Martyn Read
April 2nd, 2003, 04:55 AM
Here's something of a classic to kick off the thread.
http://www.railimages.com/album/Martyn%20Read/110303_Royal_Albert_Bridge1.jpg
http://www.railimages.com/album/Martyn%20Read/110303_Royal_Albert_Bridge2.jpg
This is the Royal Albert Bridge, which has linked Plymouth in Devon, and Saltash in Cornwall, since 1859. This magnificent structure was the design of the Great Western Railway's engineer, I.K.Brunel. It is something of a testimony to a great design that this bridge still carries all trains into and out of Cornwall to this day, 144 years later!
The bridge mechanically is something of a cross between a suspension bridge and an arch, with the arch preventing the suspension bridges forces from overcoming the outer piers. To the best of my knowledge it's a unique design.
Both these pics were taken on the 11th March this year, from the Saltash side, the first from the adjacent road bridge, and the second from the platform end at Saltash station.
At this location the River Tamar is 1100 feet wide and up to 80 feet deep at high tide. To further complicate matters, the Admiralty (Royal Navy) insisted on clearance of at least 100 feet at the highest tide to allow tall ships underneath, as the river here was used as an anchorage, (and indeed there are Navy locations upriver from here to this day.) They also insisted that the river should not be blocked during the construction, or the channels be obstructed by piers, ruling out a traditional viaduct or trestle.
The land either side, whilst high ground, was not high enough to support cables for a suspension bridge, as Brunel had already built on the Clifton (road) suspension bridge in Bristol, or at least not without massive towers, as demonstrated by the 1960's road bridge adjacent to it.
It seems amazing that these problems were all overcome, and in an age before massive cranes, or CAD, or any of the tools a modern engineer may take for granted.
Construction of the approaches was started in 1853, with the creation of a yard on the Devon shore, and the foundations for the first pier on the Saltash side being laid. Ten piers were needed on the Saltash side and Seven on the Plymouth side.
In June 1854 a massive cylinder was towed out into the centre of the river and sunk, designed to be used as a cofferdam to create the foundations for the central pier, or if neccesary as a massive diving bell, should that method not work. It was designed to split in two after use so it could be easily removed from around the pier, this structure weighed upwards of 300 tons.
The foundations of the central pier were finally completed in the Autumn of 1856, after being temporarily halted after the bridge's contractor went bust.
The two main spans, each 455 feet long, were constructed in the yard on the Plymouth side, and on the 1st September 1857 the first one (the Saltash side) was floated out into position. From the top of the arch to the bottom of the roadbeds, these spans are about 75' deep.
The spans were floated into the river on pontoons, and the tide was used to lift the spans the 100' to their final positions. The span was floated into the river on high tide, and as the tide dropped, it rested on the piers. Falsework is then added to the pontoons and when the tide rises again it lifts the bridge, whilst the tide is high the piers are built up to support the span as the tide drops again. In this way, in small increments, the spans were inched up the piers to the neccesary height. Notice the notches on the cast iron columns that support the centre.
Once the first span was in place and clear for river traffic, the second span was floated into the river on the 10th July 1958. Brunel was unable to supervise by this time as he had fallen ill.
The first train crossed the bridge on the 11th April 1859, and HRH Prince Albert opened the bridge officially on the 2nd May 1859.
Brunel did make a final inspection of what was a great acheivement, he travelled across it on a couch fitted to an open wagon, as he was too weak to walk across by this time. Brunel died shortly afterwards, on the 5th September 1859, leaving an amazing legacy in a variety of fields, much of which still serves it's users well even now.
Credit section:
All dates/details taken from "The Great Western railway in East Cornwall", by Alan Bennett. Runpast Publishing.
Right, anyone else got any bridge pics? Doesn't have to be in that much detail! smile.gif
[ 01. April 2003, 22:57: Message edited by: Martyn Read ]
http://www.railimages.com/album/Martyn%20Read/110303_Royal_Albert_Bridge1.jpg
http://www.railimages.com/album/Martyn%20Read/110303_Royal_Albert_Bridge2.jpg
This is the Royal Albert Bridge, which has linked Plymouth in Devon, and Saltash in Cornwall, since 1859. This magnificent structure was the design of the Great Western Railway's engineer, I.K.Brunel. It is something of a testimony to a great design that this bridge still carries all trains into and out of Cornwall to this day, 144 years later!
The bridge mechanically is something of a cross between a suspension bridge and an arch, with the arch preventing the suspension bridges forces from overcoming the outer piers. To the best of my knowledge it's a unique design.
Both these pics were taken on the 11th March this year, from the Saltash side, the first from the adjacent road bridge, and the second from the platform end at Saltash station.
At this location the River Tamar is 1100 feet wide and up to 80 feet deep at high tide. To further complicate matters, the Admiralty (Royal Navy) insisted on clearance of at least 100 feet at the highest tide to allow tall ships underneath, as the river here was used as an anchorage, (and indeed there are Navy locations upriver from here to this day.) They also insisted that the river should not be blocked during the construction, or the channels be obstructed by piers, ruling out a traditional viaduct or trestle.
The land either side, whilst high ground, was not high enough to support cables for a suspension bridge, as Brunel had already built on the Clifton (road) suspension bridge in Bristol, or at least not without massive towers, as demonstrated by the 1960's road bridge adjacent to it.
It seems amazing that these problems were all overcome, and in an age before massive cranes, or CAD, or any of the tools a modern engineer may take for granted.
Construction of the approaches was started in 1853, with the creation of a yard on the Devon shore, and the foundations for the first pier on the Saltash side being laid. Ten piers were needed on the Saltash side and Seven on the Plymouth side.
In June 1854 a massive cylinder was towed out into the centre of the river and sunk, designed to be used as a cofferdam to create the foundations for the central pier, or if neccesary as a massive diving bell, should that method not work. It was designed to split in two after use so it could be easily removed from around the pier, this structure weighed upwards of 300 tons.
The foundations of the central pier were finally completed in the Autumn of 1856, after being temporarily halted after the bridge's contractor went bust.
The two main spans, each 455 feet long, were constructed in the yard on the Plymouth side, and on the 1st September 1857 the first one (the Saltash side) was floated out into position. From the top of the arch to the bottom of the roadbeds, these spans are about 75' deep.
The spans were floated into the river on pontoons, and the tide was used to lift the spans the 100' to their final positions. The span was floated into the river on high tide, and as the tide dropped, it rested on the piers. Falsework is then added to the pontoons and when the tide rises again it lifts the bridge, whilst the tide is high the piers are built up to support the span as the tide drops again. In this way, in small increments, the spans were inched up the piers to the neccesary height. Notice the notches on the cast iron columns that support the centre.
Once the first span was in place and clear for river traffic, the second span was floated into the river on the 10th July 1958. Brunel was unable to supervise by this time as he had fallen ill.
The first train crossed the bridge on the 11th April 1859, and HRH Prince Albert opened the bridge officially on the 2nd May 1859.
Brunel did make a final inspection of what was a great acheivement, he travelled across it on a couch fitted to an open wagon, as he was too weak to walk across by this time. Brunel died shortly afterwards, on the 5th September 1859, leaving an amazing legacy in a variety of fields, much of which still serves it's users well even now.
Credit section:
All dates/details taken from "The Great Western railway in East Cornwall", by Alan Bennett. Runpast Publishing.
Right, anyone else got any bridge pics? Doesn't have to be in that much detail! smile.gif
[ 01. April 2003, 22:57: Message edited by: Martyn Read ]