Chenab Bridge: The tallest railway bridge
01 Nov 2022
Chenab Bridge is considered by many to be the epitome of extreme engineering and construction. It is a unique and iconic project for Afcons in terms of height, span, terrain, and attaining many firsts. The height of 359 m above the Chenab water level makes it the tallest railway bridge in the world, about 34 m higher than the height of the Eiffel Tower. A single arch spanning 467 m across the deep gorge of the river is one of the largest of its kind in the world. A massive 30,000 mt of structural steel has been used for the arch, trestles and deck. Lean principles, specifically Value Steam Mapping (VSM) and Visual Management were used to optimise the fabrication workshop operations, as follows:
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The entire fabrication and assembly process was mapped to look at three variables: range of work activities, work times and material movements. The workshop layout was designed to meet the goal of fabrication and launching of six segments without any interference.
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The layout was designed to minimise transportation and rehandling.
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The site team innovated, designed and fabricated certain fixtures onsite that helped improve the efficiency of operations. One such case was the orthotropic deck segment turning arrangement, which allowed for rotation of 55 mt to 95 mt segments comprising 354 parts. This was done to enable welding in the down-hand position, thus ensuring defect-free welding over ~6.3 km of running welding for each segment.
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Visual control boards were installed at each workstation to bring transparency, deal with surface issues and close the gaps.
Welding was carried out by automatic machines – MIG (metal inert gas), SAW (submerged arc welding), FCAW (flux cored arc welding) – to produce best quality of welds, save time and involve fewer manual interferences.
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For inspection and testing, samples were sent to New Delhi or Ghaziabad. Hence, the project set up a laboratory accredited by the National Accreditation Board for Testing and Calibration Laboratories (NABL). This is the first-of-its-kind lab at any construction site in India.
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