Islington Place Footbridge, Birmingham

Birmingham is not blessed with contemporary bridges. I've reported on the rather unimpressive Mailbox Footbridge before, and the Selfridges Footbridge, which is only a little better.

The Islington Place Footbridge spans the Birmingham and Fazeley Canal at Farmer's Bridge Locks. I've been unable to find out who designed or built it, so if you know, please post in the comments.

My initial reaction to this bridge was simply that it was completely unnecessary. It's such a short span that you could almost cross it with a few short planks and a bit of sticky tape. This is clearly a bridge where its role as a sculpture is far more important than as a crossing.

However, I ended up feeling quite a bit more generous towards the bridge. The crossed hoops work very well as a visual device, looking very different from a variety of angles, and offering a landmark while still remaining small enough not to be overbearing.

The cable array doesn't look quite right to me - I think the ties between the two hoops should run much more horizontally, but they do seem to be actually doing something, which is not the case some bridges that I've seen.

The steelwork below the deck seems a little bit over-engineered to me, but this doesn't really matter given that it's tucked mostly out of sight.

Further information:

• Google maps / Bing maps
• CanalPlan Gazeteer

Mailbox Footbridge, Birmingham

Here are some photos taken on a visit to Birmingham, of a modern footbridge across a canal. It's a rather unattractive bridge, but there are several features worthy of comment.

I haven't been able to confirm the identity of the designer or the builder, although there is a very similar design by specialist footbridge manufacturer CTS Ltd not far away.

I don't know that there's a word for this type of bridge. Most truss bridges are "through" or "half-through" structures, where the bridge deck passes between the supporting truss girders. This maximises one of the advantages of the truss form, which is its ability to accommodate a very shallow depth of structure between the footway or roadway surface and the underside of the bridge. This is often required to maintain headroom below while minimising the length of approach ramps.

This bridge, which sits just to the east of the shopping, restaurant and office development known as The Mailbox, has a three-dimensional truss supporting the deck from below. It is triangular in cross-section, with the web members arranged in Warren truss form. The deck is also fully braced, ensuring that overall the truss has sufficient torsional stiffness. As the deck is supported from its two upper chords, it is also secure against overbalancing.

However, you can see on the photo on the left that the ends of the truss terminate in a very awkward way. It's unclear quite how the truss is supported, with the bearings hidden behind a covering plate. Also, because the bottom chord is a constant section and the truss a constant depth, the entire bridge looks visually "stiff", ending abruptly where you might expect the bottom chord to curve upwards.

I believe some of this is just poor design, but some of it is due to the difficult construction history - the bridge was built before the adjacent building was started. It's far from clear how well coordinated the different construction operations and designs will have been. Whatever, the reason, the ends of the bridge look very clumsy.

The bridge parapets are in a fairly standard contemporary style, with horizontal wire infill, although the boxes for the lighting units are perhaps overly intrusive.

The decking is a cheese-grater type material, visibly perforated from below but appearing very solid from above. It will be free-draining into the canal, and may therefore be partly responsible for the poor condition of some of the steelwork below.

Underneath, the structure looks particularly unattractive, with what I presume are lighting cables and power supply units dangling from the industrial walkway material and the patchy steel frame.

There are two or three other interesting footbridges over the canals in central Birmingham, which I hope to visit and then cover here when I get a chance.

Further information:

• Google maps / Bing maps
• Canalplan gazetteer
• Construction photograph

Selfridges Footbridge, Birmingham

The now-defunct Future Systems were a firm with a very distinctive architectural style, a cross between sixties day-glo and 21st century blobitecture. They were never noted for their bridges, indeed other than the subject of this post, the structure at West India Quay may have been their only other completed span.

The bridge at the Selfridges store in Birmingham is little more than a punctuation mark bookending the utterly dotty enterprise that is the building itself. It connects Selfridges to a multi-storey car park across the road, and so is effectively one of the shop's main entrances, but it still seems very much like an afterthought.

The Selfridges building, which has a fascinating interior with a lovely atrium, is somewhat intransigent on the outside, with its silver-speckled mass offering little idea of its layout or purpose, with no windows and a minimum of other openings. How do you use a bridge to create a gateway into such a place?

The pedestrian bridge which was built studiously avoids that question, proferring an appendage that seems barely integrated with the building, and which, once crossed, presents a blank wall behind which the department store's 3rd level is hidden.

Its 37m span comprises a steel box girder, fabricated from a series of warped flat plates and segments of bent steel tubes, and supported roughly in the middle from a Y-shaped arrangement of cable stays. It is curved in plan, giving the visitor an expectation that the initially obscured view will gradually open up, only to dash it with that unhelpful blank wall.

Structurally, it is neither innovative nor hugely interesting, although clearly it must have been a complete bastard to assemble.

Steel arches spring from the box girder at varying angles, carrying a polycarbonate canopy, which is dirty but not yet discoloured (a fate which appears to await most similar materials). The canopy is combined with a stainless steel mesh parapet system, which must have been a brave choice. This kind of mesh is generally chosen for its extreme immateriality, and this high above the roadway it would have been easy for it to appear simply too insubstantial for comfort. In combinatio with the see-through canopy, however, it works well.

The bridge was designed by Future Systems and Arup, and built by O'Rourke.

Further information:

• Google maps / Bing maps
• Structurae
• Future Systems
• Selfridges, Birmingham, Arup Journal, 2005 [PDF]