Yorkshire Bridges: 31. Newlay Bridge, Leeds

Okay, this is the penultimate structure in my current sequence of posts. For this one, I headed west out of Leeds to Horsforth, to discover a real gem of a bridge.

Spanning the River Aire, Newlay Bridge was built in 1819, and is one of the oldest surviving cast iron bridges in Yorkshire. It was built by the Bradford-based iron foundry Aydon and Elwell, who also built bridges which survive at Sowerby Bridge (1816) and Walton Hall (1828). Cast iron bridges in Yorkshire date back, of course, to one of the first iron bridges in the world, built at Kirklees in 1769 (yes, ten years before that other one).

The bridge was originally constructed for £1500 at the request of landowner John Pollard, replacing a previous structure built in 1783. A halfpenny toll was charged, earning Pollard £600 per year.

Different accounts vary on what happened to the bridge in later years: Civil Engineering Heritage reports that the bridge was taken over by the Midland Railway and Horsforth Council in 1880, providing access to Newlay and Horsforth Railway Station. The Newlay Conservation Society mention that the Midland Railway built a new footbridge in 1886, which would seem odd if they had just acquired this bridge. Photos suggest the second bridge to have been just downstream, closer to the river weir.

The Pastscape website has a hugely detailed description of the bridge, so I'll not repeat that here. The bridge comprises four cast iron ribs, separated by cast iron bracing members. It spans approximately 25m.

The structure is very well apportioned. The layout and spacing of the bridge spandrel members is surprisingly modern. The edges of the main ribs, and also the centreline of the spandrel members are reinforced with small outstands, which also provide a degree of visual definition to what would otherwise be quite plain.

The stringcourse fascia is subdivided into repeating panels, with the smaller panels coinciding with the main parapet posts above. These posts are an ornate ironwork design, with plain vertical infill bars in the sections in between. Panels on the parapet credit Pollard, Aydon and Elwell.

Leeds Council are planning to refurbish the bridge in summer 2018, although I thought it looked in pretty good condition already. The parapets were repainted as recently as February 2017, although the underside of the bridge was not repainted at that time. As at Leeds Bridge, the bridge will be repainted using a High Ratio Co-Polymerised Calcium Sulfonate Alkyd paint system, specially sourced from North America. The driver seems to be the bridge's bicentennial anniversary, which falls in Spring 2019.

This is a well-preserved, interesting and historic bridge, in a very attractive setting, and well worth a visit if you are in the area.

Further information:

• Google maps
• British Listed Buildings
• Pastscape
• Newlay Conservation Society
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

Yorkshire Bridges: 27. Leeds Bridge, Leeds

This is another of the older bridges spanning the River Aire in Leeds, but far from the oldest. I previously reported on Crown Point Bridge, complete in 1842, and will shortly cover Victoria Bridge, completed in 1839. The Leeds Bridge which can be seen today wasn't opened until 1873.

However, a bridge at this site may date back at least to the 14th century. The medieval bridge was widened several times, in 1730, 1760 and 1796, before the present-day bridge was built to replace it.

The bridge visible today is a cast iron arch. A plaque on the bridge credits numerous mayors, aldermen and councillors, as well as William Henry Barlow, Consulting Engineer, and Thomas Dyne Steel, Engineer. The contractor was David Nichols, while the ironwork was provided by John Butler.

Barlow also designed the Clifton Suspension Bridge (with John Hawkshaw, completing Brunel's design), and St Pancras Station. Steel had begun his career apprenticed to James Rendel, and had wide experience in railways, mining, and industrial manufacture. According to his obituary, he became a specialist in iron roofs and bridges later in his career.

The bridge is Listed Grade II, and according to the listing, only the external arches are cast iron, with the internal arch ribs being in wrought iron and the deck in steel.

The bridge is currently undergoing strengthening and refurbishment, with a new reinforced concrete slab being installed before complete repainting takes place. The paintwork will be undertaken using a High Ratio Co-Polymerised Calcium Sulfonate Alkyd paint system, specially sourced from North America.

Further information:

• Google maps
• Wikipedia
• Structurae
• British Listed Buildings
• CanalPlanAC

Yorkshire Bridges: 24. Crown Point Bridge, Leeds

This is the next bridge across the River Aire in Leeds, proceeding west from Knight's Way Footbridge.

Crown Point Bridge was built in 1842, and is Listed Grade II. The Listing states that it was designed by George Leather, but an ICE obituary attributes the bridge to George's son, John Wignall Leather. The pair played a key part in development in the Leeds area at the time, developing the Aire and Calder Navigation, and a series of bridges, including Monk Bridge (1827), Victoria Bridge (1839) and the Stanley Ferry Aqueduct (1839).

The Crown Point Bridge was constructed to provide a connection to new areas of Leeds then undergoing development, and was authorised by an Act of Parliament in 1840. In its original form, it comprised ten parallel cast iron arch ribs, spanning 120 feet.

The cast iron elements were supplied by Booth and Co., of Sheffield's Park Ironworks, at a cost of £8,750. The total bridge construction cost was £36,000, including approach spans. Initially the bridge was tolled, although the toll was removed in 1868.

The bridge is ornate in the extreme, but it remains elegant due to the basic clarity of the different pieces - the arch ribs, spandrel X-bracing, beams and parapets.

In 1989, the bridge was assessed as unsuitable for heavy modern traffic, and Leeds City Council designed a strengthening and widening scheme, completed in 1995. The basics of the scheme can be seen from below the bridge: the two edge arch ribs on each edge of the bridge have been retained and relocated, and twelve new steel arches have been inserted in between.

The cost of the scheme was approximately £2.2m. The existing foundations were widened and strengthened with the insertion of new mini-piles. The arch ribs on the eastern face were extended in length by replacing one 7.5m segment with new longer cast iron segments: this is visible in some of the photographs, although it's certainly not immediately obvious.

The bridge alterations won a City of Leeds Award for Architecture (1996) and were Commended in the ICE Yorkshire Association Awards (1997). Photographs taken during construction can be found at the Richard's Bridges website link below, the Richard in question being J Richard Kay, former Chief Bridge Engineer for Leeds City Council.

Further information:

• Google maps
• Richard's Bridges
• Structurae
• British Listed Buildings
• CanalPlanAC

Yorkshire Bridges: 18. Stanley Ferry Aqueduct

I recently had some time on a trip to Leeds to see a few bridges, both in the city and nearby.

The first bridge I visited was the Stanley Ferry Aqueduct, which is claimed to be the largest cast iron aqueduct in the world, and possibly the first iron aqueduct to have been supported from suspension hangers. It is both a Scheduled Monument and also Grade I Listed. This photo makes it look much smaller than it really is:

Built in 1839, the aqueduct carries the Aire and Calder Navigation, a canal, across the River Calder. The structure was designed by engineer George Leather (probably with his son John Wignall Leather), and comprises a cast iron trough suspended via wrought iron rods from two cast iron arches.

Leather had originally developed a multi-span design, which met with the approval of Thomas Telford, but it was eventually decided to build a single span structure, to reduce any hindrance to water flow in the river. As built, the arches span 47.2m across the river, although the canal trough is longer at around 50m. The trough is 7.3m wide and 2.6m deep, containing some 955 tonnes of water. This phenomenal load is carried on a series of cast iron cross-frames, supported from the hanger rods.

None of this can be seen directly, as it is all hidden behind decorative colonnaded fascia panels. The bridge abutments are also hidden, disguised behind faux-Greek pavilions (you can only see the tops of these in some of my photos). The support arrangement is show in this diagram (taken from Broad's paper, see link below):

The two arches are also cast iron, each cast in seven segments, with each segment having four Vierendeel-type openings. The arch ribs taper from 1.83m deep at the crown to 3.02m deep at the supports. In contrast to the rest of the bridge, the form of the arch is surprisingly modern, compare for example the Taunton River Tone bridge.

The bridge was extensively refurbished circa 1986. Impact to the sides of the trough from large canal barges was repaired using the Metalock process. The hangers were in some cases highly corroded, and found to be carrying uneven loads (ranging from 5 to 25 tonnes), so several hangers were replaced, and all were re-tensioned. The bridge was completely repainted.

It's a magnificent structure, but not an easy one to see well. It can be viewed from a road bridge to the west, or from a field and canal towpath to the east. Closer viewpoints on its west side are within private property, and I could not get access.

If you want to see how the bridge looks from close-up, there are some good photos at the Stanley History website linked below.

Immediately to the east of the bridge, a second aqueduct was built in 1981. This is a huge, deep prestressed concrete trough structure. It resembles a dam more closely than a bridge.

East of that there is a "trash screen footbridge", which provides access along the canalside but also helps to trap the great piles of debris which wash down the Calder. All three bridges have surprisingly little clearance to the river below. When the Calder floods, the aqueduct is nearly entirely submerged.

It's a shame Stanley Ferry Aqueduct isn't more accessible for visitors: it is a one-of-a-kind structure. The Canal and River Trust held an open day at their adjacent workshops back in 2016, from where great views are possible, and perhaps they will do so again.

Further information:

• Google maps
• Wikipedia
• Structurae (1839, 1984)
• British Listed Buildings
• Engineering Timelines
• Graces Guide
• CanalPlanAC
• Stanley History Online
• The National Trust Book of Bridges (Richard, 1984)
• The Design and Construction of Stanley Ferry Aqueduct (Nogue, The Structural Engineer, 1984)
• Restoration of Stanley Ferry Aqueduct (Broad, in Conservation of Engineering Structures, 1989)
• The Bridges of Lancashire and Yorkshire (Slack, 1986)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)

French Bridges: 13. Pont au Double, Paris

The Pont au Double was originally built in 1634 to connect the Hôtel-Dieu on the Île de la Cité (an early hospital) to an annexe on the left bank of the Seine. The bridge accommodated further hospital buildings along its length, but was also open to the public as a toll bridge, with the fee being a double denier, hence the bridge's name.

This twin-arch bridge was replaced by a single arch structure in 1848 to improve river navigation, and then again in 1883 by the present-day structure, designed by Jules Lax. Today the bridge provides a key link from the left bank of the Seine to the piazza in front of the Notre Dame cathedral.

Various sources describe the bridge as wrought-iron with steel bracing, but this seems self-evidently incorrect. Seen from below, the 11 arch ribs can be seen to be made up of short cast iron segments, although the bracing may well be different in origin.

The two edge arches, and the balustrade above, are coated in copper, a highly unusual feature which makes the bridge gleam in the sunlight. The bridge was extensively refurbished around 2002-2004, and photographs from before this show the copper in its distinctive green weathered colour.

The French edition of Wikipedia refers to a copper galvanising process developed by M. Oudry, which is described in a book on electroplating of metals. The process involves specially varnishing and treating the cast iron before placing it in a bath of copper sulphate, which coats the cast iron object through the normal electrical galvanising process.

I guess the use of this process may explain the short length of the cast iron segments on the bridge, which would have to be short enough to be placed into a galvanising bath.

It's not clear how the coating was re-applied in the 2004 restoration project: there was an article in Bulletin ouvrages métalliques but I don't have a copy, so if any reader can shed more light, please do so!

I'd also be interested in examples of any other bridges where the same treatment has been applied, if there are any. It seems quite unusual, but it's certainly responsible for a key part of the bridge's beauty.

 

Further information:

• Google maps
• Wikipedia
• Structurae
• Bridge of the Week
• Planete TP
• Soundlandscapes Blog
• The History of Paris from the Earliest Period to the Present Day (Galignani, 1825)
• The Glow of Paris: The Bridges of Paris at Night (Zuercher, 2015)
• Bridges of Paris (Saint James, 2015)

Irish Bridges: 1. Ha'penny Bridge, Dublin

I had a flying visit to Dublin late last year, and have three bridges to cover here on the blog, all of them spanning the River Liffey.

The first, variously known as Liffey Bridge, the Metal Bridge, or the Halfpenny / Ha'penny Bridge, was built in 1816, Ireland's first iron bridge. It was imported from the Coalbrookdale foundry in Shropshire, England, and comprises a cast iron arch spanning 43m. When first built, a half-penny toll was charged to bridge users.

The bridge was extensively refurbished in 2001, but so far as I could tell on my visit, the bridge appears to have been very little altered.

I think this is a bridge which has aged well. The shallowness of the arch is bold and attractive, as is its shaping, with the slender crown and stout abutments. The pattern of the arch ribs seems more open and appealing than the criss-cross arch webs used on many other bridges of the time, and closely echoes Cantlop Bridge, built in England three years previously, and which was possibly designed by Thomas Telford.

I like the "two-layered" parapets, but the overhead ornamental lighting brackets are not to my taste.

Further information:

• Google maps / Bing maps
• Wikipedia
• Bridges of Dublin
• Structurae
• Halfpenny Bridge Refurbishment
• Ha'penny Bridge Restoration (video, 2001)
• The Ha'penny bridge in Dublin (De Courcy, The Structural Engineer, 1991)
• Civil Engineering Heritage: Ireland (Cox and Gould, 1998)
• Ireland's Bridges (Cox and Gould, 2003)
• Project History of Dublin's River Liffey Bridges (Phillips and Hamilton, Proc. ICE Bridge Engineering, 2003)

Scottish Bridges: 40. Craigellachie Bridge

I guess that of all the bridges we visited in Scotland, this was by far the best known.

As the "further information" section at the end of this post suggests, this is a very well-documented bridge, so I will say as little as possible about its history, and concentrate on how it looks today.

The facts, in brief: spanning 150 feet across the River Spey, Craigellachie Bridge was designed by Thomas Telford. It was his second cast iron arch road bridge of this type, the first being the now-gone Bonar Bridge. The bridge at Craigellachie was completed in 1814 at a cost of £8,200. It was extensively refurbished in 1964, and closed to all traffic in 1972. It's a Listed Building, Scheduled Monument, and an ASCE International Historic Civil Engineering Landmark.

On the day that we visited, which as with most of our trip was particularly wet, it was hard to appreciate the bridge at its best. Even in these conditions, it is a remarkable bridge. Perhaps the swollen river below just helps to emphasise why such a bold structural feat was attempted.

Compare Carron Bridge, which we had visited just over an hour beforehand. Both bridges are 150 foot span cast iron arches across the same river, with the ribs surmounted by X-braced spandrels. Craigellachie has four ribs and Carron has three. Carron was completed in 1863, almost half-a-century after its forebear, but visually it is a far poorer bridge.

The arch ribs on Carron are flat-faced girders, whereas Telford's bridge used pierced-web girders. They make the bridge look lighter and add visual texture. They are also less deep than those at Carron, although to be fair it has to be remembered that Craigellachie was designed only for highway traffic, while Carron Bridge had to carry steam railway locomotives.

This factor also accounts for the noticeably heavier spandrel members at Carron. Those at Craigellachie are amazingly slender, especially when viewed from close at hand. It's almost impossible to believe a modern highway bridge could be designed with such slender struts (and indeed, Craigellachie Bridge could not carry modern highway loads).

The pattern of the X-bracing is also different on the two bridges. At Craigellachie the spandrel members change in angle across the span such that the "diamonds" vary in angle to be roughly perpendicular to the arch rib. At Carron, they are oriented so that the "diamonds" are always vertical. That seems more rational, as their main function is to carry vertical loads from the deck down to the arch ribs, but it seems to me to be less attractive visually.

Another feature forced upon Carron by the nature of what it carries is that the deck is level, giving the bridge an appearance which rather stiff. Craigellachie Bridge has a vertical curvature which is much nicer.

While many of these features are consequences of either the loads supported or changes in engineering understanding, the last key feature which differentiates the bridges seems primarily a matter of choice. The abutment faces at Craigellachie are inclined perpendicular to the arch ribs, creating the sense that the bridge springs across the river, and also that the abutments are working properly to resist the thrust of the arch. The vertical abutments at Carron give a more precarious impression - it appears far from impossible that both the arch and the deck could just slide vertically downwards into the river.

The abutments at Craigellachie were never uncontroversial, however, because of the masonry turrets which punctuate the end of the span. These looked archaic even in Telford's day. I think they're rather pleasant, they frame the bridge visually, and look less obtrusive because they are dwarfed by the cliff face on the north-west end of the bridge.

Further information:

• Google maps / Bing maps
• RCAHMS
• Scottish Highland Bridges
• Moray SMR
• British Listed Buildings
• Wikipedia
• Engineering Timelines
• Our Transport Heritage
• ASCE
• Structurae
• The Life of Telford (Telford, 1838)
• The Life of Thomas Telford, Engineer (Smiles, 1867)
• The Reconstruction of the Craigellachie Bridge (Lowson, 1967, The Structural Engineer)
• Highland Bridges (Nelson, 1990)
• Civil Engineering Heritage - Scotland Highlands and Islands (Paxton and Shipway, 2007)
• Thomas Telford's Cast-Iron Bridges (Paxton, 2007, Proc. ICE)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)
• A Critical Analysis of Thomas Telford's Craigellachie Bridge, Scotland (Saarinen, 2011, Bath Student Conference)