Saturday, 24 March 2012

The Anniversary of Two World Famous Bridges


A Steam Train crossing the Forth Railway Bridge, Scotland. Circa 1900
Note the horse-drawn covered coach with passengers waiting at the
South Queensferry terminal in foreground.
[From my own collection]

March 2012 marks the anniversary of two iconic masterpieces of engineering - but at opposite ends of the Earth. The Forth Railway Bridge in Scotland has reached the milestone of 122 years since its opening on the 4th March 1890 and the equally iconic Sydney Harbour Bridge in Australia of 80 years, having been opened on the 19th March 1932. Both are without doubt highly significant examples of structural engineering.


The Forth Railway Bridge, Taken c. 1905-1910
[From my own collection]

The Forth Railway Bridge

The Forth Railway Bridge was designed on the cantilever principle by Sir John Fowler and Sir Benjamin Baker and built by the Glasgow based construction company Sir William Arrol & Co. A massive engineering project, the statistics are fascinating but also sobering. Spanning a length of 8,296 ft at a maximum height of 361 feet above sea level, the bridge was the first major structure to make use of steel instead of wrought iron. At its peak, approximately 4,600 workers were employed day and night in its construction which took five years. But records also show that over 450 workers were injured with 98 losing their lives [one record states 63].The weight of the bridge superstructure as constructed was 51,324 tonnes with 6.5 million hammered rivets being used. The bridge also used 640,000 cu ft of granite for pier supports and approaches, the deepest foundation being 91 feet. The total cost came to over £3,500,000 pounds.


The Forth Railway Bridge Under Construction
[Source : The National Archives of Scotland]

After completion of construction in December 1889 load testing then took place in January 1890. Two trains, each consisting of three heavy locomotives and 50 wagons loaded with coal and totalling 1,880 tons in weight, were slowly driven to the middle of the north cantilever, stopping frequently to measure the deflection of the bridge. This represented more than twice the design load of the bridge with the deflection under load being exactly as expected.

A Steam Engine Crossing the Forth Railway Bridge, Pre 1905
[From my own collection]

The bridge was duly opened on the 4th March 1890 by the Prince of Wales (later King Edward VII) who had the honour of driving home the last rivet, which was gold plated and suitably inscribed. In 2006 the bridge carried between 190 to 200 trains per day and despite a speed restriction of 50 miles per hour can handle trains weighing up to 1,422 tonnes.

Repainting of the bridge was completed in December 2011. This involved removing all previous layers of paint then applying 230,000 m2 of new paint at a total cost of £130M. This is expected to now last a minimum of 25 years before repainting will be required. An engineering report estimates the bridge will have a life span (with regular maintenance) in excess of a further 100 years. The industrious Victorian builders would never have doubted that their bridge would last the test of time.


The Piers of the Sydney Harbour Bridge under Construction, circa 1931.
Believed to have been taken from the deck of the 'S.S. Mataroa'.
[From my own collection]

The Sydney Harbour Bridge

The Sydney Harbour Bridge is an equally recognisable and famous structure.

Built under the directions of Dr J.J.C. Bradfield of the New South Wales Department of Public Works, the bridge was designed in structural steel, being built by British firm Dorman Long and Co Ltd and opened in March 1932.

With a span of 1650 feet and height of the arch at 440 feet, this makes it the fifth longest span arch bridge in the World. Large rotating steel pins fitted at each end enable the structure to expand and contract by as much as 7.1 inches without causing damage. The complete bridge weighs 52,800 tonnes and the arch itself 39,000 tonnes. Six million Australian made rivets hold the structure together, being heated to red hot then riveted into the structural steel beams using pneumatic guns. Structural welding had not been sufficiently developed at that time.

The completed bridge, as viewed from the deck of the S.S. Orontes, 1937
[From my own collection]

The four 292 feet high concrete pylons at each corner - which are purely aesthetic and serve no structural purpose - are faced with around 635,664 cubic feet of Moruya quarried granite, being designed by Scottish Architect Thomas S. Tait. The stonemasons at Moruya cut, dressed, and numbered the granite blocks, which were then transported to Sydney by specially built ships.

The Bridge Latticework, as viewed from the
South East Pylon Viewing Deck, 1937.
The railway and tram tracks are clearly visible.
[From my own collection]

Built as a combined road, rail and tram bridge, load testing took place in February 1932 with the four rail tracks loaded with as many as 96 steam locomotives. During construction 16 workers died, although only two of those from actually falling off the bridge. In later years many workers experienced deafness caused from the noise of inserting and hammering the rivets. The total financial cost of the bridge was [in Australian Pounds] £6.25 million, which was not actually paid off in full until 1988.

Each coat of paint on the bridge requires around 6,600 imperial gallons [30,000 litres] of paint, covering an equivalent area of around 120 acres [485,000 square metres].


The Bridge, as viewed from the Pedestrian
Walkway. The extended arms hold up wires
for electric rail services. Taken 1937.
[From my own collection]


The formal opening ceremony took place on the 19th March 1932, the ribbon being cut by the Hon. Jack Lang, the Labor Premier of New South Wales. But the opening was not without drama! Just as he was about to cut the ribbon a rider on horseback rode across and slashed the ribbon with a sword "in the name of the people of New South Wales". The man was arrested and the ribbon hurriedly re-tied.

The bridge is now synonymous with Sydney, also having quickly become an iconic structure which stands as a permanent monument to the inspired vision of its designers and builders.


Bibliography :

- Wikipedia
- Unless otherwise stated all images are from my own collection but may be freely copied for non-commercial use provided a link is given back to this page.


2 comments:

  1. Great story.

    I am interested to know if you combined the two bridges because they were both opened in March, or if there was some more substantial connection between the two. For example, you noted that the concrete pylons at each corner of the Sydney bridge were designed by Scottish Architect Thomas S Tait.

    many thanks for the link
    Hels
    http://melbourneblogger.blogspot.com.au/2012/03/iconic-sydney-harbour-bridge-1932-2012.html

    ReplyDelete
  2. This comment has been removed by a blog administrator.

    ReplyDelete

Related Posts Plugin for WordPress, Blogger...