Tay bridge - .PDF file.
Mention the Tay Bridge disaster today and the result is likely to be a smirk: its strongest association is famously the worst poem, by the worst poet, published in English. Written — perpetrated might be a better word — by William Topaz McGonnagall, it begins:
“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 shall be remembered for a very long time.”
and goes sharply downhill from there.
So far, so amusing: bring out the comedy Scottish accent and get orating. But a look back into the Engineer archives will quickly banish the smiles. The disaster was horrible and unprecedented: at the height of the Victorian age of heroic engineering, in the crucible of the industrial revolution and the homeland of the steam railway, a showpiece of engineering collapsed while a train was crossing it. Nobody survived; there were sixty known victims, but only 46 bodies were ever recovered. It’s now believed that as many as 75 people died (McGonnagall’s fact-checking was a bad as his poetry).
The Engineer’s report on the disaster shows a publication in shock. ‘The daily newspapers have told the world all that is known abou the circumstances of the catastrophe; and we have no intention of again going over the harrowing details,’ it says. ‘It is our province… to consider how and why the bridge fell.’
Even this ultra-rationalist magazine admits its unease over the collapse of the bridge. ‘Its fall is beyond any question in some way a reproach to the engineering science of Great Britain,’ it says. ‘Our only comfort is that nothing of the kind has ever happened before.’
The report details the construction of the bridge; the way its iron supporting towers were supported on brick pillars (which, in fact, still survive alongside the bridge that replaced the ill-fated structure); and the changes that were made to the design by chief engineer Thomas Bouch as the bridge was built. It seems to discount the idea that the winds blowing directly against the side of the bridge on the night of the disaster, with gusts now estimated to be as high as 80mph (129km/hr), could have caused the central section of the bridge to topple. ‘There can be no doubt that the wind blew with the force of a hurricane,’ it says. ‘We shall assume that it exerted the, in this country, almost unparalleled pressure of 60lb on the square foot.’ But the girders were well cross-braced and even this force should not have been enough to break them, it concludes.
The report also discounts the idea that the train was blown off the rails and struck the inside of the box-girder construction above the train line; it was travelling too slowly, it says. In fact, nothing in its analysis shows up any obvious engineering weakness; the report concludes that it awaits the result of the enquiry.
When the enquiry finally reported, it concluded that the bridge had been ‘badly built and badly maintained.’ The cast iron in the structure was not strong enough, owing to problems at the foundry that had supplied it; moreover, the cross-bracing in which The Engineer had so much faith was inadequate to stand up to repeated stress of high storms, and had been weakened in the years before the collapse. Bouch never worked again, and his previous designs were condemned: he died in October 1880. His obituary in The Engineer, mentions his “rough rule-of-thumb modes of procedure and reasons for “putting a bit on and taking a bit off”.’
Going back to the lamentable McGonnagall, although his poem is dreadful, the ending is something that no engineer could deny:
“For the stronger we our houses build
The less chance we have of being killed”