Post the famous battles of Chamb Jouria (1965) and the Indo-Pak war (1971), the Government of India decided to improve the transportation network near the international border with Pakistan, by connecting the city of Katra with Banihal in the erstwhile state of Jammu and Kashmir (now a Union Territory). Among the many strategically important projects under this initiative was the project to construct a 345-km-long Jammu-Udhampur-Srinagar-Baramulla Rail Line (JUSBRL), inclusive of numerous bridges and tunnels. This project was of utmost importance due to its geographic location near the border. Among the many bridges on the line is the Chenab bridge in the Reasi district of J&K, considered to be the world’s tallest and longest single span rail arch bridge with the crown of the main arch standing at 359 meters (above bed level).
The Chenab Bridge was declared a national project in the year 2002. The aim of the project was to expand the single lane bridge, constructed in 1932, to a double lane bridge that would enhance connectivity in the strategic border state of Jammu and Kashmir. Prior to this project, the single-lane bridge could only take the load of vehicles of a restricted class, while the new bridge would allow enhanced Class 70R loading, reducing traffic bottlenecks.
Sitting on an extremely active seismic zone amid mountainous terrain, the Chenab bridge on the Katra-Banihal rail line is the world’s seventh largest arch-shaped bridge. The 1,315 meters long bridge is currently being constructed at a cost of US$ 184 million. The remarkable features of the Chenab bridge include a 467-meter main arch and its structural components (pier and arch) that are masses of steel trusses. The arch is filled with concrete sealed steel boxes and will ensure that the bridge can withstand hostile weather conditions like wind speeds of 266 kmph and temperatures as low as -20⁰C. For the construction of the arch bridge, the world’s largest cable crane (length 915m) is being used on-site.
Safety and durability: The bridge has been designed and is being constructed keeping in mind a life span of 120 years. Given the vulnerability and sensitivity of the region, explosion proof steel and concrete elements are being incorporated in the structure as a protective measure to guard the bridge from possible terrorist attacks. The highly seismic prone and weak rock mass, characteristic of the area, is of major concern and for this purpose the stakeholders have carried out site-specific seismic hazard analysis to ensure the site is safe for construction In addition, the bridge is currently being equipped with a GIS enabled online monitoring and warning system.
Challenges: Given the complexity of the project’s geographical location, a number of hurdles had to be overcome at different stages of the construction lifecycle. However, a major concern for the stakeholders was to ensure that the flow of the Chenab river was not obstructed in any manner.
Before the design and construction of the Chenab Bridge began, the Konkan Railways Corporation, the project owner of the bridge, established the use of Indian Railway Standards (IRC) in all phases of the construction lifecycle. However, the design team was also allowed to use UIC Standards, British Standards, and other international standards, as required and preferred.
To address the geographical adversities and complexities at the project site, Konkan Railways Corporation, mandated the creation of a 3D model of the bridge as per the recommendation of the architects, planners and designers. To create the 3D model, the design consultant chose Tekla Structures, a parametric modeling tool for delivering the 3D model of the bridge design, instead of 2D drawings. Using the 3D model, the team was able to optimize the quantity of material required for construction and optimize the construction efficiency as well. Additionally, the 3D model was used to automatically detect clashes and take corrective measures to reduce errors and ensure accuracy. High accuracy and an enhanced level of development (LOD) of the 3D model allowed the bridge components to be constructed/prefabricated in temporary workshops on the project site.
MicroStation was used to assess the maps given by Survey of India and reduce the interoperability issues on the site. The initial survey done via drones enabled the designers to attain steady coordinates and dimensional accuracy. STAAD – a structural analysis and design software application — was used for overall designing, and RM Bridge (for viaduct design) was used to analyze the structural behavior of bridge components. The use of Bentley’s ContextCapture for construction planning and monitoring empowered the project teams to effectively carry out inspections, ensuring safety and adherence to timelines. Also, the team utilized OpenRail Designer to transfer the bridge design from a straight singular alignment to a curved double-lane alignment.
Value Proposition: An estimated 225 resource days amounting to US$ 40,000 were saved using reality modeling and drones for surveying, mapping and creating 3D design models. The use of digital technologies also reduced safety hazards and identified potential issues in advance, thus allowing for better and more holistic management of the project. A reduction in construction inspection time by almost 80 percent also led to savings of about US$ 100,000. Overall, by improving connectivity with the international border and also within Jammu and Kashmir, the Chenab bridge will benefit the economy at large.
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