working on a paper for college, bridge over the straights of gibralter, need input?

heres what i know about the place,

-warm water

-high waves

-deep water

-strong current

the place is an engineers aquatic nightmare, but what else makes it so difficult to accomplish the task of building a bridge over the place, and have they tried before.

i just need some general info for my college engineering and english classes, any [intelligable] info will do.

thanks in advance.

2 Answers

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    Well, here's a few items:

    The work is performed at height, so there is a big danger to workers dying in a fall.

    The work is between two sovereign nations, passing over international waters, who would approve such a project? Spain, Morocco? What country is on the other side? And who gets the vote on the water? The International Maritime something or other? In the US, a bridge could look for approval from the "War department" back before the 1960s, I suppose now it would be the Army Core of Engineers or the State Department somehow, but someone has to look out for the health of the shipping channel. How much ship traffic goes through the area?

    The work is over a major shipping channel, so the height of the bridge must be high enough to not interfere with boats below, and how tall does it have to be according to maritime requirements?

    Then you've got your usual incredibly large span, say 4,000 feet, maybe, I have no real idea of how wide that straight is, but you can research it for yourself, but if we're over 4,000 feet span, you're looking primarily at a suspension bridge or a cable stayed bridge, there is also a strong possibility that the maritime/shipping will not permit any piers in the water, which would add to the cost of construction if the span could have been shorter.

    I don't know what we've got there for seismic activity, but the straight must have water currents passing through at high/low tide, so you also have to investigate bridge piers for scour if there are going to be (intermediate supports) piers in the water.

    The longer the bridge is, the more likely it is to have problems with vibration/wind, which means you're going into the wind tunnel to try to address that and keep the bridge stiff enough to prevent problems, which adds to the cost of design, and the final question is if there is demand for such a bridge and if so, what will it carry? Pedestrians only seems unlikely to get built, so we have to at least add cars, and that sounds dicey as well, so you'll also want trains, and once you've got trains, are you talking about freight trains (slow and heavy) or passenger trains (light and fast and might cause the bridge to vibrate as it goes across), and in Europe, I believe the two types of train do not run on the same tracks, so you might have to choose between freight traffic, or passenger rail (high speed TGV in French, or whatever the Spanish name for that is), and the last question is if the rail standard in Algiers/Morroco is the same as that in Spain. And the bridge has to satisfy everyone involved, including groups that will oppose it based on looks, the environment, and other issues. And let's not forget thermal expansion which is going to be significant in a 4,000 foot long bridge. Do the two approaches have the same elevation above sea level, or does the bridge need to slope, between continents? You can spend a lot of money on the approach spans of a suspension or cable stayed bridge because you need them to balance the load on the main span. So you might need 2,000 foot approaches on both sides.

    Source(s): I'm a structural engineer, but I don't design bridges.
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  • 1 decade ago

    There was a cable show on this subject, I can't remember but it was Discovery, TLC, or maybe the History Channel. I'm sure a web search would lead you to the program.

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