A loch, some falls and a bridge #buildingpassions #10favstructures

Loch Etive is a Scottish sea inlet or fjord north of Oban in the Highlands.

Back in the 19th Century it was decided to extend the railway from Oban northwards and the big issue was whether to go round Loch Etive or across it. Unlike other lochs it had a shallow part at a place called ‘The Falls of Lora’. The name was apt as when the tide comes out of the loch it produces a standing torrent of water.

The engineers (John Wolfe Barry and partners) knew it would be too difficult to place any part of a bridge directly in that part of the loch, so needed to come up with a different, not too expensive solution for the trains to cross. They decided on a single span cantilever action bridge made from steel.

What is a cantilever bridge? The most famous example then and still with us is the Forth Rail Bridge, also in Scotland, for which the huge amounts of steel were supplied, like at Loch Etive and Tower Bridge, by William Arrol and Company of Glasgow.

The Forth Rail Bridge in Scotland (Wikimedia Commons)

The Forth Rail Bridge was over-specified due to the high winds in the wide sea estuary where it was located – by contrast the bridge over Loch Etive would shorter and could be based on a simpler design, but using the same cantilever principle. The rising bascule leaves on Tower Bridge also acted as movable cantilevers, extending out from the tower bases to meet in the middle of the River Thames.

When the Connel Ferry Bridge was completed in 1903, it became the world’s longest single span cantilever bridge (the Forth Rail Bridge had double spans!). It was soon taken over by other bridges, but I feel it set a precedent and it is still with us now for road traffic only.

This is the first post in a series of 10 favourite structures featured in the book ‘Building Passions’ by Nick von Behr. The 11th post will try to rank the structures in order of appeal.

Brunel, Barry and ‘modern’ Victorian architecture eBook by Nick von Behr – 9781916225701 | Rakuten Kobo

The book cover image above should always be credited as follows: Arpingstone (https://commons.wikimedia.org/wiki/File:Tower.bridge.7.basculecloseup.london.arp.jpg), size and alignment by Elisa Vernazza, https://creativecommons.org/publicdomain/zero/1.0/legalcode

The e-book is currently available to order at https://www.kobo.com/gb/en/ebook/brunel-barry-and-modern-victorian-architecture

The story behind structures #Built

Roma Agrawal is publishing her book ‘Built: the Hidden Stories Behind our Structures’ on 8 February.

I’m fortunate to know Roma and we share common interests in opening up (structural) engineering to a wider base, particularly getting more females into a profession traditionally dominated by men.

One of the stories Roma writes about in her book is on the Quebec Bridge in Canada. It’s a bridge I don’t know too well so I decided to find out more using my favourite search tool, Google of course! This brought up the Wikipedia reference used in the above hyperlink. If you want to delve further you can connect to other steel cantilever bridges around the world including the Connel (Ferry) Bridge by Sir John Wolfe Barry, and the most famous example of all, the Forth Railway Bridge built by John Fowler and Benjamin Baker (a close friend and business partner of Wolfe Barry).

But what is so special about the Quebec Bridge?

It is a world record holder as the longest spanning cantilever bridge ever built – this was to prove the downfall of the first version of the bridge which collapsed during construction on 29 August 1907 with the loss of many lives. Roma will tell you more in her book.

Famous bridges aren’t the only structures to have stories behind them. The building you live in may have more than one stor(e)y. Perhaps not as exciting or indeed tragic as the Quebec Bridge …

 

 

A Benjamin Baker’s dozen

There are 13 days until we commemorate the death of Sir John Wolfe Barry, one hundred years ago.

The play on words in the title of this blog is obviously to do with the number thirteen, but also allows me to tell you a bit about Sir Benjamin Baker.

Baker was a close friend and business associate of Wolfe Barry and like John was also President of the Institution of Civil Engineers. He is most famous for designing and building between 1883 and 1890 with Sir John Fowler the iconic Forth Rail Bridge in Scotland, which still stands and functions as it was intended.

The steel for the bridge was supplied by William Arrol, who also provided the steel for Tower Bridge and the Connel Bridge, both built by Wolfe Barry.

Benjamin Baker went on to design and construct a number of docks with Sir John including the Royal Edward at Avonmouth near Bristol. Subsequently he  built the new Aswan Dan in Egypt to tame the Nile, no doubt well informed about the nature of river currents and movement of sediment.

Like Barry, Sir Benjamin has a stain glass window commemorating him in Westminster Abbey.