Saturday, November 12, 2016

Engineering marvel

Dr.Banarsi Lal and Dr.Shahid Ahamad
Reasi district is famous for various renowned places and Chenab Rail Bridge is another feather that Reasi district is going to add in near future.In Reasi district of Jammu and Kashmir Chenab Rail Bridge is under-construction and is located between the two places viz.Bakkal and Kaori.
The length of this bridge is 1,315m-long bridge and height is 359m. Once completed, it will be the highest rail bridge in the world and even 35m higher than the Eiffel Tower.This bridge will be a part of Jammu-Udhampur-Srinagar-Baramulla rail line project being undertaken by the Ministry of the Indian Railways. It is expected that this bridge will have a lifespan of 120 years. It is hoped that this bridge will contribute immensely to the economic development of the state and help in providing better transportation accessibility within the state and the country.
In Jammu and Kashmir transportation facilities are poor especially in the far-flung mountainous terrains. The Government of India recognized the transport problems of the state so construction of a national railway project that will connect J&K with the rest of country was therefore proposed.The Chenab Bridge project was launched in 2003 as part of this proposal.It is expected that the 345km-long railway line between Jammu and Baramulla regions will enhance transportation within the State and across the nation. The railway line will traverse along Jammu-Udhampur-Katra-Qazigund-Baramulla. Construction of the Jammu to Udhampur section was completed and has been opened. Work is progressing on the Udhampur to Baramulla section.The world famous place Katra (due to Shri Vaishno Devi Shrine) has been connected by the railway line with the rest of nation.The project includes construction of several bridges and tunnels along the route, of which Chenab Bridge is one of them. The project was suspended in 2008 due to construction challenges. The alignment of the entire project was reviewed to propose solutions for the challenges faced. The reviewed work was submitted to the Railway Board and finally it was approved in 2009. The design of the bridge, however, was approved in July 2012.
Chenab Bridge is first of its kind in India and forms a massive steel arch. Our country has no design guidance for such massive structures. Based on experiences drawn from similar projects worldwide, the design practices for the bridge are being followed.The deep Chenab river valley under the bridge is prone to high wind pressure which is to be expected to be risking factor for the stability of the bridge.Norway-based Force Technology Laboratory conducted various wind tunnel tests to understand the effects of wind speed, static force coefficients and gust buffeting. The bridge is designed to resist wind speeds of up to 260kmph. The seismic nature of the project zone was also considered during its design.The bridge will include 17 spans, as well as the 469m main arch span across the Chenab River, and viaducts on either side. The main span of the bridge will include two 36m-long approach spans. It will be built as a two ribbed arch with steel trusses made of concrete-filled sealed steel boxes. The structure will be supported by two 130m-long, 100m-high pylons on either end through cables.Steel is used to construct the bridge as it will be more economical and able to resist temperatures of -20C and wind speeds of above 200kmph. As the state is prone to frequent terrorist attacks. In order to enhance safety and security, the bridge will be made of 63mm-thick special blast-proof steel. The concrete pillars of the bridge are designed to withstand explosions. In order to safeguard the bridge a ring of aerial security will be provided. An online monitoring and warning system will be installed on the bridge to protect the passengers and train in critical conditions. Footpaths and cycle trails will be provided adjacent to it. The bridge will be painted with a special corrosion-resistant paint, which remains for many years.
The Chenab Rail Bridge is being constructed in hilly terrain which is a very difficult and isolated place.While constructing this bridge the Chenab River water is not obstructed which is a great challenge. Around five kilometers road was specially constructed to reach the foundations of the bridge. The deck of the bridge is partly in straight horizon and partly in curves. It is situated on a transition curve with changing radius.  Its construction is carried out in stages following the gradual change in the alignment. This is the first time a bridge is being constructed incrementally on a transition curve. World largest cable cranes and derrick are used to construct the bridge.  It is expected that the construction of the bridge require 25,000mt of steel, 4,000mt of reinforced steel, 46,000m³ of concrete and eight million m³ of excavation. The bridge is blast proof and it can withstand even 40 tonnes TNT of explosives and an earthquake of 8.5 intensity on the Richter scale.
The review work of the alignment was carried out by the Amberg and mainly executed by the Konkan Railway Corporation. Design and construction of the bridge was done by the joint venture of Afcons Infrastructure, Ultra Construction & Engineering Company of South Korea and VSL India. Consultancy services are being taken by the Finland-based WSP Group and Germany-based Leonhardt Andra. The pylons of the bridge designed by VCE Consult ZT-GmbH and Jochum Andreas Seiltransporte installed the cables for the pylon.Painting services are given to AkzoNobe for the bridge. It is hoped that this place will become a visiting spot for the tourists after completion.
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