Worcestershire Bridges: 8. Upton-upon-Severn Marina Footbridge

This is the last of the current trio of bridges from Worcestershire, and it's the most modest of the set.

When a new marina was built at Upton-upon-Severn, it resulted in the lengthy of an existing footpath running alongside the River Severn. The inlet entrance to the marina passed directly across the line of the footpath. Following protests, the footpath was reinstated, with the aid of a short timber footbridge across the marina entrance.

It's essentially a simple structure, although with peculiar echoes of the main highway bridge in the same town.

It's a three-span bridge with an arched profile, as is the case with the Upton-upon-Severn bridge. It has two timber beams along each edge, which behave as continuous girders rather than via any arching action. Indeed, there appear to be half-joints in the timber beams, which should be visible in the photos if you look closely. For a bridge of this short a span, these are essentially unnecessary.

The main beams support simple plank decking, and the timber balustrade is simply bolted to the outside face of the main beams. The bridge deck sits on two timber trestle piers.

Is it pretty? Not especially. Ingenious? No, I wouldn't say so.

Timber bridges remain rare throughout the UK, largely due to a lack of familiarity with their design amongst engineers reared on steel and concrete, and indeed, I haven't been able to identify who designed or built this bridge. It would be nice to see more of them, albeit without the unnecessarily deep beams used here.

Further information:

• Google maps / Bing maps

Worcestershire Bridges: 7. Upton-upon-Severn Bridge

The bridge over the River Severn at Upton-upon-Severn is the most recent of several structures at this site. It's the only crossing of the river for some distance upstream and downstream, and although Upton is now a somewhat quiet town, it must once have been an important centre for trade.

It isn't known when a bridge first replaced a ferry at Upton, but a wooden bridge was present when John Leland visited in 1539. By 1576, work had started on a stone bridge, but this was not fully completed until 1609. One span of the bridge was destroyed during the English Civil War, but later repaired. In 1852, the entire structure was washed away by floods.

Two years later, a new bridge was completed. This had four wrought iron spans, the furthest west of which could be retracted onto its abutment to allow taller vessels to pass. The opening procedure was not quick, and in 1882 the retractable span was replaced by a swing span, pivoting on the abutment.

Once into the motor age, it was apparent for some time that the swing bridge was unsuitable for the new loads it had to bear. In 1935, tenders were invited for a new, electrically-operated swing bridge, but the prices received were unacceptably high. In 1940, the present bridge was designed by Worcestershire County Council (county surveyor and bridgemaster B.C. Hammond), approximately 100m upstream of its predecessor. The contractor was Thomas Vale & Sons Ltd, with the steelwork fabricated by Horseley Bridge & Thomas Piggott Ltd.

The abutments from the old bridge remain, and the line of the former bridge is clearly visible in the Google and Bing aerial photographs linked below. There is an associated viaduct to the east over the Severn flood plain, which was built in 1940 of reinforced concrete, but recently rebuilt.

The new river bridge has three spans, with a main span of 200 feet (61 metres), keeping the piers out of the river and reducing impediment to flow. It was built at a higher level than the original bridge, a vital decision given the Severn's propensity to flood (see the images at SABRE, linked below). It was reported to be a larger version of the 1935 Jubilee Bridge built at Fladbury, but the latter bridge has girders only below deck level.

Upton-upon-Severn Bridge is unusual amongst highway bridges in having girders which extend both above and below the deck. The "half-through girder" design is common on rail bridges, where it minimises the depth from the rails to the underside of the bridge, in turn minimising approach gradients and disruption to existing highways. At Upton, this solution was presumably chosen to minimise the level of the roadway, reducing the cost and extent of the approaches.

Although unconventional, it's clearly not unattractive, and the bridge gives the impression in elevation of being more slender than it really is. The shallow arched profile disguises what is a three-span semi-continuous girder - continuous over the piers, with cantilever arms supporting a suspended middle span via half-joints.

The footways are supported on stiffened steel plates, while the road deck, with its heavier loads to carry, relies on a steel troughing deck.

The main girders have very large vertical stiffeners at frequent intervals, particularly visible on their traffic face. Sizeable stiffeners are required in a half-through bridge to provide "u-frame" action, preventing the top flange from buckling sideways in the parts of the bridge where it is in compression. However, with the half-jointed bridge construction, there will be very little significant compression in the top flange, so it's less clear what purpose these stiffeners serve.

The girders have a hat-shaped top, which is non-structural and presumably there to discourage people from walking along the top of the girders.

A plaque on the bridge incorrectly attributes the building of the bridge to Worcestershire County Council, and also states that the bridge was "one of the last of riveted construction to be built in England". In fact, riveting only died out some two decades later, still being used on bridges such as the Barton High Level Bridge (1960), Runcorn Widnes Bridge (1961) and Thelwall Viaduct (1963).

Further information:

• Google maps / Bing maps
• Upton Upon Severn - The Bridges (includes several historic paintings and photographs of the bridge)
• The bridge at Upton [PDF] (lots of informative background on the 1940 rebuilding)
• SABRE
• Structurae
• The Ancient Bridges of Wales and Western England, E Jervoise, 1936
• Bridges in Britain, G Bernard Wood, 1970
• A Century of Bridges: An Illustrated Guide to all the Bridges that cross the Severn, Chris Witts, 1998
• An Encyclopaedia of Britain's Bridges, David McFetrich, 2010

Worcestershire Bridges: 6. Lowesmoor Railway Bridge No 10

I did a short series of posts on bridges encountered in Worcestershire last year. I have three stragglers, further bridges in the area which may be of interest, of which this is the first.

A canal was opened between Birmingham and Worcester in 1815, shortening the route for freight barges between the manufacturing centre of Birmingham and the River Severn. Within a few decades, railways were taking over as the principal means of long-distance transport, and a new railway from Worcester to Hereford was built in about 1860. Its line crosses the Worcester and Birmingham canal at Lowesmoor, in Worcester.

The railway had to cross both the canal and the narrow roadway of Westbury Street, two very different spans. It's not clearly recorded who designed the railway bridge, but Pevsner's guide attributes it to Charles Liddell, who was the Engineer with overall responsibility for the railway line.

Liddell was clearly familiar with metal bridges, having previously accepted Thomas Kennard's design for the trussed Crumlin Viaduct on the Newport, Abergavenny and Hereford line. However, a brick bridge was chosen at Lowesmoor.


I'm guessing the unusual arch form resulted because a single span over both canal and roadway would have required a fairly shallow arch rise to avoid encroaching into the roadway headroom. This would have led to greater arch thrusts and more expensive foundations. The twin span arrangement which was built is charmingly eccentric, entirely because of the presence of a large oculus above the small roadway arch.

The Pevsner guide already linked suggests that the round hole was to reduce the weight of the bridge, as was famously done on the Pontypridd Bridge, although the saving at Lowesmoor must have been small. A greater saving in weight could have been made by extending the roadway arch up to the full height of the bridge. However, the thrust from the canal span arch at a higher level would have unbalanced the central pier, requiring a strut at the pier's mid-height. The circular hole may have resulted from a combination of these considerations - saving weight while ensuring the arch forces had load paths in the right places.


The result is not a spectacular bridge, or even one which is especially ingenious. However, I've never seen another bridge quite like it, and it definitely has charm.

Further information:

• Google maps / Bing maps
• CanalPlanAC Gazetteer

Worcestershire Bridges: 5. Holt Fleet Bridge

Continuing north from the Sabrina Bridge, the last structure I visited on this particular trip was Thomas Telford's Holt Fleet Bridge, which is the next span across the River Severn (there's an 1844 iron arch bridge at Bevere Island, but it only spans part of the river).

Telford's cast iron arch at Holt Fleet was completed in 1828, and spans 46m across the Severn, carrying a roadway. It was built by William Hazledine, and is now Listed Grade II. It replaced a ferry, and is now the only highway crossing in the 12 mile stretch of the Severn between Worcester and Stourport.

As originally built, the bridge had five cast iron ribs supporting the deck via X-shaped lattices. The ribs were cast in 6.8m long segments. The bridge was strengthened and widened in 1928, by encasing both the upper and lower members of each 1m deep rib in a slab of reinforced concrete. The more vertical spandrel struts were also encased in concrete, and the original 32mm thick iron deck plates were replaced with a concrete beam-and-slab deck. I imagine that access for inspection and maintenance between the two arch slabs must be difficult if not impossible.

The concrete works have deteriorated considerably since then, with a 7.5 tonne vehicular weight limit recently placed on the bridge following inspection and assessment work. At the time of writing, considerable work is planned throughout 2011 and early 2012 to refurbish the bridge, with design by Halcrow. This will involve essentially reconstructing the reinforced concrete struts from scratch. The photos here show that the condition is poor, with extensive spalling, and rust staining in places.

It will be good to see the bridge improved from its current somewhat dilapidate state. Nonetheless, it's a fine structure, and a good example of Telford's work. There's a similar Telford bridge at Eaton Hall in Cheshire, which preserves the cast iron spandrel tracery and is much better looking, plus of course his classic span at Craigellachie. Galton Bridge, at Smethwick, is also cited as similar, but seems to me to have a different spandrel bracing pattern.

Further information:

• Google maps / Bing maps
• Structurae
• Engineering Timelines
• Wikipedia
• Civil Engineering Heritage: Wales & West Central England (Cragg, 1997)
• A Century of Bridges (Witts, 1998)

Worcestershire Bridges: 4. Sabrina Bridge

From the brand-new Diglis Bridge, head north through Worcester town centre. First you'll come to John Gwynn's 1781 road bridge, the only road bridge in Worcester. Next, it's the Worcester to Hereford Railway Bridge, built in 1860 (with its river spans replaced in 1905).

The next bridge is, like Diglis, a cable-stayed footbridge, the Sabrina Bridge. This was built in 1992 for £617,000 by Morrison Shand Construction Ltd, designed by YRM Anthony Hunt Associates. As at Diglis, it has a single A-frame tower on the west river bank, with an asymmetric span arrangement. The main span is 62m, with a 3m wide deck.

The bridge is generally in steel, with timber deck planks with added anti-slip surfacing. When first built, the bridge attracted criticism for its slippery surface (presumably untreated timber), which led to a number of insurance claims and had to be replaced.

The really interesting feature of this bridge is the form of its deck, which consists of a series of steel tubular trusses spanning between the points of cable support. The deck is hinged at the connection points. This converts the bridge from the static indeterminacy of a normal cable-stayed bridge into a determinate structure.

This simplifies design, and also the construction of a bridge, as the cable stiffness has no effect on the stresses within the deck, allowing the cables to be adjusted freely during construction. The bridge then largely comprises a series of rigid triangles pinned to each other.

However, this is not a structural approach I've seen anywhere else. The hinges may be difficult to maintain, and the advantageous load distribution offered by a continuous stiffening girder is lost. You might expect the bridge to be more vulnerable to dynamic excitation, but I didn't find that to be the case.

An asymmetric cable-stayed bridge results in significant out-of-balance horizontal reactions at the end of the deck, due to the force in the deck balancing the main span cables. On Diglis Bridge, I guess this force is taken into the pylon base and then perhaps balanced against the back-stay anchors via a buried strut. At Sabrina, the force is tied back by diagonal bracing members visible in the photo above right, running from top right to bottom left.

The pylon is of the simplest form possible, and is noticeably more slender than on the Diglis structure. It's adorned with the arms of Worcester's twin town, Kleve (in Germany), but this doesn't detract too much from the pylon's appearance. Personally, although Sabrina's pylon is slimmer, I prefer the more sculpted form of the one at Diglis.

Sabrina Bridge is an unusual structure, and I'd be interested to know of any other cable-stayed bridges which share its hinged deck form.

Further information:

• Google maps / Bing maps
• Structurae
• A Century of Bridges (Witts, 1998)

Worcestershire Bridges: 3. Diglis Cycle Bridge

Diglis Bridge is one of a series of structures being built around the country with funding from Sustrans, who secured £50m of government money in late 2007 for their nationwide Connect2 scheme. I've recently featured another example, in Bradford. The Diglis bridge links cycleways and footpaths across the River Severn in south Worcester. It struck me that there are surprisingly few bridges in Worcester over the Severn, with this being the second of two footbridges to be built, and with there being only one highway bridge within the urban area.

It's the most modern of the various bridges I saw in Worcestershire, indeed, they had only just opened it in time for my visit (it opened on 20th July). The 66m span bridge cost £1.8m, and was built by Alun Griffiths to a design by Yee Associates and Mott MacDonald. The steelwork was fabricated by Rowecord.

The bridge's 28m tall steel A-frame pylon inclines toward the river at 22.5°. I'm not sure whether that's for engineering, aesthetic, or commercial reasons.

In terms of the structural engineering, it complicates erection of the bridge, but makes the cables slightly more effective in supporting the bridge deck, as they are closer to the vertical. However, the rear cables are less efficient, as their angle to the tower is reduced, and they must also support part of the weight of the tower. Writing in 1977, Michael Troitsky knew of only one cable-stayed bridge with a tower inclined towards the span (the Batman Bridge, in Tasmania), and I think it's probably still very rare today.

Aesthetically, I think it looks somewhat awkward. I instinctively feel that the tower should look as though it is helping to hold up the bridge. If it is going to incline, it should tilt away from the span, like a man leaning back to pull the reins on a horse.

I suspect, however, that the real reason is commercial - it may allow the cable back-stay anchorage to be brought closer to the foot of the tower, which can reduce the need to purchase additional land.

The pylon legs and the pylon crossbeam are both diamond-shaped in cross-section, as are the main deck edge members. It's an attractive feature, in particular bringing the edge of the deck to a nice crisp edge. However, looking closely along the edge of the deck, it's apparent they didn't quite manage to achieve a perfect smooth curve when the various deck sections were bolted together (it looks like it's fully welded, but the project's construction newsletters say that bolted joints are hidden under cover plates).

The pier at the end of the deck continues the diamond section theme, but unfortunately the approach ramps do not, leading to an untidy junction as shown on the photograph on the left.

The rest of the bridge is unexceptional although reasonably well detailed. The bridge decking consists of aluminium planks, while the parapets are of a post-and-wire type that's now very common, with the main feature of interest being the "Y"-shaped arrangement for the posts (surely not a nod to the architect's surname?) Lighting is recessed into the parapet handrails, as now seems de rigueur.

Overall, it's an unspectacular but attractive structure. It wasn't especially busy when I visited, but to a certain extent it's just one stage in a wider plan to expand footway and cycle links south from Worcester along the Severn. It will be interesting to contrast it with Worcester's other cable-stayed footbridge, which I'll cover in the next post.

Further information:

• Google maps / Bing maps (aerial imagery visible at the time of posting dates from before bridge construction)
• Worcestershire Council bridge website (includes construction newsletters and photographs)

Worcestershire Bridges: 2. Powick Bridges

From Croome Park, we head a little west and north, to the outskirts of Worcester, to visit two bridges, one old, and one older.

Both bridges are in Powick, and carry the highway across the River Teme, a tributary of the River Severn.

Old Powick Bridge is over 500 years old (dating at least to 1447), and is a five span masonry arch bridge. Two spans cross a mill stream, with the other three passing at high skew (about 30°) over the River itself. Between the arches are massive piers with substantial cutwaters. The bridge is protected as a Scheduled Monument, as well as being a Grade I Listed Building. Historically, it's best known as the site of one of the opening skirmishes in the English Civil War.

When later engineers came to build arch bridges in brick, skew presented a major challenge, with a number of complex schemes developed to ensure that so far as is practical, the stresses in the masonry remained perpendicular to the mortar beds. The article on skew arches at Wikipedia gives a great illustration of the problems (and incidentally, is by far one of the best articles I've seen on Wikipedia). It also links to many of the original books and articles written on the subject over the years.

Bridges of this vintage with this high a skew are unusual - it would have been far simpler at the time to change the road alignment and cross the river without skew. The old Powick Bridge is what may be termed a "false skew arch", as the masonry courses are parallel to the arch springing rather than perpendicular to the direction of span (see picture). In theory, this results in a tendency for the arch voussoirs to slide out of position. The Powick Bridge has certainly required repair on numerous occasions throughout its history, as will be readily apparent from the photographs, but I think its sheer weight probably prevents the skew from causing any structural problems.

What makes the bridge particularly attractive is the combination of its offset cutwaters with its meandering alignment, which can be seen in the aerial photos at Google linked below. It makes walking across a more interesting experience, with varying perspectives on offer.

The two northern spans over the mill stream appear to be more recent in construction. The water mill was converted to a partly hydroelectric power station near the end of the nineteenth century, and now contains residential apartments overlooking the bridge.

The narrow bridge clearly created limitations for transport, and in 1837 a new cast-iron bridge was opened a short distance downstream.

New Powick Bridge was designed by C.H. Capper, and is a cast-iron arch bridge spanning 21m across the Teme. It is Listed Grade II.

Seven arch ribs support the bridge deck on X-braced lattices. The deck was converted to reinforced concrete in 1957 and 1968, and has recently (2008) been rewaterproofed.

There are two 5m span side arches, providing flood relief and footpath or cattle creep access. These are of a slightly different style to the main arch, being pointed. I like how the curved invert to the opening is exposed, giving the impression of an oval opening rather than just an arch portal.

Further information:

• Google maps / Bing maps
• The Ancient Bridges of Wales & Western England (Jervoise, 1936)
• Civil Engineering Heritage: Wales & West Central England
  (Cragg, 1997)

Worcestershire Bridges: 1. Croome Park Bridges

Right, I'm back from a couple of trips and have a backlog of bridge photographs to post here. First, a few from Worcestershire, both ancient and modern, and then a couple of significant footbridges from Yorkshire will follow.

Croome Park is a property and parkland developed on behalf of the 6th Earl of Coventry in the 18th century by the landscape designer Lancelot 'Capability' Brown. Various elements of this beautiful but intensely artificial park were contributed by Robert Adam and James Wyatt. Over the years, much of it fell into disrepair, but the National Trust has been carrying out restoration work since 1996.

There are various bridges at the site, several of which were designed by James Wyatt and recently restored by Capps and Capps Limited. One is a small stone arch, and there are three wrought iron arch footbridges spanning various arms of an artificial lake.

The ornamental bridge is described in The National Trust Book of Bridges as "building bridges for the adornment of the landscape as much as for the fulfillment of practical needs". The formula for landscape gardens developed by Brown and others generally involved water features, and frequently a bridge was called for both to cross the water and to appear reflected in it. Stone Palladian bridges were popular, but so were decorative iron bridges.

The three footbridges at Croome all have a very practical purpose, forming links in a footpath encircling the garden lake. All are arch bridges, with the arched bridge deck supported by delicate haunches below, in wrought iron imitation of cast iron style. How much the "truss" parapets contribute to the bridges' strength and stiffness, I don't know. They certainly didn't move much underfoot (although it was fairly easy to get them wobbling sideways). The longest of the three has a sign warning that no more than three persons should stand on it at once.

There are two things I like about these bridges.

The first is their lightness. The arch itself is exceptionally slender by modern standards, and the curved haunching below so delicate that it's hard to see that it offers much support. The parapet is refreshingly flimsy and open, something that would be hard to achieve in a modern structure.

And indeed, that's where much of the appeal lies: these elderly bridges, designed by someone who certainly was not a bridge specialist, are far lighter than their modern equivalents, while still feeling sufficiently robust. It's a challenge from the past to the present - how can we too, design bridges which are striking in their presence yet elegantly minimal in appearance?

The second thing I like is the use of the parapets as a structural element. This is something which is still a feature of modern footbridges, as in the identikit Vierendeel truss designs which bedevil the urban landscape. However, these modern equivalents have a far heavier appearance than the Croome Park structures. I'm sure there's more still to be done where the parapet, as here, contributes to the bridge's strength without providing the sole structural support.

Further information:

• Google maps / Bing maps