Fourteen cables of Vidyasagar Setu will be replaced over the next eight months in what is being termed as the first comprehensive overhaul of India’s largest cable-stayed bridge.
The bridge spans 823 metres across the river Hooghly.
Ahead of replacing the damaged cables, a team of senior engineers from the Hooghly River Bridge Commissioners (HRBC), which maintains the structure that was inaugurated in 1992, will conduct a load test of the bridge to find out how the remaining cables oscillate in the absence of any vehicle.
Structural experts from a French engineering company will join the HRBC team to calibrate the performance of the bridge’s cables between Monday night and early on Tuesday, when no vehicles will be allowed on the structure.
“We have identified 14 cables that need to be replaced. The proposed test without any vehicle on the bridge will reveal how the remaining cables are transferring the structure’s load,” said a senior HRBC official.
Vidyasagar Setu, at times colloquially called second Hooghly bridge, has 152 cables. There are two sets of piers at both ends that hold the cables.
Each cable comprises three layers. The innermost layer is made of a bunch of non-galvanised cables and the outer layer, which is visible from outside, is made of rubber. There is an intermediate layer which is made of wax and prevents water seepage.
Vidyasagar Setu was built at an estimated cost of around Rs 388 crore. The construction continued for 22 years.
The 14 cables that will be replaced have the innermost core damaged, senior HRBC engineers said.
“The cables will be brought from Germany and fitted under the supervision of experts. Each cable costs around Rs 5 crore,” said a senior official of the finance department. “The cables are being made especially for Vidyasagar Setu.”
The core of the new cables will be better equipped to fight corrosion, engineers said.
“Once the 14 cables are replaced, we will draw up a plan for the second round of changes,” an engineer said.
The bridge attracts close to 90,000 vehicles every day. Officials said the vehicle count has been increasing steadily since the state secretariat shifted to Nabanna from the Writers’ Buildings after Mamata Banerjee took over as chief minister.