3.4.4 MSS TRINITY
Trinity, the 1,700-tonne, 157-metre long, movable
scaffold system (MSS), built the central part of the
carriageway. The machine – essentially a giant
concrete mould – constructed 11 road deck spans,
creating one seamless structure. Approximately
14,200m 3 of concrete was used during construction of
the central road deck section, measuring a total
length of around 715m.
The MSS was specially made for the Mersey Gateway
Bridge project. While most machines of this kind
typically only build bridge spans of up to 60m, Trinity
was specifically designed to be able to cast spans of
up to 70 metres.
Figure 17: Trinity starts work
With its work done, and with sustainability as a key
objective of the whole project, Trinity was dismantled,
reused and recycled. It took construction teams
around two months to take the machine apart as they
comprised approximately 1,200 components, 3,000
actual parts, and over 60,000 bolts.
The main element of the MSS Trinity, the steel
structure, is to be transported to Slovakia, where it is
planned for re-use in the construction of a bridge in
Bratislava. The casting cell will be recycled separately
as this particular section was a bespoke piece
specifically designed for the Mersey Gateway Bridge.
Figure 18: Final concrete pour
3.4.5 MSS WEBSTER
MSS Webster was specially designed and built to
construct the curved viaducts leading to the main
bridge. The machine was named by Halton
schoolchildren after local engineer John James
Webster who built the Widnes Transporter Bridge.
Webster is 157m long and 8m high. It is 22m across at
its widest point and weighs 1,700 tonnes. In total it
constructed eight spans of the South approach
viaduct to create its central box section using 9,205m 3
of concrete.
logistics. Additional pumps were used on top to give
access to the concrete. After completion of the works
MSS Webster will be dismantled and also transported
to Bratislava to join its fellow MSS Trinity, which is
being used to build a new bridge over the River
Danube.
Webster was assembled piece by piece approximately
12.5m above the ground around the first pier of the
South approach viaduct, involving the project’s
biggest ever crane lift - it was lifted into place with
two giant cranes, one crane weighing 700 tonnes and
the other 750 tonnes, working in tandem to hoist into
place the 77m-long, 240 tonne main girder section.
Operation of the MSS Webster above the Manchester
Ship Canal required extra planning and a change in
3/2017
Figure 19: Webster above the Manchester ship canal during the
concrete pour