Showing posts with label Tyneside. Show all posts
Showing posts with label Tyneside. Show all posts

12 June 2014

Tyneside Bridges: 10. Redheugh Bridge


At last, this was the final bridge in the IABSE Study Tour of north-east England.

Completed in 1983 to a design by Mott, Hay and Anderson,  the present Redheugh Bridge is on the site of two former crossings. The first was the most interesting: an innovative cable-stayed design by Thomas Bouch, which survived from 1871 to 1897.

Spanning 160m, the current bridge is a post-tensioned concrete box girder structure. An attractive steel box girder design had been proposed by MHA in 1966, but this was abandoned when a spate of failures of this type of bridge occurred, coinciding with a rise in steel prices which rendered a sufficiently strong design uneconomic.

The bridge has a twin-cell single box configuration, with utility services carried inside the box - gas pipes in one cell, and electricity cables and a water pipe in the other cell. Holes in the concrete box are provided for ventilation and as drainage in case the water main should leak.

The bridge was constructed using the balanced cantilever technique, with a series of 3m long in-situ concrete sections. It was completed a year after the Byker Metro Viaduct, another post-tensioned concrete balanced cantilever bridge built nearby. The Byker bridge was more innovative, being built using glued precast units, the first of its type in Britain, and I think it was also far more successful aesthetically. However, it's fair to note that the Byker bridge carries significantly lower loads, and has much shorter spans, so the pressure to adopt only the most economic solution will have been a little less.

That concludes my tour of bridges in the north east of England. I have a backlog of other bridges to report on here, and hope to start my next series of reports soon.

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22 May 2014

Tyneside Bridges: 9. King Edward VII Bridge


This bridge was built in 1906 to supplement Stephenson's 1849 High Level Bridge, which had proved to be a severe constraint on railway traffic across the Tyne. The King Edward VII Bridge eliminated the need for trains to complete a reversing operation at Newcastle railway station.

It was built by Cleveland Bridge, who have been a frequent presence in this series of posts, having also been responsible for the QEII Metro Bridge, Tyne Bridge, Infinity Bridge and Middlesbrough Transporter Bridge. It was designed by Charles Harrison, nephew of Thomas Harrison who had prepared the working drawings for the High Level Bridge.

In his book British Railway Bridges, David Walters describes this structure as "the last great bridge of the Railway Age in Britain". This seems a little unfair, as Sunderland's impressive Queen Alexandra Bridge, by the same designer, opened three years later. Even the King Edward Bridge's designer himself said of it that "there was nothing very striking in the design of the bridge". When the design and construction was discussed at the Institution of Civil Engineers, almost all the discussion related to the sinking of the foundation caissons.

Comparing the King Edward Bridge to its High Level predecessor, there are significant differences, reflecting the six decades which separate them. Stephenson's bridge incorporated considerable elements of cast-iron, which would later become discredited on the railways following a number of bridge failures. The old bridge had six spans of 125 feet, while the new structure had four spans ranging from 200 to 300 feet. It belonged to the age of steel, and so could avoid the need for so many expensive piers and foundations.

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17 May 2014

Tyneside Bridges: 8. Queen Elizabeth II Metro Bridge

Heading further west along the Tyne, we came to a group of three bridges which are considerably less well known than those in the immediate centre of Newcastle and Gateshead.


Designed by WA Fairhurst and Partners, and built by Cleveland Bridge, the Queen Elizabeth II Metro Bridge opened in 1981. It was built to carry the Tyne and Wear Metro, the first major modern light rail system in the UK. With a main span of 168m, I think it's probably the longest spanning light rail bridge in the country. It's also the longest span over the Tyne (the Tyne Bridge is 162m, while Redheugh Bridge reaches 160m).


In form, the bridge is a three-span continuous through truss girder bridge, although it was constructed as two balanced cantilevers. It's a striking, impressive structure, but I don't find it beautiful.


Perhaps its most interesting feature is the paint scheme. The bridge was not originally blue, but was repainted in 2006 in its present white and blue colours. At the same time, 140 lights were installed as part of artist Nayan Kulkarni's Nocturne artwork, which projects changing colour patterns onto the bridge at night.


Whatever it may look like at night, the effect is interesting in the day time. The "inner" parts of the truss members are painted white, and the effect is to make the truss members appear more slender than they really are. At first I found the effect quite disorientating.

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11 May 2014

Tyneside Bridges: 7. High Level Bridge

If you keep heading west along the River Tyne, you keep stepping back in time, at least, until you reach the High Level Bridge. 2001, 1928, 1876, then finally 1849, which is when Robert Stephenson's High Level Bridge was completed.


Stephenson was in the vanguard of railway bridge engineering when he designed the High Level Bridge.

Two years before, in 1847, his cast-iron bridge over the River Dee for the Chester and Holyhead Railway, had collapsed while carrying a train, killing five people. Stephenson's design for that bridge had been deeply flawed, and he was lucky to survive the subsequent commission of inquiry with his reputation largely intact.

Working with William Fairbairn, Stephenson designed and built two tubular wrought iron rail bridges, at Conwy (1848) and Britannia (1850). These were hugely innovative, and although the tubular concept was a dead end, they were the forerunners of modern box girder bridges.

The High Level Bridge was in my opinion a greater achievement for Stephenson, although it too built upon the work of another engineer. Benjamin Green had proposed a design for a bridge at this site, to consist of tall stone arches carrying a roadway, with iron girders supported above to carry a railway. We had encountered one of Green's bridges, at Ouseburn, earlier the same day. (Another claimant to the design was William Martin, an eccentric philosopher, who published a pamphlet illustrating a very similar design, and claimed that Stephenson had stolen his idea).

Stephenson adapted Green's concept by eliminating the stone arches and by using cast-iron arches to support both roadway and railway. Hollow vertical pillars extend above and below the arches; above, to support the railway, while below, they conceal wrought-iron tie rods from which the road-deck is suspended.

From a distance, the appearance is pleasant and unfussy. From road-deck level, this is less true, with a plethora of structural elements and bracing present.

Originally, the bridge carried a two lane roadway (with tram tracks, for a time), but now carries only a single lane, one-way, for buses and taxis only. The bridge remains a significant industrial monument, but its limited capacity has become clearer over time.

The bridge was extensively refurbished between 2001 and 2008, at a cost of £40m.

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01 May 2014

Tyneside Bridges: 6. Swing Bridge

As my trip headed west along the river Tyne, it was like a journey back through time. From the Millennium Bridge (2001), we next visited the Tyne Bridge (1928). Then we arrived at the Swing Bridge, which was completed in 1876.


The Swing Bridge was also the site of the earliest bridges between Newcastle and Gateshead, the Old Tyne Bridges of 1270 and 1871, and before that possibly the Roman Pons Aelius.


It's not my favourite of the bridges over the Tyne. Its shallow trussed form is somewhat nondescript, not to mention structurally irrational. The more obvious arrangement has a peaked form over the central support, as on New York's Macombs Dam Bridge, to take just one of many examples. The arched form of the Tyne Swing Bridge seems to be pretending to be something completely different to what it really is, although with the construction of the Millennium Bridge, it does lead to a nice visual relationship between the three arched bridges in a row.


I do like the central operations room, with its jaunty seaside cap, all positioned directly over the roadway to give the operator the best views of both river and road traffic. The bridge no longer opens frequently, only about 4 times a week.


Perhaps my favourite feature of the bridge is its parapets, which are a very simple metal mesh, made up of woven metal strips and painted white.

It's interesting to compare this with the other moveable bridge on this stretch of river, the far more flamboyant Gateshead Millennium Bridge. The Swing Bridge is the more efficient solution, with the weight of both spans well balanced so as to minimise loads on the operating machinery. Of course, this comes at the cost of a large pier in the middle of the river. In theory, there's an operational risk that the operator and machinery can become isolated if the equipment breaks down while the bridge is in the open position, but I doubt this will have happened often.

Perhaps more interesting is what the two designs say about the different attitudes to economy, to extravagance, and to discretion, between Victoria and modern times. Is it imaginable that a bridge like the Swing Bridge could be built here today, and is that a good thing, or a bad thing?

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29 April 2014

Tyneside Bridges: 5. Tyne Bridge

We followed the River Tyne westwards, visiting each of its bridges in sequence.


After the Gateshead Millennium Bridge, we travelled back in time over seven decades, to the Tyne Bridge, completed in 1928. This was only the latest in a series of bridges, dating back nearly two millennia to when the Romans first built a bridge here.

Designed by Mott, Hay and Anderson, the Tyne Bridge (1925-1928) was widely compared to the nearly contemporaneous but much larger Sydney Harbour Bridge (1923-1932). Both bridges were built by Dorman Long and Co., and the French engineer Georges Imbault was involved in both cases (Imbault also designed the Middlesbrough Transporter Bridge, which we had visited a day before). A further common factor was the presence of Ralph Freeman, consultant to Dorman Long, who took the lead design role on the Sydney bridge.

The Tyne Bridge appears structurally more rational than its Sydney contemporary. Both bridges are trussed steel arches, from which a road deck is suspended. Both bridges feature prominent but structurally redundant towers above their arch springings. However, the Tyne Bridge is in the form of a proper two-pinned arch, with its steelwork converging on massive hinges at either end. The Sydney bridge is essentially a copy of Gustav Lindenthal's Hell Gate Bridge (1916), with tall trusses at each end to give the impression that the towers are more than architectural book-ends.

The towers for the Tyne Bridge were originally intended to serve both as warehouse space, and also to house lifts providing access from the riverside to deck level. However, the warehouse floors were never installed, and the lifts have long since fallen out of use. It would be interesting to see whether they could be brought back into use to serve a fresh purpose today.

The arch was built by cantilevering from each side, with the steelwork restrained by an array of temporary cables. McFetrich reports that some of the cables were later re-used for the same purpose on the Sydney Harbour Bridge. The expense of temporary works involved in this form of construction is why such bridges are only rarely built today: it is far cheaper to build a cable-stayed bridge and to incorporate the stay cables directly into the permanent works. It's therefore interesting to imagine how different Newcastle and Gateshead would look if the Tyne Bridge were to be proposed afresh today.

For me, the most interesting element of the Tyne Bridge is not its massive main span, but the approach viaducts, particularly on the Newcastle side of the river. These thread their way across historic city streets and between buildings. On large city-centre bridges like this, the approaches are generally the cause of the greatest disruption and destruction when the bridge is built, and they can come to dominate a cityscape in quite an unpleasant way. The approaches to the Tyne Bridge seem to me to fit very well with the scale of the surrounding buildings, and to fit well in that context.

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20 April 2014

Tyneside Bridges: 4. Gateshead Millennium Bridge

I'm still (very slowly) writing up bridges from the second day of last year's IABSE Study Tour of north east England. At last, we came to the mightiest bridge of the tour, the Gateshead Millennium Bridge.

Because I'm struggling to find time to write for this blog, I'm mainly just going to offer you a series of photos with brief comments. But really, this bridge can speak for itself.


This is the classic view of the bridge, taken from the north bank of the Tyne. The weather was fairly miserable when I visited, but that doesn't detract much from this remarkable view.


From a distance, it's not just the arch which is striking, it's also the slenderness of the deck. There's a lot of metal in that deck, but it doesn't look like it from here.


Viewed from the west, the deck appears less slender, as from this side you're looking at the main deck edge girder, not the sharp edge of a walkway cantilever.




The arch is kite-shaped in cross-section, with a curved front face and a sharp rear edge. This simple feature provides the vast majority of the bridge's visual interest, offering a fresh and interesting geometry from almost every perspective.



The deck offers a game of two halves, separating foot from cycle traffic and employing two different surfaces. On the right hand side of the second image, the deck hides a stiff steel box girder. This curves in plan to make it long enough to gain the sufficient navigational height over the river without making pedestrian gradients too steep. On the left hand side, lighter weight aluminium deck panels are supported on transverse cantilever arms.

The two halves are separated by a step and a perforated metal "hedge", which acts as a windbreak and also incorporates space for seating.


A glass "shed" at the south end of the bridge sits above the machine control room, and provides space for the bridge operators to receive guests. A matching glasshouse at the north end is available for other use, e.g. exhibitions, but was unused when I visited.



Each end of the bridge is supported on a giant steel hinge. Below this, a steel fin protrudes downwards. Hydraulic rams act against this fin to raise (or lower) the bridge, and their action has to be carefully coordinated to prevent twist occurring.

The form of bridge is fundamentally inefficient when considered as a moveable structure: it is unbalanced in almost every position, and therefore the loads on the rams are considerably greater than the loads borne by most moveable bridge machinery. The foundations must resist commensurate forces.


On our visit, we were lucky enough to get access both to the hydraulic ram pit and also to the bridge control room. This is the main control panel.



It's a hugely impressive piece of both engineering and architecture, quite deserving of its many accolades and awards. It has been suggested that this is one of the most expensive footbridges ever built, and that's probably true, especially for the width of obstacle crossed. But it's a hugely iconic structure, a tribute to the ingenuity and perseverance of its designers, and certainly one of the most lasting monuments to have emerged from the turn of the millennium.

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