Local Goa News

Wednesday, August 3, 2016

Snags and stress trouble Goa’s major bridges

PANAJI: Three major bridges across two main rivers of Goa, all under stress for some time are examples of problems arising from construction snags and inadequate maintenance in the face of aggressive salinity conditions in Goa, sources said. The rehabilitated Mandovi bridge, 29-year-old Borim bridge and Zuari bridge at Cortalim have developed stress and are being used with restrictions to squeeze more life out of them due to their importance to the state's economy.

The collapse of Mandovi bridge on July 5, 1986, has been attributed to corrosion of the prestressed cable in most of the balanced cantilevers, which weakened the precast concrete segment of the superstructure.
The bridge was demolished and rebuilt after some years, but only light traffic has been allowed over it as a precautionary measure.
But, state planners committed the same mistake of using the Mandovi model for the Borim bridge in mid-1980s and it has been reported to be in distress for over a decade.
The Zuari bridge linking Cortalim and Agasaim built in 1983 is no different and had to be repaired in the 1990s. While the government has imposed load restrictions on Zuari bridge, the Borim bridge continues to be allowed to all types of traffic.
"Strict supervision and quality control during construction of projects like these executed from huge public funds is important," a source said.
PWD officials concede that pre-stressed cantilever bridges in India have developed stress due to their vulnerability to corrosion and improper grouting. "Maintenance is one major component due to environmental aggression, especially high levels of salinity that corrodes the bridges," the source explained.
While an eight-lane cable stayed bridge has been proposed as an alternative across Zuari, the fate of Borim bridge is unknown. The 30-year-old bridge has been a vital link carrying the heavy traffic diverted from the Cortalim bridge since mid-90s.
PWD closely monitored the bridge for vibrations and evaluated the extent of the damage caused by corrosion. The department has also periodically closed it for vehicular traffic for inspection and recording of deck levels. A Amtrthanathan, former assistant executive engineer, TWAD senior civil engineering, Nagercoil, Tamil Nadu, who later studied the case of Mandovi bridge collapse stated, "The main reason for the corrosion thin layer of deck " in-situ " concrete wherein the perstressed high tensile steel cables were embedded and the fact the most of the cables were not cement grouted to protect the wires and seal of the voids between the individual HT wires (a bundle of 12 wires of 7mm. diameter from a cable) and the sheathing pipe through which the cables were threaded."
Citizens have often raised a concern over the safety of bridges and neglect in their maintenance. "There should be an audit of all government works executed by PWD or GSIDC to ensure that the works done with the tax payers money are completed as per the desired standards of quality," J L D'Souza, a structural engineer said.

TOI Goa News

No comments:

Post a Comment