Specials

All about India’s Longest Rail-Road Bridge

February 2019

India recently welcomed one of its biggest landmarks! The country’s longest rail-cum-road bridge—Bogibeel Bridge over river Brahmaputra in Assam—was recently inaugurated, after having encountered several engineering and other challenges, almost 22 years after its foundation stone was laid in January 1997.

Bridging the Brahmaputra has always been a daunting task owing to its ferocious and unpredictable behaviour, high currents and turbulent waters, widespread erosion of the banks, short working period and high seismicity and remoteness of the area. With the width ranging from 1.2 km to 18 km, the Brahmaputra has been bridged only four times in the past; HCC holds the distinction of building two of these bridges and has now successfully led the fifth bridge, at Bogibeel, to its completion. Achieving this project was not an easy task. Part of the Assam Accord 1985, the foundation stone was laid in January 1997. However, works were awarded in 2008 to a contractor for construction of foundations and substructure of the bridge. And, in November 2011, HCC (with 51 per cent share) in a JV with DSD Brouckenbau GmbH, Germany (20 per cent share) and VNR Infrastructures (29 per cent share), received a Rs 9.87 billion order from the Northeast Frontier Railway to construct the superstructure of the rail-cum-road bridge.

Strategic importance
Situated 17 km downstream of Dibrugarh and Dhemaji, the bridge spans the Brahmaputra and will connect the town of Dibrugarh in the south to Dhemaji to the river’s north. At 4.94 km, it will provide connectivity to nearly 5 million people residing in upper Assam and Arunachal Pradesh by reducing travelling time from these two states to three hours. It will also give easy and direct access to upper Assam from the rest of the country through the north bank.

Besides, the Indian Railways will use the bridge for the transportation of coal and is most likely to run 50 trains per day on it in coming months. Owing to its location, the bridge will be of strategic importance to India as it will significantly enhance the ability to transport troops and supplies to its border in Arunachal Pradesh.

Structural specs
Bogibeel is among India’s first and only fully welded bridge constructions. Construction of trusses using welding makes the connection between the components a permanent one. A welded bridge not only reduces maintenance costs but adds to the longevity of the superstructure. The superstructure is a steel concrete composite and this is the first time European codes and welding standards were adhered to in the construction of a bridge in India. “The fabrication of steel material has been done to Euro 1090 standard (code for constructing steel structure),” says RVR Kishore, Project Director, HCC. “The welding methodology is the main advantage in the project.”

The rail-cum-road bridge is a double-decked bridge with two railway tracks on the lower deck and a three-lane road on the upper deck flanked by footpaths on each side.

An engineering marvel
The location of Bogibeel Bridge falls in Seismic Zone-V. To offer good stability to the heavy spans (1,700 mt), they have been provided with seismic restrainers.

Also, a major factor in successful completion was the detailed planning, which HCC successfully followed. But it was certainly a challenge to mobilise the required skill and manpower to retain them in the region. As Kishore says, “The project involved about 350 qualified welders and 120 engineers, and we had to constantly keep them motivated to stay and work in this remote area.” Indeed, this is a true example of teamwork, detailed planning, efficient strategising and pathbreaking technologies to gift India yet another engineering marvel—estimated to be durable and serviceable for 120 years.