For projects valued between £3 million and £50 million.
Sponsored by SKM (Sinclair Knight Merz).
Impetus for the replacement of Bishop's Bridge came from the need to radically improve vehicle access to Paddington Station to cope with increased passenger traffic from the Heathrow Express service.
The plan was to widen the viaduct to four lanes with a completely new structure. Constraints included buildings either side of the road line and the need to avoid any risk to the railways underneath. A crucial operation was the dismantling of a big truss bridge which, if done in situ, would have required a massive crash deck above the main-line railway and extensive line possession.
The clever response was to hoist the truss and park it 10m vertically from its original position, using strand jacks mounted on four temporary towers. This allowed for new foundations, on to which the major section of new bridge deck could then be slipped lengthways into position after its preassembly on the rebuilt canal/railway sidings/Metropolitan Line section of viaduct. The new bridge thus formed the demolition crash deck for the old truss.
And the main dismantling operation could take place remote from the sensitive main lines by using a multi-wheeled transporter to roll the old structure along the new bridge deck.
The discovery and rescue just before demolition of Brunel's neatly interlocking ironwork at the canal bridge was handled well, with minimal impact on the progress of the job.
Client Westminster City Council Co-promoters BAA and Network Rail Cost £24.6 million Principal designers Cass Hayward, Scott Wilson Contractor Hochtief (UK) Construction