India to get first runway on a river
An engineering marvel is getting ready at the Chennai airport — a runway bridge across the Adyar River that can even take the weight of an A380 aircraft. The bridge is being built so that the secondary runway can be extended over the bridge to the other side of the river. The country’s first bridge over which a runway will be laid, will be supported by 477 pillars. Around 2,440 prestressed concrete girders will be placed over the pillars to make it an integrated structure. The bridge will be 200m long across the river and 462m wide. About 50% of the work on the bridge has been completed. Airports Authority of India (AAI) is hoping to complete the works by November this year. ‘‘This bridge is different from the regular bridges built over roads. This is going to be an integrated structure consisting of piers, girders and concrete embankment so that load of aircraft will be distributed evenly across the structure,’’ said airport director Hareendranathan E P. The bank of the river has been widened from 140 metres to 200 metres after an hydraulic study was done to calculate the future water flow requirement. ‘‘We’ve taken a no-objection certificate from the public works department and has widened the banks so that there will be ample space for water to flow under the bridge,’’ an AAI official said. These steps are being taken to prevent flooding of the runway. ‘‘We’ve kept the height of the runway and the bridge a couple of metres above the 2005 flood level,’’ he added. “During the summer, the river bed is dry. So, works are progressing rapidly to construct the pillars and to place girders over them before the rains set in. There will be nine rows of 53 pillars. The prestressed girders are fabricated in a separate unit set up near the work site. The concrete is set using steam,’’ an official said. Consolidated Construction Consortium Ltd (CCCL) is building the bridge while a joint venture of KGL and BCPL is building the secondary runway extension. AAI started works to extend the 2,035m secondary runway by 1,400 m, including 835 m on the northern side of the river in January 2009. Most of the work on the extended portion of the runway has been completed. Once the construction of the bridge is over, the runway will be laid over it across the river. The airport has started to increase the level of the existing secondary runway to make it align with the extended portion, said an AAI official.