Dee Bridge disaster

The railway accident on the Dee Bridge was a major railway accident that occurred on 24 May 1847 in Chester, Cheshire, on the North Wales Coast Line of the Chester and Holyhead Railway by a bridge collapse and five death toll.

Conditions

The double-track bridge was built to a design by Robert Stephenson and completed in September 1846. They spanned the Dee with three spans of more than 30 meters in length each. Each span consisted of four reinforced with wrought iron cast iron beams, the cast and wrought iron components were riveted together. Two bearers carried one of the two tracks. On the beams wooden beams were placed, on which the rails were mounted. As a material property of the cast iron was known that it could stand pressure very good, but very brittle reacted with stretching and bending and could break.

A few hours before the accident gravel was over the wooden sleepers on which the rails were mounted, been erected to prevent the thresholds could catch fire due to lost of steam locomotives burning coal or slag. This precaution was taken because a short time before, had caught on fire this way, an engineered by Isambard Kingdom Brunel Railway Bridge of the Great Western Railway in Uxbridge, London and had burned Robert Stephenson.

The bridge in Chester had been taken ( Her Majesty's Railway Inspectorate ) before commissioning of the railway supervisory authority.

The train consisted of a locomotive with a tender, a baggage car and three passenger coaches, one of the first and two of the second car class. Only " two dozen " travelers should have been on board.

Circumstances of the accident

Although the bridge so was new and without any complaints, it came to the accident: The local train from Chester to Ruabon was (seen from Chester off) on the last bridge girders, as the outer of the two cast-iron support of the substructure of the road broke. Locomotive and Tender succeeded yet, solid ground to reach the cars of the train but fell in the ten meter deep flowing Dee. Five people - three travelers, the heater and the platoon leader - died, nine passengers were seriously injured.

Investigation

The local first investigation into the incident by the coroner gave the designer before negligence.

The investigation of the railway supervisory authority revealed that the cast iron due to the changing load - when a train drove over the bridge - and relief - when he left the bridge again - become brittle and was therefore broken. Tests showed that bent the carrier at each crossing by several centimeters. The gain through the wrought iron elements could not compensate for this, as they were anchored itself only in cast-iron elements. The total construction was therefore considered to be defective. The weight of the recently deposited gravel contributed certainly to the accident.

Robert Stephenson, however, claimed that the locomotive had to be derailed and caused thereby impact against the bridge have let this break. But this was not credible because the locomotive was not crashed, but the train driver immediately drove to the nearest train station and the local staff taught by accident. The Scottish engineer William Fairbairn is, after he had examined a number of incidents in the construction sector in the use of cast iron, Stephenson warned at a meeting of the Institution of Civil Engineers in London even several months before the construction of the bridge due to the mechanical behavior of cast iron beams against employ them in bridge construction. Overall, the reputation of Robert Stephenson as engineer suffered by the accident significantly damaged.

The report of a royal commission of inquiry into the causes of the accident then spoke out in 1849 against the use of cast iron in load-bearing structural elements in the construction of railway bridges.

Consequences

Nevertheless, as in the following years to a number of other accidents, in which the use of cast iron for structural elements ( with ) was the cause, the most famous of which the collapse of the Firth of Tay Bridge in 1878. Was only after the railway accident at Norwood Junction 1891 and a review of all bridges analogous construction by John Fowler said this was in favor of exchanging all relevant structures.

The bridge over the Dee at Chester was rebuilt after the accident in wrought iron again.