Yorkshire Bridges: 33. Western Bank Bridge, Sheffield

Ah, it was good to get out and see an actual bridge again.

I'm not quite sure how I missed this beauty on my previous visits to Sheffield, but never mind.

It was built in 1969 to a design by Ove Arup and Partners and architect Yuzo Mikami. I say "it", but actually there are two bridges here, as shown in the cross-section below.

The bridges carry the steeply sloping A57 Western Bank highway above a pedestrian concourse area in the University of Sheffield campus. They are two-span structures, supported on single bearings below their tetrapodal centre pier, and a pair of bearings at each end.

The bridges were built in a period when the University campus was expanding, and the growth in road traffic had led to the highway being upgraded to a dual carriageway. Up to 10,000 pedestrians were reported to be crossing the road every day before the bridges were introduced.

The reinforced concrete slab decks vary in depth, being 1.2m deep over the central support and 0.84m at the abutments. It's a subtle feature that is not immediately obvious visually due to the large footway cantilevers on the edges of the deck.

Both decks are slightly curved in plan, but as can be seen in the photos, the main bridge deck slabs are straight, with the edge cantilevers varying in width to provide the curve.

From above, there is very little of interest to see. The interest is in the space created underneath the bridge. From below, this is a concrete roof held up on finger supports and providing some shelter from the weather. Glass blocks allow light through the central strip, and recently new lighting has been installed to make this a more attractive space at night.

It's a classic of modernist design, with some similarities to both Kingsgate Footbridge (1963) and Drochaid a' Chaolais Chumhaing (1984). The attraction is in its balance between the monolithic and the skeletal; it's clearly one "thing", like a sculpture, rather than one thing sitting upon another thing, like a conventional two-span road bridge.

The tetrapod supports have an interesting blend of straight and curved geometry: the outer edges form an inverted pyramid, while the inner surfaces of each arm are profiled with the curves of two intersecting hyperbolas. I'm not 100% convinced about the way the arms meet the deck slab and wonder whether a different detail would have been preferable e.g. having the arms project slightly from the side faces of the slab to give more of a "cradling" effect.

The sloping faces in front of the abutments were a conscious design choice, not so much to provide seating as to avoid the "tunnel" effect common to subways with vertical walls. The aim is to integrate the bridge with the adjacent landscaping. I guess the central tetrapods represent a similar visual impulse.

The block seating around the supports is not original. I wonder to what extent it was added to stop drunken students from bashing their heads into the angled support struts?

The concrete appears to have weathered well, and I'm left wondering why such a well-designed bridge isn't a little better known.

The article about the bridge in Arup Journal is well worth reading, including some excellent photographs, design drawings, explanations of the structural analysis, and an unexpected anecdote about students in mini-skirts.

The bridge was rewaterproofed, repaired and had new bearings installed in 2016.

Further information:

• Google maps
• The design and construction of Sheffield University Concourse (Ranawake, Gordon and Tune, Arup Journal, 1969)
• An Encyclopaedia of British Bridges (McFetrich, 2019)

Yorkshire Bridges: 32. Manchester Road Footbridge, Bradford

This is the last bridge in my current series of bridges in Yorkshire. This one is not in Leeds, where most were, but in nearby Bradford.

I wrote about this design in September 2010, before it was built:

To me, the whole effort is uninspired and unattractive, a step backwards visually, and certainly a lost opportunity to exploit the opportunities of structural engineering.

The bridge was designed in sympathy with the Manchester Road bus shelters project, with the same vocabulary of slightly disjointed bright red structural steel. The bridge takes pedestrians and cyclists over the busy main road, connecting to a wider network of pathways.

The bridge was designed by Bradford Council's in-house engineering team, and built by Eric Wright Group. I don't know who the steelwork subcontractor was, and I'm not aware of an architect. It won a Certificate of Excellence from the ICE in 2013.

Visiting the bridge "in-the-flesh", I certainly had to revise my original opinion. Whatever was I thinking?

The Big Red Bridge (as it is apparently known), is big, and red, and more than a little absurd. Obviously, the colour makes it stand out from its surroundings, but I like how it signposts itself so well. You want to go there, from here? The path is obvious.

Like the bus shelters, it is something of a jumble. The bridge supports come in at least three different flavours, but everything is related. I like the way the steel H-sections in the supports are connected together with stiffened intersections.

The central tower, which seemed to be nothing but an impertinent appurtenance, makes sense as an extension of its support, and as a waymarker that anchors the whole assembly visually.

Even the corrugated iron parapet infills lose something of their inherent naffness when painted red and united with the rest of the bridge.

I think it's a very interesting and surprisingly visually attractive bridge, with a bold and very self-consistent sensibility, that fits well into its site.

Further information:

• Google maps

Yorkshire Bridges: 26. Victoria Quays Footbridge, Leeds

This is a nice little bridge just a short distance away from the Centenary Bridge in Leeds.

It spans a basin between Flyboat House and Dock House, just off Navigation Walk, part of the Victoria Quays development, a series of waterside warehouses converted into residential property.

The basin doesn't especially need to be spanned, it's not huge, but no doubt the bridge provides some convenience for residents. It is a private structure, and can be seen but not used by the public.

Timber truss footbridges are reasonably unusual in the UK, and this one had the look of being historic, although it is not. It's form and details are interesting, and explained by the fact that it comprises two roof trussed removed from the adjacent Flyboat House, and used to create a bridge.

Judging from photos of restoration works undertaken by RDF Building Limited in late 2014, much of the timber was in poor condition and was presumably replaced. However, I think the bridge may date to 1986, when the warehouse buildings were converted.

Further information:

• Google maps

Yorkshire Bridges: 19. Lofthouse Interchange

From Stanley Ferry, I was heading north towards Leeds. My next stop was the Lofthouse Interchange, the magnificent junction between the M1 and M62 motorways, which can be viewed from Long Thorpe Lane on its northern side, for anyone so inclined.

The Lofthouse Interchange may be magnificent, but it's also notorious. Built in 1967, it is a three-level interchange, with the M62 crossing above the M1, and an 800-foot diameter roundabout built above both motorways to accommodate all interchanging traffic. It looks fantastic from above, but it creates a terrible bottleneck, due to the conflict between traffic streams entering the roundabout.

In 1999, major improvements were made by the introduction of new link roads connecting the western arm of the M62 to the northern arm of the M1. However, many conflicting movements remain on the roundabout, and it is known both for congestion and for collisions.

Highways England are consulting on a scheme to improve the junction, although there's no information yet on what this may actually involve. The best long-term solution would be to completely separate all slip road movements, but that is likely to be both hugely expensive and hugely disruptive during construction.

One casualty of any radical change could be the junction's distinctive "banana piers". Judging from the degraded state of the concrete on these, that may not be such a bad thing.

The designers of the Lofthouse Interchange were looking to solve two structural engineering problems, at a time when computer structural analysis was not as ubiquitous as it is today. The first was the concern that mineworkings in the area could lead to settlement of the bridges.

The common solution to this at the time was to introduce as much articulation as possible, so, for example, using a series of simply supported spans rather than continuous beams. The second concern for the engineers was thermal expansion and contraction of the curved bridge decks on the tall support piers.

The issue is not entirely clear: for short simply-supported spans, sliding could be accommodated by bearings on the top of each pier, and the piers designed accordingly. I think the issue here is that the designers wanted the decks to be connected together so that there was only one expansion joint at the end of each bridge: the decks are therefore connected to the pier via fixed bearings (permitting rotation under settlement), all expanding from one abutment.

In any event, the "banana piers" were the solution. The "banana" element is hinged at its base, and supported from a cruciform-section concrete strut hinged top and bottom. The effect of this is that the bridge deck can expand along the direction of its curvature while both deck and pier remain stable. It is a simplistic, statically determinate solution, which today would probably be dealt with by designing the piers to be flexible enough to accommodate thermal movement.

The outcome is one of those highly distinctive structural solutions that the Yorkshire motorways are filled with (see also past posts on Droppingwell Footbridge, Smithy Wood Footbridge, Needle Eye Bridge etc).

Further information:

• Google maps
• Engineering Timelines
• Motorway Archive
• SABRE
• CBRD
• Concrete Quarterly No. 80 (1969)

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)

Yorkshire Bridges: 17. Link Bridge, Eyre Lane, Sheffield

I'll finish off this set of posts regarding bridges in Sheffield with a little thing, a link bridge which spans across Eyre Lane.

This links two sections of Sheffield Hallam University, the Arundel Building and Charles Street Building.

I don't know who the structural engineer was, but the architect is Bond Bryan Associates, collaborating with Corin Mellor of David Mellor Design, who are much better known as a designer of cutlery than of bridges. The Mellors once had a workshop on the site.

The bridge combines three materials: glass for the side elevations, weathering steel for the roof and floor, and stainless steel for the decorative ribs.

There's not a great deal more to say: it's short, and it's sweet.

Further information:

• Google maps
• Public Sector Build Journal

Yorkshire Bridges: 16. Pond's Forge Footbridge, Sheffield

Okay. I think we all need to draw a deep breath before looking at this utterly baffling bridge.

This little curiosity is just next door to the Park Square Bridge. It forms one of two approach ramps to a footbridge over the Park Square roundabout, with the other ramp and main structure being much less interesting steel box girder spans. This ramp provides a main access route into the Pond's Forge International Sports Centre.

My only source of information on this structure comes from an ICE leaflet titled "Sheffield: A Civilised Place". This states that the footbridge was required by the client to be "interesting and imaginative", against which criteria it must be considered a great success. If anyone out there can share more information, please do!

At first glance, it seems like some weird preying-mantis version of a cable-stayed bridge, but I suspect this is not correct. At one end of the bridge there is an elevated tower, with two spindly arms cranked towards the span as if holding it up, but it seems unlikely this element can carry any significant load, in the absence of back-stays. The cables themselves are very slender, and they connect not to the bridge deck, but to the upper ends of parapet posts (again, with nothing to balance any horizontal force in the wires). I think these parts are essentially decorative, or perhaps helping slightly to resist twisting of the walkway.

I wondered whether the bridge might be half-through U-frame structure, with the perforated parapet plates acting as the webs, but note that there is no upper compression member, and that these plates are discontinuous before the upper end of the span: the main part of the bridge has parapet plates and posts inclined inwards, but towards this end of the span there are vertical walls contiguous with the mast pieces.

The parapet posts are almost grotesquely over-sized, and are aided/abetted by horizontal parapet rails which seem quite superfluous. My sense is that that parapet posts, which continue under the deck to form clamp-shaped support frames, are simply a series of transverse frames holding up both deck and balustrades.

Every second parapet post is connected at its upper end via two diagonal wires to the lower end of intermediate posts. These positions are then wired to nodes below the deck. I wondered if this might form some kind of stiffening truss, but there are no longitudinal chords. Perhaps they restrain the parapet posts against longitudinal movement, but the parapet panels are quite capable of doing that. Again, I'm left unable to decide whether they help a little to restrain twisting, or are simply decorative.

At the opposite end of the bridge from the "support" tower is a second tower, supporting what looks like an empty signboard. This is connected by wires to a baffling collection of bits and pieces below the bridge deck, but I think all this is doing nothing more than holding up the tower and its (empty) signboard.

The parapet "clamp" frames sit on a single tubular member running below deck, with a combined relationship something like a spine and rib cage. So far as I can tell, this single tube, dwarfed by the massive but seemingly over-wrought metalwork above it, is a simple beam supporting the main span and resisting both bending and torsional effects. This tube is connected to support frames at either end and hence to ground.

I think I have rarely encountered such a confused, confusing shambles of a structure. It is "interesting" in the way that a car-crash is interesting: it's difficult to look away from the sheer horror. It is "imaginative" in the way that a David Smith sculpture is imaginative: a creative juxtaposition of geometries in three dimensions. But a sculpture's primary function is visual, not structural.

In principle, I'm all in favour of whimsy in bridge design. Bridges, especially on a small scale, do not all have to be po-faced and technologically constrained. I'd quite like to like this bridge.

But I don't.

Further information:

• Google maps

Yorkshire Bridges: 15. Park Square Bridge, Sheffield

Park Square Bridge is one of several bridges built for the introduction of Sheffield's Supertram system, completed in 1994/5. This tram system's three branch lines converge in a delta junction just to the west of Park Square, and this bridge carries the western branch above Park Square roundabout and up onto Commercial Street (hence the bridge's other name, Commercial Street Bridge).

Alongside other major Supertram structures, the bridge was designed by Sheffield City Council's in-house team, Design and Building Services. That seems barely imaginable today, it's hard to think of a UK local authority with the capability to design such a major structure any more.

The bridge spans 75m (with two smaller approach spans making a total length of over 100m), and was built by Balfour Beatty, with steelwork by Watson Steel (now part of Severfield).

The main bridge span is a bowstring arch. Inclined steel arch ribs are braced overhead and tied with steel girders, which form the edge members in a ladder-deck arrangement. The bridge deck is a 250mm thick reinforced concrete slab composite with the ladder-deck crossbeams. The deck carries a non-structural concrete slab, containing the tram rails, drainage channels and stray current protection system. The deck is suspended from the arch by 60mm diameter steel hangers.

Although the three spans are each simply-supported, the structural deck slab is continuous, to avoid leaking joints, and a paper on the bridge design states that there are "concrete hinges" in the slab above the piers.

The superstructure sits on reinforced concrete piers and abutments, with concrete blockwork cladding, and these are supported on piles down to bedrock. The design language is a little post-modern, I think, with an elaboration of detail and a type of mock-classical architecture that seems at odds with the high-tech or modernist sensibility of most bridges of recent decades.

The bridge span was driven by the highway layout and the presence of a large culvert below ground. However, Supertram planners were also keen to have a "gateway" structure at this prominent position. A cable-stayed alternative was considered but rejected. The choice of a bowstring arch allowed a low construction depth to be employed, minimising the length of approach ramps.

The designers sought to maximise maintainability by avoiding closed structural sections, so the arch rib is a channel section with the open face downwards (similar to another bowstring arch the other side of the Pennines, in Salford).

According to the paper, "careful treatment" was given by the designers to the parapets and to the anti-climb blisters on the arches. The latter are pretty horrible looking, but not enormously so given the scale and clarity of the rest of the bridge.

The arch ribs are pin-ended, which I find really quite odd. Are there other modern bowstring bridges with this detail? The design paper offers no explanation for why this choice was made. It isn't visually incongruous, but I think hinges should generally be avoided in main members of bridges unless there's a very good reason.

Behind the hinges, there are thrust blocks comprising a group of vertical steel stiffening ribs, which transfer the arch thrust into the end node of the tie girders. As you can see in the photograph, they double as a handy waste receptacle.

On the whole, I think this a well-designed bridge, generally with clarity of form and well-proportioned. It is, however, let down by some of the detailing, and not only the impromptu waste-bins, the lumpen parapets or the blisters.

There is a pastel colour scheme used to distinguish between a hierarchy of components, both the hanger assemblies and also the connection of these to the tie girders, which for my taste has been over-elaborated. The use of this number of pale colours is not very successful, as they are simply impossible to distinguish under most lighting conditions. A smaller number of complementary colours would have been enough.

The bridge was the winner of an ICE (Yorkshire) Award in 1994/1995, and Commended in the National Steel Design Awards.

Further information:

• Google maps
• Wikipedia
• Structurae
• LUSAS
• Commercial Street Bridge, Sheffield, UK (Wilson and Jones, First International Conference on Arch Bridges, 1995)