Aesthetics versus function : the fall of the

Numerous new bridges were needed when the railway line from London to Holyhead in Wales was built in the 1840s. The project’s chief engineer, Robert Stephenson, chose a cast iron girder design to cross the river Dee just outside Chester, and the bridge was finished in November 1846. About six months later, on 24 May 1847, a local train was crossing the final span when one of the girders failed suddenly, sending most of the train crashing into the river below. Five lives were lost. The accident created a national furore, and Stephenson came close to being accused of manslaughter for the design. We have reviewed the witness evidence and concluded that the bridge probably failed by fatigue due to a defect at a sharp corner in a flange on a girder. The corner was present in a cavetto moulding, which had presumably been added as an artistic flourish.