The GB£1.35bn Queensferry Crossing has been opened by the Scottish Government to replace the Forth Road Bridge as the main road route between Edinburgh and Fife.

Queensferry Crossing

The Queensferry Crossing opened at the end of August. Image courtesy of KlausFoehl/Wikimedia

Linking traffic over the Firth of Forth between Edinburgh, at South Queensferry, and Fife, at North Queensferry, the 13.7m long bridge has taken six years to complete.

Peter Curran, international bridge director at Ramboll, which led the Design Joint Venture (DJV), working for main construction contractors Forth Crossing Bridge Constructors (FCBC) group, said: “We have been working on the Queensferry Crossing since 2009 and it has been both a challenging and rewarding experience.

“I’m immensely proud of the role Ramboll has played in delivering such a landmark structure. We have pushed the boundaries of innovation in its design and have continued working closely with the contractors to optimise its delivery.”

Three towers

At up to 210m high, the three towers, constructed in stages using a climbing formwork system, make the Queensferry Crossing the tallest bridge in the UK.

The overlapping stay cable design provides extra stability to the structure, particularly the central tower.

The stay cables cover a 160m length of the deck at mid-point along the two main spans. In total, there are 288 stays ranging in length from 94m to 420m.

39.8m wide deck

Suspended by these cables 50 metres above high tide, the main deck, with a width of 39.8m, offers four lanes of wind protected traffic, plus two hard shoulders.

The deck was designed using software that calculates loading in all elements of the bridge.

Computer models were created to analyse the whole bridge, with additional three dimensional models for load cases applied to the model to simulate the self-weight of the bridge, various traffic loadings and climatic conditions such as temperature effects and wind.

134 deck segments

The deck is formed of 134 composite steel and concrete segments, made of 110 standard segments, 12 starter segments and 12 approach viaduct north segments.

Each of the deck sections was fabricated in China before being shipped to the Forth estuary to be fitted out prior to installation.

All the tower foundations bear on the top of the rockbed, which eliminated the need for expensive and time-consuming piling onto the hard rock that underlies the whole crossing, said Ramboll.

Steel foundations

The foundations for the North and South towers are founded on 25-30m diameter circular steel caissons sunk to the top of the bedrock some 40-50m below water level.

The DJV included Sweco and Leonhardt Andra and Partners, while FCBC comprised a consortium of Hochtief, Dragados, American Bridge International and Morrison Construction, helping deliver the crossing and surrounding road approaches.