Tay Bridge disaster caused by the 'Millennium wobble'

The fault that caused London's Millennium footbridge to wobble has been blamed for the worst structural engineering failure in British history.

Seventy-five people died when the central navigation spans of the Tay Bridge collapsed, sending a train and six carriages plunging into the Firth at Dundee in hurricane- force winds 123 years ago.

For years experts have argued over the exact cause of the tragedy, many believing that the force 11 gale had made the locomotive collide with one of the 85 spans supporting the single-track bridge.

But new evidence discovered by a forensic engineer, Dr Peter Lewis of the Open University in Milton Keynes, attributes the blame for the accident to an uneven section of rail track in the middle of the bridge.

Although the official inquiry into the tragedy concluded that the single-track bridge had been "badly designed, badly constructed and badly maintained", it was not able to specify exactly how the disaster had been caused. Sir Thomas Bouch, who designed the structure and whose career was ruined by the scandal, claimed the wind had blown the train from the track into the bridge and that the shock of the collision had caused the lugs on the nearest tower to break and cause the collapse.

But by using the latest technology to enhance digitally the original photographs of the bridge and examining witness statements from the time, Dr Lewis has been able to pinpoint an uneven section of rail track on the centre of the bridge, which may have caused an unbearable strain on the structure as trains passed over it.

"We've used the computer as a virtual microscope to magnify the images to such an extent that we can see the evidence clearer than the original Board of Inquiry could."

Dr Lewis said the misalignment of the track, which was suppressed by solicitors during the inquiry, caused trains to move from side to side with "enormous momentum" as they crossed the bridge.

The effect, he argues, was similar to that of hundreds of people transferring their weight from one leg to the other as they walked across the Millennium Bridge over the Thames, causing it to sway.

From The Tay Bridge Disaster

by William McGonagall

... Oh! ill-fated bridge of the Silv'ry Tay,

I must now conclude my lay,

By telling the world fearlessly without the least dismay

That your central girders would not have given way

At least sensible men do say,

Had they been supported on each side with buttresses,

At least many sensible men confesses,

For the stronger we our houses do build, The less chance we have of being killed.