The construction of Chenab Bridge (world’s highest rail bridge by Indian Railways to connect Kashmir with the rest of India by 2021), is going on and is expected to complete by 2021. After completion of construction, Chenab Bridge will be the world’s highest railway bridge as well as the bridge having widest span in the Indian broad gauge railway network.
This railway arch bridge is under construction between Kauri and Bakkal in the Reasi district of Jammu and Kashmir in India. After completion Chenab Bridge will span the Chenab River at a height of 359 m (1,178 ft) above the river, making it the world’s highest rail bridge. The base supports for the bridge were completed in November 2017, and thereafter the construction of the main arch began.
Project of Northern Railways
This mega project of constructing a railway line between the towns of Udhampur near Jammu and Baramulla on the northwestern edge of the Kashmir Valley, in the Indian Union Territory of Jammu & Kashmir. In 2002, this the Chenab Bridge project was declared as national project.
The most challenging part of this railway project is the large number of tunnels (totalling 63 km in length) as well as bridges (7.5 km) to be constructed on the highly rugged and mountainous terrain of the Himalayas. Amongst, all the challenges, the most difficult part of this railway project is believed to be the crossing of the deep gorge of the Chenab River, which is located near Salal Hydro Power Dam.
Apart from the Chenab Bridge, a smaller, arch bridge is also proposed on this new railway line which was the 657 m (2,156 ft) long, 189 m (620 ft) high Anji Khad Bridge between Reasi and Katra over the Chenab river tributary river. However, due to the specific geology of the location, this proposal was abandoned by the railway, and a cable-stayed bridge is proposed.
Design and Construction
After long and careful considerations, and taking into account the economy, aesthetics, and availability of local expertise as well as construction materials, the world’s highest rail bridge (Chenab Bridge) was designed as a large span single arch steel bridge with approach viaducts on either side. The arch of the Chenab Bridge is two-ribbed, which is fabricated from large steel trusses. In order to assist in controlling wind-induced forces on the bridge, the chords of the trusses are sealed steel boxes, which are internally stiffened and filled with concrete. Due to the concrete filling, internal painting will not be required.
Through the use of continuous construction, number of bearings has been minimised, specially on the approach viaduct. It helps in reduction of maintenance and inspection efforts, as well as improves the riding quality. The viaduct piers of Chenab Bridge are made up of concrete, whereas the piers near the arch are made up of steel.
The design of major arch rail bridges requires considerations of a number of additional parameters, such as second order effects, global stability, fatigue, composite action, etc. Further, it also requires that such a bridge is designed so as to have a consistent level of reliability for all load cases, and also the construction standards and design standards should match.
Key Design Considerations
Some of the design considerations taken into account for Chenab Bridge are as follows:
- Computation of wind load effects has been conducted as per wind tunnel tests
- As per BS codes, limit state philosophy of design has been decided to be followed
- Provision of Euro code 8 for ductility detailing of very tall and hollow rectangular RCC piers
- Site specific seismic spectra developed by Indian Institute of Technology (IIT) Roorkee
- Provision of long welded rail (LWR) over the bridges and resulting force calculation as per UIC – 774-3R guidelines
- Design checking for fatigue as per BS codes
- Blast resistant design used
- Redundancy has been provided in the structures, for lower level of operation during mishaps and in the situation of collapse in extreme cases of one pier failure
- Deformation limits as per comfort criteria of UIC – 776-2R and UIC 776 -3R guidelines