Wednesday, October 04, 2006

Bridging the gap 

Those familiar with Caracas will know it is a city that is in a fairly high mountain valley and that to get there from the coast (which is where the airport happens to be) requires a long drive up through mountain passes, through tunnels, and over very steep ravines. Earlier this year a bridge over one of the ravines, in-spite of intense efforts to save it, collapsed creating a traffic nightmare (for details on the old viaduct and what the route is like see this previous post).

Now the government is working furiously to build a new bridge over that ravine. The new bridge will be a good deal longer than the old one and instead of being an arched span will consist of spans over seven tall concrete tower. The first two towers are largely complete and the rest will have to begin rising soon to meet the completion deadline of April 2007. Lets look at the progress so far:

In this last picture you should be able to note something important – how steep the ravine wall right next to the towers is. It was precisely these steep ravine walls which slide ever downward with the rains that ultimately felled the original viaduct. So I have been wondering how they planned to guard against that with this bridge.

The answer can be seen in this picture:

They have hallowed out the ravine wall around towers and put up a concrete wall with steel reinforcing beams that are drilled into the ravine wall. This should serve to protect the tower and at the very least if any damage is seen in the wall remedial action can be taken before it effects the towers. Looks like a lot of extra work but it also looks like a necessary solution - such are the challengers of building durable structures in such a challenging environment as Venezuela:

Here are some more pictures of those walls:

Look carefully in this picture and you can see several more of these walls already built where the other towers will be built:

Finally here are some pictures of the work on the top of the towers as they rise:

It’s interesting how the scaffolding is actually hung from the top of the tower as it rises rather than built all the way up from the bottom. I don’t think I’ve ever seen that before. Regardless, I won’t be applying for those jobs anytime soon.


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