Delayed, but Barapullah-III bridge to give Delhi a first | Delhi News

NEW DELHI: The Public Works Department will build Delhi’s first ‘extradosed’ bridge over the Yamuna in the third phase of the Barapullah elevated corridor project.
A bridge of this sort is built using the main elements of the box girder technique and cable-stayed towers. Compared with a purely cable-stayed bridge, such as the Signature Bridge, an extradosed bridge has much shorter stay-towers.


PWD said that the extradosed technique was chosen because of the long span between the supporting pillars of the bridge. The bridge has the second longest span for a bridge in Delhi and the bridge deck is 545 metres in length.
“The span between the four piers is 127 metres each, this being the second largest span in the city after the Signature Bridge,” said a PWD officer. “This was done in anticipation that in future if there is a plan to make a waterway on the river, then there should be enough room and the bridge should not come in the way.”
According to the officials, whenever the distance between the pillars is long to medium length, there arises the need to stabilise the bridge. Since the pillars can’t themselves hold the girders, an ‘extra dose’ of strength is given to the structure with boxed girders.
India’s first extradosed bridge was Nivedita Setu over the Hooghly in Kolkata, West Bengal. Measuring 880 metres in length and connecting Howrah with Kolkata, the bridge was constructed by Larsen and Toubro Limited, the same company that has been engaged for the construction of the Barapullah Phase III bridge.
Working in the Yamuna has been challenging. Last year, one of the pillars meant to support the bridge tilted due to the strong flow of the river. PWD is taking care to prevent a recurrence. It is making a ‘well foundation’ on the riverbed to give strong support to the pillars. The pillars are 50 metres deep in the river, going past the riverbed and the ‘wells’ are around 14 metres in diameter, under which circular pads of concrete have been placed in several layers.
The remaining two pillars, which are on the ground, have a span of 82 metres. The bridge is approximately 11 metres from the ground. The flow force of the Yamuna at the spots where two pillars have been erected has been estimated and the piers have been built to bear the tilt pressure. PWD is going down to a depth of up to 50 metres to construct the base of the pillars.
As a safety measure, the cables on the bridge are connected to stress sensors on the towers holding the German-made cables. The sensors will send alerts to the authorities about the stress levels on the deck of the bridge.
“The extradosed technique is being used in certain parts of India to makes the bridge deck rigid and strengthen it, unlike the flexibility in the bridge deck of cable-stayed bridges,” said Lakshmy Parameswaran, former chief scientist at Central Road Research Institute and a bridge expert. “The bridge also becomes more economical and safer. Currently, the government has its own guidelines regarding the use of the extradosed method in bridge construction.”

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