{{Short description|1847 railway accident in England}} {{More citations needed|date=July 2010}} {{Use British English|date=August 2014}} {{Use dmy dates|date=April 2026}} {{Infobox public transit accident | name = Dee bridge disaster <!-- Image --> | image = Dee bridge disaster.jpg | image_size = | image_alt = | caption = <!-- Maps --> | image_map = | image_map_alt = | image_map_caption = | pushpin_map = | alternative_map = | pushpin_map_alt = | pushpin_map_caption = | mapframe = | qid = | mapframe_zoom = | coordinates = {{Coord|53.1865|-2.9047|display=inline,title|region:GB_scale:20000}} <!-- Details --> | date = 24 May 1847 | time = ~18:25 | location = [[Chester]], Cheshire | location_dir = | location_city = | location_dist_km = | location_dist_mi = | country = England | line = [[North Wales Coast Line]] and [[Shrewsbury–Chester line]] | operator = | owner = | service = | type = | cause = Bridge fail <!-- Statistics --> | bus = | trains = 1 | vehicles = | passengers = 22 | crew = | pedestrians = | deaths = 5 | injuries = 9 | damage = | property = <!-- Route map --> | route_map = | route_map_state = | route_map_name = <!-- Footnotes --> | footnotes = [[List of rail accidents in the United Kingdom|List of UK rail accidents by year]] }}
The '''Dee Bridge disaster''' was a [[rail accident]] that occurred on 24 May 1847 in [[Chester]], England, that resulted in five fatalities. It revealed the weakness of [[cast iron]] beam bridges reinforced by [[wrought iron]] tie bars, and brought criticism of its designer, [[Robert Stephenson]], the son of [[George Stephenson]].
==Background== A new bridge across the [[River Dee, Wales|River Dee]] was needed for the [[Chester and Holyhead Railway]], a project planned in the 1840s for the expanding [[British railway system]]. It was built using cast iron [[girder]]s produced by the [[Horseley Ironworks]], each of which was made of three large castings [[dovetail joint|dovetailed]] together and bolted to a raised reinforcing piece. Each girder was strengthened by wrought iron bars along the length. It was finished in September 1846, and opened for local traffic after approval by the first Railway Inspector, General [[Charles Pasley]].
==Accident== [[File:Scene of the Railway Accident, at Chester, the Dee Viaduct - ILN 1847.jpg|thumb|Scene of the Railway Accident, at Chester, sketched by a 16 year old, [[Alfred William Hunt]], and printed in ''[[The Illustrated London News]]'' of 29 May 1847]] On 24 May 1847, the carriages of a local passenger train to [[Ruabon]] fell through the bridge into the river. The accident resulted in five deaths (three passengers, the train guard and the locomotive [[fireman (steam engine)|fireman]]) and nine serious injuries.<ref>{{Citation| last=Simmons| first= Capt. J.L.A.| author-link=Lintorn Simmons| title=Report to the Commissioners of the Railways| year=1847| page=16| url=http://www.railwaysarchive.co.uk/docsummary.php?docID=1806| via=Railways Archive| access-date=10 December 2016}}</ref>
The bridge had been designed by [[Robert Stephenson]], and a local inquest accused him of negligence. Although strong in compression, cast iron was known to be brittle in tension or bending, yet the bridge deck was covered with [[track ballast]] on the day of the accident,{{vague|date=March 2021}} to prevent the oak beams supporting the track from catching fire. Stephenson took that precaution because of a recent fire on the [[Great Western Railway]] at [[Hanwell]], in which a bridge designed by [[Isambard Kingdom Brunel]] had caught fire and collapsed.<ref>{{cite book |author=Commissioners of Railways |title=Report of the Commissioners of Railways |date=1848 |publisher=Her Majesty's Stationery Office |location=London, England |pages=103–104 |url=https://books.google.com/books?id=2HAxAQAAMAAJ&pg=PA103| via=Google Books}}</ref><ref>{{cite book |last1=Brindle |first1=Steven |title=Brunel: The Man Who Built the World |date=2006 |publisher=Phoenix Press |location=New Haven, Connecticut, USA |page=80 |isbn=9781780226484 |url=https://books.google.com/books?id=s6Y6AgAAQBAJ&pg=PP80| via=Google Books}}</ref><ref>{{cite report |url=https://www.railwaysarchive.co.uk/docsummary.php?docID=4049 |title=Accident Returns: Extract for the Accident at Hanwell Bridge on 26th May 1847 |via=The Railways Archive |first=J. |last=Coddington }}</ref>
==Investigation== The investigation was one of the first major inquiries conducted by the newly formed [[Railway Inspectorate]]. The lead investigator was [[Lintorn Simmons|Captain Simmons]] of the [[Royal Engineers]], and his report suggested that repeated flexing of the girder weakened it substantially. He examined the broken parts of the main girder, and confirmed that it had broken in two places, with the first break occurring at the centre. He tested the remaining girders by driving a [[locomotive]] across them, and found that they deflected by several inches under the moving load. His conclusion was that the design was basically flawed, and that the wrought iron [[truss]]es fixed to the girders did not reinforce the girders at all. The same conclusion was reached by the jury at the inquest. Stephenson's design had depended on the wrought iron trusses to strengthen the final structures, but they were anchored on the cast iron girders themselves, and so deformed with any strain on the bridge.
Stephenson maintained that the locomotive [[derailment|derailed]] whilst crossing the bridge, and the [[impact force]] against the girder caused it to fracture. However, [[witness|eyewitnesses]] said that they saw the girder break first, and that the locomotive and tender were still on the track at the far side of the bridge. Indeed, the driver raced on to the next station to warn of the accident and prevent any traffic using the line. He then came back on the other side and drove to Chester where he gave a similar warning. <!-- ==Cause of accident==
The accident occurred a few hours after the track had been ballasted. The final girder cracked in the middle when the locomotive crossed it, allowing all the carriages to fall into the river Dee {{convert|50|ft|m}} below. The extra weight of the ballast undoubtedly helped cause the accident.{{Citation needed|date=July 2010}} The design of the bridge was seriously flawed, although different authors have emphasised different problems. Lewis and Gagg state that failure occurred in [[tension (mechanics)|tension]] at the bottom of the girders, exacerbated by [[stress concentration]]s.{{Citation needed|date=July 2010}} Henry Petroski notes that the wrought iron bars would tend to exacerbate [[compression (physical)|compression]] in the beams and, because they were eccentric, they increased the tendency towards failure by [[buckling#Lateral-torsional_buckling|lateral torsional buckling]].{{Citation needed|date=July 2010}} That suggestion does not explain the brittle cracking however. It is more likely that the beam cracked by [[fatigue (material)|fatigue]] from a sharp corner in the lower flange by repeated flexing of the girder{{Citation needed|date=April 2009}}. At a meeting at the [[Institution of Civil Engineers]] in London only a few months before, [[William Fairbairn]] had warned Stephenson of the problem related to cast iron girders in the construction of the bridge, but his advice was ignored.{{Citation needed|date=July 2010}} There had been several failures involving such girders which Fairbairn had investigated, and found them to be flawed. He thought the design itself was poor{{Citation needed|date=April 2009}} because the trusses could not reinforce the girders, being attached directly to their ends. -->
==Royal Commission== {{Unreferenced section|date=July 2010}} [[File:Curzon Park Chester2.jpg|thumb|right|Modern railway bridge in [[Chester]], spanning the river between [[Curzon Park]] and the [[Roodee]]. Photo taken at high [[tide]].]] A subsequent [[Royal Commission]] (which reported in 1849) condemned the design and the use of trussed cast iron in railway bridges, but there were other failures of cast-iron railway underbridges in subsequent years, such as the [[Wootton bridge collapse]] and the [[Bull bridge accident]]. Similar failures occurred in the [[Inverythan crash]] and the [[Norwood Junction crash]]. All the structures used untrussed cast iron girders, and generally failed due to [[Casting defect#Gas porosity|blowholes]] or other [[casting defect]]s within the bulk material, which were often completely hidden from external view.
The Norwood accident in 1891 led to a review of all similar structures by [[Sir John Fowler, 1st Baronet|Sir John Fowler]], who recommended their replacement. Cast iron had been used very successfully in [[the Crystal Palace]] of 1851 and the [[Crumlin Viaduct]] in South Wales (built in 1857), but the first [[Tay Rail Bridge]] of 1878 failed catastrophically due to its poor use of the material, putting the cast iron lugs on the columns into tension. The [[Tay Bridge disaster]] stimulated engineers to use steel, as exemplified by the [[Forth Bridge]] of 1890.
The Dee bridge was later rebuilt using [[wrought iron]].
==See also== {{Portal|Cheshire}} *[[List of bridge disasters]] *[[List of structural failures and collapses]] *[[Structural engineering]] *[[Structural failure]]
==References== {{Reflist}} * {{cite journal| first1=P.R.| last1=Lewis| first2=C.| last2=Gagg| journal=Interdisciplinary Science Reviews| volume=45| issue=29| year=2004}} * {{cite book| first=P.R.| last=Lewis| title=Disaster on the Dee: Robert Stephenson's Nemesis of 1847| publisher=Tempus Publishing| year=2007| isbn=978-0-7524-4266-2}} * {{cite book| first=Henry| last=Petroski| title=Design Paradigms| year=1994| isbn=0-521-46108-1}} * {{cite book| first=LTC| last=Rolt| title=Red for Danger| publisher=Sutton Publishing| year=1998}} * {{cite book| first=Roy| last=Wilding| title=Death in Chester| year=2003| publisher=Gordon Emery| isbn=1-872265-44-8}}
==External links== *[https://www.researchgate.net/publication/42796082_Aesthetics_versus_function_The_fall_of_the_Dee_bridge_1847 Aesthetics versus function: The fall of the Dee bridge, 1847] *[http://freepages.genealogy.rootsweb.com/~mossvalley/mv/chester-accident.html Contemporary account of accident] *[http://www.open2.net/forensic_engineering/riddle/riddle_01.htm Examination of Tay and Dee bridge disasters] {{Webarchive|url=https://web.archive.org/web/20080514055019/http://www.open2.net/forensic_engineering/riddle/riddle_01.htm |date=14 May 2008 }}
{{Railway accidents and incidents in the 1840s}} {{Railway accidents in the United Kingdom, 1815–1899|state=collapsed}}
[[Category:Bridge disasters in the United Kingdom]] [[Category:Bridge disasters caused by engineering error]] [[Category:Railway accidents and incidents in Cheshire]] [[Category:Railway accidents in 1847]] [[Category:1847 in England]] [[Category:History of Chester]] [[Category:Bridges across the River Dee, Wales]] [[Category:19th century in Cheshire]] [[Category:May 1847]] [[Category:1840s disasters in the United Kingdom]]