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When finished later this year, the St Ann Way Bridge Link at
Gloucester Quays will provide a vital link to Gloucester’s inner ring road and
represent a key stage in the regeneration of the City.
The project is a joint venture between English Partnerships,
British Waterways and the developer, Peel Holdings. The design brief was for a
contemporary styled single span bridge, with an efficient and reliable
electro-hydraulic lift deck, typical of a modern Bascule design. The bridge
would not only serve a practical function in terms of integrating the
development around Gloucester Quays, it would also become a striking waterway
gateway to the historic Gloucester Docks.
Bennett Associates were appointed by lead consultant White Young
Green, to provide the exemplar design for the mechanical, electrical and
hydraulic elements that would form the lifting mechanism for the road bridge.
The bridge is being installed and constructed by Griffiths, who have appointed
Davy Markham to develop and manufacture the exemplar design of the mechanical,
electrical and hydraulic equipment. Rowecord have fabricated and installed the
structural deck.
The bridge is 28 metres long and 15.7 metres wide. The structure
rotates 69° about a horizontal axis to form a 12.5 metre wide, infinite height
navigation channel. Sitting 6 metres above the Gloucester to Sharpness canal,
most boats will be able to pass beneath the bridge.
The deck weighs approximately 200 tonnes with an additional 100
tonnes of counter-weight situated behind the pivot in the tail section of the
bridge. The counter weight reduces the load on the two 420mm diameter bore,
200mm diameter rod lift cylinders which are extended to cause the deck to
rotate. When in the lowered position, the tip of the bridge rests on the
approach span and two tail locks engage at the back of the bridge to secure the
deck in position.
Constructed from steel with white concrete abutments, the bridge
was designed to be extremely low profile in order to preserve the existing views
of the city. The main bridge deck was built in five separate sections and then
welded together once on site. Once the concrete and steel counter weight was
added, the whole deck was launched into place using special jacks and hydraulic
pushing cylinders which slid the deck over the canal.
Bennett Associates’ involvement will continue during the
construction of the bridge in a supervisory capacity. They will be on hand to
ensure that the design is executed as intended and in accordance with the design
drawings and specification documents that they produced.
"One particularly challenging aspect of this project is the
isolation of the main lift cylinders from traffic loads when the deck is in the
lowered position. This has been overcome with additional hydraulic reservoirs
that allow oil to leave the cylinders as the deck deflects" said Michael
Thorogood, Design Engineer at Bennett Associates.
The simple, minimalist design of the bridge, which is due to be
complete by Spring 2008, will also provide access to new cycle and pedestrian
routes being constructed along the canal towpaths. The two canal banks were
joined for the first time in mid-January, as the final section of decking was
put in position.
Costing £10 million, the bridge will improve Gloucester’s
transport infrastructure by linking the inner relief road to the newly completed
south-west bypass. This will provide access to the massive Gloucester Quays £250
million re-development scheme, as well as a variety of other leisure, commercial
and residential projects. The bridge will be paid for by English Partnerships as
a contribution to the regeneration of central Gloucester.
January 2008
For further information, please contact Michael Thorogood at M
G Bennett & Associates Ltd on 01709-373782
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