Scottish Bridges: 47. Balmoral Bridge

The shortcomings of the suspension bridge at Crathie led to a desire from the Royal family for a more robust vehicular bridge across the Dee at this location, close to the entrance to Balmoral Castle. This was designed by Isambard Kingdom Brunel, doyen of Victorian bridge engineering, and completed in 1857. It was, apparently, to prove unpopular with Queen Victoria and Prince Albert, on account of its lack of ornamentation.

The bridge, which spans 39m, consists of two plate girders at either side, supporting the roadway deck. The girders are pierced with diamond-shaped openings towards the top, such that from the roadway, they seem somewhere between a plate girder and a lattice truss. It's thought to be one of the earliest surviving plate girder bridges in Scotland.

The road deck consists of tarmac surfacing on timber planks, which span longitudinally between iron cross-girders. Repairs were undertaken in October last year due to deterioration of the timber, with propping inserted between the main girders below the end bays of the bridge deck. A more comprehensive strengthening and refurbishment scheme is due to take place next year.

Further information:

• Google maps / Bing maps
• RCAHMS
• Engineering Timelines
• British Listed Buildings
• Scottish Highland Bridges
• Aberdeenshire SMR
• Royal Deeside
• Highland Bridges (Nelson, 1990)
• Civil Engineering Heritage - Scotland Highlands and Islands (Paxton and Shipway, 2007)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

West Country Bridges: 5. Royal Albert Bridge

What is there that I can sensibly say about Isambard Kingdom Brunel's greatest bridge (pictured, above left)?

First, the facts. The bridge was opened in May 1859, four months before Brunel's death. The two main spans of 138.7m are achieved using giant lenticular trusses in wrought iron. The upper chord of the truss is a single tube, oval in cross-section, 5.1m wide and 3.7m high. The lower chord consists of wrought iron chains, with vertical members carrying the loads from the deck into both chords. It's a design with split personalities - as well as the idea of the lenticular truss, you can think of it as a bowstring arch bridge, or as a self-anchored suspension bridge in which the main cable forces are anchored into an overhead strut rather than into the deck.

In this respect, the design was a development of Brunel's 1852 bridge at Chepstow, where again a simplified suspension arrangement relies on tubular strut for its anchorage (although at Chepstow, the strut was circular). Another predecessor was Brunel's 1849 bowstring arch at Windsor.

The Royal Albert Bridge also owed more than a little debt to Brunel's great friend and rival Robert Stephenson. His High Level Bridge in Newcastle was also completed in 1849, and has a series of bowstring arches carrying the roadway, with the railway on a separate deck above the arches. The idea of superimposed systems may have influenced the Royal Albert Bridge, but another Stephenson design was even more relevant, the Britannia Bridge.

Opened in 1850, the two main spans at Britannia were very similar to Royal Albert, at 140m. The same method of erection, by floating out and lifting vertically, was also used on both bridges. The Britannia Bridge (along with a related structure at Conwy) had pioneered the use of riveted wrought iron box girders, although used in a beam arrangement rather than as struts as in the more complex Brunel design. Stephenson had even suggested the use of an oval box girder at Britannia, although William Fairbairn's preference for a rectangular section proved more appropriate.

Brunel's Royal Albert Bridge was a more sophisticated design all round, but not of a type which would see much further use. The first major Warren truss bridge had been built in 1852, and lattice trusses such as the Runcorn Railway Bridge were soon to come into favour. Truss bridges were simpler to assemble than box girder designs, and used significantly less material. Nonetheless, Brunel's lenticular truss certainly didn't stand alone, with several other examples built by von Pauli and Lohse in Germany, and by Lindenthal and the Berlin Iron Bridge Company in America.

None of this is to detract from the Royal Albert Bridge. It may have been a technological dead end, but it remains a remarkable design and a spectacular structure.

I particularly like the texture of the main arch girders, with the riveted plate form very visible. The evidence of handicraft is a welcome contrast to the more impersonal surfaces that modern welded construction produces.

Perhaps less appealing are features which I presume to have resulted from strengthening works over the years. Chief amongst these are the diagonal bracing members immediately below the suspension chain, which aren't visible on older photos, and detract from the clarity of the structural system.

Further information:

• Google maps / Bing maps
• Wikipedia
• Structurae
• Engineering Timelines
• English Heritage
• royalalbertbridge.co.uk
• Royal Albert Bridge (Buxton-Smith, 2007, student paper)
• British Railway Bridges (Walters, 1963)
• British Railway Bridges and Viaducts (Smith, 1994)
• Civil Engineering Heritage: Southern England (Otter, 1994)
• Cornwall's Bridge and Viaduct Heritage (Kentley, 2005)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

Did Brunel design the Clifton Suspension Bridge?

Can this be true? A new book by Adrian Vaughan on the famous engineer Isambard Kingdom Brunel is reported to claim that he didn't even design one of his best known structures, the Clifton Suspension Bridge (pictured right, courtesy of Damien Everett on Flickr).

Vaughan's earlier book, "Isambard Kingdom Brunel: Engineering Knight-errant", was a revisionist critique of the widespread view of Brunel as not merely a giant amongst engineers, but very nearly the greatest Briton ever. It drew extensively on archive research to depict a designer who was confrontational, dictatorial, and prone to making over-quick decisions which frequently led to his projects going well over budget. It sought quite consciously to provide a counter-balance to the widely read LTC Rolt biography of Brunel, which by all accounts bought quite deeply into the mythology of a Victorian hero.

The new book that has provoked the headline is Vaughan's follow-up, "The Intemperate Engineer: Isambard Kingdom Brunel in His Own Words". I haven't seen it, but understand it includes many of Brunel's letters and seeks to depict both his genius and his fallibility.

It's certainly not news that the Clifton Suspension Bridge wasn't entirely Brunel's design. His initial 1831 proposal didn't start on site until 1836, and money ran out in 1843. Work on the bridge only restarted in 1862, three years after Brunel's death, with the design revised by William Henry Barlow and Sir John Hawkshaw. In part, changes were made to the bridge width and suspension chain arrangement to make use of chains that became available from the recently dismantled Hungerford Suspension Bridge. Changes were also made to the tower design. But the span and general conception remained as Brunel had proposed.

This situation is hardly unusual even today. Is Stonecutters Bridge the design of Halcrow and Flint and Neill, who (like Brunel) won the design competition and developed the basic concept, or of Arup, who completed the detailed design and made various changes to the scheme? And even if one engineer at any of these firms were put forward as the key engineer responsible, how much did they personally contribute?

The modern era, with design tasks shared across a diverse team, is not that different from the Victorian period. Identifying, and lionising, the big names may help personalise history, but essentially it's the engineering version of the lamentable tendency to see national history as the history of royalty. Suggesting that Brunel designed the bridge at Clifton pays proper tribute to the central figure in its creation, while obscuring a more complex reality.

It's also worth considering to what extent Brunel's present-day reputation is based on his forceful personality as much as on his actual engineering achievements. Was he a better engineer than Thomas Telford, Robert Stephenson, or lesser known contemporaries like Thomas Kennard? There seems to me to be an almost willful desire in the popular media to treat Brunel as heroic in the manner of a great general, to gloss over his many flaws and the fact that many of his enterprises were disasters. Like Stephenson, his greatest bridge designs were spectacular and perhaps revolutionary, but rarely of such importance that they became templates for wider adoption.

It's interesting, perhaps, that most popular histories relating to civil engineering are of the royalist type: biographies of the famous names. I can't think, off hand, of any popular books that get to grips with the wider social aspects of the 19th century revolution in scientific bridge design, although there are certainly specialist histories that address it.

Of course, a headline that simply stated "new biography confirms what we already knew in old biographies" is neither going to sell newspapers nor justify a journalist's time and expenses. The need to manufacture controversy is understandable. What I'm less clear on is the underlying need to propagate a heroic mythology, and to defend it against any inquisition, however plausible.