KOCHI: Palarivattom flyover, which has been closed since May for repair works, is all set to undergo a major makeover. A report filed by Delhi Metro Rail Corporation (DMRC) principal advisor E Sreedharan to the government recommends dismantling all 17 reinforced cement concrete (RCC) spans.
In the report filed to Chief Minister Pinarayi Vijayan on July 3, the Metro man recommended that there was no strengthening necessary for the foundation. Similarly, no strengthening of special spans of prestressed concrete (PSC) girder was needed. Instead, metalbearing has to be replaced with more robust ones. However, modifications have to be made in piers, pier caps and RCC spans.
“Piers and pier caps should be strengthened with RCC jacketing suitably designed. Vertical reinforcement of pier jackets should be taken to the pile cap reinforcement and bonded. All the 17 RCC spans have to be dismantled and replaced with PSC girders with at least one diaphragm in addition to the end diaphragm beam and a new deck slab provided.
Continuity of the deck slab should be ensured over the piers,” said in the report. DMRC has estimated a `18.71-crore restoration work to be done. This includes `2 crore for dismantling and carting away RCC spans, `1.71 crore for jacketing piers and pier caps and `15 crore for new PSC decks. Time frame set for the restoration is 10 months. Visual cracks were seen in 97 out of 102 RCC girders. Crack width up to .38mm was recorded against the permissible limit of .236mm.
These crack widths noted were without a live road. With a live road, the crack widths are likely to increase further. In a coastal environment, this leads to corrosion of reinforcements affecting strength and durability. Sreedharan is also sceptical about strengthening the concrete with low viscous epoxy resin.
“The quality of concrete being in doubt, I have strong reservations whether wrapping with carbon fibre fabric can restore this girder to the required structural soundness and even if restored, what would be the durability of these girders? Perhaps, not more than 20 years, whereas 100 years life expectancy is needed in these girders,” the report read. According to Sreedharan, if the cost estimated by IIT Madras is more than 50 per cent of the replacement cost, then the option is a total replacement of RCC girders with PSC girders.