Editing Benjamin Baker (engineer) (section)

==Bridges==
{{Unreferenced section|date=July 2010}}
[[File:Original Tay Bridge before the 1879 collapse.jpg|thumb|Original Tay Bridge from the north]]
[[File:Tay bridge down.JPG|thumb|Fallen Tay Bridge from the north]]
He published a timely book on Long Railway Bridges in the 1870s which advocated the introduction of steel, and showed that much longer spans were possible using this material. The book is remarkably prescient for the way the properties of steel could be exploited in structures.

===Tay bridge disaster===

In 1880, Baker was called as an [[expert witness]] to the inquiry into the [[Tay Bridge disaster]], in which part of the bridge failed and collapsed into the water. Although he was acting on behalf of [[Thomas Bouch]], the builder of the first railway bridge across the Tay, he performed his role with independence and tenacity. His testified against the theory that the bridge was blown over by the wind that night. He made a meticulous survey of structures at or near the bridge, and concluded that wind speeds were not excessive on the night of the disaster. The official analysis of the failure suggested that a wind pressure of over 30 pounds per square foot was needed to cause toppling of the structure. Baker examined smaller structures in the vicinity of the bridge and concluded that the pressure could not have exceeded 15 pounds per square foot on the night of the bridge failure. Such smaller structures included walls, ballast on the track on the bridge, and both signal boxes either on or very near the bridge.<!-- Expand - did he offer a theory of the failure? This seems a gaping hole in content. -->

[[File:A Street Railway in New York - 1876 engraving.jpg|thumb|A street railway in New York 1876]]
Baker said in his statement to the court that he had built over {{convert|12|mi|km}} of railway viaduct, referring to his design of the [[elevated railroad]] in New York City in 1868, some of which still survives in [[Manhattan]] (unused). 

By this time he had already become established as an authority on bridge construction. Shortly afterwards he was engaged on the work which made his reputation with the general public: the design and erection of the [[Forth Bridge]] (1890) in collaboration with [[Sir John Fowler, 1st Baronet|Sir John Fowler]] and [[William Arrol]]. It was an almost unique design as a large [[cantilever bridge]], and was built entirely in steel, another unprecedented development in bridge engineering. Stiffness was provided by hollow tubes which were riveted together so as to make sound joints. Baker promoted his design in numerous public lectures, and arranged demonstrations of the stability of the cantilever by using his assistants as stage props.

===Forth Bridge===
[[File:Bb-forthrailbridge.jpg|thumb|Forth Bridge]]
[[File:L-gelenktraeger14.png|thumb|Stability of the cantilever]]
With [[Sir John Fowler, 1st Baronet|Sir John Fowler]], he designed and engineered the [[Forth Bridge]] after the Tay bridge collapse. It was a [[cantilever bridge]] and Baker gave numerous lectures on the principles which lay behind his design. [[Thomas Bouch]] had originally been awarded the contract but he lost it after the Tay Bridge Inquiry reported in June 1880. The bridge was built entirely in steel, much stronger than cast iron. He used hollow steel tubes to create the cantilever, and it was then the largest bridge of its kind in the world. The bridge is regarded as an engineering marvel. It is {{convert|8296|ft|abbr=on}} in length, and the double track is elevated {{convert|151|ft}} above high tide. It consists of two main spans of {{convert|1710|ft}},  two side spans of {{convert|675|ft}}, 15 approach spans of {{convert|168|ft}} and five of {{convert|25|ft}} ).[3] Each main span comprises two 680&nbsp;ft (210 m) cantilever arms supporting a central 350&nbsp;ft (110 m) span girder bridge. The three great four-tower cantilever structures are 340&nbsp;ft (104 m) tall, each 70&nbsp;ft (21 m) diameter foot resting on a separate foundation. The southern group of foundations had to be constructed as caissons under compressed air, to a depth of 90&nbsp;ft (27 m). At its peak, approximately 4,600 workers were employed in its construction. Initially, it was recorded that 57 lives were lost however after extensive research by local historians, the figure has been revised upwards to 98. Eight men who fell from the bridge were saved by boats positioned in the river under work areas. More than 55,000 tons of steel were used, as well as 18,122 m³ of granite and over eight million rivets. The bridge was opened on 4 March 1890 by the Prince of Wales, later [[Edward VII of the United Kingdom|King Edward VII]], who drove home the last rivet, which was gold plated and suitably inscribed. A contemporary materials analysis of the bridge, c. 2002, found that the steel in the bridge is of good quality, with little variation.

The use of a cantilever in bridge design was not a new idea, but the scale of Baker's undertaking was a pioneering effort, later followed in different parts of the world. Much of the work done was without precedent, including calculations for incidence of erection stresses, provisions made for reducing future maintenance costs, calculations for wind pressures made evident by the [[Tay Bridge disaster]], the effect of temperature stresses on the structure, and so on.

Where possible, the bridge used natural features such as [[Inchgarvie]], an island, the promontories on either side of the firth at this point, and also the high banks on either side. The remains of [[Thomas Bouch]]'s first attempts at his bridge can also be seen on the island.

The bridge has a speed limit of 50&nbsp;mph (80&nbsp;km/h) for passenger trains and 20&nbsp;mph (32&nbsp;km/h) for freight trains. The weight limit for any train on the bridge is 1,422 tonnes (1,442,000&nbsp;kg) although this is waived for the frequent coal trains, provided two such trains do not simultaneously occupy the bridge. The route availability code is RA8, meaning any current [[Rail transport in Great Britain|UK locomotive]] can use the bridge, which was designed to accommodate heavier steam locomotives. Up to 190–200 trains per day crossed the bridge in 2006. A structure like the Forth Bridge needs constant maintenance and the ancillary works for the bridge included not only a maintenance workshop and yard but a railway "colony" of some fifty houses at [[Dalmeny Station]].

"[[Painting the Forth Bridge]]" is a colloquial term for a never-ending task (a modern rendering of the myth of [[Sisyphus]]), coined on the erroneous belief that, at one time in the history of the bridge, repainting was required and commenced immediately upon completion of the previous repaint. According to a 2004 ''[[New Civil Engineer]]'' report on contemporary maintenance, such a practice never existed, although under [[British Rail]] management, and before, the bridge had a permanent maintenance crew.

A contemporary repainting of the bridge commenced with a contract award in 2002, for a schedule of work expected to continue until March 2009, involving the application of 20,000 m<sup>2</sup> of paint at an estimated cost of £13M a year. This new coat of paint is expected to have a life of at least 25 years. In 2008 the total cost was revised upwards to £180M, and projections for finishing the job to 2012. In a report produced by JE Jacobs, [[Grant Thornton]] and [[Faber Maunsell]] in 2007 which reviewed the alternative options for a second road crossing, it was stated that the estimated working life of the Forth Bridge was in excess of 100 years.<ref>{{Cite book|title=Forth Replacement Crossing Study Report 5 : Final Report|publisher=JE Jacobs Faber Maunsell / AECOM|year=2007|pages=24}}</ref>