Tay Bridge disaster enquiry
"The scene at the Tay-bridge station to-night is simply appalling. Many thousand persons are congregated around the buildings, and strong men and women are wringing their hands in despair."
Wilhelm Westhofe, The Times, 29th December 1879
Beautiful Railway Bridge of the Silv'ry Tay!
Alas! I am very sorry to say
That ninety lives have been taken away
On the last Sabbath day of 1879,
Which will be remember'd for a very long time.
William McGonagall, The Railway Bridge of the Silvery Tay
The terrible Tay Bridge disaster of 1879, which claimed the lives of 75 people, remains vivid in the public consciousness in part due to McGonagall's torturous but memorable poem. Sir Thomas Bouch (1822-80), engineer to North British Railway, and well known for his economical bridge and viaduct designs, had been commissioned to design a rail bridge across the wide Firth of Tay by NBR. This was the time of railway-mania and the company was in stiff competition with the west coast Caledonian Railway. Having spent much of shareholders' investments in lobbying Parliament, time and money were of the essence.
From the start the project was mismanaged. Inadequate soundings were taken and when construction began sand was found where rock was expected, an inauspicious beginning. Bouch hastily redesigned the brick piers in cast iron but failed to amend his specification or supervise the casting. Having provided quotes that came in just under the inadequate budget, the contractors and fabricators were careless in their execution, and Bouch failed to keep a close eye, visiting the site only rarely.
Five days after the bridge's dramatic collapse on the evening of 28th December, a public enquiry opened, chaired by Henry Cadogan Rothery, Commissioner of Wrecks. He was supported by Colonel Yolland (Inspector of Railways) and civil engineer William Henry Barlow (1812-1902, brother of Peter Barlow). Baker was to act as an expert witness, called by Bouch as part of his defence. Baker was considered a rising star in the engineering world at this point, and a man whose "judgment ... was rapid, tolerant, and sagacious, and always carried great weight".
By this time, Baker's reputation in civil engineering and bridge building was well-established. He had designed innumerable bridges and viaducts, including contributing to the the first elevated railway in New York, the 'El', mostly of wrought iron. He had published a book in 1870 that argued for the superiority of steel over iron for long-span bridges. And more tellingly for Bouch, he had undertaken extensive experiments to examine the effects of wind pressure on structures in relation to the transportation by sea of the ancient Egyptian obelisk Cleopatra's Needle
, which now resides beside the Thames in London.
For Bouch's main defense was that a gale of exceptional force had caused the bridge to collapse. He had followed the recommendation of the Astronomer Royal on the expected wind load and was given the figure of 10lbs per sq ft, with gusts of up to 40lbs per sq ft. He had used these figures for spans of up to 61m but did not amend his calculations when site conditions caused him to extend the spans.
Baker took on his role as expert witness with characteristic seriousness. Unfortunately for Bouch, his careful observations of wind impact on surrounding structures lead him to conclude that the wind on that fateful evening was strong but not extraordinary. It was found that the bridge was shoddily detailed and constructed and designed for too low a wind load. Bouch's reputation was ruined and the NBR abandoned his designs for both the replacement bridge and an ambitious suspension bridge across the Firth of Forth. Bouch died 10 months after the collapse, though most probably from an illness contracted during the bridge's construction rather than shock as suggested by some.
Baker was often called upon for professional advice during his career, on projects around the world. The Tay Bridge disaster had a particular impact on his work, though, as it affected the engineering approach he and Fowler were to take on the design for their best-known work, the Forth Rail Bridge
main references BDCE2
portrait of Baker
courtesy Institution of Civil Engineers