Forth Bridges: Spanning Three Centuries of Engineering Innovation | The B1M


When the Queensferry Crossing completed, it
joined the Forth Road Bridge and the Forth Rail Bridge as the third striking engineering
icon to cross the Firth of Forth in Scotland. The three bridges – the first completed
in the 19th century, the second in the 20th and the latest in the 21st century – represent
three centuries of engineering excellence. Here, we take a look at the crossings and
discover how each one represents the engineering pinnacle of their day. There has been a crossing route over the Forth
since Margaret Queen of Scotland founded a ferry to take pilgrims north to St Andrews
in the 12th Century. Now almost 1,000 years later, the three crossings
form an important part of Scotland’s transport infrastructure infrastructure. The ferry remained the only way to cross the
Forth until the Victoria era, when the rapid expansion of the railways became the catalyst
for a permanent crossing. Bridging the 1.55-mile span would connect
Edinburgh to Fife and dramatically reduce the rail travel time between London and Aberdeen
from 13 to 8 and a half hours. The resultant bridge, completed in 1890, is
the world’s most famous cantilever and an iconic symbol of Scotland that in 2016 was voted
the country’s greatest man-made wonder. A milestone in civil engineering, the bridge
was the first major structure in Britain to be formed of steel, with the majority of previous
bridges – much like the contemporary Eiffel Tower – constructed from cast or wrought
iron. Designed by Benjamin Baker and Sir John Fowler,
the bridge also furthered the wide-scale adoption of cantilevers as the most effective means
of constructing long-spans. The pair famously demonstrated this cantilever
and central girder principle with the human cantilever at a lecture to the Royal Institution
in London in 1887. As the 521 meter span was almost four times
as large as any railway bridge previously built in the United Kingdom, construction
of the Forth Bridge posed immense challenges. Each of the three main towers is supported
on four separate granite foundations, constructed within iron caissons. From these towers the
arms of the bridge were extended outwards. This demonstrated the buildability of a cantilever
system as construction takes place by building out from one support using no temporary support
structure. the bridge’s structure supported itself and provided a platform for the workmen. In total 50,000 tons of steel were used in the
superstructure, held together with over 6,500,000 rivets. When it opened in 1890 the Forth Bridge had
the world’s longest single cantilever span. It is still in operation and now carries 200
trains every day. In 2015, the bridge was designated a UNESCO World Heritage site. The rail bridge would remain the sole crossing
over the Forth for the next 70 years, and it was only the rise of a different form of
transport – the car – that prompted the development of a second bridge. While the first proposals for a road bridge
were made in 1923 it wasn’t until the 1950s that construction on a crossing actually began. Like its older sister, the Forth Road Bridge
is itself a cutting-edge piece of engineering. The suspension bridge was the largest in Europe
when it completed and including its approach viaducts stretches for over a mile and a half. The 1,006 metre main span is supported by
two a 59 cm think main cables, each made up of 11,618 wires. In total 30,800 miles of wires were aerially
spun back and forth across the estuary to build up the main cable using a method that
was new in Europe. To up-skill operatives in this new technique, a dedicated new training school was set up in South Queensferry. The Forth Road Bridge opened to traffic in
1964 and was designated a Category A listed structure in 2001. Unlike the rail bridge, the Forth Road Bridge
has not stood the test of time. Corrosion and increasing traffic loads led to the towers
being strengthened in the 1990s and the 768 hanger ropes being replaced in 2000. Despite these renovations and significant
investment, in 2007 a new bridge was commissioned. Billed as the largest Scottish construction
project “in a generation”, this new bridge – the Queensferry Crossing – now stands
proudly alongside its illustrious neighbours. The striking piece of engineering is the tallest
bridge in the UK and the longest three-tower, cable-stayed bridge in the world. It largely replaces the existing road bridge, is expected to carry 24 million vehicles each year and will remain open in all weathers. Learning from the previous bridge, the Queensferry
Crossing has been designed with longevity in mind. Key to this is the fact that each of the individual
cables can be replaced as part of the bridge’s regular maintenance – and significantly
this process can take place without having to close the bridge to traffic. The structure is a double world record breaker.
In 2013 the largest continuous underwater concrete pour saw 16,869 cubic metres of concrete
poured into the water-filled south tower caisson. Before the bridge’s decks were connected
to each other, the 322m cantilevers were certified by the Guinness Book of Records
as the longest cantilevers ever built. Remarkably this vast construction project,
that was built in extremely challenging site conditions over 200 metres above the surface
of the Forth, was completed £250 million under budget. It now stands alongside the Forth Road Bridge
and the original Forth Bridge as a modern engineering great – and together the three
structures visibly demonstrate three centuries of engineering innovation. If you enjoyed this video and would like to
get more from the definitive video channel for construction, subscribe to The B1M.

73 thoughts on “Forth Bridges: Spanning Three Centuries of Engineering Innovation | The B1M

  1. I absolutely love seeing pictures/footage of bridges under construction. Always fascinating to see the engineering involved.

  2. I live in South Queensferry 🙂

    They are planning on building a visitor centre that will allow you to walk to the top towers of the original Forth Bridge (the rail bridge)

  3. I was there a year ago. All three bridges are impressive. The old one looks like bathing dinosaurs.
    Thank you for your excellent video.

  4. I'm surprised you didn't mention the old Forth Railway Bridge that collapsed killing many rail passangers. Hence why the current Forth Railway bridge is so overly engineered to gain the confidence of the public that the crossing was safe

  5. It's funny, I don't have any real life connection to any of these bridges, but I somehow managed to learn about both of them completely independently. I've driven over the old road bridge hundreds of times in Euro Truck Simulator and have spent hours studying the history and construction of the rail bridge to help me with designing a fictional bridge in a story. They both feel like familiar landmarks to me at this point, yet I had no idea they were right next to eachother until I saw this video.

  6. Please. These bridges cross the Firth of Forth NOT the "Forth of Firth". That made my ears bleed. Firth is a Scots word meaning estuary and the Forth is the river whose estuary is crossed by the bridges. Apart from that, a well put together video – well done!

  7. The only good thing about the second fourth bridge is that you get a beautiful view of the original fourth bridge. In my opinion, the original is the most beautiful bridge I've ever seen in person. This video just made me appreciate it that much more.

  8. Hi thanks for posting. My father came from Leith but married in Northern Ireland and came to live in Larne. I remember visiting Scotland for holidays and crossing on the ferries and looking up at the Rail Bridge awesome it was as a young lad. I've crossed two bridges and hope some day to cross the new one. Thanks again

  9. Great video. I understood it as the new bridge was built because the old road bridge was in a poor state. Will the old bridge be closed?

  10. The forth bridge, the first bridge built in a series of bridges that contains only three bridges. Well done Scotland, your counting abilities are on par with Microsoft (yes I am aware of the spelling diferance)

  11. If you take the word of the Scottish Government, "once in a generation" means for about 2 years and then we'll try again because it didn't go as planned

  12. "The Forth of Firth"!! Morons, if you can't even get the name of the water correct, how can we trust anything you say?

  13. While the bridges were built so far apart (era/century), given that they are so close (geographically), it would have been much nice that they had some similarities in design (aesthetics not engineering), the view of all three while a cool reminder of how far we have come, is IMO an eyesore.

  14. I may be mistaken, but I believe the existing first bridge replaced a railroad bridge which collapsed. The fact that the existing first bridge is over-designed (way more structure than is really needed) was in part a reaction to the previous collapse. None the less, the existing first bridge is still a text book case in engineering. (I see there is a similar comment to this one, below.)

  15. forth of firth? haha its the firth of forth, like the firth of Cromarty. Firth is a scots word for coastal waters, Forth is the river that the bridges span

  16. These three bridges in the Edinburgh metropolitan area are engineering marvels for times they were conceived and constructed. This shows good the UK can be with innovation when they set their mind to it.

  17. My buddy's girlfriend, college-educated, believed that bridges, like rocks and trees, are provided by nature and then men decorate them with steel "and stuff".

  18. I wish yall'd done a video on the Ohio River crossings project. Its been done now but at over 4b dollars was the largest project in the US at the time. Began construction in 2012 and finished in 16, it was two large bridges spanning the Ohio River at Louisville, KY, US to southern Indiana and complete reconstruction of "spaghetti junction" in downtown Louisville where three interstates meet. I65/I 71/I64. The second bridge linked I265 together. Was reminded of it from this video because the two different centuries of the now two bridges side by side at the downtown crossing. 1964 and 2016. It was something to see. Thanks for your work.

  19. *You think the Forth bridge is impressive, you should see the designs for the Thyrd and Fith bridges!*

  20. Excellentbut ruined by not putting thw measurements of yhe bridge in feet and yet used miles. It is miles yards feet and inches. Metric should never be used unless it is used in imperial first.. After all in 1890 and 1964 we were imperial. Metric is most patonising..

  21. Thanks for a very educational video. I appreciate the inclusion of photos of construction of the Forth Bridge.
    I remember travelling between the Queensferry’s on the ferries – see 1.12 – as a child in the 1950’s, with the Kincardine bridge being 5he only alternative if queues were long.

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