Manchester Bridges: 24. Brabyns Park Bridge, Marple

Now here's a tale of woe.

Nathaniel Wright exemplified the manner in which the industrial revolution wrought huge changes on British Society at the end of the 18th and beginning of the 19th century. He made his fortune from coal mining in Derbyshire, and associated closely with other entrepreneurs such as Samuel Oldknow, who was the main driver behind construction of the Peak Forest Canal, connecting the Derbyshire coal mines through to Manchester.

In 1800, while the Canal was just finishing work on Benjamin Outram's Marple Aqueduct, Wright purchased the Brabyns Hall estate nearby. The estate lies immediately to the east of the Peak Forest Canal, occupying the land between the canal and the River Goyt. As one improvement to the estate, Wright commissioned Salford Iron Works to construct a bridge across the river, providing access to and from nearby Compstall village. The Salford firm's engineers James Bateman and Thomas Sherratt had previously in 1795 supplied a pumping engine for one of Wright's collieries.

The new bridge was in the form of a cast iron arch, possibly the first such bridge in this part of England. The design was broadly patterned after Thomas Telford's 1797 Cound Arbour Bridge, with three cast iron arch ribs, each with a series of iron circles filling the spandrels. Variations on this theme were common, another example being the 1810 Tickford Bridge, but Telford had moved on, using the more rational diamond-pattern spandrels in his 1814 Craigellachie Bridge, for example.

The bridge is decorated with the date and name of its maker, and the lightweight iron parapets feature an ornamental "W" in the middle, for the owner Wright, who died five years after the bridge's completion, in 1818.

So far as is known, the Brabyns Park span is the only bridge to have been built by the Salford Iron Works. It spans approximately 14m (46ft) and is 2.7m (9ft) wide. The central rib was cast in two halves, joined in the middle. The external ribs were cast in six pieces, with each half subdivided into three parts: an upper rib, a lower rib, and the circular spandrel elements. The arch ribs were stabilised by tie bars at their lower level, and by cross-bracing at the upper level. The original decking comprised timber planks.

 In 1991, a structural assessment of the bridge labelled it dangerous, and a "temporary" bailey bridge was installed directly above it, remaining there until 2007, when the bridge was finally refurbished, following a lengthy campaign. Photographs of the bridge taken in 2007 immediately prior to refurbishment show the bridge to be horribly neglected, although how much of that was due to the difficulty of maintaining it with the bailey bridge in the way is hard to tell.

The bridge is Grade II Listed, but it was a lengthy battle to secure Heritage Lottery funding for its restoration, and then to agree exactly what works would be carried out. A design by engineers Scott Wilson Kirkpatrick (now submerged into AECOM) was eventually accepted after much debate.

In 2003, the campaigners had commissioned a report by local engineering lecturer and historic bridge specialist Tom Swailes. According to the report, the main issue with the bridge when it was closed in 1991 was the condition of the timber decking. Swailes took the view that:

"Future loads on the bridge will be no greater than the loads that it safely carried for 178 years. It is interesting to apply modern computer-based structural analysis techniques to old structures, but the results of such theoretical analyses must almost always be disbelieved unless verified by tests on the structure itself."

The subsequent involvement of "proper" consulting engineers seems to have been a curse. The designer's drawings proposed significant alterations to the bridge, over and above what may have been required for simple restoration. As Swailes noted in his report, despite its neglect the bridge had stood the test of time.

That was clearly not enough. The main structural alterations involved the bonding of steel plates to the central arch rib, the renewal of corroded bracing elements and the addition of new transverse bracing between the arches. These have relatively minimal impact on the appearance of the bridge, and you may struggle to see them on my photographs. In any event the underside of the bridge is not seen by most people, and is difficult to view even from the river bank.

The larger issues for the engineers (or for the technical approval authority at Stockport Council, perhaps), were the presence of a gas main, a small water main, and electric cables, which seem to have been previously laid on top of the deck planks; and the height and strength of the existing parapet railings, which were now judged to be inadequate.

Measuring from the engineer's drawings, the original parapets are approximately 1.15m tall (although it will have been less when fill material had been piled onto the bridge decking to cover the gas main). This could not possibly do, the parapets had to comply with modern standards and be 1.4m tall (the modern requirement for cyclists). The solution to this, and also to accommodating the utilities, was to install new parapets connected to steel hollow sections sitting entirely on top of the existing bridge, with the hollow sections also used to contain the utilities.

The campaigners were evidently not very happy. On their website they indicated their regret:

"This means that in the future, perhaps with technological improvement or an enlightened approach to safety standards, or a combination of both, the modern intervention could all be removed and the old bridge will be revealed intact underneath."

No such technological improvement was ever needed: simply an "enlightened approach" that recognised that an existing historic structure could be considered to be perfectly acceptable whether or not it complied with modern standards. Nobody is going around rebuilding ancient castles (or installing 1.4m tall balustrades on the battlements) simply because the original builders couldn't foresee the stupidity of 21st century compliance-drive engineering culture.

Quite what the local planning authority, or English Heritage (now Historic England), thought is difficult to say. They certainly should have demanded that the engineers think again. Reading through the excellent restoration campaign website, one thing that jumps out at me is the absence of any mention of a specialist conservation engineer or conservation architect. The result, in my opinion, was deeply unfortunate.

The new parapets are painted a different colour to the original bridge, with a view to disguising them when the bridge is viewed from a distance. I don't think it succeeds: the elevation of the bridge is intact but the parapets are hard to miss. Seen from the perspective of crossing the bridge, the visual impact is much worse, essentially ruining what was a fine and historic structure. Reaching over the new parapets to push against the old ones, it seemed to me that the original parapets were quite strong enough.

The difficulty with hoping that this can be put right in the future is that not only was the opportunity lost at the time when funding was available, but that so much of the funding was seemingly unnecessary. It is perhaps unfair to criticise those involved when not in possession of all the information that they had, but at best the treatment of the Brabyns Park bridge is a crying shame, and at worst it's the inevitable but disastrous outcome of foolishness and incompetence.

Further information:

• Google maps
• Grace's Guide
• British Listed Buildings
• A Brief History of the Park, the Iron Bridge and the People Involved in its Construction (Whittaker and Clarke, 2006)
• Bridge restoration campaign website (well worth a visit - hugely informative!)
• Bridge restoration photographs

Manchester Bridges: 23. Marple Aqueduct

Yes, yes, I know, it's not really in Manchester. Want to make something of it? No? Good.

It's sometimes difficult to imagine how the pre-industrialised landscape would have looked near the end of the 18th century. Some canals had been constructed earlier (e.g. the Bridgewater Canal opened in 1761), but canal mania only really took off in the century's final decade. The Peak Forest Canal, authorised by an Act of Parliament in 1794, was part of that explosion of canal-building.

So far as was possible, canals needed to be level to be economically viable. The Peak Forest Canal connected mines at Dove Holes to Manchester, with two level stretches of water (the Upper and Lower Peak Forest Canals) separated by a 64m tall flight of locks at Marple. Immediately south of the locks, the Lower canal crosses the valley of the River Goyt, and between 1794 and 1800 a huge aqueduct was built here.

It must have been a tremendous endeavour, considering the scale of the stone blocks that make up the finished structure. The enterprise was largely promoted by industrialist Samuel Oldknow, and the engineers were Benjamin Outram and Thomas Brown, and William Broadhead, Bethel Furness and William Anderson were appointed as the contractors. It is claimed to be the tallest masonry aqueduct in the United Kingdom, and over the six years of construction, seven construction workers died.

The aqueduct's most distinctive visual feature is the series of circular openings in the spandrel walls of all three spans. These were presumably intended to reduce weight, and were not a new idea: William Edwards had used them for his fourth and final bridge in Pontypridd in 1756; John Smeaton included them on Coldstream Bridge in 1767, albeit filled with loose stone. No doubt there are other examples. They add visual interest to the bridge but I don't think they lighten its appearance: compare Rennie's Lune Aqueduct, completed in 1796 while the Marple structure was being built, which scarcely looks much heavier.

Tie bars were inserted in the central span in 1860 by engineer Charles Sacre. Use of the canal had declined during the 19th century, with Marple Railway Viaduct being built alongside the aqueduct in 1863.

Decline eventually lead to ruin, with one spandrel wall of the aqueduct partially collapsing in January 1962. British Waterways proposed demolishing the structure and replacing it with a pipeline, but additional funding was found from the local authority to rescue the aqueduct, and in 1966 the restored bridge was declared a Listed Building, Grade I. The canal itself was rescued from dereliction and reopened in 1974.

The aqueduct was altered again in 2018. Until that point in its history, the aqueduct had only one parapet, on the towpath side. The other side had only a very low wall. According to the Canal and River Trust, people had been recorded nearly falling from that edge, and some people were even playing a dangerous game of leaping across the canal to land on the unsecured edge.

It was agreed to add a new parapet, designed by Knight Architects and Arcadis, and manufactured by Bisca. This is a bespoke design in stainless steel, with the top rail left unpainted, and uprights painted matt black. In a nod to the Peak Forest Canal's benefactor Samuel Oldknow, the arrangement of the metalwork evokes the warp and weft of cotton-weaving.

It feels a little odd, having such high-quality metalwork in a place where the ordinary public are remote from it, but it must have been some challenge to navigate the demands of parapet standards and the difficult constraints of modifying such a historic structure.

Viewed along the aqueduct, the new parapet gives an impression of solidity, while viewed looking across, it is much more transparent. Engineers will note that the location where the woven bars intersect is the weak point. I did wonder if the design is not a little over-done when something more minimal may have sufficed, but I didn't find it too objectionable.

Further information:

• Google maps
• Wikipedia
• Structurae
• British Listed Buildings
• Engineering Timelines
• Grace's Guide
• CanalPlan
• Transport Trust
• Restoration of the Marple Locks and Aqueduct
• The National Trust Book of Bridges (Richards, 1984)
• Civil Engineering Heritage: Northern England (Rennison, 1996)
• An Encyclopaedia of British Bridges (McFetrich, 2019)

Manchester Bridges: 22. Spinningfields Footbridge

This is the second of two new footbridges over the River Irwell, connecting central Manchester to neighbouring Salford. I covered the other one in the previous post.

Neither bridge could be justified on a cost-benefit analysis of journey time saved. Greengate Footbridge is particularly absurd in that respect, being only 5m away from an existing foot-accessible bridge. The £1.5m Spinningfields Footbridge is a little better, shaving maybe 3 or 4 minutes off a journey walking across the nearest existing bridges (Bridge Street to the north New Quay Street to the south). However, both bridges act as gateways, as ways to improve the permeability of the urban fabric, enhancing the feeling of accessibility as much as the reality of it.

Greengate Bridge's minimalist appearance shows the structural engineer in full retreat, a functionary whose role is quite literally to support the architectural vision with as much discretion as can be mustered. Sited between Greengate and Spinningfields, Santiago Calatrava's Trinity Footbridge is the exact opposite, the structural engineer as flamboyant showman, the centre of attention.

Spinningfields Footbridge lies somewhere between the two extremes. The structural engineering takes centre stage, but not at the visual expense of everything else in the immediate vicinity. It's a very sophisticated piece of engineering, but retains a sense of modesty and a great deal of elegance. I reckon it's the finest contemporary footbridge in Manchester, and one of the best in Britain.

Designed by Ramboll (based on appearance, their former Whitbybird team rather than their former Gifford team), this is a design that distils many years' bridge design experience, matching a simple and beautiful overall concept to a super-careful attention to detail. It was built by Eric Wright.

The River Irwell at this point has high banks and so far as I can tell is not regularly navigated, nor prone to flooding. This gives designers the opportunity to "hide" all the bridge structure below deck level, something that is not always an option. Ramboll have used that as a cue for a lenticular form, deepest in the middle where the highest bending forces are found.

I described a generally similar bridge in Manchester two posts back, and discussed how the form can be seen in several different ways, one being that it is an "under-spanned" self-anchored suspension bridge. This is like a normal suspension bridge but with the suspending cable below the bridge deck rather than above it. Instead of being hung below the cable, the deck sits above it on struts. Instead of the main cable's tension force being anchored into the ground, it is anchored to the bridge deck itself, which therefore must resist compression. It's a design which can sit much more lightly on the ground than the normal suspension bridge.

Bridges of this type can be prone to torsional flexibility, a tendency to twist. I've seen several designs where the deck and cable are connected by a triangulated structure to create a skeletal "torsion box" which can resist this twisting – indeed, the Leech Street Footbridge is of that type. The Spinningfields bridge is considerably more adventurous.

The key feature of the bridge is that it is curved in plan, as is the supporting cable, although it follows a different line. The two are connected by individual struts, with no triangulation. The struts themselves are of folded steel plates, giving them necessary stiffness, and this is cleverly integrated with folded-plate deck bracing. There are clear echoes here of the ribbing on Lune Millennium Bridge (by the same designers), which I featured here not long ago. I have to say that I find it startling that so trimmed-down a structure is stable, and would need to see the engineering drawings to really understand how it works.

The Y-shaped parapets and the knife-edge fascia are reminiscent of the Chelsea Bridge Wharf Link Bridge, yet another Whitbybird / Ramboll design, and in my view are very attractive. Lighting is incorporated into the handrail, and there's further lighting below the deck level to illuminate the bridge structure at night. The triangular fascia does a great job in making the edge of the deck look extremely slender. The decking is permeable aluminium sheeting, allowing rainfall to drain freely through to the river.

I found vibration to be quite perceptible, although the amplitude is low enough not to cause any distress. Feedback on the Skyscrapercity website indicates I'm not alone in noticeing the movement.

A seating bench is provided on the deck, which I guess may make it a popular sandwich or smoking spot for workers from nearby offices. The deck is up to 4.5m wide, which is pleasingly generous.

Overall, I think this a real gem of a bridge, structurally daring yet in no way ostentatious, and one which deserves wide recognition.

Further information

• Google maps / Bing maps (both sites currently show images pre-dating bridge construction)
• Structurae
• Skyscrapercity (includes pre-construction visualisations, and construction photos)
• Manchester Confidential: New city centre footbridge lands
• Salford Online (installation video)
• Suave Aerial Photographers (great aerial photos of bridge installation)
• Salford City Council

Manchester Bridges: 21. Greengate Footbridge

Britain’s major cities can be divided into those with a strong connection to the underlying landscape, and those where the landscape has been obliterated or appears featureless, lending a decided lack of character to the urban fabric, which architecture and town planning struggle to rectify. In the former camp are the river cities, London, Bristol, Newcastle and Glasgow among them, where a major river was the reason for the city’s existence and continues to anchor its layout, as well as those with central parkland, such as London (again), or Edinburgh (the latter particularly well-blessed in this respect). In the latter camp you will find Birmingham and Manchester, city centres defined primarily by the relationship between their shopping centres and railway stations (or worse, by an inner ring road).

Manchester appears to have recognised this deficit for some time, with a long-held desire to shift commercial and leisure activity westwards, into the less economically sensitive Salford, in the process reconnecting to the city’s main natural waterway, the River Irwell (which defines the Manchester / Salford boundary). I’ve previously visited Santiago Calatrava’s Trinity Bridge, a typically elaborate structure which spans this river and which sought (with, I think, limited success) to trigger riverside regeneration.

There’s no real shortage of road crossings of the River Irwell, but successful development in Spinningfields on the river’s east bank, and the planned Greengate development on the river’s west bank, have triggered the construction of two new footbridges within the last year. These form part of a wider River Irwell masterplan intended to make it a far more central feature in city life, including the construction of new riverside paths and walkways.

In this post, I’ll cover the recently completed footbridge which forms a gateway to Greengate, and in my next post I’ll address the bridge at Spinningfields.

The Greengate footbridge has been built to the north of Trinity Bridge. Its east end sits close to Manchester Cathedral, and its west end spills out towards a new plaza area which I assume to be the first part of the as-yet unbuilt Greengate scheme.

It appears to be something of an unnecessary indulgence, sitting as it does no more than 5m away from the existing Victoria Bridge, which already provides a perfectly serviceable foot crossing of the river. Evidently, the Greengate developers don’t see that as a suitable entrance to their grand scheme, and I can certainly imagine that the lack of a new bridge would enhance the sense of the development as peripheral to the city centre, rather than as a continuation of it (much of the area on the Manchester side was re-developed following the 1996 IRA bombing, but this stopped well short of the riverside, a missed opportunity).

The river here sits deep below the surrounding streets, particularly the east bank, and consequently there is no structural rationale for supporting the structure from above. The designers therefore had to use other means to create the sense of a gateway, and these relate mainly to the quality of the finishes on what is, by any standards, a very minimalist contemporary design.

From many angles, the bridge structure seems almost to disappear, something enhanced by combining generous overhangs on the concrete bridge slab with inclined faces to its supporting spine girder. This means that you have to walk some distance beyond the bridge before you can see its primary structure at all.

The spine beam is a steel box girder, which supports a series of precast concrete deck slabs. The bridge abutments are hidden behind the existing riverside wall facing, enhancing the overall impression of minimalism. I can imagine the foundations to have been significant challenges, particularly on the east side where it can be seen that the riverside wall is actually voided in construction, with a series of arched recesses visible.

The bridge has structural glass balustrades topped by stainless steel handrails. The balustrading extends beyond the bridge at both ends, and defines it as merely the opening element in the plaza’s hard landscaping. The result is a very contemporary design. I guess that at night it may merit a “blade of light” description, although I haven’t been able to locate any night-time photographs.

A typical question with all-glass parapets is their susceptibility to vandalism, and the ensuing cost of occasional replacement panels. As a result, they are usually limited to well-policed internal use, in shopping centres and similar settings. Time will tell how well they survive in the Manchester / Salford city centre.

I haven't been able to find any information on the bridge's designer, contractor, or cost, so if anyone can provide further detail, please post in the comments.

Further information

• Google maps / Bing maps (current images pre-date bridge construction)

Manchester Bridges: 20. Leech Street Footbridge

On my same visit to Manchester which took me to the New Islington Bridge, I also spotted another footbridge in the same vicinity which I thought merited inclusion on this blog. It’s not a spectacular, or architecturally exciting bridge, and it doesn’t seem to have been the result of any design contest or had any publicity. Indeed I have searched but failed to find any details of the client, designer or builder.

It's the third interesting modern footbridge I've encountered spanning Manchester's Rochdale Canal. As well as the one at New Islington (which Leech Street is about a quarter of a mile to the south of), there is the minimalist Architects Bridge in Castlefields.

The main reason I thought it was of interest is simply because it’s a representative of a bridge form which is very rare, certainly in the UK, the lenticular bridge.

Terminology is never exact in this area, and the bridge can be thought of variously as an untriangulated lenticular truss (Brunel’s Royal Albert Bridge being the pre-eminent example of a lenticular truss in the UK); as an inverted bowstring arch (where the “arch” is in tension rather than compression, and the reverse is true of the deck); or as an "underspanned" self-anchored suspension bridge, where the suspension cable is below the deck rather than supported above it from towers.

Bridges of this form are rare because it’s normal for the geometry of a span to be determined by the conflicting imperatives of maximising clearance above the obstacle it crosses, and the need to minimise the level of the bridge deck, avoiding costly approach structures. I’ve covered some historical examples here before, at Roxburgh Viaduct and Elgin, and will share a more modern example shortly. Other historical examples include Robert Stevenson’s proposal at the River Almond, and Alexander Nimmo’s proposal in Ireland, while other modern examples in the British Isles include Arup and Wilkinson Eyre’s bridge near Limerick. There are also variants on the form where a level truss has been substituted for the lenticular elevation, as in the rather ugly Mailbox bridge in Birmingham. A list of similar modern bridges is given in Ruiz-Teran and Aparicio's paper (see further information, below).

Where conditions do allow its use, it’s a form of bridge with the potential for remarkable slenderness, because the compression member is combined with the load-supporting bridge deck, both of which require a certain thickness to resist, respectively, buckling and the effects of local concentrated loads. Combining the two therefore minimises the overall depth of material when the bridge is seen in elevation, to an extent only otherwise possible in a suspension bridge, which requires obtrusive towers and often expensive foundations.

Seen in that context, Leech Street Footbridge is not one of the greatest examples of the form. Rather than using a slender bar or thin cable as the tension member below the deck, it is all of tubular steel. This is, on the whole, cheaper to assemble, with the weight of the steel tubes offset by not needing to fix or tension cable elements.

Even so, I think the bridge has considerable simple charm, all of it down to the inherent attractiveness of the structural form. It would be nice to see more bridges of this sort, and looking at this example, it's hard not to imagine they could be built quite cheaply.

Further information:

• Google maps / Bing maps
• CanalPlanAC Gazetteer
• Developments in under-deck and combined cable-stayed bridges (Ruiz-Teran & Aparicio, ICE Bridge Engineering Journal, 2010)

Manchester Bridges: 19. New Islington Footbridge

It was October 2008 when I kicked off a series of "bridge competition debris" posts with a discussion of Manchester's New Islington Bridge. As with several bridge design competitions organised round about that time by RIBA, it garnered its fair share of attention, with 87 entries submitted for what was expected to be a relatively low-budget scheme.

The project demanded a new pedestrian bridge to span the Rochdale canal and an adjacent canal basin, connecting footpaths in several directions and at different levels. After the initial attention, it all went very quiet, and I thought the project had died due to lack of funding. Last year, I discovered this wasn't actually the truth, and the winning bridge had been built, seemingly with little fanfare.

Designed by Gollifer Langston Architects with Stockleys and Michael Hadi Associates, it's currently something of a bridge to nowhere. For canal towpath users, it's highly useful, but it was intended to be a focal point for a regeneration scheme that vanished down the black hole of the recession.

I've included a couple of the original competition images above, both to note how faithful the final bridge is to the original concept, but also to wonder whether from those images anyone could have predicted the reality of the bridge as-built. Particularly with the colour drained away, the real-life bridge is a little dull, squat even.

In form, it's a pathway which wends its way above a three arms of the canal, supported along one edge by a metal spine. The spine is triangular in cross-section, but feels more like a sheltering wall than a structural element. It allows the bridge deck itself to be very thin, minimising the length of the approach ramps.

The spine is a triangular steel truss in structural form, clad on both faces in perforated sheet metal. Unlike many contemporary footbridges, the structure is not the star here.

The bridge’s lack of colour is a particular disappointment given the canal setting – bridges over canals are often colourful, as may be glimpsed in the background of some of my photographs. If eventual development of the area introduces more attention-grabbing architecture, this will matter less, but for now the bridge is a gloomy monolith, a cheerless crescent offering only views of a wasteland.

The bridge is also let down by its construction. Minimalism thrives on sleek, simple lines, with well-crafted materials. Some of my photographs show kinks and unevenness in the parapets and their cladding, making the whole enterprise look considerably cheaper than I imagine was intended.

The bridge does feature one little conceit for those who look hard enough - printed onto its underside are the words "CAST NO SHADOW", which will appear reflected in the canal should it ever be perfectly flat. If you squint hard at the photograph on the right (click to enlarge), you may be able to see this.

The bridge was one of the few “concrete” achievements of a spate of post-millennial bridge design contests organised by RIBA. Many of its stillborn siblings were the victims of general economic malaise, and others perhaps continued the millennial trend for structural flamboyance beyond its natural lifespan. There is therefore, perhaps, an argument that understatement was what was necessary for an architecturally-led design on this budget to actually be made reality.

Compare Bootle’s Pennington Road Footbridge, the only other RIBA footbridge contest design of its period to reach completion, which I featured here in October 2011. That was also modest in conception, but I think better detailing and construction left it at least a moderate success.

Further information:

• Google maps / Bing maps (images currently available predate bridge construction)
• RIBA competition press release
• Skyscrapercity (includes construction photos)

Manchester Bridges: 18. Media City Footbridge

I had been waiting to find out when the new Gifford and Wilkinson Eyre-designed Media City Footbridge in Manchester was due to open to the public, only to discover on a chance visit at the end of September that it was in fact already open.

It's an asymmetric bobtail swing bridge, spanning across the Manchester Ship Canal. It's 83m long overall, with a 63m main span. To the north, it provides access to the new Media City development in Salford, the new home to several departments of the BBC. On the south bank, it currently connects to the Imperial War Museum North, but will eventually link in to a new ITV studio development.

The bridge deck is supported by a harp-style cable-stay layout. The cables support one edge of the deck, and connect to eight steel masts in a fan arrangement which I previously likened to a giant skeletal hand. I think perhaps the design visualisations were a little unflattering, as now that I've seen the (nearly) finished structure, it is a much more attractive creature.

The odd assemblage of masts arises from the formalism of the geometry. The cables establish a harp arrangement in elevation (i.e. they are parallel when viewed from that angle), and are tangential in plan to the curved edge of the deck. This creates a geometry where the cables must be supported at eight separate positions in space, rather than from a single mast.

The supported edge of the deck is a deep triangular steel box girder, paired with a shallow box below half of the deck itself. These provide the necessary torsional and bending stiffness, and support the other half of the deck via a series of cantilevered ribs, visible in the photo (click on any image for a full size version). The alignment of the edge girder is not quite perfect, but I don't imagine the casual observer will notice. The image also shows the flared width of the backspan, which conceals a concrete counterweight used to balance loads on the pivot pier.

The sharp edge of the box girder is such that it's depth is almost completely disguised, with the upper surface appearing as a streamlined fascia, and the lower surface disappearing into shadow along with the rest of the bridge soffit. On the face of the girder adjacent to the deck, glazed panels act to obscure it, and these conceal light fittings which help illuminate the deck at night and distract further from the beam's structural mass.

The cables connect the masts to the rear of the back-span, and the anchorage points have been adapted to provide jaunty little seats. Between the anchorages, users can walk straight into the future ITV site, although the steps and handrails were still under construction when I visited. People walking towards the Imperial War Museum bypass the anchorages completely. The detailing of the anchorages and seats is very nicely done. In the background of the photo you can see the Museum on the right, and on the left is the Lowry Millennium Bridge, which I've visited previously.

As with many Wilkinson Eyre designs (see for example South Quay and Swansea), a conscious effort has been made to treat the two bridge parapets differently. I've already mentioned the east parapet, which does an impressive job of hiding the main deck girder. While I was on site, there was at least one panel of the lightbox where the glass had shattered, and several more temporarily dismantled - I'm not sure whether this was to work on the glass or on the light fittings. This is a reasonably well-used and well-policed location, so I would hope that vandalism isn't a recurring issue.

The west parapet is a post and rail system in stainless steel, with some lighting concealed in the uprights. You can also see in the photograph above right how the deck surfacing is divided, with a resin/grit finish to the underlying steel box girder on the right, and aluminium decking panels on the left.

One element of the bridge I particularly like is the detailing of the mast pedestal (the large silver cylinders are uplighters). Each mast sits on a stainless steel ball bearing. You can also see the bottom edge of the mast, which is lens-shaped in cross-section. The cigar-like masts have been cut, bent and re-welded from basic circular hollow sections, and I think the result is visually very attractive.

Not all the detailing is perfect. I particularly disliked the cover plate to the north expansion joint, which is in two hinged sections to be manually flipped out of the way before the bridge is opened. It looks like an afterthought rather than something properly considered.

The bridge's main visual feature is the way the mast and cable array changes as it is viewed from different perspectives. The simple harp-like arrangement of the cables is clear only from the main elevations, and from other angles it is clear that their geometry is much more complex. The photo above right shows that they appear warped when viewed from the north end of the bridge.

Not every part of the bridge adjusts to changing perspective so well. The deck's vertical curvature is a careful compromise between canal navigational clearance demands and the geometry of the canal banks, with the deck ramping down at 1:15 to meet the ground. While the curve looks gentle from most locations, the S-shaped curvature of the west edge of the deck is such that in a foreshortened view, the deck looks to have broken its back. The same thing can be seen on the Tradeston Bridge in Glasgow, which shares the S-curve in plan. I doubt that anyone other than over-fussy bridge designers will spot it, however.

Quibbles aside, I was very pleasantly suprised by the Media City Footbridge. I had completely underestimated the quality of the design beforehand. I would now say it is well up there amongst the best major pedestrian bridges built in the UK in modern times, a genuine rival to the same design team's Gateshead Millennium Bridge. It has been shortlisted for an Institution of Structural Engineers Award, and deservedly so.

Further information:

• Google maps / Bing maps (current images pre-date bridge construction)
• Wilkinson Eyre
• Gifford
• Atkins Bennett / Eadon Consulting
• KGAL
• Rowecord
• Media City Footbridge, Salford Quays (Curran & Thompson, IABSE Symposium 2010)
• Media City Footbridge, Salford, UK (Marks, Thompson & Curran, IABSE Symposium 2011)
• Media City Footbridge, Salford Quays (Curran & Thompson, Footbridge 2011)