Delhi Metro Rail Corporation (DMRC) yesterday (Wednesday, 24th June 2020) commenced the casting work of U-girders which would be installed on the elevated section of the upcoming Janakpuri West–RK Ashram corridor.
Over the years, DMRC has mainly used precast structures, such as Box-girders, I-girders and for some sections, U-girders to construct its corridors. U-shaped girders are precast and pre-tensioned on which track laying can be done quickly. For its Phase-IV project, DMRC has decided to standardise the usage of U-girders for the entire network to save time and also lower construction cost.
Compared with other types of girders, the 28-metre-long U-girders drastically reduce construction time, but due to their length, require absolute precision during construction. Transporting these girders from the casting yard also becomes a tricky proposition. DMRC had earlier used U-girders for construction of Airport Express Line and on the Dilshad Garden–Shaheed Sthal. On the Noida–Greater Noida section, 27-metre-long U-girders had been installed.
“This is a major milestone for DMRC, as despite severe crunch of workforce due to the ongoing pandemic and various other lockdown-related constraints, the casting yard was readied within a record period of 94 working days,” said Anuj Dayal, executive director (corporate communications), DMRC.
Dayal said every month 56 U-girders shall be produced at the yard in Mundka and total 2,200 different pre-cast components required for construction will be cast at this yard. Dayal said metro projects across the world are extensively using U-girders. “After casting, these girders are brought to the site and launched with the help of high capacity cranes or launchers,” he added.
“Absolute care has to be taken regarding the maintenance of all measurements and technical parameters during the casting process,” he said. “At the casting yard, 10 U-girder casting beds have been put up for the job. A dedicated quality control laboratory has also been set up to monitor all quality related parameters.” Compared with conventional girders, which are 2.2 metres to 2.5 metres long, U-girders used by DMRC are 28 metres long. The longer length means one span between two pillars can be constructed overnight compared with five to six days in case of conventional girders.
Apart from the benefit of saving time, the U-girders that DMRC plans to use for the Phase-IV project will also have built-in sound barriers, apart from built-in cable support. The 28.9-km long Janakpuri West–RK Ashram Marg corridor is an extension of the Magenta Line (Botanical Garden-Janakpuri West) and will come up with 22 stations. Construction work on this section had started in December last year.