India's longest U-girder launched on suburban rail corridor in Bengaluru

Bengaluru: K-RIDE has just launched the first 31-metre-long, single-span precast U-girder — the longest in India — on the Mallige Line of the Bengaluru Suburban Railway Project (BSRP). 

The U-girder, cast at Gollahalli in January 2024, was launched between 9.45 pm and 10 pm on Tuesday at Yeshwantpur as part of work to build the Baiyappanahalli-Chikkabanavara line, a K-RIDE official said. 

Rail Infrastructure Development Company (Karnataka) Limited, or K-RIDE, is the government agency implementing the 149-km BSRP. 

U-girders are U-shaped, pre-tensioned and precast girders used in rail-based public transport projects. They ensure quality and save construction time because their extra length helps reduce the number of foundations as well as piers. 

While metro projects typically use 28-metre-long U-girders, the BSRP will be using longer ones, according to K-RIDE. 

A U-girder requires 69.5 cubic metres of M60-grade concrete and weighs 178 tonnes. After being cast in the yard, it is transported to the worksite and launched over piers using high-capacity cranes/launchers. 

Unlike box girders, which consist of multiple, post-tensioned segments between two piers, just one U-girder is enough to build a span between two piers. A single-span U-girder can be built in a single night, as against six to seven days required to construct segments. The segmental box girder also weighs much more than the entire span of a U-girder, K-RIDE said. 

According to K-RIDE, 450 U-girders will be launched on the Mallige Line's eight-kilometre elevated section between Hebbal and Yeshwantpur. Nearly 60 U-girders have been cast so far at Gollahalli. 

The Mallige Line deadline is December 2026.