The new Mersey Gateway Bridge, located approximately 15 miles south-east of Liverpool has a total length of 2200m, with a cable stayed section of 1000m over the river Mersey, divided in four spans of 181, 294, 318 and 205m. The location of the three towers is conditioned by the environmental constraints and their height is different. The North approach viaduct has a total length of 700m divided in 11 spans with a typical span legth of 64m, while the total length of the South approach viaduct is 500m divided in 8 spans of 70m. The deck has no intermediate expansion joints in the whole length and the fixed point in placed in the central tower, which is monolithically connected with the deck.
The deck is a post-tensioned box girder with a depth of 4.60m. The width of the bottom flange is 7.80m and the webs are inclined 45 degrees. The total width of the deck in the cable stayed section is approximately 34m and variable in the approach viaducts, reaching a maximum of 43m close to the North abutment. The deck has transverse ribs spaced around 6m.
The deck of the approach viaducts is built in three stages: in the first one, the bottom slab, the webs, part of the top slab and the section of ribs between webs are cast with Movable Scaffolding System; in the second one the top slab is completed in the section between webs, and the cantilevers are cast with a form traveler in the third stage.
The work done by FHECOR includes: Tender Design and Detailed Design of the approach viaducts superstructure (DJV with Flint&Neill/COWI). Design and ICE of temporary elements.