Footbridge Awards 2011 - aesthetics up to 30m span

Excellent! Those spiffy bloggers at Frame and Form have provided some images of the structures shortlisted for these awards, kindly saving me the bother and making it easier for me to comment on some of the entrants. So far, they've posted pictures of the entries under the short span (below 30 metres) / aesthetics category - go to their post for the images, I won't repost them here.

Judged purely on aesthetics, I'd want the Castleford Footbridge to win. It's a beautifully well-judged structure, tip-toeing gracefully across the river like a slow-motion ballerina, artful and expressive without ever having to be inappropriately demonstrative. It doesn't exhibit the need to show off, but its sinuous layout, use of the main girders as benches, and extensive presence of timber, all offer a humanistic approach to bridge design that's entirely appropriate to its setting.

Lisbon's Glass Bridge is technically impressive but somehow a bit inert, too simply cylindrical. The Corporation Street Bridge in Manchester does it better, as did the Glazen Brug in Rotterdam.

The Bracklinn Falls Bridge, at Callander in Scotland is another structure which is undoubtedly interesting but not necessarily "beautiful". I plan to visit it at some point and cover it in more detail. The combination of huge, rustic tree trunks with more modern timber and steel elements is striking, as is the setting. However, the triangular elevation, while robustly pragmatic, has no finesse to it.

I find the Buitengragt Pedestrian Bridge, in Cape Town, South Africa, more disconcerting than attractive. The deck is supported by stays from an inverted steel pyramid. It gives an impression of instability, and its hard to see why a stayed bridge was justified for such a short span at all.

The Yale Hillhouse Pedestrian Bridges, in Connecticut, USA, are not my favourite bridges for overall appearance, but I hugely admire their ingenuity. I recall seeing these previously, and the perforated, corrugated steel webs remain a delight. The corrugations help to stiffen the upper member of the side trusses against buckling, as well as preventing buckling of the webs themselves, while allowing the web plate to be very thin. The perforations hark back to Ithiel Towne's 19th century lattice trusses, one of many old truss designs ripe for reinvention.

Together, these two features significantly reduce the weight of the girders (although clearly only at the expense of much increased fabrication costs). An article in the ASCE's Civil Engineering magazine explains more. It's a shame this design isn't in the "technical short span" category, it's a very impressive piece of structural engineering.