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| Name | The Royal Albert Bridge or Saltash Bridge is one of I K Brunels's masterpieces. |
|---|---|
| Who | |
| Owner | Network Rail |
| Design | I K Brunel, Chief Engineer |
| Contractor | I K Brunel (when first contractor went bankrupt Brunel took on the task) |
| Where | |
| 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..... |
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| What | |
|---|---|
| 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 |
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| 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 Abutments: Bearings: |
| Sentences |
Caissons: Abutments: Bearings: |
| Words |
Caissons: Abutments: Bearings: |
| 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 |
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