Showing posts with label Derbyshire bridges series. Show all posts
Showing posts with label Derbyshire bridges series. Show all posts

13 September 2020

Derbyshire Bridges: 5. Headstone Viaduct

This will be my final "Derbyshire Bridge" for now, and this one is a well-known historic classic, Headstone Viaduct, also often known as Monsal Dale Viaduct. It is the star of a famous London Midland and Scottish Railway poster used to attract tourism to the Peak District, depicting a deservedly spectacular location (albeit with some artistic license!)

The viaduct was completed in 1863 as part of the Midland Railway company's Manchester, Buxton, Matlock and Midland Junction Railway. This railway has a long and complex history, which (if so inclined) you are better off reading at Wikipedia than I am repeating in any detail here. Suffice to say that the route connected Derbyshire to Manchester through the hilly terrain of the Peak District, and substantial civil engineering works were required.


It seems a wonder now that there were ever funds available to build a railway through such difficult terrain, necessitating not only major viaducts but a number of substantial tunnels. Perhaps it is worth imagining what the nature of the highways of the time must have been, for this to have been an attractive alternative.

The viaduct has five arches each spanning 50 feet (15.5m), and is roughly 25m tall. It originally carried two railway tracks, emerging from a tunnel in the steep hillside to the east and then passing along the flank of another hill to the west.

The railway was closed in 1968, and the route was converted to the Monsal Trail for cyclists and walkers in 1981. The closest you can come now to reliving the steam train experience would be to hurtle westwards on a bicycle at speed from the tunnel mouth into the open air, taking in the views with a sense of astonishment and relief.

The viaduct design has been credited to William Henry Barlow, perhaps best known for the design of another Midland Railway project, the St Pancras train shed. Headstone Viaduct is far from his most notable bridge: along with John Hawkshaw, he completed Brunel's Clifton Suspension Bridge, and he also designed the replacement for Thomas Bouch's ill-fated Tay Bridge. However, Midland Railway engineer Frederic Campion may have held more direct responsibility.

The construction of the arch barrels is a little peculiar. The facing voussoirs on each arch comprise seven rings of brickwork (an inner two bonded together, and then five outer rings), down to springing level. The piers and spandrel walls are in rubble stonework, and stone is also used for the lower part of the inner face of the arch barrel. The upper parts of the arch barrel are in brick. It seems an odd arrangement.

Brickwork is also extensively employed above two arches on the south elevation, possibly associated with remedial work completed in 1907-8. I doubt that many visitors notice!

The overall impression is robust but not excessively so - the scale and nature of the bridge is entirely appropriate to its setting. It's interesting to wonder what would be built if a similarly beautiful valley were to be crossed by a new railway today.

The Victorian polymath and art critic John Ruskin (something of a 19th century Brian Sewell) certainly didn't appreciate either the railway or the viaduct, writing:
"There was a rocky valley between Buxton and Bakewell, once upon a time, divine as the Vale of Tempe ... You Enterprised a Railroad through the valley - you blasted its rocks away, heaped thousands of tons of shale into its lovely stream. The valley is gone, and the Gods with it; and now, every fool in Buxton can be in Bakewell in half an hour, and every fool in Bakewell at Buxton; which you think a lucrative process of exchange – you Fools everywhere."

As is often the case, age provides architecture not only with grace, but it also elevates the perception of the location as a whole. Without the viaduct, this could just be any other pretty green Pennine dale. The viaduct is the centrepiece, the thing that visitors peering down into the valley from above all point their cameras towards.

It also provides a fine platform from which to view the surrounding greenery. Many visitors descend the path from the nearby Monsal Head car park to admire the viaduct and the tunnel entrance without going any further. An encounter with England's green and pleasant land need not require a lengthy trek.

It is certainly worth taking the time to go a little further and follow the path below the viaduct. From above it is impressive, but dwarfed by the surrounding landscape. From below, the opposite is true, it is a stone giant soaring overhead, framing shorter views and guiding the curious visitor eventually to the banks of the River Wye, ultimately responsible for carving this landscape over unimaginable years past.

It has obviously been a site for a more interactive visitor experience in the past. Signs on the viaduct draw attention to metal bars, suspended from the arches and stretched between the stone piers. These are intended to prevent people from leaping off the viaduct attached to a rope and swinging underneath. Certainly nobody was trying it when I visited.

Part of the railway line was reopened as a "heritage" service in 1992. There are broader ambitions to reopen the whole route as a "proper" railway, with Monsal Trail "reprovisioned", whatever that means. Personally, I think it would be a real shame if it denied people the chance to get up close and personal with the trail, its tunnels and viaducts.


Further information:

09 September 2020

Derbyshire Bridges: 4. Railway Viaduct, Edale Road, Hope


This is another 1970s structure built to replace one of the original bridges on the Hope cement works railway line (for context on the railway, see my earlier post).

The original 1929 bridge was a reinforced concrete trestle structure 347ft (106m) long, with eight spans of varying length. A 13ft (4m) wide deck slab spanned onto rail-bearers and crossbeams, which were supported from raised concrete girders on both edges of the deck. These then sat on reinforced concrete columns, braced with horizontal members to create H-frames.

The viaduct actually consisted of two structures, with a double-trestle in its middle and a copper expansion joint separating the two. The end trestles were buried within approach embankments, and will have provided stability against longitudinal loads from the railway. There is an image in Concrete and Constructional Engineering magazine which shows the finished viaduct:


There is also a photograph on designer Geoff Bond's website showing the 1929 structure hidden behind the new bridge, presumably pending demolition.

The present bridge is a 5-span post-tensioned concrete viaduct, carrying the railway over the Edale Road and the adjacent River Noe. I think it looks rather elegant in an artist's impression from 1973.

The main feature that makes it unusual is the way in which the lower flange of the box girder is extended outwards. Normally, such bridges extend only the upper flange (to form the road or railway deck), there is no obvious benefit to complicating things by extending the lower flange. Geoff Bond was a member of the design team at Oscar Faber and Partners, and his website indicates that the rationale was "to resist reverse bending moments and severe locomotive shear stresses".

I'm left slightly puzzled, and would love to have been able to find more information.


Further information:
  • Google maps
  • Reinforced Concrete Bridges in Derbyshire (Concrete and Constructional Engineering, 1929)

06 September 2020

Derbyshire Bridges: 3. Hope Catenary Footbridge

This bridge carries what is now a public footpath across the Breedon Cement works railway line in Hope. See my previous post for some background on the railway line.


I haven't been able to work out whether this bridge, built in 1974, replaced an earlier bridge or perhaps a foot level crossing. Its construction may have been necessitated by the widening of the railway from one track to two tracks at this time.

It was the first stress ribbon bridge to be built in the United Kingdom, and I believe it remained the only one until the completion of the Kent Messenger Millennium Bridge in 2001.

The 1974 footbridge was designed by Oscar Faber and Partners (later merged into Faber Maunsell, now part of AECOM), and both A.A.W. Butler and Geoff Hope claim credit for the engineering design. It was built by A. Monk and Company.

Butler had worked on the Elephant and Castle Shopping Centre and the M1 Calder Bridge while at Gifford and Partners, before joining Faber in 1968. Bond had designed the Windsor End Footbridge for Buckinghamshire County Council, and worked on refurbishment of the suspension system for Marlow Bridge. He had joined Faber by 1969 and then worked for a time in Nigeria before returning to the UK to work on bridge designs for the Hope cement works (this one, and also the subject of my next post). Bond's potted autobiography is a hugely entertaining read, revealing that Bond's engineering career was essentially a mistaken diversion for a man clearly with wider interests to pursue.

It isn't immediately clear why Butler and Bond opted for a stress ribbon design. In his 1977 paper describing the bridge, Butler suggests that appearance was of "paramount" importance in a sensitive landscape, and it is worth bearing in mind that the site was originally much more open in appearance than it is today. The cutting slopes rise around 6 metres above the level of the railway track, and rock is present close to the top of the cutting.

Butler indicates that interference with rail traffic during bridge construction was a further concern. The bridge spans 34m, is 1.8m wide, and is 0.16m thick (increasing to 0.38m thick over a short length towards the abutments). However, during preliminary design the design team considerd both an in-situ ribbon slab and one made of precast segments. The in-situ variant was chosen on cost grounds, but it's hard to see how it can have been less disruptive to the railway!


The superstructure of any stress ribbon bridge is economic in its use of materials (here it is just the deck slab, 12 prestressing cables, and steel parapets). The bridge hangs like a catenary and the cables are employed both to carry tension to the foundations and to pre-compress the deck concrete. The concrete provides the walking surface, protects the cables against corrosion, and ensures the bridge is sufficiently stiff under loads.

Although the bridge deck is economic, the tension loads inherent in the bridge form can result in expensive foundations. The tension is partly resisted by four ground anchors at each end of the bridge, but the designers struggled to provide sufficient restraint in this way, and opted to also install concrete struts which pass down the cutting slope and below the railway. In the final design as built, the struts, in conjunction with the mass of the abutments, are sufficient to resist all dead loads and the ground anchors are only required to resist the effects of live loads.


The in-situ concrete ribbon was constructed on timber formwork supported on scaffolding, with steel beam supports over the railway to minimise disruption. I imagine that very few stress ribbon bridges have been built in this way.

In 2002, the bridge was used as a test site for bridge dynamic measurement. This recorded a first vertical natural frequency of 2.44 Hz, and a modal damping ratio of approximately 0.5%. Vibration was certainly perceptible when I crossed the bridge, especially when I asked a companion to jump up and down. Perhaps this is the reason why signs restrict the bridge to no more than 20 persons at a time, although I doubt it ever encounters that many at one time (Butler's paper mentions a design live load of 6kN/m2, which is clearly far more than 20 persons).

The bridge was very difficult for me to photograph due to tree growth, so I can recommend Geoff Bond's website for photographs taken shortly after construction.


This is not by any means a significant bridge in the context of international stress ribbon bridges. Within the British context, the main reason for taking note is that its very rarity shows how difficult it can be for engineers to find opportunities to depart from the tried-and-tested. It's always nice to find the instances where engineers did indeed escape from the conventional rut.

Further information:

04 September 2020

Derbyshire Bridges: 2. Railway Bridge, Castleton Road, Hope - Update

Many thanks to crisb who commented on my previous post about this bridge, drawing my attention to a number of publications from 1928-29 shedding further light on its history.

The bridge was mentioned on several occasions in the journal Ferro-Concrete: The Review of Reinforced Concrete. I believe this may have been promoted by L. G. Mouchel and Partners as a way of publicising the Hennebique system of reinforced concrete, for which they held the UK license.

The 117ft (35.7m) long bridge was described as having one 54ft (16.5m) central span, and two 21ft (6.4m) side-spans, sized to allow for future widening of the road. As well as being used in production of cement, the local limestone was crushed to form the aggregate for the concrete used in the bridges. Tests were undertaken to demonstrate that sufficient strength would be achieved.

The journal included this picture of the bridge under construction:


An article appeared in Concrete and Constructional Engineering magazine in 1929 on "Reinforced concrete bridges in Derbyshire". This noted the client as Messrs. G. and T. Earle Ltd., the owner of the cement works, and stated the design engineer as being Mouchel's firm. Messrs. F. Mitchell and Sons Ltd. were identified as the contractor.

This article confirmed the key dimensions of the bridge, also reporting that the structure comprises a 7.5" (190mm) thick reinforced slab, carried on 24" x 9" (610mm x 229mm) secondary beams at 4'3" (1.3m) centres, these supported from the main edge beams.

According to Ferro-Concrete, the completed bridges were "of most artistic appearance".

01 September 2020

Derbyshire Bridges: 2. Railway Bridge, Castleton Road, Hope

It has been a while since I've been able to get out and about visiting bridges, but during the summer I got to see a few bridges in Derbyshire. The first three all carry a private railway line to Breedon Cement Works near Hope.

This area was historically a lead mining area, and it was not until 1929 that quarrying of limestone began on a large scale and a cement works was built.

The cement works operated for several years before the Peak District National Park was created in 1951. Once the National Park came into being, agreement was reached for the vast bulk of the cement produced here to be transported by rail rather than road (amounting to over 1.5 million tonnes of cement annually). The cement works operates its own private railway track connecting onto the main Hope Valley railway line. The tracks pass under and over a number of bridges, some of which are of surprising interest.


At least one of the original bridges survives, carrying the railway across Castleton Road. This is a three-span reinforced concrete bridge (perhaps appropriately, given its purpose to help transport cement). Presumably it dates from around 1929 as well. I haven't found any information on who designed it, or built it, or whether an architect was involved along with the engineer. One website suggests this bridge was "something of a showpiece for the works", which I guess might have been true.


There is some traditionalist looking detail on the elevation of the bridge but the arched/haunched main beams are left unadorned. The beam-and-slab deck is a little like what would be called a ladder-deck bridge today, but it is in line with many early reinforced concrete structures patterned after the joist-and-floor layout familiar from iron and timber buildings. The internal arches to the piers are a nice detail that would be omitted in a more modern structure.


There are dents and scrape marks to the underside of the main beams, caused by over-height vehicles. Viewed close up, it looks as though the original reinforced concrete has been overcoated with a thin layer of additional material at some stage.

It's good to see this bridge surviving reasonably well, but it's the bridge in my next post that is the real highlight along this railway, and the reason I visited.

Further information:

12 January 2020

Derbyshire Bridges: 1. Cathedral Green Footbridge


As with my last post, the title of this post is not an indication to expect lots of posts about bridges in Derbyshire, it's just a placeholder for the future. If you have suggestions of interesting bridges to visit in Derbyshire, let me know via the comments.

Derby's Cathedral Green footbridge was opened in 2009, following a design competition held in 2007. The design, by Whitbybird (team members now dispersed into Move Architecture and Ramboll), was for a moveable cable-stayed pedestrian bridge. Mechanical engineering design was undertaken by M G Bennett and Associates Ltd (team members now in Eadon Consulting).

Spanning the River Derwent, the bridge is around 57m long with a 22m tall central mast. As well as creating a new river crossing, the intention was to contribute to revitalising the Cathedral Green open space.

The bridge deck is cranked in plan, with an 19m back-span and 38m main-span, supported by stays from a tilted mast. The back span crosses a historic mill race. The reason the bridge is moveable is not for navigation, but to allow the bridge to be moved clear of the main river in times of flood.

In this arrangement, the layout is intended to allow pedestrians to continue to use both riverside walkways, an arrangement that is best understood either from the aerial view on Google Maps, or from this video:


The ability to retain the riverside walkway in an open position seems slightly unnecessary, as the mill race is covered over and hardly an obstacle any more. When I visited, the riverside path was also closed in both directions for construction work.

The asymmetry of the bridge led to the mechanical engineering being relatively unusual. The bridge rotates about a central pintle bearing, but its main supports are a wheel under the central area, and a second wheel at the rear of the back-span, which resists uplift and runs in a curved track. A hydraulic motor drives a pinion against a rack at the rear of the back-span when the bridge is required to rotate.

A further pair of wheel-bearings lock the other-end of the main span in place, the load in these being highly dependent on the thermal state of the bridge. It's interesting to think while crossing the bridge that it is so carefully balanced on just a few individual wheels.

The site looked so neglected and overgrown when I visited that I doubted the bridge still opened, but it seems that it does. Indeed, the impression of neglect was considerable, as will be obvious from some of my photos. The benefits of a stainless steel parapet are clear, although the mesh infill has been severely dented in several places, and adorned with love-locks.

So many "designer" bridges of the millennium years share the same conditions of grime and disrepair now. It was easier for aspirational local government bodies to secure capital funding for ambitious new infrastructure than to provide the funding for their proper maintenance.

This bridge is a case in point. I visited on a grey, overcast day at a time when the city centre was largely devoid of activity. It took a feat of imagination to see how this bridge may have looked soon after opening, well-used and glowing in the sunshine.

The bridge design is impressive and well-considered (there's a technical paper referenced below which is well worth reading if you can get hold of it), but on the day I visited it felt very much like seeing an expensive sports car covered in dust and with insulting messages finger-painted in the dirt.

Further information: