormous structure.
Reducing costs with MagnaDense concrete
Engineering company Ramboll decided on the use of a counterweight constructed using stainless steel and filled with MagnaDense high density concrete. This allowed for smaller weight and thus reduced the overall size of the counterweight and steel box. The use of high density concrete provided the project with significant cost savings due to the reduction in the size of the stainless steel counterweight box and surrounding structure & foundations.
We supplied 350 tonnes of MagnaDense to the project, which was pumped 40 metres into the counterweight box already in place on the bridge. The complete project took 34 weeks to complete, with the bridge opening to the public in June 2018.
Alongside the cost savings achieved, the counterweight also provides environmental benefits. The use of the counterweight on the Bascule bridge acts as a hydraulic aid, providing additional lift when the bridge is rising or returning to its position. This conserves vital energy because they do not require the hydraulic cylinders for the same length of time.
The Wirral Docks project
The overall project involved the decommissioning and removal of two of the bridges, with the modernisation of an additional bridge, named ‘C’; formerly a bascule bridge, it was updated to a flat deck bridge in the refurbishment. Other works in the project included the updating of pedestrian and cycling areas. The overall project cost in the region of £7.5 million.
International bridge projects
For the construction of many bridges MagnaDense concrete is used for either:
- Pillars / pylons
Some examples of bridges using our natural MagnaDense are:
- Great Belt bridge – Denmark
- Samuel Beckett bridge – Ireland
- Kallo Sluice bridge – Belgium
- Öresunds bridge – Sweden/Denmark
We have a FREE detailed Case Study available for some of these projects upon request. Contact your region sales manager for more information.