post-tensioned box girder - description of the erecting?

[haras]

I'm civil engineer from Germany-i've to describe my site in english and have problems with finding apropriate terms for launching technology. We build a post-tensioned box girder-superstructure in Dresden. We erect it from the pear - pour the concrete into the formwok (about 4m-segments)on one side of the pear, after it set, we stretch the tendons and do the same on the other side, ten back another side until we reach the middle of the span. Then we move with the equipment to the next pear and build the next part.
How do you call this kind of erecting?
Where can I find in internet descriptions of bridges built in the same technology?
Thanks
haras

 

[wiktor]

The process you are desribing is called balanced cantilever construction. Put this into your search window and this'll yield some web site detailing the process. Typically this technology is used with the elements casted on the ground (so called match casting), but it's mot making big difference.

http://www.pubs.asce.org/catalog/40314.html

http://www.murray-river.net/news/btbridge.htm

Good luck!

 

[Ingenuity]

haras,

It is also called "free cantilevering method" and was invented by a German engineer Ulrich Finsterwalder. In 1965, the Rhine Bridge near Bendorf was one of the first to use this technique.

Finsterwalder was an engineer with Dywidag of Germany - if you contact Dywidag at:

http://www.dywidag-systems.com/edocs/index.htm

they should be able to send you some relevant technical info.

Both precast and cast-in-place segments are common today, depending on the resources available in you area.

HTH

 

[austim]

Hi, haras.

The earliest balanced cantilever bridges were all done using the in-situ method that you have described to us.

(I would use the description - "In-situ balanced cantilevered construction&quot

One such bridge (which has been close to my heart ever since I worked in the team which designed it) is the Medway Bridge, built in the UK, and opened to the public in 1963.

If you cannot find copies of these papers at a technical library in your vicinity, then you should be able to download them (for a price) at

http://www.iceknowledge.com

That link gets you to the Institution of Civil Engineers Virtual Library, where you can search the entire set of papers published by the ICE from 1836 onwards, read the abstracts, and purchase downloaded copies of any that interest you.

 

[austim]

Hi, ingenuity.

If you don't mind paying (£5 for ICE members per downloaded paper, £15 for others), then you should be able to download all that you want (/are prepared to afford ;-)). I haven't actually downloaded anything from the site myself yet, but I have a strong aversion against purchasing anything on the any website.

Yes, you are correct with the Medway geometry - 200 foot main cantilevers, 100 ft suspended span, 312.5 ft anchor spans.

At 500 foot we held the world record for a PSC girder span for quite some time. Not a bad effort, when there was no such thing as a British Standard Code of Practice for Prestressed Concrete at the time.

To the best of my knowledge, there has never been any problem of excessive creep deflections.

The only 'problem' that I have heard of arose from a general review of UK bridges for compliance with current codes and tolerance for modern loads. I understand that the powers that be/were decided that the web reinforcement did not provide sufficient reserve for modern ultimate load requirements. Although there was no evidence of any cracks or other defects, I believe that some degree of strengthening was undertaken.

 

[austim]

Hi, ingenuity.

When I said "not bad when there was no such thing as a BS Code of Practice..." I should of course have added - and no Finite Element analyses, no matrices, no computer. (Just our slide rules and one electro-mechanical calculator that clattered away and made so much noise that we couldn't think when it was dividing).

 

[maldor]

The first time that method was used was in 1930 in the construction of the Santa Catalina bridge, over the Peixe river, in Brazil. The engineer was BAUMGART, and the bridge was a REINFORCED concrete bridge with 68 m. central span.
In 1937, the method was used in England in other r. c. bridge of 3 continuous spans (18.30 m + 48.70 m + 18.30 m) (I ignore the name of the engineer).
Later, Finsterwalder applied the method to prestressed concrete. I think Finsterwalder used it first in the Lahn bridge (1950); there are several bridges built with that technique before the Bendorf bridge over the Rhine river was built (1964).