Town and City Bridges
27th October 2000 Back to Bridges back to Home Page
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Motorways, ring roads, and many other roads, large and small, have cut across or between many communities. In earlier times, railways did the same thing. Many bridges and subways were needed in order to allow people across. Railways can present less of a problem than roads. Level crossings with automatic barriers can cope in the case of flat ground, because of the relative infrequency of trains. They are the equivalent of traffic lights for roads, but the frequency and speed of road traffic is such that pedestrians and trains are not allowed across major roads and motorways without bridges or tunnels. As you approach or enter a large town, you are likely to go over or under a railway track, a bypass, a ring-road, or a large road such as a motorway. If you go over a bridge, then unless the route below is in a cutting, your own route will have embankments and bridges, which exert a significant effect on the area. You may even pass over something as large as the Chiswick viaduct and Hammersmith flyover. If you are going under the other route, the visual impact of your own entry is affected. In many cases, large roads pass over smaller ones on beam bridges, which cut straight across the view, and if the major road has four or six lanes and a central reservation, the effect will be almost that of a short tunnel. Seldom do the designers make a slot in the central reservation, separating the bridge into two halves, and letting some light into the tunnel. Here are some examples of bridges over roads into Gloucester and its suburbs. |
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The last five pictures above show a typical small railway bridge in a town. It comprises two separate plate girder bridges, allowing easy spanning for the decks. The bridges are rather too close to let much light in, but a wider separation would have meant wider embankments for a considerable distance, as railway tracks cannot include sharp bends. The gaps between the plate girders are spanned by a series of smaller I-beams. These in turn are bridged by a large number of little arches, except near the abutments, it being a skew bridge. This was once a common design. It is shown in the last picture, which also shows the degradation of the end wall caused by deposition from running water. |
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