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Incremental launching - Applications

The advantages and disadvantages of incremental launching are given below.

Advantages:

●There is no need for false work to support the deck during casting in the spanned area.
●The deck is cast at one location, hence improving concrete quality control and saving on formwork.


Disadvantages:

●Nearly all the sections of the deck would experience both sagging and hogging moments during launching that are higher than the moments in an instantaneously built deck.
●Deck has to be straight or of constant curvature.
●Special bearings are required at the supports.
●A jacking system is required to push the segments forward.
●Launching is carried out by specialist contractors that could result in increased price.

Caption: Jules Verne Viaduct incremental lauching method

See also Concrete Society Current Practice Sheet 151, Incrementally launched concrete bridges, by Simon Bourne (Benaim), CONCRETE, July 2007, pp. 7–8. [Note that copies of Current Practice Sheets can be downloaded form the Members´ Area of the Concrete Society web site.]

Launching method and casting yard arrangement Launching nose
Image courtesy of Freyssinet Image courtesy of Freyssinet Image courtesy of Freyssinnet
 
Acknowledgement: Gifford Consulting
 

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