One of Brunel’s best ideas

Royal Albert Bridge, Saltash, Devon

Royal Albert Bridge, Saltash, Devon

The career of Isambard Kingdom Brunel (1806-1859) is punctuated by two great bridges.  His first major project was the Clifton Suspension Bridge, begun in 1831 but completed posthumously in 1864.  Towards the end of his life he devised and constructed the Royal Albert Bridge, Saltash, to carry the railway across the Tamar into Cornwall.

Throughout his working life his professional rival, Robert Stephenson (1803-1859), was also a close personal friend and ally.

Brunel supported Stephenson at the enquiry into the Dee Bridge collapse in 1847, which first exposed the weakness of long cast-iron girders to support railway locomotives.

The two of them regularly discussed how to bridge wide waterways at height as Stephenson designed the High Level Bridge in Newcastle-on-Tyne (1849) and the box-girder bridges at Conwy (1849) and Menai (1850).

A suspension bridge such as Brunel’s design at Clifton was useless to carry a railway, because the weight of the locomotive would cause the chains to deflect dangerously.

When Brunel took the South Wales Railway across the River Wye at Chepstow in 1852, crossing from an abrupt cliff to a flat flood plain, his solution was to brace the suspension chains with circular tubes.

His great bridge across the wide Tamar estuary, linking Devon and Cornwall by rail, had to leave 100 feet of headroom for passing ships.  Its approaches had to be on curved viaducts.

So his freestanding central spans combine the three classic types of bridge – beam, arch and chain.  He developed the Chepstow design by changing the circular tube to an oval profile, bowed in the form of a convex truss to brace the vertical suspension chains.

Each span was fabricated in turn on the Devonport bank of the river, floated out into the stream and then jacked into position, three feet at a time, as the piers were built.

Brunel conducted the complex positioning of the first, western span in a two-hour process, watched by thousands in complete silence until the Royal Marines Band struck up ‘See the Conquering Hero Comes’ to signal success.

By the time the bridge was finished in 1859 Brunel was so ill that he missed the royal opening ceremony.

He only once saw his great work in its completed state, when he was drawn gently across the bridge in a coach secured to an open rail wagon.

He died on September 15th the same year, and his friend Robert Stephenson followed him a month later on October 12th.  Both of them suffered from what was then called Bright’s disease.

The Cornwall Railway subsequently added the tribute ‘I K BRUNEL – ENGINEER – 1859’ to each end of the bridge.

The Royal Albert Bridge is a destination on the Railways of Devon (June 12th-16th 2017) tour.  For further details, please click here.

 

Leave a Reply

Your email address will not be published. Required fields are marked *