Delhi Metro Rail Corporation (DMRC) has readied the design to reconstruct an expansion-joint-less, four-lane flyover at Palarivattom on the lines of the one at Edappally to replace the one whose cracked girders will be pulled down, Metroman E. Sreedharan has said.
While 100 of the 102 girders and the deck above will be pulled down, the piers and pier caps will be wrapped using reinforced concrete. The method is stronger and durable than carbon-fibre-wrapping that had been suggested earlier, he added.
The design was readied in advance on Chief Minister Pinarayi Vijayan’s suggestion, to save on time. “He wants me to recommend someone to supervise the rebuilding work, and I will get back to him in two weeks. The work will be executed by the Kozhikode-based Uralungal Labour Contract Cooperative Society Ltd,” Mr Sreedharan told
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The estimate and tender documents will be readied in 15 days. “DMRC will not be associated with the reconstruction work since our personnel here who are engaged in metro work are being diverted to other work sites. Neither will I supervise it. I will give technical guidance, in my personal capacity,” the Metroman said.
Elaborating on the scale of damage sustained by the flyover, he said since 97 of the 102 girders had suffered major or minor cracks within less than three years of the flyover being commissioned, casting doubts about the safety and longevity of the structure.
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“The replacement of girders will ensure that the flyover on the Edappally-Aroor NH Bypass has a lifespan of 80 to 100 years.
“The girders, which were built using the deck-continuity method, will be replaced with pre-stressed girders as was done on the Edappally flyover which was built by DMRC. The two special spans at the centre of the flyover will not be replaced. Thus, vehicles can continue to go beneath the structure,” he said.
Pre-casting will be done away with at the flyover site, so that the existing girders can be simultaneously pulled down without throwing traffic into disarray.
All bearings must be replaced. Care will have to be taken so that vehicles can proceed without being caught in snarls and by making optimal use of space on service roads, Mr. Sreedharan said.
Debris disposal
On how the broken debris of girders and deck slabs will be disposed off, he said care would be taken not to break them into pieces. “Rather, they will be cut in a definite pattern, like say five by three metres, and transported to coastal areas facing sea erosion. The girders and slabs can be erected like a wall on the waterfront. They will last for decades, thus preventing environmental degradation,” he observed.
A team of structural engineers from IIT-Chennai had submitted a preliminary report earlier this year, saying that the flyover should be strengthened by using the carbon-fibre-wrapping method, which could take up to three months. This was followed by a joint inspection of the structure by Mr. Sreedharan and renowned structural engineer Mahesh Tandon. Based on the site inspection and findings in the IIT report, they submitted a report to the government that the girders must be rebuilt at a cost of approximately ₹18.50 crore to ensure the longevity of the flyover.