Setu set for repair debut

The 22-year-old Vidyasagar Setu is set to undergo its first major repair work but for commuters it will not be a bridge to avoid as humps are being put in place for vehicular movement while mission mend-it is on underneath.

By Subhajoy Roy
  • Published 8.06.15
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The 22-year-old Vidyasagar Setu is set to undergo its first major repair work but for commuters it will not be a bridge to avoid as humps are being put in place for vehicular movement while mission mend-it is on underneath.

For more than a month, humps are being built at the Howrah end of the southern flank of the second Hooghly bridge. Two humps, each spanning the approximate width of a traffic lane, have been built. A third, covering the remaining width of the flank, will be erected soon.

Repair work on the flank will start on the bridge once the third hump is in place.

Similar humps will later be built on the northern flank, which vehicles headed for the city take, as well. The structures will all be removed once the repair is over.

The humps - about one foot, 300mm to be exact, high - will allow vehicles to ply unhindered while repairs on the bridge's belly continue underneath.

Engineers said a problem in an expansion joint of the bridge, which allows a portion of the structure to expand and contract with the rise and fall in temperature, would need to be fixed and components replaced.

Expansion joints at both the Howrah and Calcutta ends need repairs but the problem is more pronounced at the Howrah end, right above the western bank of the Hooghly.

"It can be said that this is the first major repair of the bridge," said Asim Majumdar, project manager (works) of the Hooghly River Bridge Commissioners, the custodian of the bridge.

An engineer of Mageba, the private company that has bagged the Rs 3.39-crore contract for the repair and replacement job, explained their task.

A 457-metre span of the bridge across the Hooghly has expansion gaps at both ends to facilitate adjustments in keeping with the change in temperature across seasons. The gaps are not visible to commuters as they are covered by iron plates.

A span is a single concrete structure used in making a bridge or flyover. Usually, a bridge or flyover comprises multiple spans.

"The expansion gap is variable. When temperatures are low and the span contracts, the maximum gap can go up to 1,905mm. During summer, the gap reduces to 1,025mm," said Mageba project engineer Arijit Ghosh, who will supervise the repairs.

There are 10 lamella beams resting above bearings that slide when the span expands or contracts. "There is some problem in this entire mechanism. We have to identify and fix it," Ghosh said. "If this problem is not fixed, it may damage the bridge."

The engineer said the humps on the Howrah-bound flank would be ready in seven-10 days, after which work on the expansion joint will start.

S.R. Banerjee, the vice-chairman of the Hooghly River Bridge Commissioners, said the repairs would be over in four months - by the end of September.

The 823m-long Vidyasagar Setu was opened to public in October 1992. The Howrah and Calcutta-bound flanks are 17.5m-wide each. The carriageway is at a height of 26m above the river.