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?

Further information:

• Google maps / Bing maps
• Wikipedia
• Structurae
• Engineering Timelines
• British Listed Buildings
• Bridges on the Tyne
• Our Transport Heritage
• William Armstrong: Magician of the North
• The Bridges of Northumberland and Durham (Graham, 1975)
• A Celebration of Bridges between the Tweed and the Tees (Hartley and Brown, 1995)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• Crossing the Tyne (Manders and Potts, 2001)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

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.

Further information:

• Google maps / Bing maps
• Wikipedia
• Structurae
• Engineering Timelines
• British Listed Buildings
• Bridges on the Tyne
• Archive construction photos from Dorman Long
• The Building of the New Tyne Bridge (video)
• The Tyne Bridge (Mountney, The Structural Engineer, 1928)
• Tyne Bridge, Newcastle (Anderson, Proc. ICE, 1930)
• British Bridges (1933)
• The Bridges of Northumberland and Durham (Graham, 1975)
• A Celebration of Bridges between the Tweed and the Tees (Hartley and Brown, 1995)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• Crossing the Tyne (Manders and Potts, 2001)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

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.

Further information:

• Google maps / Bing maps
• Wikipedia
• Structurae
• Engineering Timelines
• Bridges on the Tyne
• Gateshead Council (lifting times, visitor details etc)
• LUSAS
• Ramboll
• Wilkinson Eyre
• The Gateshead Millennium Bridge (Clark and Eyre, The Structural Engineer, 2001)
• Crossing the Tyne (Manders and Potts, 2001)
• Gateshead Millennium Bridge (Brownlie, Footbridge 2002)
• Bridge Builders (Pearce and Jobson, 2002)
• Bridges (Torres Arcila, 2002)
• 30 Bridges (Wells, 2002)
• Gateshead Millennium Bridge, UK: fabrication, assembly and erection (Butterworth, Carr, and Kassabian, ICE Bridge Engineering, 2003)
• Gateshead Millennium Bridge, UK (Curran, Structural Engineering International, 2003)
• Gateshead Millennium Bridge - an eye-opener for engineering (Johnson and Curran, Proc. ICE, 2003)
• A critical analysis of the Gateshead Millennium Bridge (Blandford, University of Bath, 2007)
• Footbridges (Baus and Schlaich, 2008)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)
• Masterpieces: Bridge Architecture + Design (Van Uffelen, 2010)

Tyneside Bridges: 3. Byker Metro Bridge

The third and most recent high-level bridge to cross the Ouseburn Valley is the Byker Metro Viaduct, completed in 1982 for the Tyne and Wear Metro.

It is 815m long and curves in between the Ouseburn Viaduct (1839) and Byker Bridge (1878).

I only had time to visit its western end, which spans the valley. Much of the viaduct, at its eastern end, runs at about 6-7m above ground level, and is visually less imposing.

The bridge was the first glued segmental precast prestressed bridge to be built in Britain. The main spans are 69m long, with haunched concrete box girders supported on twin-stem piers. The bridge's appearance was considered significant enough for the design to be presented to the Royal Fine Art Commission in 1975.

The form of construction lends itself to a site where there was highly restricted access for plant. The concrete segments were precast off site, and winched down the valley slopes on temporary tracks. The length of each segment was just narrow enough to allow it to pass through an opening in the bridge piers, allowing the segments to be manoeuvred along a very narrow construction strip. They were then lifted and erected using the balanced cantilever method. Each segment was bonded using epoxy glue, and stressed in place with short length bars. Further prestressing was added in later stages.

The segments were "match-cast" i.e. each one was cast against its preceding segment, to ensure a perfect fit. Sawteeth keys in the webs, still visible in the completed structure, help align the units during erection. In practice, this method requires very careful measurement and control, as errors have the potential to accumulate over multiple segments. This is exactly what happened with the Byker Metro Viaduct, with a significant twist detected as more segments were added. Special segments had to be cast to correct the twist.

The finished bridge is aesthetically striking, and I think very successful. The plain finishes to the concrete deck contrast with a vertically ribbed finish on the piers and precast parapets. The ribs are nicely detailed, splaying out as the piers widen out towards their base. Horizontal feature grooves have been included on the piers to disguise construction joints.

The splayed piers both give an impression of considerable stability (required to resist centrifugal loads from the metro vehicles), but also make what are quite substantial concrete sections look quite elegant.

I think this is easily one of the most impressive and well thought out bridges on this scale to have been built in Britain.

Further information:

• Google maps / Bing maps
• Structurae
• Engineering Timelines
• Northern Architecture
• Tyne and Wear Metro: Byker Viaduct (Smyth, Benaim and Hancock, Proc. ICE, 1980)
• British Railway Bridges and Viaducts (Smith, 1994)
• A Celebration of Bridges between the Tweed and Tees (Hartley and Brown, 1995)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• Engineering Architecture (Benaim, Ingenia, 2002)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

Tyneside Bridges: 2. Byker Bridge

The second bridge to be built linking the crests of the Ouseburn Valley was the Byker Bridge, built in 1878 to a design by Robert Hodgson. Hodgson had been Robert Stephenson's Resident Engineer for the construction of the Newcastle High Level Bridge, and the original Byker Bridge very much resembled a railway structure, with its tall brick arches.

When first built, users of the bridge had to pay a half-penny toll, although this was withdrawn in 1895.

According to the ICE's Civil Engineering Heritage book, the bridge was widened in 1902, to cantilever the footpaths beyond the edge of the brickwork; and then the widening was "improved" in 1985, adding prestressed concrete beams on cantilevers to support both footways and new crash barriers.

Clearly, "improved" is used only in a technical sense, as the widening has utterly spoiled the appearance of the bridge. The original bridge appears not to have been a great beauty - its tall piers taper slightly, which seems attractive, but the semi-elliptical arches look awkward.

Now, the stubby little concrete cantilevers look quite horrible, and the effect of the deck widening is to hide the crowns of the arches, "squashing" them unpleasantly.

Further information:

• Google maps / Bing maps
• Structurae
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

Tyneside Bridges: 1. Ouseburn Viaduct

I'm continuing my series of posts on the bridges of north-east England which I visited as part of an IABSE study tour last year. The second day of the tour had begun with a visit to the delightful Cragside Iron Bridge. From there we went to Newcastle-upon-Tyne.

Three tall bridges span the Ouseburn Valley in Newcastle-upon-Tyne. The Ouseburn Viaduct was the first of the trio to be built, in 1839, to a design by John and Benjamin Green. To place it in context, it was built ten years before Stephenson's High Level Bridge in the same city, and was completed in the same year as Brunel's Maidenhead Bridge for the Great Western Railway. At this time, anything other than a brick or masonry bridge remained relatively unusual on the railway.

Brunel's famous timber railway viaducts in Cornwall would not be completed for another two decades, but timber structures were springing up in various other places. In the same year as the Ouseburn Viaduct, the timber Scotswood Bridge was completed in Newcastle. Within the next decade, timber arch viaducts would be completed at Etherow and Dinting Vale, both near Manchester.

The Ouseburn Viaduct, along with the Willington Viaduct built at the same time on the same railway line, was originally a timber arch structure, built using the Wiebeking system. This involved the use of laminated timber sections, made from Baltic softwood, and preserved by Kyanising.

The timber bridge lasted for three decades, and was replaced in 1869 by the wrought iron bridge which remains there today. The pattern of the ironwork closely followed the geometry of the original timber structure.

In 1885, the bridge was widened, doubling the number of arch ribs, to carry additional railway tracks. Since then much of the valley floor has been infilled, hiding the original stone piers, which appear to have been much taller in old images and drawings of the bridge.

This wasn't an easy bridge to photograph, half hidden by trees and by adjacent structures.

There's a lovely quote in Benjamin Green's ICE paper concerning this bridge, from another consulting engineer:

"It appeared to me that to cross the Ouse Burn and Willington valleys, would be a work of so much labour and cost, that I would not conscientiously recommend the Committee to prosecute their plan. These difficulties, however, are likely to be removed, and most effectually surmounted by the great scientific and practical knowledge of Mr Green, who proposes to pass over them by bridges of peculiar construction, and at a comparatively light expense. To him I would most willingly transfer that responsibility, having no pretensions to skill in bridge building myself."

Further information:

• Google maps / Bing maps
• Structurae
• LNER Encyclopaedia
• On the arched timber viaducts on the Newcastle and North Shields Railway (Green, Proc. ICE, 1846)
• British Railway Bridges and Viaducts (Smith, 1994)
• A Celebration of Bridges between the Tweed and the Tees (Hartley and Brown, 1995)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)