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A new 15-kilometre elevated irrigation structure near Bangalore in southern India is very noteworthy, but not only for its impressive dimensions – it also carries a road on top!
In the Indian state of Karnataka, a new aqueduct has just been constructed to enable much-needed irrigation water to flow from the Krishna river to the Vijayapur district. But this is no ordinary elevated canal structure; it has been constructed with a road on top, running along its entire length of almost 15km, to facilitate the movement of people and goods as well as water.
The aqueduct has over 400 simply supported spans, each 30m long, on piers that are up to 30m high. The trough-shaped spans of pretensioned, precast concrete weigh 230 tonnes each, and were lifted into position using two 500-tonne cranes. Following placing of deck slabs on top to provide the road surface, these were fixed in place using in-situ concrete. The canal was dimensioned to facilitate a flow rate of approximately 14m3/s.
A total of 1660 structural bearings were required to support the superstructure, four under each span. The use of spherical bearings was initially proposed by the aqueduct’s design, but mageba’s Kolkata office team was glad to provide some very valuable advice in this regard. Considering the aqueduct’s construction methodology, as well as the loads, translations and rotations to be accommodated etc., they proposed the use of elastomeric bearings instead. These are typically much easier to install – particularly in cases such as this where they do not require to be anchored in place thanks to sufficient minimum load and friction, and where their compressibility enables a lack of perfect load distribution among a set of bearings to be automatically compensated. As an added bonus, they are also significantly less expensive than spherical bearings. However, the specified Indian design standard for bridge bearings did not allow the use of elastomeric bearings where seismic forces might apply – a problem which could be overcome by instead designing and manufacturing the bearings in accordance with the European standard EN 1337.
Having settled on this optimal solution, mageba India designed, manufactured and supplied the 1660 LASTO®BLOCK elastomeric bearings (Type B, using CR elastomeric material) in a span of just one year, including testing as appropriate. These were supplied with the CE label, attesting – on the basis of external, independent evaluation and monitoring – to their design and fabrication in accordance with EN 1337.
The change to elastomeric bearings helped accelerate the aqueduct construction programme, enabling it to be completed in just two years, and the installation supervision provided by our local team helped ensure that every elastomeric bearing will perform as expected for many years to come. A remarkable performance by our colleagues in Kolkata? Actually, it’s the level of service we aim for every day, in all our locations around the world – let us support you like this on your next project!
Bridge designer: Root Design Technocrat Pvt. Ltd.
Contractor: Shankaranarayana Construction Pvt. Ltd.
Client: Krishna Bhagya Jala Nigam Ltd.