Five Interesting Bridges
A post, from a Civil Engineer, about interesting bridges is pretty much the least imaginative thing on the internet. I scorn those bloggers who stick to such easy topics; where is your imagination?
So, here’s a run-down of some interesting bridges that I have been on; I’m sure that such a foray into the abstract realm of artistry will be enough to reboot the cannon of international writing…
I really hope you’re not anticipating some amazing international exposé on innovative bridge architecture…
I expect the majority of people who have seen this bridge know it as the “Give Peas A Chance” bridge. Built between 1902 and 1906 it carries the Great Western Line; originally across the River Misbourne, and then in the 1980s the M25. It’s not, however, the fairly standard blue-brick masonry arches that give this structure its appeal, it’s the apparent plea for the humble vegetable, which has shone like a beacon to all ‘5-a-day’ activists since ever I’ve known it.
Despite popular opinion, the slogan was not the act of a desperate Mother trying to get their child to finish their greens. The truth is that it’s the tag of a London Graffiti artist, who augmented his identifying ‘PEAS’ with ‘GIVE’ and ‘A CHANCE’ after his continual arrests.
Lets us leave the dizzying heights of the M25 (but not for long…) and return to humble Florence, where 17ft naked men take credit for slaying giants. Beating Blackfraiars by about 670 years, this bridge supports a thru-structure across the river. With the street of shops cantilevering-off from the edge of the parapet, it looks like something cobbled together from a Ghibli film. As an engineer, I can’t help but marvel at the ‘lets just stick some buildings on the sides of this bridge’ approach.
Confusingly, it’s probably one of the few structures that owes a debt of gratitude to Hitler, who is fabled to have personally intervened to save it from the destruction of all the bridges of Florence during the great retreat of 1944. There is also a €50 penalty for putting a padlock on the bridge; although the two facts are possibly unrelated.
I imagine the majority of people who have seen this bridge know it as “that ugly bridge on the M25.” I should point out, at this juncture, that there is more to British architecture then the M25. Until 2000 it was the only cable stayed railway bridge in Europe; and quite rightly so. The basic cable stayed bridge is one of the worse structural forms for railway traffic- the low deck stiffness means that concentrated wheel loads can’t distribute, and can even form a ‘wave’ that passes along the flexible bridge.
Unperturbed by the ill-fated railway suspension bridge of Captain Samuel Brown, Stressed Concrete Design Ltd and Redpath Dorman Long tendered a money saving solution to the 120 yard M25 crossing: They would use a pre-stressed concrete suspension bridge to overcome the 28o skew that had made more traditional forms uneconomical. Although technically interesting, the a tall concrete parapet edge-beams required for deck rigidity give the appearance of a bridge already complete, without the absurdly tall towers topped with bulbous points (for torsional stiffness) stringing it up. If you want to get an engineer to admit that architects aren’t a complete waste of space- mention this bridge.
Taramakau Hokitika Industrial Line Bridge
Taramakau, New Zealand
You’ve got two watch the video to truly appreciate the economic nature of this bridge. Not only does it take the State Highway 6 West Coast traffic, in both directions, across its single, enclosed, lane; but it triples-up (should that ever be an expression) as the rail route of the Hokitika Industrial Line. Aside from perhaps letting pedestrians chance their luck, it’s hard to think how the Kiwi’s could get more out of this piece of put-upon infrastructure.
On a much smaller scale, visitors to Porthmadog in Wales can also enjoy the road/rail experience; avoiding the narrow-gauge Welsh Highland Railway track that runs along Britannia bridge.
Puttgarden – Rødby Rail Crossing
Puttegarden, Germany to Rødby, Denmark
I expect some of you might consider that this isn’t, in a technical sense, a bridge. But, if a bridge is a piece of infrastructure that provides passage over an obstacle- then surely this must count, and even if it doesn’t, the lift onto the ferry is a hinged bridge structure of interest in its own right. The way the train simply drives on to, and then back off of, the ferry is one of the wonders of the world (for me, at least); frankly it makes the 2mm differential movement surrounding track/structure interaction look like childs-play.
In writing this article I’ve learnt that Rail/Ferry crossings are not, infact, as uncommon as all that. I still, however, remember boarding a train from Hamburg to Copenhagen during my youthful travels. As the train began to slow beside the Baltic Sea, I glanced around for a bridge, and then announced that there had to be a tunnel (in my engineering ignorance) before looking on in awe as the train drove into a ferry.