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Construction : Special Project | October 2016 | Source : CW-India

Bridge of Steel

A permanent bridge has been finally installed in Sonprayag at the Himalaya - this time, a modular steel one.
In June 2013, devastating floods and landslides in the Himalaya caused the destruction of an existing bridge at Sonprayag in Uttarakhand. A quick but temporary bridge was erected, but was washed away on two occasions by floods again in June 2015. That´s when Acrow Bridge, an international bridge engineering and supply company, was roped in to install a permanent bridge in Sonprayag - this was opened to traffic in May 2016. The remote site is part of the route taken by pilgrims on the trek to Kedarnath Temple, which is about 3,600 m above sea level. Unlike previous crossings, the new structure can take two lanes of traffic.

Modular steel advantages
Constructing a long, conventional bridge in-situ would not have been too feasible owing to Sonprayag´s challenging topography. Also, while a conventional bridge would take more than three years to build, an Acrow steel span of any length can be operational in days with minimal construction machinery and unskilled labour. What´s more, as it is fabricated in a controlled environment, the quality of a prefabricated structure is much better.

´The assembling speed for an Acrow bridge compared to a conventional one is significant,´ affirms professional engineer Bill Killeen, President and CEO, Acrow Bridge. ´Sonprayag was a complicated build, yet we finished it in six weeks. The roads made it impossible to transport a conventional long steel girder or concrete beam to the job site. Logistically, modular steel bridges are easier to transport. Acrow was given a contract in June 2015; the bridge arrived on site from the US in October 2015, about 20 days earlier; the assembly work commenced on February 10, 2016, and was completed around March 25, 2016.´

Construction techniques
The superstructure was made of Acrow prefabricated modular steel bridge parts and the substructure was an amalgamation of locally excavated stone and reinforced concrete.

The 60-m, clear-span bridge was customised with modular components to address local conditions. ´A beneficial feature of the Acrow prefabricated modular bridge is that it rarely needs customising,´ shares Killeen. ´This bridge comprised standard components off the shelf. We understood that heavy highway lifting equipment was unable to travel to the project site at Sonprayag. So, it was essential that the bridge be built such that a large crane was not needed. We chose a method of assembly called ´launching´, where the bridge is ´rolled´ into place.´

Necessary rollers and hydraulic jacks to perform the launching and eventual set-down onto the abutments were supplied by Acrow. For construction, a bulldozer was used to push the bridge out over the river. A forklift would pick up the parts and bring them to a small hydraulic crane for placement. The hand tools were supplied by Acrow along with the bridge. The modular Acrow components used for the bridge were shipped in standard ocean containers to India and delivered by compact and manoeuvrable trucks with a length of 6.5 m.

Design and support
The Acrow structure was funded by the World Bank. The bridge delivered to the project site cost about Rs 8.1 crore and the assembly cost did not exceeded 10 per cent of the delivered price. External consultants were not needed, which helped reduce costs.

The bridge can support a 70-tonne tank or a 100-tonne truck. ´It is also designed to support full crowd loading covering the 5.5-m-wide road surface and the two 1.5-m-wide footpaths,´ adds Killeen. ´The pedestrian crowd loading adds up to about 250 tonne of weight. The abutments used to support the 60-m span were tall and complex to ensure adequate space would exist between the bridge and the river water during monsoons.´

Project details
Location:
Sonprayag, Uttarakhand.
Type:
60 m clear span bridge.
Height:
2,400 m.
Cost of bridge:
Rs. 8.1 crore.
Consultant: ICT Intercontinental Consultants and Technocrats.
Tel:
011-4086 3000.
Website:
www.ictonline.com
Civil contractor:
Crew organised by Uttarakhand Disaster Recovery Initiative.
Tel: 0135-266 9815.
Website:
www.ukdisasterrecovery.in
Contracting agencies:
Uttarakhand Disaster Recovery Initiative.

- SERAPHINA D´SOUZA


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