Saltash Bridge

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Name The Royal Albert Bridge or Saltash Bridge is one of I K Brunels's masterpieces.
Owner Network Rail
Design I K Brunel, Chief Engineer
Contractor I K Brunel (when first contractor went bankrupt Brunel took on the task)
Latitude N 50 24' 27.5"
Longitude W 04 12' 12"
When 1859 - just before Brunel died
Why Carries Cornish main line railway over the Tamar River
Links Plymouth Devon and Saltash, Cornwall Royal Navy required the river to be operational at all times with 30 m. clearance above high tide
What Read more.....
How to read the bridge Read more.....



Pictures by David Blockley

Overall type Wrought iron arch and suspension chains
Width 5.13 m. - single track railway
Length 666.8 m.
Spans Two main spans of 139 m. and 17 approach spans (10 on Cornwall side and 7 on Devon side)
Clearance 30 m.
Materials Wrought iron



How to read the bridge Read more about the book metaphor...
Chapter 1 Tubular arch of the self reacting girder
Paragraphs Each ellipitical tube, 5.1 m. wide and 3.7 m. deep.
Sentences Lengths of tube with internal stiifeners between internal diaphragms
Words Curved pieces of plate, flat plate and angle stiffeners, rivets
Letters Wrought iron
Chapter 2 Chains of the self reacting girder
Paragraphs Each panel of chains and suspenders, diagonal, horizontal and cross bracing members along and across the length of the bridge. Note the hangers are pinned at level of chains.
Sentences Individual chain and eyebar links
Words Eyebar links, 100 mm. pins, gusset plates, lugs
Letters Wrought iron
Chapter 3 Deck
Paragraphs Span of each deck is supported at 22 points.
Plate Girders: 2.4 m. deep and spans 141.7 m.
Cross girders: 0.33 m. deep and 5.1 m. long.
Sentences Plate Girders: Length between stiffeners
Cross girders: Individual girders
Words Plate Girders: Plate, rivets, lugs, rails, ballast
Cross girders: Plate, rivets
Letters Wrought iron
Chapter 4 Foundations
Paragraphs Caissons: Compressed air
Sentences Caissons:
Words Caissons:
Letters Wrought iron
Grammar Technically the bridge is a way of taking forces from up in the air down to the ground. So imagine the flow of those forces through the structure. Think of a train standing on the brdge and how its weight is transmitted through the bridge to the ground.

This bridge is one of Brunel's masterpieces. The arch and the chains are self reacting to make a single girder - this was used in the erection process as each girder was lifted separately. The outward thrust at the ends of the arch is balanced by the inward pull of the suspension chains. The deck hangs from the chains and from the arch - the distribution of forces is complex and the structured is not statically determinate. However without any of the modern means of analysis he judged where the major forces flow from the deck to the chains and arch in some sort of reasonable proportion so that the end reaction forces balance. The bracing is everywhere quite light. That between the suspension chains and the deck form an N frame and between the arch and the chains is cross bracing. There is also cross bracing between the hangers either side of the arch tube. There is a horizontal link between the cross bracing and the links. Notice that it is omitted for the two end panels of each girder.
Erection The two bridge spans were built on the shore. They were floated into position on pontoons and then jacked up. Massive hydraulic cylinders under the centre of each end of the truss lifted the span 0.92 m in one day - one end at a time. The masonry was progressively built up under the supports after each lift at each end. Cast iron octagonal columns were used for the supports at the central pier.
References Hopkins H J, "A span of bridge", David & Charles, Newton Abbot, 1970
The Royal Albert Bridge, Saltash web site