Forth Bridge

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Coordinates: 56 ° 0 ′ 0 ″  N , 3 ° 23 ′ 20 ″  W.

Forth Bridge
Forth Bridge
use Railway bridge
Crossing of Firth of Forth
place South Queensferry , North Queensferry
construction Cantilever truss bridge
overall length 2523 m
Longest span 521 m
Clear height 46 m
start of building 1882
completion 1890
planner John Fowler , Benjamin Baker
location
Forth Bridge (Scotland)
Forth Bridge

The Forth Bridge is a double-track railway bridge over the Firth of Forth , the far inland estuary of the River Forth in Scotland , and a World Heritage Site .

The cantilever bridge had at its opening in 1890, the largest wingspan world of all bridges. She had to cede this record to the Québec Bridge in 1919 .

It is considered to be the first bridge that, in contrast to the wrought iron used until then, was made entirely of steel .

location

The Forth Bridge is part of the railway line that runs from Edinburgh across the Firth of Forth, Fife Peninsula and Firth of Tay to Dundee and further along the east coast to Aberdeen .

It stands about 13 km west of Edinburgh between the places South Queensferry and North Queensferry at a narrow point, which is formed by a rock spur protruding from the north into the river mouth. In the middle of the river mouth is Inchgarvie , a small rock island that serves as the foundation for the middle bridge pier. The tidal range of more than 6 m and the strong tidal currents caused particular problems during construction when steel parts of ships were to be lifted directly to the bridge. The surrounding area is so high that the railroad does not have to negotiate any special inclines to reach the required clearance height of 46 m (150  ft ).

About 900 m further inland is the Forth Road Bridge , a four-lane suspension bridge opened in 1964 . A little further inland is the Queensferry Crossing , a cable-stayed bridge on which the M90 motorway has been running over the Firth of Forth since August 30, 2017 .

27 km further west is the Kincardine Bridge , a swing bridge opened in 1936 for road traffic, which was relieved in 2008 by the neighboring Clackmannanshire Bridge .

history

Before the bridge was built, a ferry shuttled between North and South Queensferry . If the ferry service had to be stopped due to bad weather or if you did not want to risk the crossing for fear of seasickness or for other reasons, the only alternative was the detour over the bridge 37 km further inland in Stirling .

The first ideas for a fixed link arose as early as 1805 when a tunnel with two tubes was proposed. In 1818 the proposal for a chain bridge followed , which was also not pursued any further. In 1860 the North British Railway began test drilling for a bridge designed by Thomas Bouch . The project even received the required legal approval, but was dropped due to economic changes at the railway company.

In 1873 the Forth Bridge Company was founded to build a chain bridge, also designed by Thomas Bouch, with two openings each 488 m (1600 ft) wide. The four participating railway companies, the Great Northern , the North-Eastern , the Midland and the North British Railway were to finance the construction and then ensure sufficient traffic over the bridge to generate the planned dividend of 6% per year. In the same year legal approval was given and Sir William Arrol & Company , Glasgow , was commissioned with the construction work. However, their execution was long delayed by various circumstances, so that the central pillar on Inchgarvie was only in progress when the Firth-of-Tay Bridge near Dundee, also designed by Thomas Bouch, collapsed on December 28, 1879. All further work was then stopped. The investigation into the causes of the accident shook public trust in the bridges planned by Thomas Bouch so much that a completely redesigned bridge was considered necessary.

After a new tender for the bridge, the engineers Sir John Fowler and Benjamin Baker received the order to plan a more stable bridge, the appearance of which should give passengers back confidence in the construction. In 1881 the final version of the draft, agreed with all parties involved, was accepted by the railway companies and the authorities. In July 1882 the legal approval was given and the financing agreement of the railway companies involved was adjusted accordingly - with a dividend reduced to 4%.

On December 21, 1882, Tancred, Arrol and Co. were commissioned to carry out the new design.

Construction work on the bridge took seven years and was completed in December 1889. In January 1890, stress tests were successfully carried out. On February 24, 1890, a train with the directors of the railway companies involved drove over the bridge several times. On March 4, 1890, the opening ceremony was held by the Prince of Wales , later King Edward VII , who set the gold-plated “last rivet” made for it.

There was already great public interest in the bridge during the construction period; numerous high-ranking personalities such as the Prince and Princess of Wales, the Emperor of Brazil Dom Pedro II , King Albert of Saxony , Leopold II , King of the Belgians, and Naser ad-Din , Shah of Persia , visited the construction site and the finished one Bridge. Apparently no state guests were invited to the opening ceremony, but the representatives of various foreign specialist authorities; the Prussian Ministry of Public Works dispatched the bridge construction engineer and construction officer Georg Christoph Mehrtens , who worked on many large bridges in Germany.

description

and display information about the image
Firth-of-Forth railway bridge panorama in 2007, maintenance work is taking place on the areas covered in white

The Forth Bridge is a cantilever bridge with Gerber girders , the superstructure of which was made entirely from Siemens-Martin steel for the first time . The bridge is supported by three mighty pillars , each consisting essentially of four tubular steel columns that are stiffened by diagonal tubes and numerous trusses . The diamond-shaped brackets protrude laterally from these pillars, the lower chords and diagonal struts that carry the greatest loads, in turn, made of tubes, while the upper chords and numerous struts used for stiffening are designed as lattice girders. These brackets carry the hanging brackets, which appear graceful in relation to the overall structure . Longer viaducts connect on both sides of the bridge, which connect the high-lying surroundings to the actual bridge structure.

Demonstration of the principle of the Forth Bridge

Concept illustration

Since large, wide-span cantilever bridges were not yet widespread, efforts were made to gain the public's trust in the new bridge through practical demonstrations. The famous photo was taken in which John Fowler and Benjamin Baker, sitting on chairs, with outstretched arms each hold two rods attached to the chairs, which represent the lower chords of the boom under pressure, while the arms symbolize the upper chords, which are only exposed to tensile forces. The brick pallets attached to the outside form the counterweight to Kaichi Watanabe , a Japanese engineer who was also involved in the construction of the Forth Bridge, who was sitting on the "hanging bracket" .

Technical details

The pillars are 100.6 m (330 ft) high from their granite bases. Its four supporting tubes are vertical in the side view, but are inclined inward in the longitudinal view. Their center distance is 36.6 m (120 ft) below and tapers up to 10 m (33 ft). In the longitudinal direction, the load-bearing pipes of the two outer, identical piers have a center distance of 44.2 m (145 ft), while those of the inner pillar are 79.3 m (260 ft).

The six booms are each 207.3 m (680 ft) long and are identical except for differences in the end connections of the outermost booms. These are mounted on the end pillars of the viaducts and weighted with built-in counterweights to prevent lifting that the opposite boom could cause under the load of the suspension bracket and two trains meeting on the suspension bracket.

The two 106.7 m (350 ft) long suspension girders are also identical, which correspond to a conventional truss bridge with a straight lower chord and a slightly curved upper chord.

The bridge therefore has two main openings of 521.2 m (1710 ft) and two side openings over the bank and the shallow water near the shore of 207.3 m (680 ft) each.

Forth Bridge (South Queensway - Edinburgh)

The pipes in the piers and booms are up to 3.6 m (12 ft) in diameter and up to 106 m (350 ft) long. They are stiffened on the inside with longitudinal and transverse ribs and were made on the construction site with large riveting machines.

The bases of the pillars rise up to a height of 5.5 m (18 ft) above the flood. They were founded with the help of caissons .

In the south there is a viaduct made of granite pillars with 10 bridge spans of 51.2 m (168 ft) each, which is connected to the 10.4 m long abutment via 4 masonry arches with center distances of 20.1 m (66 ft) . In the north, the corresponding viaduct consists of 5 bridge fields of 51.2 m (168 ft) each, 3 masonry arches with different center distances of 11.3 m + 9.5 m + 14.0 m (37 ft + 31 ft + 46 ft ) and an abutment 4.3 m (14 ft 1 ″) long.

The total length of the structure is therefore 2,522.6 m (8,276 ft).

The railway tracks, which run horizontally over the entire bridge, are led over the viaducts on parallel-belted lattice girders, with a continuous girder bridging two fields. In the cantilever bridge, the tracks also run on lattice girders, which virtually form a bridge in the bridge. On both sides of the tracks there are narrow footpaths for the railway and bridge personnel that are not accessible to the general public.

The entire structure consists of around 54,000 tons of steel and is held together by 6.5 million rivets. The stone pillars or substructures are made of granite and come from a quarry in Aberdeen .

Construction began with the pillars of the viaducts and the caisson work for the foundations of the bridge piers. The three main pillars were then installed. The cantilevered booms were built from the main pillars. The suspended beam were, contrary to their name in the balanced cantilever construction of the booms from. Its two halves were put together on a cloudy day with even temperatures.

Up to 5,000 people were employed on the construction site at peak times. Depending on the counting method, 57 to 73 people died in accidents, an order of magnitude that was considered acceptable for such projects at the time.

  • View into the structure

  • Part of a boom and its suspension bracket

  • A freight train in the bridge

  • Southern viaduct

  • Cruise ship MS Europa 2 at the Forth Bridge

  • Forth Bridge in October 1972

present

In 2002 and 2012 the Forth Bridge was completely renovated. It continues to operate regularly, with around 200 trains crossing it every day.

The Forth Bridge was added to the List of Historic Civil Engineering Landmarks by the American Society of Civil Engineers in 1985 . In the summer of 2015, the building was added to the UNESCO World Heritage List .

In August 2013, plans were announced to set up a publicly accessible viewing platform on the bridge, about 100 meters above the water. The platform was supposed to open in 2017 but was not built. The bridge is used for viewing tours as part of individual events with a tightly limited number of participants.

Individual evidence

  1. ↑ Unless otherwise stated, the information in this article is based on: Wilhelm Westhofen: The Forth Bridge. Reprinted from Engineering, London 1890. Reprinted from Wikisource
  2. ↑ Centralblatt der Bauverwaltung , Volume 10, 1890, No. 8A (from February 26, 1890), p. 84.
  3. ↑ Pillar spacing: 680 ft + 350 ft + 680 ft = 1710 ft. The 1700 ft specified in the diagram for the opening on the right are a typo.
  4. ↑ Forth Bridge Facts & Figures on the official website
  5. ↑ Historic Scotland for the Forth Bridge Forum (ed.): The Forth Bridge, Nomination for Inclusion in the World Heritage List, Nomination Document . 2014, ISBN 978-1-84917-144-1 , digital version ISBN 978-1-84917-145-8
  6. ↑ Entry in the UNESCO list. Retrieved July 6, 2015 .
  7. ↑ Plan for viewing platform at top of Forth Rail Bridge. BBC News, August 27, 2013, accessed September 1, 2013 .
  8. ^ Alastair Dalton: £ 125 view of a lifetime for Forth Bridge visitors. Article dated December 21, 2014 on The Scotsman
  9. ↑ forth bridge experience

Web links

Commons : Forth Bridge  - album with pictures, videos and audio files