The first complete repair and renovation of the upper deck of road-cum-rail Saraighat bridge over river Brahmaputra in Guwahati, was completed and opened for traffic on June 20.
The old Saraighat bridge was the first bridge over the mighty Brahmaputra that was opened more than 56 years ago. The bridge was undergoing repair since March 23 and was closed for traffic. The repair work, which had started on March 23, has been completed in 89 days, within the three-month target set for the work.
Almost 500 workers were engaged to carry out the challenging task of replacing 54 slabs on the upper deck along with replacement of 11 expansion joint slabs and expansion joints.
During the entire repair period, the lower deck was operational for rail traffic.
The methods adopted to replace 54 deck slabs and the 11 connecting expansion joints involve breaking down the concrete slabs, expansion joint slabs and removing the expansion joints.
On an average 75 workers per day were engaged in breaking the slabs and 45 workers per day were engaged in carrying these broken pieces away and cleaning.
The repair and replacement of the upper deck slabs of the bridge were particularly difficult because of the fact that train movement on the lower deck was continuing without any disruption.
For this, special permission was obtained from Commissioner of Railway Safety (who works under the Ministry of Civil Aviation to maintain autonomy). Accordingly, special temporary scaffolding was erected under the Upper Deck to collect broken pieces from the deck.
After breaking down of the old concrete slabs and the expansion joint slabs, fresh 10mm thick steel plates were laid and welded to the bridge over which high-strength concrete was laid to make the deck slabs.
More than 500 tonnes of the steel plate and reinforcement rods have been used for the deck slabs alone.
Once the deck-slabs were ready and the expansion joints were replaced, 50 to 65 mm thick heavy-duty Semi-Dense Bituminous Concrete (SDBC) was laid over the entire deck to facilitate vehicular movement.
To ease the bumps over the expansion joints, 150 mm thick aluminium plates were laid over them under the SDBC. This will make driving over the bridge comfortable even at high speed.
Road markings, painting of side beams, side railing and fixing of car eyes has been done for improvement of aesthetics.
The Saraighat rail-cum-road bridge, built and maintained by the Railways, was inaugurated in 1962 and was the first bridge over the Brahmaputra river.