The new Queensferry Crossing and the myth of the never-ending task of ‘painting the Forth Bridge’
When you have a bridge that is regularly closed to lorries due to safety fears in high winds, then you have a problem.
When that bridge carries a crucial road connecting Edinburgh to Fife, it’s quite a serious problem.
And the solution is a real feat of structural engineering.
This news item may have escaped your attention because it hasn’t received much coverage south of the border. But later this month, a new bridge will open across the Firth of Forth.
The Queensferry Crossing is the longest three-tower, cable-stayed bridge in the world. It’s a 2.7km (1.7 mile) structure and the innovative design makes the bridge stronger, meaning the towers and the deck can be slimmer and more elegant.
Designed to replace the old Forth Road Bridge, once fully open it will have motorway status with a 70mph speed limit and no pedestrian access.
The old Forth Road Bridge will then be used only for public transport, cycling and walking.
As well as looking stunning, the new bridge has impressive wind-shielding, with 3.5m-high baffle barriers to break up and deflect gusts of wind. Tested in a wind tunnel and on road sections near the bridge, project officials are hopeful that the barriers will mean the bridge never needs to be closed.
The structure rises up 207m above high tide (683ft), which is about the same as 48 double decker buses piled on top of each other.
At a cost of £1.4 billion, this is one of the biggest civil engineering projects undertaken in Britain in recent years, and has created over 1,000 jobs.
Once the towers were put in place, engineers used boats and cranes to lift the decks into place, in an impressive feat of engineering. The bridge features 23,000 miles of cables, 150,000 tonnes of concrete and 200 planes’ worth of steel.
After it opens on 30th August, it will close again to allow pedestrians the once in a lifetime opportunity to walk across it, before it becomes a two-lane motorway.
And what of the third bridge that crosses the Firth of Forth?
It’s an often quoted myth that once painters finish work on the original Forth Bridge (the rail bridge) they have to start painting it all over again.
But it turns out it was restored and painted with a new coating back in 2011, and it won’t need to be painted again for 20 to 25 years.
So as of the end of this month there will be three fully functioning bridges crossing the Firth of Forth, and not a single paintbrush in sight.
If you have bridges to build, or need help with any other structural projects, please don’t hesitate to get in touch.