The expansion joints of the 40-year-old Chetla bridge that links south Calcutta and the city’s west have been replaced for the first time since the bridge was commissioned.

The Kolkata Metropolitan Development Authority (KMDA), the custodian of the bridge, will also remove 125mm of bituminous layer from the bridge to reduce unnecessary load on the structure. The extra bituminous layers were created over the years when bitumen layers were added without scraping off the older layers.

“Ideally, the thickness of the bituminous layer on the bridge should be 65mm. The bituminous layer on the Chetla bridge is 190mm thick. We will scrape off everything and lay a fresh layer that will be 65mm thick,” said an
official.

Removing and then laying a fresh bituminous layer can be done within a fortnight, cordoning off portions of the bridge.

The 250-metre long, four-lane bridge running over the Tolly’s Nullah and located near the Keoratala burning ghat, is used by hundreds of vehicles daily. The movement of buses was stopped on the flyover a few years ago, however, autorickshaws, taxis and private cars take the bridge to reach Chetla, New Alipore or further west from the Rashbehari crossing.

“We started replacing the four expansion joints of the bridge three months back. We had to cordon off portions of the bridge as the work progressed. The last expansion joint was replaced a couple of days ago. That barricades in the area will be removed on Monday,” said a KMDA
official.

An expansion joint is a gap between two deck slabs of a bridge, which allows room for expansion and contraction of the concrete deck slabs with temperature variations. A mild steel structure in the expansion joint at the Chetla bridge will absorb this expansion and contraction.

The replacement of expansion joints along with the removal of the extra bitumen layers will cost ₹80 lakh.

KMDA officials said a health study of the bridge had recommended replacing the expansion joints and removing the extra bituminous layers.

“We are now working on the bridge’s superstructure. We also have plans to undertake some retrofitting work in the bridge’s substructure,” said another KMDA official.

The removal of the additional bituminous layers is likely to start in the days between the end of Madhyamik examinations and the start of higher secondary examinations, said an official. To prevent any traffic snarls, no infrastructure work, unless unavoidable, will be allowed while board examinations are on.

The KMDA had set up a committee of experts to conduct a health assessment of the bridges and flyovers under its custody following the collapse of the Majerhat bridge in September 2018.

KMDA sources said the agency has already completed the retrofitting, as per recommendations of the experts, of Chitpore bridge near Bagbazar, Chingrighata flyover and Ultadanga flyover. Retrofitting, which strengthens an old bridge, is also being done at the Baghajatin railway overbridge.

The retrofitting of a few other bridges like the Dhana Dhanye Setu in Alipore , Jibananda Setu in Sealdah and the Karunamoyee bridge in Tollygune is still on the cards.