The Queensferry Crossing is one of the most striking engineering icons of the twenty-first century. It is the UK’s tallest bridge and the world’s longest three-tower, cable-stayed bridge. Linking Edinburgh with the county of Fife it stands proud alongside its illustrious neighbours, the world famous Forth Bridge and Forth Road Bridge.
Addressing the official opening ceremony on 4th September 2017, 53 years to the day after officially opening the Forth Road Bridge, Her Majesty the Queen said "The three magnificent structures we see here span three centuries, are all feats of modern engineering and a tribute to the vision and remarkable skill of those who designed and built them."
The Queensferry Crossing provides resilience to the strategic road network on the east coast of Scotland and enables essential maintenance works to be carried out on the existing Forth Road Bridge, which is now used by pedestrians, cyclists, emergency services and public transport.
Scottish Council for Development and Industry Chief Executive, Mark Bevan commented: “The Queensferry Crossing is a key addition to Scotland’s transport infrastructure which will safeguard and strengthen Scotland’s economic prosperity. The problems experienced with the existing bridge have highlighted why this new infrastructure was necessary to provide resilient connectivity for people and goods on this major artery of our economy. We strongly supported the building of a new crossing and will continue to engage with our members on the future mobility needs of the Scottish economy. Everyone involved in the opening of this majestic addition to the bridges over the Forth should be proud of their achievement, and we are sure it will continue to be inspirational for those who use and visit it, especially those who would like to develop the skills to meet our next infrastructure challenges.”
Stay cable design
One of the most striking features of the new crossing is its overlapping stay cable design. This beautiful cable configuration provides extra stability to the structure, and the Center Tower in particular, facilitating the slender design of the towers. More on the cable design.
Suspended by these cables 50 metres above high tide, the main deck offers 4 lanes of wind protected traffic, plus two hard shoulders. Each of the deck sections was fabricated in China before being shipped to the Forth estuary to be fitted out prior to installation. More on the deck.
At up to 210 metres high, the 3 slim towers make the Queensferry Crossing the tallest bridge in the UK, and 50 metres higher than the earlier road bridge towers. They were constructed in stages using an innovative climbing formwork system. More on the towers.
The geology of the Forth estuary is complex and called for different approaches to the foundations of each tower. All 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. More on the foundations.
As well as creating an iconic structure, which has come to represent the modern progressive Scotland, the bridge facilitates active & public transport and has reduced emissions through improved traffic flows. Reducing carbon during design and construction was also an important focus. Through challenging the design and employing innovative approaches, many tonnes of carbon have been saved
During the detailed design of the scheme Ramboll identified that the Ferrytoll Viaduct on the approach to the northern end of the main crossing could be re-engineered to offer significant benefits in cost, programme and embodied carbon. The original design utilised a much longer viaduct however we were able to show that by some minor changes to alignment we would be able to replace a significant proportion of the concrete structure with an embankment formed from site won material. This change simplified construction, reduced traffic disruption, reduced construction materials (saving 7000 tonnes of embodied carbon) and removed the lorry movements & its associated emissions that would have been required to dispose of the embankment material off site.
Offsite Construction, Onsite Assembly
Offsite construction, onsite assembly techniques were used throughout the Queensferry project. The factory environment in which the 25m to 30m diameter circular steel caissons were fabricated to the steel main deck sections before being lifted into place 50m above the Firth of Forth to the sign and signal gantries used to manage traffic flows around the Crossing minimised embodied carbon. These factory fabricated components were also installed with all flooring, fencing and electrical equipment prior to erection over the road which also improved quality and reduced disruption during construction and into operation.
Predictive Asset Maintenance
During the design of the Queensferry Crossing the opportunity for a new proactive predictive approach to asset management was developed. Through the installation of sensors across the structure it has been possible to create a digital twin of the Crossing. This digital twin takes data from the sensors and provides real time data on its structural health. It also enables its performance under normal conditions to be modelled alongside emerging trends or anticipated changes in loading to predict problems before they happen. This not only reduces operational costs and enables maintenance work to be planned well in advance, it ensures work is only undertaken when necessary, thus reducing disruption to the Crossing’s users and associated carbon.
Three centuries of engineering innovation
The Queensferry Crossing sits within a beautiful bridgescape representing three centuries of engineering innovation. The Forth Bridge was built in 1890 and was the first steel bridge and longest cantilever bridge span in the world at the time. Its iconic design was recognised in 2015 when it was made a UNESCO world heritage site.
The Forth Road Bridge, a classic suspension bridge was opened in 1964. At the time, it was the longest suspension bridge outside of the USA. Although a major feat of engineering at the time, the bridge was no longer deemed viable as the long-term main crossing over the Firth of Forth in 2006, due to the cabling showing signs of corrosion. As a result construction on the Queensferry Crossing began in 2011.
The stunning Queensferry Crossing forms the centrepiece of a major upgrade to the important cross-Forth transport corridor in the east of Scotland. The 22km footprint includes major improvements to the surrounding road networks and connects the M9 and M90 together for the first time. The project also integrates smart motorway traffic management technology, the first such implementation in Scotland.
Ramboll is proud to have led the Design Joint Venture (DJV), which includes Sweco and Leonhardt Andra and Partners. The DJV worked for main construction contractors Forth Crossing Bridge Constructors (FCBC), a consortium of Hochtief, Dragados, American Bridge International and Morrison Construction, helping deliver the crossing and surrounding road approaches.
Peter Curran, DJV and Ramboll Project Director for Queensferry Crossing commented “Working on a project of this scale and importance is a real privilege. We have been working on the Queensferry Crossing since 2009 and it has been both a challenging and rewarding experience. We have worked hard in pushing the boundaries of innovation in order to develop a competitive tender design and have subsequently continued our endeavours during the construction process in close collaboration with the Contractors and Clients teams in order to optimise its delivery. It really is awe-inspiring to look out onto the Firth of Forth and see the contribution we have made to such an amazing bridgescape”.
The project to design and construct the bridge has been recognised within the industry for its innovation and efficient delivery. Already the project has collected the following major awards.
- Chartered Institution of Highways & Transportation (CIHT) – Major Project award winner
- Ground Engineering – Project of the Decade, voted by Ground Engineering readers
- Scottish Transport Awards – Outstanding Project in a Generation
- Construction News – Project of the Year, >£30m
Quote from Mark Bevan reproduced courtesy of Transport Scotland.