BANGALORE (Metro Rail News): A 31-meter long, single-span U-girder, has been successfully cast for the first time in India for the Bengaluru Suburban Rail Project at Casting Yard, Devanahalli.
For the Mallige Line
It is an important milestone in the construction of the Bengaluru Suburban Rail Project. The ‘Mallige’ line or Corridor 2 includes the construction of around an 8 km viaduct or elevated section, from Hebbal to Yeshvantpura, using such U-girders.
First Time in the Country
Applauding the feat, Dr M.B Patil, Hon’ble Minister for Heavy & Medium Industries and Infrastructure Development, Govt. of Karnataka said “It’s a momentous occasion that a single span 31-meter-long pre-tensioned U-girders has been successfully cast here in Bengaluru, for BSRP. It is the first time in the country that such a 31-meter U- girder will be used for rail-based transport infrastructure. I have always believed that the Bengaluru Suburban Rail Project with its many innovations, is not just going to be a game changer for Karnataka but will also change the way we visualise commuter rail travel.”
What are U-Girders?
U-girders are U-shaped, pre-tensioned, precast girders that allow the track to be laid right away. U-girders are widely used in metro projects all over the world since they not only ensure superior quality but also save construction time.
General Practice
So far, 28- meter-long U- girders have been used in other metros. These girders are cast in the yards and will be transported to the location and launched over piers using high capacity Cranes/ launchers. It requires careful planning and accuracy to cast these U-girders in casting yards, away from the cities.
Specifications of the U-Girder
Below are some technical descriptions for the pre-tensioned 31m U-girder:
- One U-girder requires 69.5 cubic meters of concrete
- M60 grade concrete
- One U-girder weight: 178 tonnes
- Corridor 2 alone requires 450 such U-girders.
- Designed for Codal provision applicable to Indian Railway and Metro construction.
A solid Teamwork
An engineering marvel, this 31m U-girder has been designed by Assystem STUP for BSRP and proof-checked by IIT/Madras. Third-party design evaluation has been done by a General consultant (JV of Egis, Aecom and WSP). Entire supervision, precision execution, and quality control were closely monitored by KRIDE to ensure that technical parameters were as per the approved structural design, before and during concreting, also extreme caution was exercised in the casting yard.
Efficiency at its Peak
While box girders feature multiple segments between two piers which are post-tensioned, one single-span U-girders spans between two piers. As opposed to the six to seven days required for segmental construction, one single-span U-girder between two pillars can be built in a single night. The segmental box girder weighs much more than the entire span of a U girder. Unlike box girders or I-girders, track laying on these girders can be done right away. The use of a 31-m single span will reduce the number of piers, and foundations as compared to 28-m girder and save time for completion of civil works.
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