Metro saves cost, time on IGI line with giant girders

New Delhi: With the countdown having started for the Commonwealth Games, Delhi Metro's express link to the airport is fast nearing completion.
To expedite the process and make it more cost effective, Delhi Metro Rail Corporation (DMRC) is making use of gigantic 25 metre-long girders to join spans on elevated stretch of the section.
The technique is being used for the first time in India. Earlier it was used only in China and Taipei. Airport Express Line, which is scheduled for a October 2010 opening, has to be constructed on a very tight deadline. So, DMRC officials decided to use the large girders, each weighing about 120 tonnes, in place of segmental construction technique. Till now, the concrete spans between two pillars on which the tracks are laid were made of 12 small segments, which were joined together with metal cables and stressed. But now, DMRC is going to have two gigantic concrete slabs of 25 metres length, which will be placed side-by-side on top of the piers (pillars) to create the foundation of the elevated stretch.
The bigger spans work out to be more economical and also speed up pace of the construction. Officials said it takes about a week to join the space between two pillars using segmental construction while the bigger spans can be put in place in just one day.
With so many benefits, why is the technique not used for construction of all stretches? DMRC officials explain that it can be used only in areas where there is enough space near the construction site. This is because the concrete girders are made at a casting yard and transported to the construction site on specially designed trailer trucks which are 35m long and have 64 tyres.
10/01/09 Times of India

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Categories: Airports Jan 2009